<<

THE EXTRACTION OF AND

SITUATES FBQM AQUEOUS SOLUTION BY

ORGANIC SOLVENTS

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

3y EIWAED JONATHAN SCHARF, B. Ch. E. , M. Sc.

******

The Ohio State University 1957

Approved "by:

Adviser Department of Chemical Engineering AOlDJOWIiEDGHMMT

The author would like to express his appreciation to hie adviser. Dr. 0 . J. Geankoplis, for his generous assist­ ance and helpful advice.

Grateful acknowledgement is made to the American

Cyanamid Company for their financial assistance hy means of a fellowship for the years 1953”5 5 -

il TABLE OF CONTENTS

Page ABSTRACT ...... 1

INTRODUCTION ...... 1*

A. General 1* B. Importance of Cobalt and Nickel to Industry . 1* C. Metallurgy of Cobalt and Nickel .... 8 D. Liquid-Liquid Extraction ..... 10

LITERATURE EE V I E W ...... 12

A. The Extraction of Salts, General . . 12 B. The Extraction of Cobalt and Nickel Salts . . 12 C. Extraction of Nitrates ...... 22 D. Extraction of Other Metal Salts .... 2? E. The Extraction of Metal Chelates .... 30

STATEMENT OCF THE P R O B L E M ...... 32

THEORY ...... 31*

ANALYTICAL M E T H O D S ...... 37

A. Solvent Search ...... 37 B. Extraction with n-Butanol . .... 48

EXPERIMENTAL P R O C E D U R E ...... 62

A. Equipment ...... 62 B. Extraction Procedure ...... 66 C. Verification of Extraction Procedure . . . 68 D. Ternary Diagram ...... 70 E. Materials Used ...... 71

EXPERIMENTAL D A T A ...... 7I*

A. Solvent and Additive Search ..... 7^ B. Distribution with Normal Butanol .... 7^ C. Solubility Determination with Normal Butanol . 85

TREATMENT AND DISCUSSION OP D A T A ...... 92

A. Calculations ...... 92 B. Discussion of Solvent Search Data . . . 9^ C. Distribution with Additive Data .... 98

iii TABLE OF CONTENTS (Continued)

Page

TREATMENT AND DISCUSSION OF DATA (Continued)

D. Selection of Solvent and Additive . . . 102 E. Studies with Nonaal Butanol ..... 103 F. Process Application ...... 130

CONCLUSIONS...... 133

SUGGESTIONS FOB 3UBTHEB INVESTIGATION .... 135

NOMENCLATURE 137 BIBLIOGRAPHY ...... I39

AUTOBIOGRAPHY ...... 144

iv LIST OF TABLES

1 MATERIALS USED ......

2 SOLVENT SEARCH DATA AT 25.0° C.

3 DISTRIBUTION IN SYSTEMS: METAL NITRATE - WATER - SOLVENT - ADDITIVE AT 25.0° C......

4 EFFECT OF METAL CONCENTRATION ON SYSTEM: NICKEL NITRATE - WATER - N-BTJTANOL AT 25.0° C.

5 EPPECT OP METAL CONCENTRATION ON SYSTEM: COBALT NITRATE - WATER - U-BUTANOL AT 25.0° C.

6 DISTRIBUTION IN THE SYSTEM: NICKEL NITRATE - - WATER - N-BUTANOL AT 25.0° C.

7 DISTRIBUTION IN THE SYSTEM; COBALT NITRATE - NITRIC ACID - WATER - N-BUTANOL AT 25.0° C.

s DISTRIBUTION IN THE SYSTEM: NICKEL NITRATE - COBALT NITRATE - WATER - N-BUTANOL AT 2$, 0° C.

9 EPPECT OP ON THE SYSTEM: NICKEL NITRATE - WATER - N-BUTANOL ......

10 EPPECT OP TEMPERATURE ON THE SYSTEM: COBALT NITRATE - WATER - N - B U T A N O L ......

11 SOLUBILITY ENVELOPE PQR TEE SYSTEM: NITRIC ACID - WATER - N-BUTANOL AT 25.0° C. .

12 EPPECT OP METAL NITRATES ON THE SOLUBILITY OP N-BUTANOL IN AQUEOUS NITRIC ACID SOLUTION AT 23*0 C......

13 EPPECT OP NICKEL NITRATE ON SOLUBILITY OP AQpEOUS NITRIC ACID IN N-BUTANOL AT 25.0° C.

14 SEPARATION FACTOR, A , WITH VARYING NITRIC ACID CONCENTRATIONS . . . . .

15 TIE LINE DATA POR THE SYSTEM: NICKEL NITRATE - NITRIC ACID - WATER - N-BUTANOL AT 25.0° C.

v LIST OP FIGURES

Page

1 MEASURED ABSORBANCE OP CONCENTRATED HCL SOLUTIONS OP COBALT BY A FISHER A. C. ELECTROPHQTOMETER 39 2 MEASURED ABSORBANCE OF SULIUBIC ACID SOLUTIONS OF COBALT BY A BECKMAN HK-2 SPECTROPHOTOMETER 43

3 MEASUEEID ABSORBANCE OF COMPLEX OP NICKEL BY BECKMAN DU SPECTROPHOTOMETER 46

4 MEA&JEED ABSORBANCE OF SULIURIC ACID SOLUTIONS OP NICKEL BY A BECKMAN BK-2 SPECTROPHOTOMETER 50

5 TYPICAL BECKMAN DR-2 SPECTROPHOTOMETER CURVES FOR SOLUTIONS OF COBALT AND NICKEL 55 6 THE EPPECT OF METAL NITRATES AND N-BUTANOL ON NEUTRALIZATION OF NITRIC ACID . 60

7 CORRELATION BETWEEN ALCOHOL MOLECULAR WEIGHT AND DISTRIBUTION COEFFICIENT OF NICKEL NITRATE AT 25.0° C...... 97 8 DISTRIBUTION IN THE SYSTEM! N-BUTANOL - NICKEL NITRATE - WATER AT 25.0° C. WITH VARIOUS ADDITIVES ...... 100

9 DISTRIBUTION IN THE SYSTEM: N-BUTANOL - COBALT NITRATE - WATER AT 25.0° C. WITH VARIOUS ADDITIVES ...... 101

10 EFFECT OF METAL CONCENTRATION IN THE SYSTEMS: METAL NITRATE - WATER - N-BUTANOL AT 25.0° C. 105 11 LOG-LOG PLOT OF DISTRIBUTION IN SYSTEMS: METAL NITRATE - WATER - N-BUDANOL AT 25.0° C. 106

12 LOG-LOG PLOT OF DISTRIBUTION IN SYSTEMS! METAL - WATER - CAPRYL ALCOHOL 108

13 DISTRIBUTION OF COBALT NITRATE BETWEEN N-BUTANOL AND AQUEOUS NITRIC ACID AT 25.0° C. 109 14 DISTRIBUTION OP NICKEL NITRATE BETWEEN N-BUTANOL AND AQUEOUS NITRIC ACID AT 25.0° C. 110

VI LI SI G3T FIGURES (Continued)

Page

15 DISTRIBUTION OP NICKEL NITRATE BETWEEN N-BUTANOL AND AQUEOUS NITRIC ACID AT 25.0° C. (CBOSS PLOT) 111 16 SEPARATION FACTORS IN THE ST SEEMS: METAL NITRATE - WATER - NITRIC ACID - N-HJTANOL AT 25.0° C. 115 17 DISTRIBUTION OP COBALT IN THE SYSTEM: NICKEL NITRATE - COBALT NITRATE - WATER - N-BUTANOL AT 25.0° C ...... 117 18 DISTRIBUTION OP NICKEL IN SYSTEM: NICKEL NITRATE - COBALT NITRATE - WATER - N-BUTANOL AT 25.0° C. . 118

19 DISTRIBUTION IN THE SYSTEM: METAL NITRATE - WATER - N-BUTANOL AT VARIOUS 120

20 THE DISTRIBUTION OP NITRIC ACID BETWEEN WATER AND N-BUTANOL AT 25.0° G., COBALT NITRATE PRESENT 121

21 THE DISTRIBUTION OP NITRIC ACID BETWEEN WATER AND N-BUTANOL AT 25.0° C. , NICKEL NITRATE PRESENT 122

22 AQUEOUS IN SYSTEM: METAL NITRATE - WATER - NITRIC ACID - N-BUTANOL AT 25.0° C. 124

23 OROANIC PHASE DENSITIES IN SYSTEM: COBALT NITRATE - NITRIC ACID - WATER - N-BUTANOL AT 25.0° C ...... 125 21* ORGANIC PHASE DENSITIES IN SYSTEM: NICKEL NITRATE - NITRIC ACID - WATER - N-BUTANOL AT 25.0° C...... 126

25 PHASE DIAGRAM FOR THE SYSTEM: NITRIC ACID - WATER - N-BUTANOL AT 25.0° C. . 129

vll ABSTRACT

The separation of cobalt and nickel has long "been of commercial and academic importance. In recent years, considerable interest has been shown in the use of liquid-liquid extraction to separate mixtures of inorganic compounds. Detailed studies concerning the extraction of the and the of cobalt and nickel have been reported.

Good separation of cobalt and nickel was obtained by extraction of the chlorides. Separation in the system was poor. The nitrates of cobalt and nickel could easily be formed by the nitric acid of , concentrates, and in-process materials containing the two .

Therefore, an investigation was carried out to study the use of liquid- liquid extraction as a method of separating cobalt and nickel nitrates.

In addition, it was hoped that the Investigation would add to the fun­ damental knowledge of extraction relationships of systems containing inorganic compounds.

The first series of tests was made to determine the distribution data for the pure metal nitrates between water and a variety of organic solvents at 25.O0 0. In these tests each metal was equilibrated sep­ arately, and the effects of several foreign electrolytes on its distri­ bution characteristics were determined. Distribution runs were then carried out with the best solvent.

The distribution of cobalt nitrate or nickel nitrate between water and organic solvents was generally low in all cases. Distribu- -»2 tion coefficients in favor of the organic phase ranged from 10 * to

1 10-5. Alcohols were the best extractants for both cobalt and nickel.

Foreign electrolytes did not appreciably change distribution character­ istics. Foreign nitrates, including nitric acid, increased distribu­ tion slightly at low metal concentrations. However, as metal concen­ tration increased, the distribution approached that obtained when no additive liras present or fell below that value. Foreign chlorides generally decreased extraction of both metals. No appreciable separa­ tion of cobalt and nickel was gained by the use of any of the additives.

Normal butanol was chosen in conjunction with nitric acid to determine extraction characteristics with cobalt and nickel nitrates.

Distribution coefficients with n-butanol were higher than those for any of the other solvents used. The study of the effects of nitric acid on distribution afforded a comparison with other investigations where cobalt and nickel had been extracted in the presence of inorganic acids. When each metal was equilibrated separately at 25.0° 0. , dis­ tribution coefficients were on the order of magnitude of 10”1 to 10“2.

Distribution increased with increasing metal concentration. It was also found to depend on the total content of cobalt and nickel in the aqueous phase. Increasing nitric acid concentration increased distri­ bution slightly at low metal concentrations, At high metal concentra­ tions, increasing acid concentration decreased extraction of the metals. This trend was unlike that found In the sulfate and chloride

systems of cobalt and nickel, where the corresponding Inorganic acids were quite beneficial to extraction. Separation factors were low, and

varied with both acid and metal concentration. Maximum cobalt-to-nickel 3 separation factors were about 1*5 when the metals were equilibrated without additives. Nitric acid decreased the separation slightly. The

distribution of both metals decreased somewhat with increasing temper­

ature.

It was concluded from the experimental work that the separation

of cohalt and nickel nitrates by liquid-liquid extraction is not com­

mercially feasible* This conclusion was reached on the basis of the

distribution of the metal nitrates vrith a variety of or^pnic solvents.

Distribution coefficients in favor of the organic phase were generally

low. The addition of foreign electrolytes did not favorably effect the

distribution characteristics. Calculations based on data obtained with

n-butanol showed that some separation of cobalt and nickel nitrates

could be gained by liquid-liquid extraction. However, such large

volumes of solvent would be required that the cost of such an operation

would be prohibitive. INTROBUOTIOrr

A. General

Cobalt and nickel are metals "basic to commerce and essential to

the national defense. They are often found associated together in

ores. However, their uses require that these metals or their salts

"be marketed in comparatively pure forms. There are, of course, numer­

ous methods for separation of these metals, "but these methods are

generally difficult and expensive. The introduction of new technology

for their separation could well "be expected to lower their market

and help to ease their shortage through increased production. "Exten­

sive deposits containing low contents of cobalt and nickel exist

in the free world today. They remain largely undeveloped, however,

since production of the metals from these ores would be economically

unfeasible under present conditions of technology. In recent years,

much interest has centered on the use of liquid-liquid extraction for

the separation of metals. The extraction and separation of several

cobalt and nickel salts have been investigated. Little work has been

done on the extraction of cobalt and nickel nitrates, however. Since

the nitrates of cobalt and nickel could be easily formed by nitric

acid leaching of ores or concentrates, a process for separation of

these nitrates might be of considerable importance commercially. The

present study was undertaken with this partially in mind.

B. Importance of Cobalt and Nickel to Industry

1. Uses for Nickel

Nickel has the unique characteristic of improving one or more of 4 5 the properties of most metals and alloys to which it is added. ThiB

metal and more than 3000 of its alloys are used principally for resist­ ance to in combination with strength and ductility. Special uses for nickel and its alloys include catalysts, communications, tem­ perature control, and permanent . Its salts are used for a variety of purposes including metal plating (l).

2. tTses for Cobalt

The bulk of the consumption of cobalt is now in the form of alloys.

It finds important use in tool and high temperature alloys for

gas turbines and Jet engines. Cobalt is used in and Stelllte

type alloys which do not tarnish, are resistant to many chemical rea­

gents, and retain their strength up to visible red heat. Other uses

for cobalt are found in , driers, catalysts, and for

combating cobalt nutritional deficiencies in livestock (2 ).

3. Current Production Estimates

The consumption of cobalt and nickel has steadily increased over

the years with the finding of new uses. Production has increased as well but increased use and the stockpiling of these critical metals by

the government has created periodic shortages. The free world production of nickel was probably about 212,000 short tons in

1955 of which the United States as usual consumed about 50 per cent.

For cobalt the free world production in 1955 was estimated at 1^,000

(1) Kirk, S. 1. and Othmer, D. P., Encyclopedia Chemical Tech-. nology, Vol. 9, p. 271, The Interscience Encyclopedia, N. Y. (195^). (2) Ibid. , p. 193. 6 short tons (3). Her© also, the United States consumed its usual lion's share of production. The rest of the free world consumed 23 per cent less cobalt than the United States.

4-* Present Sources and Be serves

While the United States consumes the majority of the free world1 s cobalt and nickel production, it produces only a small fraction of the total. Silicate, arsenide, or sulfide ores of nickel are found in numerous countries. However, over 90 per cent of the free world's nickel is produced from Canadian sulfide deposits. In nature, cohalt is usually associated with nickel and/or .

Cohalt and the associated metals are combined with or sul­ fur or both. Commercial production of cobalt has been largely as a by­ product in the recovery of other metals. Relatively little ore has been mined primarily for its cobalt content. The majority of the free world's supply of cobalt is obtained from African sulfide and arsenide ores as a by-product from copper recovery processes. Cobalt ores rarely con­ tain over 0.2 per cent cobalt. Nickel contents of several per cent have been found in some nickel ores.

The largest known reserves of nickel are the extensive lateritic ores of . Nickel is associated with iron, cobalt, , , manganese, silica, and small amounts of other metals in these ores. The ores contain only about 1.5 per cent nickel, 0.2 per cent cobalt, and 40 to 50 per cent iron (4). These nickel-iron ores were

(3) Davis, H. W., Eng. Min. J., 52. No. 2, 98 (1956). (&) Kirk, B. E. and Othmer, D. P., op. cit., p. 271. refined as an emergency operation during World War II. The operations were later abandoned as being economically impractical. Recently, how­ ever, there have been indications that interest is again being directed toward production from these deposits. Similar deposits also exist in

South America and the .

Many ores contain appreciable amounts of both cobalt and nickel.

The relative amounts of the two metals sometimes affects the selection of the method required to separate them as will be shown later. Use of a liquid-liquid extraction operation to separate cobalt and nickel would be necessarily concerned with the ratio of the two metals in the ore. The following is a list of various ores, concentrates, and in- process metals with their respective cobalt-nickel ratios (5 , 6 , 7 , 8 ).

Oobalt-lTickel Location Ratio in Ore

French - ore from property of La Societe Mlniere du Bou-Azzer et du Graara 3.2 Co/Hi

Cobalt, Ontario - hand sorted ore 1.8 Co/Ei

Finland - Outokumpu deposit lr2 M/Co

Canada - Lynn Lake concentrate 4.67 Hi/Co

Burma - Burma Corporation (in-prooess metals)

Matte I.25-3.O Hi/Co Speiss

(5) Young, R. S., Cobalt. pp. 8-20, Reinhold Publishing Corpora­ tion, N. Y. (1948). (6) Anon., Min. Fng., &, Mp, 6 , 565 (1956). (7) Caron, M. E., J. Metals, !§§., 67 (1950). (8 ) Forward, F. A. and Mackiw, V. E., J. Metals, Eo. 3» 457 (1955). 8

Location Cobalt-JTlekel JBatio in Ore

Ctermax^ - Mansfield 15 Hi/Co United States - Blackbird District, Idaho (in-process metals) 19 Co/Mi

United States — jfredericktown, Missouri l.h Ni/Co

Cuba - lateritic iron ores 12.3 Mi/Co

U.S.S.R. - oxidized nickel W O Ni/Co

0. Metalf u j ^ of Cobalt and Hlckel

1. General Methods

It 1b difficult to present a coherent picture of the metallurgy

of cobalt and nickel. The ores of these metals vary so widely in char­ acter that they cannot be treated by any common process. Also, many of these processes are considered trade secrets and little information has been made public in regard to specific processes. In general, these processes include a combination of pyrometallurgy, hydrometallurgy, and chemical processes. In few cases are both cobalt and nickel produced

from the same ore. Separations which are made for recovery of both metals are generally carried out by treating an acid or neutral solu­

tion of the cobalt and nickel salts with an alkaline oxidizing agent.

Under such conditions, cobalt is differentially oxidized and precipi­

tated. This process is applicable to solutions with a Co/Ni ratio of approximately four or higher. On© process, the Mond process, has been used to produce high purity nickel metal. It is based on the fact

that metallic nickel combines readily with monoxide at about 60° C. to form nickel carbonyl gas, NiCOO)^, leaving the impurities including cobalt as a residue. Subsequent heating of the nickel car­ bonyl gas at about 180° C. forms cobalt-free nickel containing approx­ imately 99*9 per cent nickel. The process is expensive and hazardous.

2. Never Methods

It is well known that cobalt and nickel and a number of other metals combine with ammonia in aqueous solution to give complex ions of the form Me( n+ where wMeB refers to the metal cation. The properties of such metals have found practical applications in commer­ cial recovery of copper, nickel, and cobalt from various ores.

Ammonia leaching processes have been reported in connection with both Cuban lateritio ores (9) and refining of Canadian Iynn Lake ores

(10). In the latter case, the process was designed to recover copper, cobalt, and nickel from sulfide ores. With an ammonia pressure leach of the concentrate, ammonia in combination with dissolved con­ verted cobalt, nickel, and copper to ammines, to an oxidized form, and iron to a hydrated oxidized form. The resulting iron com­ pound was insoluble in ammonia solution and was discarded along with insoluble s. Copper was subsequently removed by boiling the pregnant liquor. The thiosulfates, formed in the oxidation of sulfur, decom­ posed, precipitating copper as copper sulfide. Nickel could then be preferentially precipitated as metal by a precipitation method

(9) Caron, M. H., J. Metals, 1S£, 67 (1950). (10) Ibrward, T. A. and Mackiv, V. N., J. Metals, 2.* No. 3» **57 (1955). 1

10 developed 'by Sherritt Gordon Mines and Chemical Construction Company.

D* Liauid-Llauid Extraction

Liquid-liquid extraction, as a chemical engineering operation, has been used with success for many years (ll). It is a means of separation and purification of materials based upon chemical characteristics rather than such physical properties as and relative volatility. When physical characteristics prohibit such separations by distillation or other processes, extraction often provides the only alternative short of chemical reaction.

The ma,1or drawback to liquid-liquid extraction processes is that these processes must always be followed by a solvent recovery process, and this is usually a distillation process. Itar this reason, the com­ bined extraction and solvent recovery system must be more economical than any other single process or combination which might be applicable.

Most of the successful applications of liquid-liquid extraction belong to the organic chemical field. This operation finds use in refining; recovery of penicillin and dilute ; in the manufacture of phenol, aniline, and D.D.T.; and a wide variety of other fields. More recently, however, attention has been drawn to the possibilities of separation and purification of metal salts by extrac­ tion. Luring World War II, it was necessary to obtain uranium In a very pure state for the atomic energy program. This metal was desired with a purity such that it contained less than iCP^ per cent of such

(11) Treyhal, B., Liquid Extraction. pp. I-**, McGraw-Hill Book Co., Inc., H. Y. (1951). 11

me tale as 101:011, cadmium indium, and others. To do this, the uranium was converted to uranyl nitrate with nitric acid and extracted into

di-ethyl ether. The extent to which this was used for purification

is not known. However, operation on a large industrial "basis has "been

reported (12, 13). Many studies of extraction of other metal salts

have "been made, but so far as is known, only on a laboratory scale.

(12) Treybal, B., ap. si£., p. 392. (13) Anon., Ohem. Eng., jgL, Ho. 13* 80 (l95**)» LITERATURE REVIEW

A. Tfrg.Jfrtractlpp of Metal Salts. General

Numerous studies on the extraction of metal salts have been over the years. The majority of these have been concerned with the extraction and separation of micro-amounts of the metals for analytical purposes. A survey including all of these investigations would be lengthy and unwarranted for use with the present study. Studies where micro-amounts of materials were extracted or where other factors make them pertinent to the extraction of cobalt and nickel nitrates have been reviewed below. For a complete review on extraction, the publi­ cations by Craig (14), Treybal (15), or West (16) should be consulted.

B. The Extraction of Cobalt,.and Nickel Salts

Several studies have been made on the liquid-liquid extraction of the salts of cobalt and nickel. To date, no commercial applications resulting from these studies have been reported. The separation of the chlorides of cobalt and nickel appears to have some promise, as does the separation of cobalt and nickel sulfates in thiocyanate solu­ tion.

1. The ffitretee of_ Cobalt and Mckel

Templeton and Daly (17) reported studies of extraction with

(14) Craig, L., Anal. Chem., 26, 110 (1954). (15) Treybal, H. E., Ind. Eng. Chem., iffi, Ho. 3. 511 (1956). (16) West, T. S., Metallurgia, 103 (1956); 52. 91. 132, 185, 234. 292 (1956). (17) Templeton, C. C. and Daly, L. E., J. Am. Chem. Soc., 22. 3989 (1951); J. Phye. Chem., 5£, 215 (1952).

12 13 systems of the type n-hexyl alcohol-water-metal nitrate. These sys­ tems, where the metal nitrate was cobalt (II), nickel, ,magne­ sium, or nitrate, were investigated up to in the liquid-liquid region at 25° C.

All of these systems exhibited similar behavior in the concentrated region; i.e., the salt concentration in the organic phase was nearly proportional to a high power of the aqueous salt concentration. Data obtained showed that zinc and cobalt (II) have nearly identical distri­ bution characteristics. They were about 50 per cent more extractable than magnesium nitrate. Calcium nitrate was only about one-tenth as extractable as cobalt (II) , zinc, or magnesium nitrates. Uickel ni­ trate, as compared to cobalt (II) nitrate, behaved in a complicated fashion. At low concentrations it was less extractable than magnesium nitrate; as concentration was increased, it became more extractable than magnesium nitrate; and finally at the highest concentration it was more extractable than cobalt (II) or zinc. In all cases, the distribution was quite low. The highest distribution coefficients were only on the order of 10”1. In all cases distribution increased with increasing aqueous salt concentration.

Besides determining the order of extractability of the various nitrates, the above studies included measuring the ratio at which water was carried into the or^rnic phase by the metallic nitrate. The data on the latter was not believed to be sufficient grounds for writing definite chemical formulae for the hydrates of the various metal ni­ trates in the organic phase as had been done by some investigators for Ik

other system a (18). Bather the value of the data rests in the fact

that it furnished a relative measure of the hydration of the cations.

Although no experimental data were obtained for addition of for­

eign electrolytes to the above systems, qualitative experiments were

performed by addition of calcium nitrate to cobalt (XI) or nickel (II)

nitrate. It was believed that calcium nitrate was effective in salting

out both the cobalt and the nickel salt into the organic phase.

2. _0hlorides_ of Cobalt, and Hickel

Garwin and Hixson (19) studied the use of liquid-liquid extraction as a means, for separating cobalt and nickel chlorides. Preliminary

investigation showed that cobaltous chloride was dissolved by solvents with one properly in common - namely the inclusion in the molecule of a polar functional involving oxygen. Hickel chloride was found

to be dissolved only by the lower molecular weight alcohols. Capryl alcohol was selected for subsequent inve st igat ion because of the high anhydrous salt solubility ratio in this solvent. Also, this solvent possessed other convenient properties such as low solubility with water,

Distribution coefficients using capryl alcohol to extract cobal­

tous or nickelous chloride varied considerably with metal salt concen­

tration. Both salts showed a tenfold change over the range studied.

Distribution coefficients for both metals showed dependence on metal

(18) Katzln, L. I. and Sullivan, JD 0., J. Phys. Colloid Chem., 55, 3k6 (1951). (19) Garwin, L. and Hixson, A. N., Ind. Eng. Chem., *&, 2298, 2303 (19^). 15 salt concentration only, regardless of the relative cobalt to nickel salt ratio. However, the distribution coefficient of the more easily extracted salt (0o012) was so low (4 x 10“ 2 at best) that it was con­ cluded that enormous quantities of solvent would be required for its extraction. In addition, the separation factor or ratio of the distri­ bution coefficients was poor, averaging about 1.6 in favor of the cobalt.

Continued study showed that capryl alcohol preferentially extrac­ ted cobaltous chloride from aqueous solutions when HCl or CaCl2 was present. The increase in the cobalt distribution coefficient was on the order of 1000-fold with either added electrolyte present. The niokelous chloride distribution coefficient also increased, but much more slowly, and an improved separation was thereby effected. Separa­ tion factors ranged from 40 to 90 with HOI and from 10 to 17 with CaCl2 present.

It was noted that the inor^nic chlorideB with high activity coefficients, such as HOI and 0a012, produced a gradual change in the color of cobaltous chloride from red to in the aqueous phase.

With the same electrolytes, nickel showed no apparent color change.

Brdicka (20), in a polarographic study of red and blue cobaltous chloride solutions, observed a large positive shift in the cathodlc deposition potential of cobalt as its solution was turned from red to

(20) Brdicka, R,, Collection Czechoslov. Chem. Communs., 2, No. 8 , 489 (1930). 16 blue b|jr the addition of calcium chloride. This was explained as indi­ cating a considerable increase in the activity of the cobalt ion. It is possible that this increase in activity accounts for the increased distribution and Increase of separation of cobalt over nickel by ex­ traction with capryl alcohol.

Kylander and Garwin (21) investigated the extraction of cobaltous chloride with capryl alcohol in a spray tower. The electrolyte chosen was HC1. Por the runs made, the ratio of cobalt to nickel in the ex­ tract was on the order of 200 to 1. This was obtained with about a

1*3:1 cobalt to nickel ratio of the salts in the feed, showing that considerable separation of these two salts could be obtained in an extraction tower operated under steady-state conditions. The fact that this separation was somewhat greater than the equilibrium separa­ tion seemed to indicate a lower mass-transfer rate for the nickel than for the cobalt.

3. fffrgjaaXfeftgg. -Q&. .SftfaaU?. A detailed study of the extraction of iron, cobalt, and nickel sulfates xra-s performed by Schlea (22). He first made an exhaustive study to determine the best solvent for the extraction of the metal sulfates. A large number of solvents were equilibrated with each metal at 25° 0. The distribution coefficients, when each metal was equilibrated separately, were quite low for all solvents, being on

(21) Kylander, B. L. and Garwin, L., Chem. Eng. Progress, 186 (1951). (22) Schlea, C. S., Dissertation, Ph.D., The Ohio State University (1955). 17 the order of 10 .

The group of solvents which gave the highest distribution coeffi­ cients were the organic acids. However, the acids showed little or no separation between the metals cobalt and nickel. Such acid solvents as the tri-alkyl phosphates failed to extract the metal salts, indi­ cating that the extraction by acids was due to the reaction of the acids with the metals. Tests showed that the sulfate ion was not ex­ tracted by the acid solvents. Thi3 further supported the theory that the metal extracted from the aqueous phase was replaced by a hydrogen ion from the acid solvent. The compound in the organic phase could than be considered to be the salt of the acidic solvent. The only group of solvents, other than the acids, to show readily measurable extraction were the alcohols.

A few solvents, such as the , exhibited an apparent pref­ erential extraction for nickel. These solvents extracted such a small amount of metal, however, that the accuracy of the analysis of the metal content in the organic phase was questionable. Therefore, it was concluded that the apparently favorable sepax*ation factors for the extraction of the metal extractions were in doubt.

Three separate inorganic sulfates were equilibrated with the metals in systems containing some of the solvents possessing the bet­ ter distribution characteristics. These additives, the inorganic sulfates, were sulfuric acid, ammonium sulfate, and sodium sulfate.

In all cases, the ammonium sulfate and the sodium sulfate decreased extraction. Sulfuric acid increased extraction with alcohols, but 18 decreased extraction with other solvents which showed a slight degree of extraction when no additive was present* On this "basis and on the

"basis of the comparatively higher distribution characteristics of al­ cohols, n—butanol was chosen for a solvent and sulfuric acid chosen as an additive for further extraction studies.

With n-butanol as a solvent and sulfuric acid as an additive, the following factors were determined: The distribution coefficient for the metals increased over 100 times when up to 250 grams of sulfuric acid per liter were added as compared to the same system with no addi­ tive. Highest values were about 0.01. Separation factors were low, the maxi mm cobalt to nickel ratio was about 1.4, the may | mm iron to nickel and iron to cobalt separation factors were about two. Separa­ tion factors varied only slightly with increased sulfuric acid concen­ trations when metal concentrations were high, but increased when metal concentrations were small. At low concentrations of acid, increased metal concentration effected a decrease in the distribution coefficient of cobalt and nickel. Distribution coefficients, when the metals were equilibrated together, were 50-80 per cent lower than when each metal was equilibrated alone. Distribution coefficients could be doubled by increasing the temperature from 25° 0. to 70° 0.

Schlea concluded from his work that the separation of iron, co­ balt, and nickel sulfates by extraction was not commercially feasible.

The distribution coefficients were quite low and the separation factors were poor. Large volumes of solvent would be required. Also, the cost of sulfuric acid, compared to its beneficial effect, would be 19 prohibitive.

Perchlorates of Cobalt and. Nickel

Moore, laren, and Yates (23) studied the extraction of cobalt (II)

and nickel (II) perchlorates with 2-octanol (capryl alcohol). They

found the distribution of the metal perchlorates to be strongly depend—

ent on concentration. The distribution coefficients were n&rkedly

higher than those of CoCl£ and ITiO^ in the same solvent as reported

by Garwin and Hixson (24). However, values for cobalt perchlorate were almost equal to those of nickel perchlorate.

lithium, calcium, and aluminum perchlorates were added to the co­ balt perchlorate to determine their effect on the distribution of the

cobalt between water and 2-octanol. The promoting effect of the added perchlorates was found to depend only upon the total perchlorate con­

centration and to be independent of the charge type of the promoting

salt cations.

Spectrophotomet r 1 c Btudies made on the 0o0l2~Li01-2-octanol-water

system (25) have provided evidence of extensive interaction of LiCl with C0OI2 la octanol. It was thus concluded that differences in the

chloride promoted 2-octanol extractions of C0 & 2 and HiCl2 are the result of specific interactions of C0CI2 with the promoting chloride.

The promoting chlorides, such as LiOl, were themselves quite readily

.... " I ' ■«' -■.....

(23) Moore, T. E., Laren, R. J., and Yates, P. C. , J. Phys. Ghem., 52, 90 (1955). (24) Garwin, L. and Hixson, A. M., pp. cit.. 2298, 2303. (25) Beaver, W. D., Estlll, ¥. E., Moore, T. E., Trevorrow, L. E., and Yates, P. 0., J. Am. Ghem. Soc., 25, 4556 (1953). 20 extracted Into the organic phase. The extraction differences, in this case, are not due to the fundamental differences in the extraction behavior of cobalt and nickel ions themselves. On the other hand, extraction promotion in the perchlorate systems of cobalt and nickel is largely a common ion effect.

5. ghlg.oygw.tg_ Since thioeyanate ions form covalent complexes with metal ions in aqueous solution, many workers have been led to study the possibility of separating metals by extracting their thioeyanate complexes. Due to the limited solubility of thiocyanates in water, however, the extrac­ tion of these complexes has been mainly limited to separation of micro­ amounts of metals for analytical purposes. Some of the studies made include the analysis of micro-amounts of ferric iron by extraction with such solvents as tributyl phosphate or ether (26, 27), the separa­ tion of zirconium and hafnium by diethyl ether extraction of the thio- cyanate complexes (28, 2.9 ), and the extraction of rare earth thiocya­ nates by n-butyl alcohol (30)•

A recent study of the extraction of the thioeyanate solutions of cobalt and nickel was reported by Bigpmonti and Spaccemela

(26) Bock, R. J., Anal. Ghem., 133. 110 (1951). (27) Melnick, L., Freiser, H., and Berghly, H., Anal. Ghem., 2£, 856 (1953). (28) Fischer, W. and Chalybaeus, W., Zeitschrift fur Anorg. Chemie, 255, Ho. 1-3, 79 (19^7). (29) Fischer, W., Chalybaeus, , and Zunbusch, M., Zeitschrift fur Anorg. Chemie, 255. Ho. b-5, 277 (19W3). (30) Appleton, D. and Selwood, P., J. Am. Chem. Soc., 62, 2029 (19*KL). I

21

Harchettl (3l). They demonstrated that large quantities of cobalt and

nickel conld he separated hy extraction with amyl alcohol. In this

case, extraction was performed on the system metal sulfate-ammonium

thiocyanate-water-amyl alcohol at 25.0° C. where the metal sulfates

involved were cohalt and nickel. This was an adaptation of a method

used by Rosenheim and Huldschinsky (32). SON By -varying the ratio of q0 + from 1 to 24 with addition of

ammonium thioeyanate, the cohalt distribution coefficient ranged from

0.14 to 2.68 , and the nickel distribution coefficient ranged from 0.18

to 0.5. The ratio of the cobalt distribution coefficient to the nickel

distribution coefficient ranged from 0.85 to 5.20. At constant —— — rr- uo + m values, the distribution coefficients and the ratio of the distribution

coefficients varied only about 10 per cent with wide variations of th®

aqueous phase metal concentrations.

Calculations showed that by using countercurrent flow with the

above system, a 99.9 per cent separation could be obtained with 17-19

theoretical stagewise contacts. Experimental runs with seven plates

yielded results only slightly lower than the theoretical value com­

puted for that number of contacts.

The differences in the extraction of cobalt and nickel as pro­

moted by the thioeyanate ions were believed to be due to complex forma­ tion. The variation of the cobalt distribution coefficient as a

(31) Bigamonti, R. and Spaccemela-Marchetti, E. , Chemica e Industrie (Milan), 36. 91 (195*0. (32) Rosenheim, A. and Huldschinsky, E. , Ber. , Jjk, 2050 (1901). 22 function of the thioeyanate concentration was purported to he due to existence of the complex Co( SON) nn_2* much lower distribution coefficient of nickel was believed to he due to its ability to form only the Hi( SOHjg complex.

Ifcg-lfe&r&di'lPB a£_gflfr<_&nd_ Nickel Acetates

In their work on the separation of cohalt and nickel, Bigamonti and Spaccemela-Marchetti (33) first studied the extraction of the ace­ tates of cohalt and nickel. Using a mixed solvent of butyl and methyl alcohols, they obtained distribution coefficients at 25° C. between

0,13 0.16 depending on the aqueous metal concentrations. However, no separation could be obtained and the acetates were abandoned. o. g^rapj&oiL fljLffitra$gg

Besides the work reviewed under the extraction of cobalt and nickel nitrates, numerous other systems concerning the extraction of metal nitrates have been reported. The majority of these latter sys­ tems concern the extraction and separation of elements of the lantha­ nide and actinide series.

1. The Extraction of. Aluminum Nitrate

Templeton (3*0 made a comparatively detailed study of the system aluminum nitrate-n-heayl alcohol-water. Distribution was of the same general order as that reported for cobalt (ll), nickel, zinc, calcium, and magnesium nitrates. Distribution, as in the previous cases,

(33) Bi^uaonti, B. and Spaccemela-Marchetti, E. , pp. cit. , 91 (34) Templeton, 0. 0., J. Phys. Colloid. Ohem., Jfe, 1255 (1950). I

23

increased with increasing aqueous metal concentration. Investigation

of the effect of pH on distribution of aluminum nitrate was made.

Addition of HHO^ or HH^QH to the system showed that pH had no effect

on the distribution. By adding aluminum sulfate to the system to change

the nitrate lon-to-water ratio while keeping the aluminum Ion concen­

tration constant, the distribution showed a third power dependence on

the nitrate ion concentration. Similarly, adding NH^^NO^ to keep a

constant nitrate ion-to-water ratio, the distribution showed a third

power dependence on the aluminum Ion concentration. Thus, the aluminum

concentration in the organic phase was proportional to the third power

of either the nitrate ion concentration or the aluminum ion concentra­

tion in the aqueous phase.

2. Extraction and Separation of Lanthanide Elements

The lanthanide elements which are generally referred to as the

rare earths, are found in nature as complex mixtures. To obtain pure

compounds of the rare earths, some method must be used to separate the

component desired from the mixture of the rare earth metals. In the

past, these separations were made by fractional crystallization In­

volving hundreds of recrystallizations. Over the past few years, con­

siderable interest has been shown for the liquid-liquid extraction of

these metals to lessen the time and labor involved in their separation.

Most of the investigations with the rare earths has involved the

extraction of the nitrates or nitric acid solutions of the metals. A

variety of solvents has been used. Tjributyl phosphate was shown to be 24 effective for separating many rare earth, nitrates (35). Templeton and

Peterson (36, 37) extracted several rare earth nitrates from water with n-hexyl alcohol. They found that separation factors on the order of

1.5 could "be obtained between elements adjacent in the .

Distribution was low however, and fairly large amounts of solvent would be required. It was noted that distribution apparently showed fourth power dependence on the metal concentration in the aqueous phase.

Butyl phosphate was used by one investigator (38) to extract cerium

(IV) nitrate from nitric acid solution. _ When equal volumes of solvent and aqueous solution were used, 98 to 99 P©r cent of the cerium en­ tered the solvent phase over a wide range of conditions. Nitric acid showed little effect on the distribution. The high degree of extrac­ tion obtained suggested the formation of a compound between the solvent and cerium (IV) nitrate. Various ethers, ketones, and alcohols have been used for extraction of rare earth nitrates from each other, from thorium, or from miscellaneous other metals (39* *H)*

In most cases, the Investigations showed promise for separation or purification of rare earth nitrates by liquid-liquid extraction.

(35) Peppard, D. P., Paris, J. P., Gray, P, E., and Mason, G. W,, J. Phys. Ghem., 52.. 294 (1953). (36) Templeton, 0. 0. and Peterson, J. A., J. Am. Ghem. Soc., 70. 3967 (19**8). (37) Tenpleton, 0. G,, J. Am. Ghem. Soc., 21, 2187 (19^9). (38) Warf, J. C., J. Am. Chem. Soc., 21, 3257 (1949). (39) Bock, B, and Bock, S., Z . Anorg. u. Allgem. Chem., 263. 146 (1950); Naturwissenschaften, 2§.t 344 (1949). (40) Asselin, G. P., Audrieth, I>. P., Comings, E. W., J. Phys. Colloid Chem., 5&. 640 (1950). (41) Imre, L., Z . Anorg. Chem., 16&, 2l4 (192?). 25 Some evidence is available to show that liquid-liquid extraction is being used to purify appreciable quantities of the rare earths (42,

*3).

3. Extraction of the Nitrates of the Actinide Elements

a. Extraction of Uranium

One of the most important applications of liquid-liquid extrac­ tion to metals concerns the purification of uranium from concentrates and spent fuels for the atomic energy program. Several studies have been reported on the extraction of uranyl nitrate from aqueous solu­ tions containing nitric acid and other inorganic nitrates by various solvents (44, 4-5 , 46 , 4-7 , 48 , 49). Warner (50) compared the distribu­ tion of uranyl nitrate between water and di-ethyl ether with the dis­ tribution for eighteen other solvents. He found that lower molecular weight solvents with sterically unhindered osygen gave the most favorable distribution. Although some solvents showed somewhat higher distribution coefficients, di-ethyl ether was the preferred solvent based on cost, availability, stability, and selectivity for uranyl nitrate when mixed with foreign salts such as cuprlc and ferric

(4-2) Weaver, B., Eapplsman, P. A., and Topp, A. 0., J. Am. Ghem. Soc., 25.» 394-3 (1953). , iN (43) Anon., Chem. Eng., 61, Ho. 13. 76 (1954). (44) Hoffman, J. I. (to U. S.A. c/o Atomic Energy Commission) U.S. Patent 2,697,122 (Dec. 14, 1954). (45) Anon., Ghem. Eng., 62, No. 10, 112 (1955). (46) Lewis, J. G. and Weech, M., Neucleonics, 13. No.3 , 18 (1955). (47) Day, R> A. and Powers, B. M., J. Am. Chem. Soc., 2i>» 3^95

C195^) - (48) Katz in, L. I. and Sullivan, J. C. , pp. pi£.. , 346. (49) Warner, R. K. , Chem. Eng. Sci. , 2. 161 (1954). (50) Warner, H. K., Australian J. Applied Science, 2. 3L56 ( 195*0 . 26 nitrate. Extraction was generally increased by addition of nitric acid or ammonium nitrate to the systems where solvents exhibited extraction.

Citing the extreme extractability of uranyl nitrate into ethyl ether, investi^tors (51, 52) postulated an f-shell covalency for the extracted compound. The partition coefficient for uranyl nitrate be­ tween water and ether was so many orders of magnitude greater than those of other nitrates that a difference in mechanism was indicated.

Bata showed that coefficients measured under thermodynamically similar conditions for manganese, cobalt, copper, and uranyl nitrates were of 7 the order 0.1:1:2:10* respectively. Evidence of four waters of hydra­ tion of the molecules in the organic phase indicated a substantially un-ionized, unchanged, covalent molecule of the probable form UOgCUO-jJg

(HgO)^. compounds isolated from organic solutions were of the forms 1102(^0^)2 * ^ an^ U02(H'0^)2*2H20*2S when "S" is a solvent molecule. Since only oxygen containing solvents dissolved uranyl ni­ trate, it was believed that the donor properties of solvent oxygen allowed strong interaction of solvent with uranyl nitrate for ready formation of neutral molecules.

b. Extraction of Thoyfom Hitrate

To produce high concentrations of U^ 3 -jjy irradiation of thorium, the thorium must be separated from uranium. Like uranyl nitrates, thorium nitrate can be easily extracted by di-ethyl ether and tributyl

(51) Glueckauf, E. and McKay, H. A., Hhture, 165. 59** (1950). (52) McKay, H. A. and Mathieson, A. R., Trans Earaday Soc., *£., **28. **37 (1951). 27 phosphate. However, since their distribution, is sufficiently differ­ ent, the separation of thorium from uranium can be easily obtained (53»

54, 55). Solvent extraction of thorium nitrate by various other sol­ vents has been reported (56, 57).

D. Ea&racblon of Other Metal Salts

1. Separation of Chromium and. Vanadium

Weinhardt and Hixson (58) found that chromic acid could be prefer­ entially extracted from vanadic acid by methy 1-isobutyl ketone. Separa­ tion factors on the order of 4000 in favor of the chromium were found.

The separation factor was greatly enhanced by adding hydrochloric acid to the aqueous phase. Both chromic acid and vanadic acid are unstable, hoy/ever, in strong hydrochloric acid solutions. As a result, it is doubtful that such an operation could be applied commercially.

2. Extraction of Chromium and Manganese

Little work has been done on the extraction of sulfate compounds of metals without the use of a complexing agent. In addition to Schlea*s

(59) work on cobalt, nickel and iron sulfates, the only other available

(53) Anderson, M. B. , U.S.A.E.C. , I.S.C. 116 , 3-18 (1950); Chemical Abstracts (195*0 1935<1. (54-) Peppard, D. P., et al., J. Am. Chem. Soc., Z 5» 45?6 (1953). (55) Cypres, B. , Bull. Centre Phys. Neucleare Univ. Libre Brux­ elles, Ho. 40 (1953). (56) Levine, H. and Grimaldi, P. S., Atomic Energy Beport No. A.E.C.D.-3186 (1951). (57) Bothsehild, B. P., Templeton, C. C., and Hall, N. P., J. Phys. Chem., 1006 (1946). (58) Weinhardt, A. and Hixson, A. N., Ind. Eng. Ghem., 42.* 1676 (1951). (59) Schlea, 0. S., op. cit. 28

Information on extraction of sulfates is Huntington's (60) work on chromic and manga nous sulfate. Investigation showed that only lower molecular weight alcohols were capable of extraction for the latter system. With n-butyl alcohol, the distribution coefficients at 25° 0. were on the order of 10“-^. Sulfuric acid greatly increased extraction,

"but at high acid concentrations the separation was poor.

3. Extraction of Ferric Chloride

It has been known for some time that ferric chloride can be al­ most quantitatively extracted from aqueous hydrochloric acid solutions by ethers. Investigators (61, 62) have shown that approximately 99.9 per cent of the ferric chloride could be extracted by isopropyl ether when the aqueous phase hydrochloric acid concentration was between

7*5”8 molar. The distribution steadily decreased for a d d concentra­ tions above and below that figure. Below about 5 molar, extraction was negligible. Distribution was found to Increase with increasing total iron at constant acid concentration. Nachtrieb and Conway (63) showed that iron (ill) could be separated from cobalt, nickel, and a number of other metals by extraction of ferric chloride from aqueous hydrochloric acid solutions with isopropyl ether. Geankoplls and

(60) Huntington, E. L., Thesis, M. Sc., The Ohio State University (1953). (61) Dodson, B. W., Porney, P. J., and Swift, E. H., J. Am. Chem. Soc., 5Sl> 2573 (19 )• (62) Axelrod, J. and Swift, E. H., J. Am. Chem. Soc., 62, 33 (19*K>). (63) Uachtrleb, H. H. and Conway, J. G., J. Am. Chem. Soc., 22.* 35*17 (19*16). 29 Hixson (64) used the system ferric chloride-iaopropyl ethejvaqueous hydrochloric acid to study mass transfer coefficients in a liquid- liquid extraction spray tower.

The abnormal distribution of ferric chloride has been subjected to much investigation (65, 66, 67). In general, it was concluded that the

ether phase iron was in the form of PeCl^'HCl or (lb01-j‘H0l)n where Bnn was a continuous function of iron concentration. The .formation of this neutral complex was believed responsible for the hi^i iron extraction.

Isopropyl ether was not singular in its ability to extract ferric chlo­ ride. Other ethers, ketones, esters, and alcohols exhibited much the

same general behavior in extraction of ferric chloride from aqueous hydrochloric acid (68, 69). In all cases, where solvents gave high extraction of iron, the complex PeClyHOl was assumed to be present in the solvent phase.

4. tflgffbllanegua. Several studies of the extraction and separation of metals have been made which are of general interest. Attempts to extract various

(640 Geankoplis, 0. J. and Hixson, A. N., Ind. Eng. Ghem., 4-2. 114-1 (1950). (65) Bachtrieb, N. H. and Conway, J. G., pp. pit., 3547. (66) Swift, E. H., Ifyers, E. J., and Metzler, D. 1., J. Am. Chem. Soc., 22, 3767 (1950). (67) J^yers, E. J. and Metsler, D. E., J. Am. Chem. Soc., £2, 37?2 (1950). (68) Euzenetsov, V. I., J. Gen. Chem. (U.S.S.R.), l£, 175 (1947); Chemical Abstracts 1948. 18a. (69) Taketsu, S. J., Chem. Soc. Jap., Pure Chem. Sect., Z4, 82 (1953); Chemical Abstracts 1953 7946g. 30 uranyl salts have “been made "but apparently they have met with lesB

success than the uranyl nitrate extraction. The extraction of rare earth thiocyanates and the separation of zirconium and hafnium by ex­ traction of their thiocyanates was previously reviewed in this section.

Recently, the separation of and was reported by

Stevenson and Hicks (70). The latter authors extracted the fluoride complexes of tantalum and niobium with di-lsopropyl ketone.

E. The..Extraction of Metal Chelates

Metal Ions in aqueous solution are surrounded by a sheath of aque­ ous ions. The coordinated water molecules in the sheath weaken the lnterionic attractions of the metal ions. This allows the metal to fit into the solvent structure more easily than the corresponding aetal salt. Replacement of these water molecules by complex or^inlc groups makes it possible to surround the ion by almost any desired envi­ ronment, and thus to alter the solubility at will. When two or more of the latter groups are tied together into a single molecule, the result­ ing compound is said to be a metal chelate. If the compound is stable and the liquid contains a large number of and other polar groups, the complex is soluble in water. These highly stable, highly chelated complexes are called sequestering agents. An important use for organic soluble chelates is solvent extraction of metal ions. The principles involved have been outlined by Mart ell (71) and Calvin (72).

(70) Stevenson, P. C. and Hicks, H. G., Anal, Chem., 25, 151? (1953). (71) Martell, A. E, , J. Chem. Ed., ^ 270 (1952). (72) Calvin, M., Experientia, 6, 135 (1950). 31 Best results are apparently obtained when the metal chelate is soluble

in the organic solvent and relatively Insoluble in water, while the unchelated metal species present are insoluble in the organic solvent employed.

While the above are idealized conditions, holds definite promise for solvent extraction of metals, numerous chelating agents have been made. Most of these agents have been used for separation

of micro-amounts of metals in chemical analysis. As far as is known,

chelating agents have not been used for solvent extraction of metals

on an industrial scale. STATEMENT OP TEE PEOBLEM

As indicated previously, the development of more economical proc­ esses for commercial separation of cobalt and nickel is needed. It has been shown that liquid-liquid extraction has definite potentialities for separation of inorganic as well as organic materials. The solvent extraction of cobalt and nickel with various anions has been studied.

Comparatively little work has been done, however, on the extraction of the nitrates of cobs.lt and nickel, formation of these nitrates by nitric acid leaching of ores, ore concentrates, or solution of Hin process,f materials could be easily accomplished. A study of the ex­ traction of cobalt and nickel and nickel nitrates is justified for two reasons: 1) it has the possibility of commercial application to the separation of cobalt and nickel; and 2) It could provide additions to the fundamental knowledge concerning the extraction of inorganic compounds from aqueous solution by organic solvents.

The purpose of this investigation is, first of all, to determine the distribution ratio of cobalt and nickel nitrates between water and a variety of organic solvents. Efext, the determination of the effect of various foreign electrolytes on distribution with several solvents is to be made. Prom these data, a solvent will be chosen with which to make a comparatively detailed study of the extraction of cobalt and nickel nitrates.

Investigation with the solvent choBen is to include determination of the effects of system variables on the distribution. These variables

32 33 are metal concentration, additive concentration, and temperature. An investigation of the distribution of cobalt and nickel nitrates when equilibrated together as corpared with the distribution of the same salts when equilibrated alone is to be made. Densities of the phases will be measured to indicate ease of phase separation. Finally, solu­ bility measurements are to be made to determine the amounts of organic solvent entering the water phase and of water entering the organic phase upon extraction with the final solvent.

The over-all objectives of the problem, then, are to investigate comprehensively the extraction of cobalt and nickel nitrates between various organic solvents and water and to investigate the effects of several variables on extraction with a chosen solvent. In addition, any information gained which might add to the fundamental knowledge of solvent extraction of inorganic materials is to be pointed out. 2HEQET

She stable diatribution

Oo/Cw st K (l)

where,

Co s equilibrium concentration of solute in

organic phase

Cw = equilibrium concentration of solute in

aqueous phase

K =r distribution coefficient

has been found to apply with very dilute solutions and those systems

where association or dissociation of the solute is negligible (73).

Since ionic compounds are dissociated in the aqueous phase, Equation

1 cannot be expected to hold. If dissociation or association occurs

in the water phase only, the relation becomes

Oo/Cw11 = K (2)

where,

n = dissociation or association number

Although Equation 1 is not applicable to most systems, it still finds use for semi-quantitative evaluation of solvents. If the variation of

the distribution coefficient with concentration is known, the evaluation

becomes more quantitative.

The term selectivity is defined in the following manner:

(73) Glasetone, S. , jEaaS&gflfe gfreffi>HL, 2nd. Ed. , p. 735, I). Van No strand Co., H. Y. (19^). 35 s9 = *1 * ^ 2 (3 ) where,

/ 3 s selectivity

E-^ s distribution coefficient of one solute

Eg = distribution coefficient of second solute

The selectivity, consequently, gives a measure of the ease of separa­ tion in a fractional extraction process. The larger the value of the selectivity, / 3 , the easier the separation. The value of /3 may he estimated from the distribution coefficients of the solutes when the distribution coefficients are obtained from measurements on individual components of solutions. This is particularly true if the mechanisms of extraction are different for each solute. Experimental check on this assumption is always required.

It can he shown for distribution systems in which the solute obeyB

Eaoult*e or Henxy's laws that a special case of the van’t Hoff equation can he written as:

dlnE = dT W BT where,

ALs = molal heat of transfer of solute between

two solvent layers

B = gas constant

I s absolute temperature

This can he integrated directly if the term Ls is assumed to he con­ stant. Upon integration Equation k becomes 36 1HK = + m (5)

where,

m at a constant

Equation 5 shows that a plot of log Z versus l/T should give a

straight line. However, definite deviation from this correlation may

be found. The term AL b can be expected to vary with temperature.

Also ionic systems cannot be expected to obey Eaoult*s or Henry’s

laws, a condition upon which Equations 4 and 5 were based. Although

such a correlation is of an empirical nature at best, it is useful

for representing the effect of temperature on distribution. t

AHALYTICAL METHODS

It was necessary to develop and verify several major analytical

methods in the study. Methods were developed for analysis of nickel

in the absence of other salts, for cobalt in the absence of other

salts, for cobalt or nickel in the presence of other salts, and for

codetermination of cobalt and nickel. An analysis for nitric acid in

aqueous and n-bsitanol solutions was developed. Analyses were also made

on stock solutions of ferric nitrate and cupric nitrate. Whenever

possible, analytical methods were checked by use of primary standards

or alternate analytical methods. Choice of a particular procedure was

based on the simplicity of the method, the amount of material needed

for analysis to obtain reasonable accuracy, and interference of other

components with tbs analysis.

A. Solvent Search

It was expected that many of the or^nlc phase metal concentra­

tions encountered in the solvent search would be small. For this

reason, methods for metal analysis were developed which could determine

amounts of metals in the milligram or sub-milligram range.

1. Organic Phase Cobalt

Organic phase cobalt was determined colorimetrically in the sol­

vent search. Residues from evaporated organic phase samples were

analyzed by measuring light absorption of concentrated hydrochloric

acid solutions of the salt. The method used involved development of

37 38 a procedure given by Toe (7^). Cobalt residues were repeatedly evap­ orated with, approximately 10 cc. of concentrated hydrochloric acid at lovr temperatures on a hot plate. Generally, three to four evaporations were used. These repeated evaporations drove off nitrates as nitric acid. Besidues from these evaporations were dissolved in concentrated hydrochloric acid, transferred to a 50 ml. volumetric flask, and di­ luted to the mark with concentrated hydrochloric acid. The absorbance of these solutions was read on a Fisher A. C. Electropho tome ter using a 650 mm. filter and 25 mm. absorption cells. Concentrated hydrochloric

(36-5 per cent HCl) acid was used in the reference cell.

The standard color curve for up to 3 milligrams cobalt/liter was prepared from weighed amounts of cobalt-smmonium sulfate. It was checked by measuring absorbance of solutions prepared from a concen­ trated cobalt nitrate stock solution. The stock solution was analyzed for cobalt by as described later.

It was found that the color curve showed deviations from Beer's law. Therefore, in analytical work, the concentration was read from the plot of concentration versus absorbance. This plot is represented in Figure 1. In a series of eleven determinations with cobalt-ammonium sulfate and cobalt nitrate, the average deviation of the measured ab­ sorbance value from the curve value was 1.77 per cent.

Maximum deviation of 6.5 per cent occurred at the lowest cobalt

(7*0 Toe, J. H., Photometric Chemical Analysis. Vol. 1, p. 172, John Wiley and Sons, Inc., N. Y. (1928) ABSORBANCE AT 650 Mi/ 02 0.3 0.4 0.6 IUEl MEASUREDFIGURE l. ABSOEBASCE Oy OOHCBHTRATBD HOI. SOLUTIONS 0 OF COBALT BT A FISHER A.O. HLSGTROPHOTOMSTER G CBL/5 ML.MG. COBALT/ 50 1.0 • COBALT NITRATE NITRATE COBALT • OF AMOUNTS WEIGHEDO OAT AMM&NIUM COBALT SULFATE OUIN ANALYZED SOLUTION Y ELECTROLYSIS BY CD 3.0 4.0 39 40 concentration (0.259 mg. cobalt). Color was stable for at least 24 hours and was assumed to be indefinitely sts.ble.

Standards containing several times the amount of sodium nitrate or calcium nitrate used in additive work were analyzed with the above pro­ cedure. The effect of these salts on the procedure was negligible or at least fell within the limits of experimental error.

The cobalt nitrate stock solution used as a check in the above procedure was analysed for cobalt by electrolysis. Electrolytic depo­ sition of cobalt or nickel is probably the most accurate method for analysis of these two metals. The general method used is described by

Hall (75). Deposition of cobalt is made from a highly ammoniacal solu­ tion, free from nickel, iron, and nitrates. Uitrates and nitric acid were removed from the cobalt solution prior to electrolysis by fuming with a small amount of concentrated sulfuric acid. For 15-160 mg. of cobalt, 100 ml. of ammonium hydroxide, 10 grams of ammonium chloride, and 0.3 to 0.4 gramB of sodium bisulfite were added to the nitrate- free solution. The solution was made up to 200 ml. in an electrolytic beaker and electrolyzed at about 4 amperes using a Fisher Controlled

Potential Electro-Analyzer. The metal was deposited on a tared plati­ num gauze electrode. The solution was stirred by a anode revolving at a speed of approximately 900 E.P.M. Deposition was com­ plete in about thirty minutes. Checking for completeness of deposition was performed by adding a small amount of water to the electrolytic

(75) Hall, D. B. , Ind. Eng. Chem., Anal. Ed., 1, 363 (1931). 41 cell. If no metal was deposited on the freshly wetted cathode surface within 15 minutes, the electrolysis was stopped. The cathode was then rinsed with distilled water and acetone. The cathode was dried hy holding it high over a gas flame, cooled, and weighed. Eesuits of three determinations involving approximately 90 nig. of cobalt showed an average deviation from the arithmetic mean of 0.24 per cent. The maximum deviation waB O.36 per cent.

2. Aqueous Phase Cobalt

Analysis of aqueous phase cobalt involved comparatively concen­ trated solutions of the metal. The colorimetric analysis of cobalt with lydrochloric acid could have been used, but it would have involved a series of dilutions of the sample, lor convenience, a colorimetric method for cobalt analysis Involving the use of sulfuric acid solutions was developed. This method was a modification of a procedure reported by Gagnon (76). The modified procedure first involved the heating of the cobalt solutions with sulfuric acid over a low temperature hot plate to concentrate the solution. After the cobalt salts had started to precipitate out of the concentrated solution, the solution was heated at higher temperatures until strong fumes of sulfuric acid were evolved. The solution was cooled, diluted to about 50 ml. with dis­ tilled water and boiled to dissolve the salts. Next, the solution was transferred to a 100 ml. volumetric flask, cooled, and diluted to the mark with distilled water. The par cent transmission of the solution

(76) Gagnon, J. , Ohemist-Analyst, No. 1, 15 (1954). k z was then read at the maximum absorption peak of $7.3 millimicrons on a

Beckman H C -2 recording spectrophotometer using XO mm. Corex cells.

Distilled water was used in the reference cell. A color cur re was

developed for the above procedure by measuring the absorbance of sul­ furic acid solutions containing various amounts of cobalt. The con­ centration of the solutions was varied by diluting a stock solution of cobalt nitrate. This stock solution was analyzed for cobalt by electrolysis as previously described.

The data shows that the system conforms to Beer’s law up to at least 300 mg. per 100 ml. The curve of absorbance versus concentra­

tion is plotted in Figure 2. This curve can be represented by the

familiar Beer’s law equation

-log T ^ q = k C

or -^518 = ® where T ^ a = per cent transmission at wave length of 518

millimicrons expressed as a decimal fraction

Aijig = absorbance at 518 millimicrons = -log T^-^q

0 sr concentration of cobalt in mg./100 ml.

k = a system constant =* 8.67 a: 10”^

For six determinations using various concentrations of cobalt, the average deviation of measured absorbance from the curve value was

1.69 per cent. The mximuia deviation was 5*17 Per cent. Maximum

deviation occurred at low concentrations of cobalt.

This procedure was not effected by sulfuric or nitric acid con­ centration. Check runs showed that calcium and sodium ions did not ABSORBANCE AT 518 M//. 0.2 0.3 0.4 0.6 0.5 GE . MEAStTEED 2.HGUEE AB3QEBAKC7 07 S0L3BBIG ACID SOLUTIONS 10 0 30 0 500 400 300 200 100 0 l i i kl 07 COBALT BT A BECKMAN EK-2 SEECTEOPEOTOMETER G CBL/ 0 ML. MG. COBALT/100 ______

1*3 44 interfere witli the analytical results. Hydrochloric acid did not inter­ fere if samples containing hydrochloric acid were evaporated to a vol­ ume of 2-5 ml. before fuming with concentrated sulfuric acid. Iren and copper were found to give serious interference with the analysis. Both metals have appreciable light absorption in the 518 millimicron region.

Analysis of cobalt with iron or copper present are described later on

In this section.

3* Nickel Analysis

A colorimetric analysis was developed and verified to determine nickel concentrations in the solvent search. Its ability to analyze sub-milligram amounts of nickel made it useful for analysis of organic phase samples containing low nickel concentrations. Aqueous phase samples contained comparatively high concentrations of nickel. Analy­ sis of aqueous phase nickel contents ty the method described below involved considerable dilution of the sample. Although it was some­ what inconvenient for aqueous phase analysis, the method described was used for both aqueous phase and organic phase analysis.

Che method used was a modification of a procedure given by Snell and Snell (77). Using the method as adapted, an aliquot of sample containing 0.5 mg. of nickel or less was adjusted to faint acidity by addition of 1:1 hydrochloric acid or 1:1 ammonium hydroxide. An

"Alkacid Test Ribbon11 was used to check the acidity of the solution.

(77) Snell, P. D. and Snell, C. T., Oolorimetrlc Methods of Apalysia, 3rd Ed., Vol. II, p. 346, D. Van Nostrand and Co., N. T. (1948). 45 Saturated " water was added dropvrise until a faint yellow color persisted and then two ml, in excess. Next, 10 ml, of concentrated ammonium hydroxide were added and the solution thoroughly mixed. After transferring to a 100 ml, flask, 35 oT aa 0«1 psr cent solution of dimethylglyoxime in 95 per cent ethanol were added. The resulting solution was diluted to volume with distilled water and mixed. The absorbance of this solution was read at a wave length of 530 millimi­ crons "by means of a Beckman DLT Spectrophotometer using 10 mm. Oorex cells. Distilled water was used in the reference cell. Oare was taken to complete the procedure within fifteen minutes after the addition of the dimethylglyoxime solution, since the developed color was not stable for more than 15 to 30 minutes.

The standard color curve was developed "by determining the absorb­ ance of solutions made up from weighed amounts of nickel ammonium sulfate and of solutions made up from concentrated nickel nitrate stock solutions. Measured absorbance of the nickel nitrate solutions served as a check on measured absorbance using nickel ammonium sulfate, a primary nickel standard. The metal content of the nickel nitrate solu­ tion was determined by electrolysis as described later. The standard color curve is presented in Figure 3. It shows that this system follows Beer’s law up to at least 0,5 mg, nickel per 100 ml. The equation representing this curve follows:

A530 = 8.575 x lCT1 C where,

0 = mg. nickel/100 ml. ABSORBANCE AT 530 Mp- 0.2 0.6 0.3 0.4 0.5 0.1 7IGUHB COMPLEX 07 NICKEL BY BECKMAN 02 . 0.6 0.4 0.2 0 r 3 / MEASURED .ABSORBANCE OP DIKETHTLGLYOXIME MG. NICKEL/ ML. 100 • NICKEL NITRATE NITRATE NICKEL • WIHD AMOUNTS WEIGHED O SOLUTION SOLUTION ZD Y EN OF MEANS BY YZED ELECTROLYSIS SULFATE F IKL AMM. NICKEL OF JXJ SPECTROPHOTOMETER i. ANAL­ 0.8

6 U 47

Eor bine determinations UBlng nickel ammonium sulfate and nickel ni­ trate, the measured absorbance showed an average deviation from the curve value of 1.06 per cent. Maximum deviation was 2.98 per cent.

Check determinations were run to show the effect of calcium and sodium on the analysis. Additions of sodium nitrate and calcium ni­ trate, in concentrations of several timeB that used in extraction runs with these ions, caused no interference in the colorimetric analysis of nickel with dimethylglyoxime.

Analysis of the nickel in nickel nitrate stock solutions was made by electrolysis. The procedure used was essentially the same as that given by Treadwell and Hall (78). A sample of nickel nitrate solution containing approximately 0.2 gm. nickel was fumed with 1-2 ml. of concentrated sulfuric acid. The nitrate-free solution was transferred to a 300 ml. electrolytic beaker. After adding 10 gm. of ammonium sulfate and 60 ml. of concentrated ammonium hydroxide, the solution was diluted to about 200 ml. with distilled water. This solution was elec- t roly zed at about 3» 0 and 0.6 amperes for approximately two hours using a Usher Controlled Potential Electro-Analyzer. A tared platinum gauze cathode and a platinum stirring anode were used. Upon disappear­ ance of the color of the solution, distilled water was added to the electrolytic beaker to check for completeness of deposition. If no metal was deposited on the freshly wetted surface of the cathode in

(78) Treadwell, E. and Hall, W., Analytical Chemistry. Vol. II, p. 143, John Wiley and Sons, N. Y. (1935)* k 8

15-20 minutes, the cathode was rinsed with distilled water and the

electrolysis stopped. The cathode was rinsed in acetone and dried "by holding it high over a gas flame. After cooling, the cathode was weighed to determine the weight of nickel deposited.

Precision for the above analysis was excellent. Three determina­

tions with nickel nitrate showed an average deviation from the arith­ metic mean of 0.2ty per cent. Maximum deviation was O.27 per cent.

Both cobalt and nickel were appreciably extracted by n-butanol, the solvent chosen for detailed study. Metal concentrations in the alcohol phase samples were in a range such that a common analytical procedure could be chosen to determine cobalt in either the aqueous or the organic phase. Similarly, a common procedure could be used for analysis of nickel in either phase.

1. Oobalt Analysis in Absence of Iron, Copper,, and Nickel

The colorimetric determination of cobalt with sulfuric acid was described in part "A" of this section for aqueous solutions. This analysis was used to determine cobalt contents of both aqueous and organic phases for most of the equilibrium extractions involving n- butanol. Special adaptations of this method were used where cobalt was determined in the presence of iron, copper, or nickel.

2. Analysis of Nickel in Absence of Iron. Ooxnoer. and Cobalt The study by Gagnon (79) on the colorimetric determination of

(79) Gagnon, J. , pp. cit.. 15. 49 cobalt indicated that sulfuric acid solutions of nickel show strong light absorption in the 400 millimicron wave length region. Using this information, it was found possible to develop and verily a color­ imetric procedure for nickel similar to the procedure for cobalt.

This procedure was used to determine both aqueous and or^nic phase nickel contents in equilibrium runs with n-butanol.

Evaporation residues containing nickel, after treatment with nitric acid, were heated with concentrated sulfuric acid until strong fumes were evolved. Nickel salts were then dissolved by boiling with distilled water. The solution was transferred to a 100 ml. volumetric flask, cooled, and diluted to the nark. The per cent transmittance of the solution was read on a Beckman DK-2 recording spectrophotometer at a wave length of 397 millimicrons using 10 mm. Cores cells. Distilled water was used in the reference cell.

The standard color curve was developed by measuring the absorb­ ance of nickel nitrate solutions at 397 millimicrons. These nickel solutions were made up by diluting a stock solution of nickel nitrate to various concentrations. The stock solution was analyzed for nickel

the colorimetric cdimethylglyoxime procedure previously reported.

Check analyses were made by electrolysis of the nickel stock solution.

Light absorbance of sulfuric acid solutions of nickel was found to be stable for at least 2b hours and was assumed to be indefinitely stable.

The plot of absorbance versus nickel concentration appears in

Jigure b, It shows that absorbance follows Beer's law up to at least

400 mg. nickel per 100 ml. The equation corresponding to this curve ABSORBANCE AT 397 M/ a 0.2 0.4 0.3 0.1 3TGOBE *»•. MEASUHED A3S0HBAHOB OS’ SULFUEIO ACID SOLUTIONS 10 0 30 400 300 200 100 0 — 03* NICKEL BI A BECKMAN IK-2 SJECTEDPHOTOMETEE G NCE/0 ML. MG. NICKEL/100 > 1

L \ ... \

50 51 was:

”^397 ~ ^ x 1® ^ ® where,

C e mg. Ni/lOO ml.

The measured absorbance for six determinations using various nickel concentrations Bhowed an average deviation from the curve value of 0.67 per cent. Maximum deviation was 2.65 per cent.

The above procedure was not affected by the presence of calcium or sodium ions. Analysis of nickel in solutions containing several times the amounts of calcium nitrate or sodium nitrate used in equi­ librium runs showed no detectable interference from calcium or sodium ions. Absorbance did not vary with sulfuric or nitric acid concentra- tion. Cupric and ferric ions did interfere with the analysis. Cuprie and ferric ionB show strong light absorption in the same wave length region as that in which sulfuric acid solutions of nickel absorb.

Special procedures were used for nickel analysis when cupric or ferric ions v/ere present.

3. Codetermination of Cobalt and Nickel

A comparatively simple colorimetric procedure was developed for codetermination of cobalt and nickel. It has been shown that the ab­ sorbance of sulfuric acid solutions of nickel at 397 millimicrons and sulfuric acid solutions of cobalt at 5*8 millimicrons follow Beer's law. The cobalt solutions absorb comparatively little light at 397 millimicrons. Similarly, sulfuric acid solutions of nickel absorb comparatively little light at 518 millimicrons. These characteristics 52 are Ideal for colorimetric analysis of cobalt and nickel in a common sulfuric acid solution.

If ions or two chemical species are to "be colorlmetrically code­ termined, they must have separate absorption peakB. If both follow

Beer’s law at the absorption peaks, the following relations hold:

A x ~ Alx + A Zx (l) and

(2) where,

Ax and Ay = total absorbance of solution at

wave length "x" and nytt respectively

A^x aud Agg = absorbance due to components

1 and 2 respectively at wave length wxn

Ajy and Agy = absorbance due to components

1 and 2 respectively at wave length “y ”

Also:

Alx » klx °1 (3)

A2x b k2x °2 W

Aly = kly °i (5)

A2y = *Zy °2 (6) where, C-l and C2 = concentration of components

1 and 2 respectively

klx and kgx - experimentally determined constants

for components 1 and 2 respectively at I

53 wave length HxH

k^y and k^y = esperimentally determined constants

for components 1 and 2 respectively at

wave length wy11

Therefore:

A. klx °1 + *2* C2 (?) and

Ay = ^ y °1 + ^ y °2 (8) By knowing the constants and measuring the absorbance of a solution

at wave lengths wxn and Hyn» equations 7 and 8 can he solved simul­

taneously for concentrations and C^.

For sulfuric acid solutions of cohalt alone or nickel alone, the

following equations have already heen experimentally determined:

ACo 518 = 8.67x10^000 (9)

ANi 397 = 8.68 x 10*^ Ojj^ (1 0 ) The absorbance of several sulfuric acid solutions of cobalt was mea­

sured at 397 and 518 millimicrons. The concentration of the solutions

was determined from the measured absorbance at 518 by means of equation

9. The system constant for absorbance at 397 millimicrons could then

be calculated from the measured absorbance at 397 millimicrons and the

calculated concentration. The system constant for nickel at 597

millimicrons was obtained in a similar manner. This provided the

constants for the following equations:

ACo 397 = 5.172 * 10-5 c0o (11)

Am. 518 «= 1.535 x 10“5 (12) I

54

Combining equations 9* 10» H » and 12 in the form of equations 7 and

8 , we obtains

A397 = 8.68 x 10“4 + 5.172 x 10-5 C0o (13)

and,

A5ia ~ 8.67 x 10-4 0Co + 535 x 10-5 0N1 (14)

Solving equations 13 and 14 simultaneously for 0qo and 0$^ we obtain: 8.66 x 10-4 0(3o = A5l8 _ 1#?80 x 10-2

8.67 x 10-4 ^ = a ^ 7_ e#96 x io~2 A^ q (16)

ftxa by measuring the absorbance of a sulfuric acid solution of the

two metals at 397 and 518 millimicrons, the concentration of cobalt

and of nickel can be calculated from equations 15 and 16 respectively.

The general procedure for codetermination of cobalt and nickel was

the same as that used to determine the separate metals with sulfuric

acid. The only difference was that the absorbance of solutions con­

taining both cobalt and nickel was measured at two wave lengths, $18

and 397 millimicrons, and the concentrations calculated as indicated

above. Pigure 5 shows a typical graph of transmittance versus wave

length for sulfuric acid solutions of cobalt alone, nickel alone, and

cobalt and nickel together as measured by a Beckman 32K-2 spectrophotom-

eter.

To check the accuracy of the procedure for codetermination of

cobalt and nickel, several measurements were made on solutions con­

taining known amounts of the metals. The results are given below: 116051 5 % % TRANSMITTANCE TTPICAL, BECKX4B IK 375 -2 400 SPEOTHOIEOTOHHTEH CU WAVLENGTH, M . / / 26 G o 25M.i/ 100ML MG.Ni 255 MG./ Co, C -236 ML 100 MG.Nf / 5 0 -2 B 200 M. 0 ML 100 / o C MG. 0 0 -2 A 425 5 TES JOB SOLnjBIC ACID SOLUTIONS OP COBALT ADD NICKEL 5 45 0 55 550 525 500 475 450 56

Hi taken Co taken Hi found Co found mg. mg. mg. mg. Hi Co

296.1 104.7 293 101.8 1.05 2.80

197.0 209.5 194 205 1.52 1.92

99.02 313 96.5 306 2.24 2.53

296.13 313 293 305 1.01 2.55

50.85 44.62 50.15 44.4 1.4o 0.50

Analysis of Cobalt In Presence of Iron

The color of ferric iron interferes with the absorbance measure­ ments of sulfuric acid solutions of cobalt. To eliminate this inter­ ference in cobalt analysis, most of the iron was removed from the cobalt samples prior to fuming with sulfuric acid. Cobalt samples containing iron were repeatedly evaporated with concentrated hydro­ chloric acid. The residues were taken up in JO ml. of 7-811 hydro­ chloric acid and extracted three times with equal volumes of iBOpropyl ether. The ether phase, which almost quantitatively extracted the ferric iron, was discarded. The hydrochloric acid phase retained the cobalt and was saved for analysis. This separation procedure is out­ lined by Kolthoff and Sandell (80).

After separation of iron, the cobalt solution was evaporated to a volume of from 2 to 5 ml. This eliminated most of the hydrochloric acid. The cobalt content was then determined colorimetrically with sulfuric acid in the same manner as that for cobalt in the absence of

(80) Kolthoff, L and Sandell, E. , Textbook Quantitative ^poT’ga.nlc Analysis, p. 91. The MacMillen Co., H. Y. (1948). I

57 ferric iron.

Check analyses were made by the above method on known amounts of

cohalt in the presence of ferric nitrate. The iron concentration was

several times that encountered in samples from equilibrium runs. The

results showed no detectable error in the analysis.

5* Analysis of Nickel in Presence of Iron

Ferric iron shows strong absorbance of light in the 400 millimi­

cron range. Even traces of iron seriously interfere in the colorimet­

ric analysis of nickel with sulfuric acid. It was found that the

separation of iron by isopropyl ether extraction did not remove this

interference completely. For this reason, nickel, in the presence of

iron, was determined gravimetrically by the standard dimetbylgiyoxime

method. Foulk, Moyer, and NhcNevin outline the method used (81).

6. Analysis of Cobalt or Nickel in the Presence of Ooupsr

Copper interferes with the colorimetric determination of cobalt

or nickel in sulfuric acid solution. A special adaptation was used to

eliminate the interference of copper in this type of analysis. The

method was similar to that used by Gagnon (82) for analysis of cobalt

in the presence of copper. Using this modification, samples of cobalt

or nickel were fumed with concentrated sulfuric acid, cooled, and the

salts dissolved by boiling with kO ml. of distilled water. Copper was

then precipitated as sulfide by adding 10 ml. of an aqueous solution

(81) Foulk, C. , Moyer, H., and MaeHevin, W. , Quantitative Chemical Analysis. 1st Ed., p. *K33, McGraw-Hill Book Co., N. Y. (1952)* (82) Gagnon, J. , pp. cit.. p. 15 58 containing $00 gm./liter of sodium thioaulfate and 10 ml, of an aqueous

solution containing 100 gm./liter of tri-sodium phosphate. After boil­ ing the mixture for 15 minutes or longer to coagulate the sulfides, the solution was transferred to a 100 ml. volumetric flask, cooled, and diluted to the mark with distilled water. The final solution was fil­ tered through dry filter paper into a clean, dry beaker. The absorbance was measured in the same manner as that used in colorimetric analysis of sulfuric acid solutions of cobalt alone or nickel alone.

Check analyses were made on samples containing known amounts of cobalt or nickel by the above procedure. Cupric nitrate was present in concentrations of several times that encountered in samples from equilibrium runs. The results showed that interference from copper was eliminated or fell within the limits of experimental error. The error in the analyses of cobalt with copper present was less than 0.16 per cent. The error in the nickel analyses was less than 0.36 per cent.

7. Analysis for Nitric Acid

Several equilibrium runs were made using rt-butanol to extract cobalt and nickel from nitric acid solution. The nitric content of both aqueous and organic phases was determined by titration with 0.2 If sodium hydroxide.

Since colored cobalt or nickel ions would interfere with colored indicators, the titrations were carried out on a Fisher Titrimeter.

The operation of the titrimeter depends on the voltage difference between two dissimilar electrodes immersed in the solution to be titrated. The end point of a titration is indicated by a sharp change 5 9 In the voltage measured. Typical titration curves showing that the presence of n-butanol, cobalt nitrate, and nickel nitrate had no effect on the titration of nitric acid with sodium hydroxide are given in jPigure 6.

Sodium hydroxide was standardized against potassium acid phthal- afce, a primary standard, using phenolphthalein as an indicator. The titrimeter was calibrated with commercial pH and pH 7 buffer solu­ tions each time it was put into use. In four verification analyses of nitric acid solutions containing 0.5 gm. nitric acid, up to 2.3 ®a. nickel or cobalt, and saturated with n-butanol, maximum error was 0.5 per cent.

8. Analysis of Ferric Hit rate and Cuorlc Nitrate Stock

Solutions

Some equilibrium runs involving extraction of cobalt or nickel nitrate by n-butanol used ferric nitrate or cupric nitrate as an addi­ tive. Since neither cupric or ferric nitrate could be dried to a constant known weight, their concentration was set by adding known volumes of stock solutions of cupric or ferric nitrate to known quan­ tities of cobalt or nickel. The concentration of the stock solutions was determined by analysis.

Samples of stock solutions of ferric nitrate were evaporated with concentrated hydrochloric acid to expel the nitrate. After taking up the residue in 1:1 hydrochloric acid, the iron was reduced with stannous chloride. Excess stannous chloride was oxidized with mercur­ ic chloride. The reduced iron was then volumetrically determined by TITRIMETER VOLTS 25 30 35 40 45 50 50 45 40 35 30 25 3TG0HE 6 THE EEFECT OE METAL. NITEATES AM) N-BUTANOL ON ON NEUTEALIZATION L 02 BASE N 0.2 ML. ' OF COBALT PRESENT PRESENT COBALT IKL PRESENT NICKEL ALCOHOL PRESENT PRESENT ALCOHOL ACID ALONE ALONE ACID NITBIC ACID

60 61

titration with. 0,1 I potassium dichromate. A 0.005 M solution of the

sodium salt of diphenylaoine sulfonic acid was used as the indicator.

This method is a standard procedure for the volumetric determination

of iron as outlined hy Foulk, Moyer, and MacKevin (83).

Samples of stock solutions of cupric nitrate were analyzed for copper "by electrolysis. The electrolysis was carried out in a solu­ tion acidified with nitric and sulfuric acids. A Fisher Controlled

Potential Electro-Analyzer was used. The general procedure is outlined

"by Kolthoff and Sandell (8*0.

(83) Foulk, 0., Moyer, H., and MacNevin, W., pp. clt., p. 351. (8*0 Kolthoff, I. and Sandell, E., pp. ci£., pp. 423-5. EXPEEBHHriAL PBOOBnJEB

A. Equipment

The major equipment requirements for the equilibrium determina­ tions were a constant temperature bath and the various items of ana­ lytical equipment.

1. Extraction Equipment

Equilibrium extractions were carried out in either 125 or 250 ml. -stoppered Erlenmeyer flasks immersed in a constant temperature bath. The constant temperature bath was the standard visibility model made by the Precision Scientific Company. The container was of glass,

12 inches high, and 16 inches in diameter. Heating and cooling coils and a one-third horsepower sparkless stirring motor were also used.

Temperature regulation was accomplished by a merc-to-merc thermoregu­ lator with an inherent control sensitivity of 0 .03° C. in conjunction with an off-on-merc-to-merc relay. The thermoregalator consisted essentially of a pair of mercury columns, the upper extremities of which were the actual contacts, sealed into a glass bulb containing dry hydrogen under pressure to suppress arcing and to prevent mercury oxidation.

Mercury contacts of the merc-to-merc relay were also sealed in diy hydrogen under pressure. The reley, pilot lamp, plug-in-receptacles, and control switches were contained in a control box remote from the bath so that the relay was not affected by handling of the bath. In addition to the intermittent control heater, the bath was supplied with

62 63 an auxiliary heater for control at higher temperatures or for rapid heating to the control temperature, adjusting the flow of cold tap water or ice water through the cooling coil in the hath, the on and off portions of the heating cycle could he made of approximately equal length for better control,

A thermometer with 0,1° C, graduations was inserted into the hath to indicate the hath temperature. This thermometer was checked at all control temperatures with National Bureau of Standards thermometers.

The hath was found to control within + 0.05° 0. except at around 70° C. where the variation was ± 0.1° C. In all cases, variations in temper­ ature throughout the hath were negligible.

Magnetic stirrers were mounted under the constant temperature hath. These stirrers consisted essentially of horizontal bar magnets rotated ty a variable speed motor. The magnetic flux actuated a glass sealed magnetic bar inside the Erlenmeyer flask centered in the bath over the motorized magnetic stirrer. The rotation of the glass sealed stirred the two-1iquid-phase mixture within the flask. Speed of the stirrer was adjusted to a point just high enough so that complete physical mixing oif the two phases was accomplished.

The Erlenmeyer flasks were totally immersed in the constant tem­ perature bath. Two rubber finger stalls were placed over the flask neck to exclude bath water from entering the flask. It was found from preliminary tests that no hath water leaked into the flasks when the dry flasks, sealed as described above, were immersed in the bath for two days. 6^

2. Analytical Equipment

Three different major items of equipment were used in making col­ orimetric metal analyses. Analysis of small quantities of cobalt was accomplished with a Fisher A. C. ELectrophotometer of the two photo­ electric cell type. This photometer was supplied with 25 mm. absorp­ tion cellB and various light filters for selecting appropriate absorp­ tion wave lengths. For analysis of small amounts of nickel, use was made of a Beckman HJ spectrophotometer. The latter instrument was a single beam instrument using 10 ram. Corex absorption cells. For most of the colorimetric work involved in the equilibrium runs with n-buta­ nol, a Beckman BK-2 spectrophotometer was used. The latter was a twin beam, ratio recording instrument. It also used 10 mm. Corex absorption cells. The absorption cells for the spectrophotometers were matched for absorption and light distortion by the manufacturer. The cells on the photometer were matched on the instrument to give identical light absorption.

A Fisher titrimeter was employed to determine the end points for titration of nitric acid. A glass electrode and a calomel electrode were used in these acid-base titrations. The instrument was equipped with a magnetic stirrer to permit automatic stirring of the solution being titrated. Before each use, the titrimeter was standardized with commercial pH ^ and pH 7 buffer solutions.

Colorimetric analyses were checked and certain metal analyses made by electrolytic analysis. For deposition of metals, use was made of a Fisher Controlled Potential Electro-Analyzer. By use of 65 controlled potential at either the cathode or the anode,the Instrument could he made to separate metals with sufficiently different deposi­ tion potentials. However, it was used in this study as a simple electroamlyzer to determine content of metal in a solution with only one metal present. The instrument was equipped with twin deposition units and heaters. Electric motors were provided to rotate the stir­ ring electrodes. These stirring electrodes were connected to the motors hy means of a collet device. The stirring electrode and the gauze electrode upon which the metal was deposited were made of plat­ inum. In addition to these electrodes, a calomel reference electrode was required to provide a reference voltage for balance of the internal circuits of this electroanalyzer.

Evaporations were carried out in a Theloo model vacuum oven made hy the Precision Scientific Company. The oven door was equipped with a glass pane to facilitate observation of the oven interior while samples were being evaporated. Samples were heated by radiation from the oven walls. This oven was equipped with a simple vacuum seal. The seal consisted of a neoprene rubber gasket mounted on the door facing the ground metal edge of the vacuum chamber. Silicone stopcock grease was spread on the gasket. When the door was held against the vacuum chamber and vacuum applied, external pressure on the door kept the seal vacuum tight. Tenperature was controlled by a bi-metallic ther­ mostat enclosed in a metal well inside the oven, control being changed by tension on the thermostat elements. Vacuum was applied to the vacuum valve on the oven through a rubber hose connected to an 66 ordinary filter pump. A filter flask was inserted into the line to prevent water from backing up into the oven in case of failure in water supply. A vacuum of 28 to 29 inches of mercury could be easily maintained with this system. In addition to the above Items, the oven was provided with a vacuum gauge, a valve to allow air to enter the oven to break the vacuum, and a thermometer to indicate oven temper­ ature at the level of the samples.

In addition to the major items of equipment, pipets, burets, mis­ cellaneous laboratory glassware, and an analytical balance were used

In the analytical work. All volumetric glassware items were calibrated for use at the temperature involved. Calibrations were made by deliver­ ing water from the particular piece of glassware to a tared weighing flask. The volume was calculated from the of water and the weight of water delivered at this temperature. Corrections at 25° C. were negligible. Corrections were made in the calculations when higher or lower temperatures were used.

B. Extraction Procedure

The procedure used in measuring distribution coefficients con­ sisted of four operations as follows* 1 ) contacting of phases at a constant temperature with mixing to ensure the attainment of equilib­ rium; 2 ) allowing adequate time for phase separation; 3 ) sampling the phases; and 4) treating the samples for analysis purposes.

1. Contacting of Phases

The contacting of phases until equilibrium was attained was accom­ plished in the following manner. First, a pyrex glass sealed magnetic stirring "bar was placed into a glass stoppered Erlenmeyer flask. Next, a measured portion of aqueous solution containing known amounts of ma­

terials and an equal volume of organic solvent were pipetted into the

flask. Generally, the amount of each phase was 50 ml. and the volume

of the flask was 125 ml. In some cases, 25 or 75 ml. portions of each were used. Where the larger volumes were used, the phases were equi­ librated in 250 ml. flasks. After inserting the materials into the

flasks, the flasks were stoppered. Two rubber finger stalls were placed over the stopper and the neck of the flask to prevent water

from entering the flask. The flask was then immersed into the constant

temperature bath and the magnetic stirrer adjusted so that the agita­

tion of the flask contents was just sufficient to physically mix the

two phases. Agitation was continued for about two hours.

2. Phase Separation

After a sufficient amount of time had been allowed for agitation,

the flask were removed from the bath and dried. The contents of the

flasks were then poured into an 8 inch long by 1 inch in diameter test

tube suspended in the bath. The foregoing operations were performed

as quickly as possible. After transferring the two-phase mixture to

the test tube, tba tube was stoppered with a rubber stopper and the

phases allowed to completely separate. The of time allowed for

separation was never less than two hours. In all cases, time allowed

for separation was several times the interval required for visual sep­

aration. 3 . Sampling of Phases 68 After complete phase separation, samples of tooth phases were

taken. Definite volumes of the top phase were withdrawn and trans­

ferred to suitable containers. The remainder of the top phase was

pipetted off until that which remained coalesced into a bubble or a

ring on the wall of the test tube. Definite volumes of the lower

phase were then pipetted into suitable containers for further analysis.

When densities of the phases were taken, a sample was pipetted into a

clean, tared weighing bottle and weighed. The density was obtained

from the volume of the pipet and the weight of its contents. When

acid analyses were necessary, they were determined by titration of the

samples used for density measurement.

^ Treatment, of Sammies for Analysis

Samples of both phases withdrawn for metal analysis were treated

to remove any organic solvent. The solvent was removed by vacuum

evaporation if it was volatile. The organic phase sample was stripped

of metal by repeated extractions with water if the solvent could not

toe readily evaporated. The combined extracts were then evaporated.

All evaporations were carried out without boiling. Usually 12 to 16

hours were required to evaporate a 5 to 10 ml. sample. If nitric acid

was present in the sample, it was neutralized prior to evaporation.

The evaporation residues were heated with concentrated nitric acid to

remove ary traces of solvent. In some cases, dilutions were made at

this point and aliquot portions taken for further analysis.

0. Verification of Sbctraotion Procedure

The following factors were considered in the verification of I

69

extraction procedure: 1) time to reach equilibrium; 2) time for com­

plete phase separation; and 3) effect of magnetic field caused by the

magnetic stirrer.

The systems water-cobalt nitrate-n-butanol and water-nickel ni-

trate-n-butanol were used for experimental investigation of the first

two factors. 3Fifty ml. of each phase were equilibrated at 25° 0. The

aqueous phase concentration before extraction was 20 grams metal per

liter. The general procedure followed was the same as that indicated

previously for the extraction procedure. The data for these determi­

nations are given below:

Metal Agitation Separation Distribution Time Time Coefficient

Co 30 minutes 30 minutes if. 70 x 10”2

Co 3 hours 3 hours 4. 70 X lo~2

Mi 30 minutes 30 minutes 4.52 X 10“2

Mi 3 hours 3 hours 4.52 x 10“2

The results indicate that thirty minutes agitation time and thirty

minutes settling time are sufficient for reaching distribution equi­

librium.

Schlea (85), using theoretical considerations, estimated the

effect of the magnetic field on extraction. He verified the results

by comparing actual extractions with and without the magnetic field

(85) Schlea, 0. S. , op. cit. 70 of til© magnetic stirrers present. Calculations from theory showed that the effect of the magnetic field on extraction of cobalt and nickel should be well within the limits of experimental error. The results with actual extractions showed this to be true. With the pres­ ent study, the same general conditions applied. In comparison to

Schlea* s work, the distribution coefficients we re higher and the abso­ lute error was approximately the same. Thus, it could be assumed that the effect of the magnetic field was negligible in this case, also.

D. Ternary Diagram

Solubility relationships for the systems water-n-butanol-nitric acid and water-a-butanol nitric acid-metal nitrate were studied at

25° C. For the first system, several water-nitric acid solutions were made up and densities measured. Distilled water and 69.8 per cent nitric acid were used. Known volumes of these solutions were pipetted into Erlennyer flasks and allowed to reach the equilibrium temperature in the water bath. These solutions were then titrated with n-butanol delivered from a microburet. Hiring the titration, the flasks were shaken continuously to ensure temperature and phase equilibrium. Near the end point, the titrant was added dropwise. The first drop of ti- trant which caused the titrated solution to remain cloudy on continued shaking was assumed to be the end point. Further titrations were made with known volumes of rt-butanol titrated with the nitric acid water solutions previously used. From the known volumes, concentrations, and densities of the components used, the points on the solubility curve could then be computed. 71 The effect of the metal nitrates on solubility was determined sim­ ilarly. Solutions of water, nitric acid, and cobalt or nickel nitrate were made up and densities measured. In all cases, these solutions contained 100 grams of metal per liter. The metal concentration was set by adding known volumes of stock solutions of the metals to known volumes of nitric acid and diluting with distilled water in a volumet­ ric flask. Titrations of the water-metal nitrate-nitric acid solutions by n-butanol and titration of n-butanol with these solutions were made up to the point where high nitric acid concentration caused decomposi­ tion of the n-butanol.

B. Materials Used

All analytical and reagent chemicals used in this study were of the highest grade obtainable from Kauffman and Lattimer Company and the Laboratory Supply Stores of The Ohio State University. The main solvent used, n-butanol, had 0.03 per cent maximum impurities and a boiling range of approximately 116 to 118° C. The cobalt nitrate used had maximum inpurities of less than O.k per cent Including a maximum of 0,07 per cent nickel. The nickel nitrate used had maxi mum impuri­ ties of 0.3 per cent including a maximum of 0.003 per cent cobalt.

All solvents and chemicals were used as received. A list of the main organic and inorganic materials used appears in Table 1 . TABLE 1. MA.TEEIA1S USED

Chemical Solvents Grade Manufacturer iso-Amyl Alcohol C. P. Coleman and Bell nrAnyl Alcohol Practical Eastman Kodak

Benzene Beagent Merck n-3u.tan.ol C. P. Coleman and Bell n-Butanol Beagent Baker n-Butanol Beagent Mallincrodt

Carhon Tetrachloride C. P. Coleman and Bell

Oyclohexanol Besearch Ma theson

Cyclohexanone C. P. Eastman Kodak n-Decyl Alcohol 0. P. Eastman Kodak

Di-Ethyl Ether Beagent Baker

Di-iso-Butyl Ketone Practical Matheson

Dodecyl Alcohol Practical Eastman Kodak

Ethyl Acetate Beagent Baker

Ethylene Glycoll Mono-Ethyl Ether Be search Matheson n-Hexyl Alcohol Practical Matheson

Methyl Ethyl Ketone Be search Matheson

Methyl-iso-Propyl Ketone Be search Matheson h—Methyl, 2-Pentanone C. P. Eastman Kodak

2-Eltropropane Practical Eastman Kodak

2-0ctanol C. P. Eastman Kodak

Octylene Glycol Be search Matheson

72 IA.BU1 1. (Continued)

Chemical Solventa Grade Manufacturer

3-Pentanone C. P. Eastman Kodak

Phenol U. S. P. Merck

iBo-Proryl Ether Be search Matheson

Tri-Ethgrl Amine Be search Matheson

Inorganic Chemicals

Calcium Chloride Beagent Merck

Calcium Nitrate Beagent Baker

Cobalt Nitrate Beagent Baker

Cupric Nitrate Beagent Baker

Perric Nitrate C. P. Mallincrodt

Nickelous Nitrate Beagent Baker

Nitric Acid Beagent Baker

Sodium Chloride Beagent Baker

Sodium Nitrate Beagent Mallincrodt

73 EXPERIMENTAL IATA.

A. Solvent and Additive Search

The first phase of the experimental program was to obtain distri­

bution ratios of cobalt and nickel nitrates between water and a variety

or organic solvents. The purpose of this was to be able to select the

solvent or solvents that showed the most promise as an extracting

agent. These data axe presented in Table 2. All runs were made at

25.0 ° C.

Effects of various additives on distribution with n-butanol were

investigated. Little investigation was made on the effect of additives

with other solvents since n-butanol showed considerably more promise

as an extractant. Spot checks were made to determine the effect of

nitric acid on the distribution of the metal nitrates using n-amyl

alcohol and 4-methyl, 2 pentanone as extractants. The data for distri­

bution in systems containing additives at 25.0° 0 . are presented in

Table 3.

B. Distribution with Normal Butanol

Normal butanol was used to determine the effects of nitric acid

concentration, metal concentration, inter-dependence of metals, and

temperature on the distribution coefficients. Data for metal concen­

tration effects are given in Table 4 for nickel nitrate and Table 5

for cobalt nitrate. These data are for the metal equilibrated sepa­

rately at 25.0° 0. Tables 6 and 7 present data concerning the effects

of nitric acid on distribution of nickel and cobalt nitrates respec­

tively. In these latter runs at 25,0 ° 0., both metal and acid

7^ U 2. SOL'SM SEABGH IMA AT 25.0 ° 0.

«„181111 OSolvent 1 4L Metal« J. ■. W #. C0 u ’ . ho. gnu/1. gm./l.

Alcoholg

1 n-Butanol Hi 21.15 8.76 x 10"1 4.14 x 10“2 — 24 n-Butanol Hi 96.50 9.76 1.01 x 10*1 — 26 n-33utanol Co 20.70 9.75 x 10’1 4.72 x 10-2 — 30 n-Butanol Co 99.60 16.00 1.605 x 10-1 — ■

22 n-Aayl alcohol Hi 20.30 3.97 x 10“; 1.95 x 10-3 — 4l n-Anyl alcohol Co 22.00 6.47 x 10-- 2.94 x lO”-' —

23 iso-Anyl alcohol Hi 20.75 4.33 x 10"; 2.09 x 10-3 40 iso-Anyl alcohol Co 22.00 5.76 x 10“2 2.62 x 10“-' —

21 n-Eezyl alcohol Hi 20.20 I.29 x 10*"; 6.39 x 10“^ — 28 n-Hezyl alcohol Co 21.20 2.15 x 10"2 1.06 x 10”3 —

29 Cyclohezanol Co 21.8 2.80 x 10-1 1.2Q x 10“2 —

19 Phenol Hi — —— *

2 2-0ctanol Hi 20.85 9.78 x 10”3 4.68 x 10“^ —

12 Octylene glycol Hi — —— *

5 n-Eecyl alcohol Hi 20.78 6.91 x 10-3 3.33 x 10“^ —

* Unable to destroy solvent - no exceptional extraction noted. IA.ELE 2. (Continued)

Son C«v» Solvent Metal K Ee marks Ho. gm./l. gn. /I.

3 n-Dodecyl alcohol Hi — — — **

Ketones

18 Methyl ethyl ketone Hi 15.15 1.18 x 10~1 7.77 x 10-3 ***

43 Methyl isopropyl ketone Co 22.55 1.0 x 10~3 4.4 x 10"5 —

7 3-Pentanone Hi 19.36 2.60 x 10-3 I.35 x 10“^ —

15 4-Methyl, 2-pentanone Hi 18.85 6.04 x 10"3 3.20 x lO-^ 27 4-Methyl, 2-pentanone Co 21.30 1.52 x io-3 7.10 x 10“5 —

6 CJyclohemruone Hi — — — *

8 Di-isobutyl ketone Hi 19.70 1.98 x 10~3 1.01 x 10-^

Ethers

20 Di-ethyl ether Hi 18.18 1.142 x 10“3 7.78 x 10-5 —

11 Isopropyl ether Hi 19.52 8.84 x I0*ij 4.52 x 10"5 — 42 Isopropyl ether Co 20.7 1.0 x IQ-3 4.8 x 10“5

** Solvent solidified. *** High solubility of ketone in water. * Unable to destroy solvent - no exceptional extraction noted. IA.BLE 2. ( Concluded)

Bun Gw. Solvent Metal V Z He marks Ho. gau/l. gm,/l.

9 Ethylene glycol mono­ ethyl ether HI 16.35 1.05 x 10~2 6.42 x 10"4 —

Comoorads

14 2-Hit ropropane Hi 19.60 6.07 x 10“^ 3.09 x 10"5 —

16 Tri-ethyl anime Hi •mm* ****

Others

10 Carbon tetrachloride Hi 19.65 2.59 X 10"** 1.32 x 10“* —

13 Benzene Hi 19.23 4. 66 x 10“^ 2.43 x 10“*—

1 Ethyl acetate Hi 18.97 1.5 x 10“^ 8.2 x 10“6 —

**** Eeaction, Hi precipitated.

->a TABLE 3. DISTRIBUTION SYSTEMS:

MEIAL NITBA.EE - WATER - SOLVENT - ADDITIVE AT 25.0° C.

Phases at equilibrium bin Cobalt or Nickel Additive Add. Metal To. conc.#

Pr^.tanpl

36 HNO3 ^9.5 Hi 22.20 9.30 x 10”1 4.18 x 10“2

37 hno3 197 Ni 26.5 1.86 7.00 x 10"2

50 bno3 197 Ni 124.2 4.60 3.70 x 10“2

31 HNO3 *19.5 Co 22.95 9.45 x 10-1 4.12 x 10"2

34 hno3 197 Co 27.60 2.82 5 1.03 x 10-1

35 HN03 197 Co 125.5 6.23 4.98 x 10“2

38 NaN03 66.8*+ Ni 20.18 8.63 x 10”1 4.28 x 10“2

44 N&NO3 115.6 Ni 20.30 9.25 x 10"1 4.56 x 10“2

48 NaN03 116.5 Ni 104.2 11.05 1.06 x 10"1 32 NaN03 66.80 Co 21.21 1.121 5.28 x 10"2

^5 NaN03 116.5 Co 20.7 1.130 5.47 x 10~2

il9 NaN03 118.5 Co 100.5 13.^ 1.33 x 10”1

39 Oa( 1103)2 116.2 Ni 20.38 1.261 6.20 x 10~2 52 Oa(N03)2 117.7 Ni 95.5 12.56 1.32 x 10”1

33a Ca( 1103)2 116.1 Co 20.20 1.560 7.72 x 10“2

53 0a(N03)2 117.7 Co 99.50 17.20 1.73 x 10”1 79 IABLE 3. (Continued)

Phases at equilibrium wriginaj. Bun Cobalt or Micfcel Additive Add. Mo. Metal conc., °v. °o. K gm./l. gnu/l. gm./l.

n-butanol (continued)

95 Ca012 100.8 Hi 21.05 6.77 x lO"1 3.21 X 10~

94 CaCl2 100.3 Hi 98.80 10.35 1.10 X 10~X

97 CaCl2 100 Co 21.42 9 . 30 X 10"1 4.33 X 10-2 96 CaCl2 101 Co 96.10 13.80 1.44 X 10"!

92 hho3 98.25 Hi 24.0 5.94 x K T 1 2.47 X 10~2 MaCI 80.23

91 HNOo 98.25 Hi 114.2 4.52 3.96 X 10-2 BaCI 80.06 _•? 93 HNOo 98.25 Co 23.90 8.93 x 10” 1 3.88 X 10 - HaOl 80.27

90 HHOo 98.25 Co 114.5 6.45 5.63 X 10-2 HaCl 80.57

99 Pe ( 3 100 Hi 99.9 13.25 1.33 X 10"1 100 Pe(N03)3 100 Co 23.05 2.06 8.93 X 1Q“2

93 Ite(H03)3 100 Co 102.5 17.71 1.73 X 10-1

104 Cu (K03)2 100 Hi 21.80 1.759 8.07 X 10“ 2

102 0u (H03)2 100 Hi 102.9 14.55 1.41 X lO-2

103 Cu (M)3)2 100 Co 20.95 2.01 9.59 X 10~2

101 0u(H03)2 100 Co 95.70 18.10 1.89 X 10-1 80'

TABLE 3. (Concluded)

Phases at equilibrium Original Eon A^d. Cobalt or Nickel No. Additive Conc#f Metal Cw* Co. K j 1. gm. /l. gm. /l.

n-amvl alcohol

4-6 HU03 49.5 Ni 21.00 3.65 x 10"2 1.7A x 10**5

4? EN03 49.5 Co 23.*+5 8.28 x 10“2 3.53 x 10“5

4-aethvl, 3-uentanone*

51 HN03 197 Ni 98.80 m m m m

* Showed no visible extraction. TABLE 4. EPF1CT OP METAL CONOEHTBATION ON SYSTEM:

N l O m BITBA33S - WATER - N-BUTANOL AT 25.0° 0.

Before Phases at Equilibrium Bon Extraction Water Phase Alcohol Phase No. K c °w> f3 w> °o. fo* gn. Ni/l. gm. /l. gm./ml. gm./l. gm./ml.

1 20 21.15 0.876 — 4.14 x 10"2

5*4- 50 52.5 — 3.42 — 6.50 x 10**2

24 100 9 6.5 — 9.763 — 1.01 x 10"1

56 150 152.2 l. 350 25.25 0.888 1.66 x 10-1

55 260.5* 2*44.5 1.555 71.50 0.996 2.92 x 10"*1

* Water phase saturated with, nickel nitrate "before extraction.

81 TABLE 5. EFFECT OF MEDAL CCHCENTHATIOH OH SYSTEM:

COBALT HIT RATE - WATER - W-BUTAHOL AT 25.0° 0.

Before Phases at Equilibrium Extraction Water Phase Alcohol Phase Run X Ho.

26 20 20.7 — 0.975 — 4.72 x 10“2 58 50 52.0 1.118 4.50 0.841 8.65 x 10"2

30 105 99.6 — 16.0 — 1.61 x 10-1

59 150 145.5 1.352 33.05 0.913 2. 27 x 10”1

57 236* 217 1.503 68.5 1.009 3.16 x 10”1

* Water phase saturated with, cohalt nitrate before extraction.

82 TABLE 6. DISTRIBUTION IN THE STSTEM: NICEEL NITEATE -

NITEIC ACID - WATER - N-BUTANOL AT 25° C.

Water Phase Phases at Equilibrium D istribution Cone. Before W ater Phase Alcohol Phase Coefficients Extraction 0 Oyj, g m ./ l . • • 0 z^o* Oy/, gn./l. E , E , N i HNO^ g a . /m l. N i HN03 g a ./ m l . Ni HNO3 N i HNO3

150 197.0 182.5 35.21 1.441 7.25 135.2 0.917 3.97 X 10“ “ 3.84

150 49.48 161.2 6.87 1.372 17.37 37.7 0.889 1.08 X 10"1 5.48

150 98.5 175.5 15.22 1.402 12.49 71.20 0.895 7.11 X 10“ 2 4.6?

100 197.0 130.0 60.75 1.327 5.46 119.2 0.910 4.2 X 10”2 1.96

100 49.48 114.2 11.90 1.260 8.93 33.45 0.871 7.81 X 10“ 2 2.81

100 98.5 119.5 26.72 1.281 7.18 63.3 O.883 6.01 X 10“2 2.37

50 98.5 61.3 43.25 1.156 3.44 52.30 0.877 5.6 X 10”2 1.21

50 197.0 66.6 91.5 1.192 3.73 100.8 0.910 5.59 X 10“2 1.10

50 49.48 55.2 20.39 1.132 3.17 27.05 0.857 5.74 X 10*2 1.33

20 98.5 24.90 54.5 1.072 1.40 44.2 0.876 5.62 X 10“2 0.81 20 197.0 27.45 111.1 1.101 2.34 90.8 0.911 8.54 X 10“2 0.82

20 49.48 23.15 28.55 1.057 0.948 22.01 0.857 4.10 X lO”2 0.77 TABUS 7. DISTRIBUTION IN THE STSTIH: COBALT NITRATE -

NITRIC ACID - WATER - N-BUTANOL AT 25° C.

Water Phase Phases at Equ.ilihrium Distrihution Cone. Before Water Phase Alcohol Phase Coefficients Extraction Cy, gm./l. p y , 0(}» 0B»/l. /50» CvJ, gm./l. K, K, Co HNO-j gnu /ml. Co HNO^ gm./ml. CO HNO^ Co HNO-j

150 49.48 151.2 7.52 1.360 21.35 36.3 0.906 1.41 X 10"1 4.83

150 98.5 167.8 16.05 1.387 16.71 70.0 0.913 9.98 X 10“2 4.37

130 197.0 188.7 37.60 1.441 10.35 131.6 0.923 5.47 X 10“2 3.50

100 49.-48 107.9 12.05 1.262 10.87 32.7 0.879 1.01 X 10"1 2.71

100 98.5 113.9 26.68 1.278 9.31 62.95 0.890 8.17 X 10"2 2.36

100 197.0 122.5 61.0 1.319 6.35 117.5 0.917 5.18X 10"2 1.93

50 49.43 54.8 20.45 1.132 3.88 27.0 0.861 7.07 X 10-2 1.32

50 98.5 58.7 42.80 1.157 3.95 52.20 0.880 6.73 X 10“2 1.22

50 197.0 65.I 90.80 1.188 4.375 100.0 0.910 6.72 X 10-2 1.10

20 49.48 23.21 28.05 1.057 0.942 21.75 0.856 4.07 X 10-2 0.78

20 98.5 23.95 55.5 1.069 1.645 44.1 0.876 6.8? X 10~2 0.80 20 197.0 26.80 110.1 1.101 2.66 91.0 0.912 9.93 X IQ"2 0.83 “ 85 concentration were varied. Data to show the interdependence of cobalt and nickel nitrates appears in Sable 8. These data, also at 25.0° C., are for equilibration of mixtures of the metal nitrates. Both the cobalt-to-nickel ratios and the metal concentrations were varied.

Table 8 has one column listing the cobalt plus nickel content of the aqueous phase. This column is to be used later for data correlation.

Temperature-cffects data are listed in Tables 9 a“d 10 for the individ­ ual metal nitrates.

0. Solubility Determination with Formal. fcitappl

Data for the solubility* envelope of the ternary diagram in the system water-nitric acid-n-butanol were determined at 25.0° C. These data are presented in Table 11. Data showing the effects of metal nitrates on this solubility curve are given in Tables 12 and 13. m s 8. DISTRIBUTION IN THE SYSTEM: NICKEL NITRATE -

COBALT NITRATE - WATER - N-BUTANOL AT 25.0° C.

(One run made using nitric acid as an additive)

Water Phase ______Phases at Equilibrium______Before Density Extraction Cy, gm./l. /?w> p o> Xj,______Sw, gnu/l. Oo Ni Oo & Ni gm. /ml. gm. /ml. Co ' IT Co Ni

20 20 21. A 21.9 43.3 I.O69 O.836I 7.77 X io“2 6.30 X 10“2

50 50 A7.3 51.2 98.5 1.027 0.86A1 1.51 X 10“2 1.20 X 10”1

100 100 92.0 97.7 189.7 1.AA5 0.9586 2.73 X 10**1 2.15 X 10"1

100 25 97.3 26. A 123.7 1.293 0.8887 1.8A X 10”1 1.A6 X 1 0 -1

25 100 25.2 99.8 125.0 1.293 0.8768 1.8A X 10"1 l.AA X 10”1

50* 50* 56.1 57.2 113.3 1.278 0.8880 7.78 X 10“2 6.1A X 10“2

* 98.5 ©n. HNO^/l. before extraction.

00 en TABLE 9 . EEEECT OP TEMPERATURE ON THE SYSTEM:

NICKEL NITRATE - WATER - N-BUTANOL

Temperature K, *. -0. 1/TJ 4 ° 3' gm./l.

5.5 3.595 96.9 1.38 x 10"1

25.0 3.355 97.0 1.04 x 10-1

69.5 2.925 97. 9.67 x 10“2

87 lAELB 10. EFFECT OF TEMPERATUHE ON THE ST STEM:

COBALT 331 TEA IE - WATER - W-HJTANOL

Temperature l/T X 10*3, K, t, °c. */ l/°K /l*

5.5 3.595 96.8 1.69 x 10-1

25.0 3.355 97.0 1.57 x K T 1

69.5 2.925 97.3 1.15 x 10"1

88 TABLE 11. SOLUBILITY ENVELOPE POE SYSTEM:

NITRIC ACID - 'WATER - N-HJTANOL AT 25.0° C.

Weight Per Cent

Nitric Acid Alcohol Water

0 79.8* 20.2

1.1 77.3 21.8

2.36 73.9 23.7

fr.17 69.5 26.3 6.32 6i(-. 6 29.1

9.62 56.7 33.8

17.5 20.9 61.7

15.8 11.7 72.5

12.5 8.70 78.9

8.6 7.90 83.5

4 > 3 7.85 87.7

0 7.32* 92.7

* Values for these data points as given by Seidell (86) show 79.7 weight per cent alcohol in the alcohol rich phase and 7.35 weight per cent alcohol in the water rich phase.

(86) Seidell, A., Solubilities s i Organic Compounds. 3rd Edition, Vol. II, p. 266, D. Van No strand Co., Inc., N. Y. (19*H).

89 TABLE 12. THE EFFECT OF METAL HIT BATES OH

THE SOLUBILITY OF H-HJTAHQL XNAQPEOUS

NITBIC ACID SOLUTIONS AT 25 .O0 0.

Composition on a metal-free basis Weight per cent Metal^8^ Nitric Water Alcohol Acid

Ni 0 9^.2 5.8

Co 0 9^.2 5.8

Hi 4. 9 89.7 5.5

Co 9.5 85.2 5.3

Hi 13.9 80.2. 6 .1

Hi 2 2 . 4 72.7 4.8

Ni 26.5 6 9 .1 4.5 Hi 3^.3 62.3 3 >

(a) A ll metal concentrations =s 100 gm ./liter "before saturation w ith alcohol. (b) Decomposition of alcohol observed.

90 TABLE 13. EFFECT OF HICKEL UITEATE OH SOLUBILITY

OF AQPEOUS HITBIC ACID IH B-HJTAHOL AT 25.0° 0.

Composition on a metal-free "basis^a) Weight per cent Hitric Acid Water Alcohol

0 17.1 82.9 2.9 16.8 80.^

k.9 15.8 79.3

5.9 15.2 78.8

7.7 13.9 7 8 . 3 ^

(a) Hlckel concentration = 100 gnu /lite r "before saturation w ith n-"butanol. ("b) Decomposition of alcohol observed. TKEAIMMT AND DISCUSSION OP BA.IA

A. Calculations

1. Distribution Data

All of these data were determined by analyzing aliquot portions of each phase at equilibrium. She analytical methods used depended upon the components present as mentioned previously. The calculation method is illustrated below for the distribution in the system nickel nitrate- nitric acid-water-n-butanol at 25.0° C. The run referred to below con­ sists of that made using 150 grams nickel and 98.5 grams nitric acid per liter before extraction.

Hun No. 62

Organic phase:

9.905 ml. sample taken for Ni analysis, ^.97 ml. sample

taken for HNO^ analysis.

Nickel content - sample neutralized and evaporated to

dryness under vacuum. Be si due treated with HNO^

and heated to fumes with HgSO^. After dilution to

100 ml. , the transmittance was measured at 397 typ.

^ 3 9 7 ~ 7 8 .2

A397 ~ 106 0 .782 = °»1C>72 Nickel content = 0.1072/8.68 x 10“^ = 123.7 mg.

Nickel concentration in organic phe.se

00 ' ifro2 1 9^905 = ',lltor Nitric acid content in organic phase volume 0.2035 N.

92 93 NaOH for neutralization = 27.65 cc.

Weight acid in sample = —? “ 0.354'

gm.

Concentration nitric acid in organic phase

Oo = J797 x °’35^ = 71.20 gm./liter Aqueous phaset

9 .9 0 5 nil. sanrple taken for Ni analysis, 9 .9 0 5 ml. sample

taken for acid analysis

Nickel content - sample diluted to 100 ml. and a 9*905

ml. aliquot analyzed for nickel as in organic phase

analysis

$1397 - 70.9 A397 = log = 0 .1h92

Nickel content = 0.1492/8.68 x 10**^ = 171.9 mg.

Nickel concentration in aqueous phase 0 _ 121*1 x -100- 1000. _ 1755ct1./i cw “ 1000 9 .9 0 5 9 .9 0 5 " 175.5 gm./1. Acid content - volume 0,2035 W, NaOH for neutralization =

11.75 ml. Weight HN03 in sanrple = ^ 7 5 . ^ P ^ g 0 .35.. 2S-63. = 0.151 gm.

Nitric acid concentration in aqueouB phase

C*, = 0.151 * ^ § § 5 = 1 5 .2 2gm. /liter

Distribution coefficients:

Nickel,

K = Cq /Cw 9^ K = 71.20/15.22 = 4.67

2. Ternary Jdagraa

The data for the solubility envelope of tie ternary diagram were obtained by titration to the cloud points. The calculation method is illustrated "below for a run using the following data:

Bun No, 104a

Quantities added:

50 ml, of a nitric acid solution of density 1.122 gnu/ml.

and of 247 gm. HNO^/liter concentration

18.2 ml. of n-hutanol of density 0.810 gm. /ml.

Weights present:

HNO3 , 50/1000 3: 247 = 12.35 gn.

H20 , 50 x 1.122 - 12.35 = 43.60 gm.

Alcohol, 18.2 x 0.810 = 14.75

Total weight:

70.70 gm.

Weight per cents:

HN03, 12.35/70.70 = 17.5 per cent

H2O, 43.60/70.70 = 61.7 per cent

Alcohol, 14.75/70.70 = 20.85 per cent

B. Discussion of Solvent Search Data

In the solvent search, the distribution of cobalt and nickel ni­ trates between water and various solvents was studied. These data could then be used to help pick one solvent for a detailed study. A solvent was desired which extracted one or the other of the metal 95 nitrates to an appreciable extent. The ideal case would be to find a solvent which quantitatively extracted one metal nitrate while not extracting the other at all. Other desirable characteristics for the solvent include low water mlscibillty, low cost, suitable melting and boiling points, stability, and availability in tank car lots.

A complete search of all available organic solvents was not possi­ ble and was unwarranted. The solvents used were restric^d mainly to those classes of solvents known to have some ability to extract metal nitrates. Thus, for example, more attention was directed toward sol­ vents with polar functional groups containing oxygen than, toward hydrocarbons.

Solvent search data showed that alcohols were the best solvents for extraction of cobalt and nickel nitrates. The ability of alcohols to extract these salts decreased with increasing molecular weight. The data for iso-anyi alcohol and normal amyl alcohol indicated that branch­ ing in the alcohol chain may increase extraction ability. However, the difference in the distribution with the two alcohols was slight. A ring compound, eyclohexanol, showed considerably greater ability to extract cobalt than did its straight chain counterpart, n-hesyl alco­ hol, The only ketone that showed any appreciable ability for extrac­ tion was methyl ethyl ketone, a solvent with high water .

The ethers, 2-nitropropane, carbon tetrachloride, benzene, and ethyl acetate showed very little extraction as compared to the alcohol3.

Tri—ethyl amine reacted with nickel to form a precipitate. The reac­ tion of amines with cobalt and nickel to form precipitates was noted 96 ty Schlea. * Organic acids were not used in the solvent search, since they are known to react equally well with hoth cobalt and nickel to pro­ vide extraction with no separation.

Figure 7 illustrates the effect of alcohol molecular weight upon the distribution of nickel nitrate between water and the various alco­ hols. The log-log plot of K versus alcohol molecular weight resulted in a relatively smooth curve. The cobalt distribution data were not plotted since they would fall on the same general curve. This type of correlation was used by Weiser (8?) in a study of the extraction of lactic acid from aqueous solution by various solvents. He found that different straight lines resulted for primary alcohols, esters, methyl ketones, and higher ketones. Distribution of lactic acid decreased with molecular weight in all cases.

There are two possible explanations for the differences in extrac­ tion of the metal nitrates with the various solvents. First of all, solvents which have greater water miscibility generally exhibited higher distribution coefficients. Thus the distribution with alcohols increased with Increasing water solubility of the alcohol. Highly water soluble methyl ethyl ketone showed a considerably higher distribution coefficient than did the other ketones. I^rdrogen bonding may also have entered into the extractability differences. In the liquid state, lower alcohols are associated through hydrogen bonds. The ability to

* See literature He view. (8?) Weiser, E. B. , Dissertation, Ph.D., The Ohio State University (195*0. 97

Figure 7. correlation between alcohol

MOLECULAR WEIGHT AND DISTRIBUTION COEFFICIENT

OF NICKEL NITRATE AT 25.0° C.

,001

O NORMAL ALCOHOLS • I SO-ALCOHOL 0 SECONDARY ALCOHOL

0 0 0 1 10 too 1000 SOLVENT MOLECULAR WT. 98- form hydrogen 1)01x48, or the strength of the "bonds, decreases In the following order: phenols, tertiary aliphatic alcohols, secondary ali­ phatic alcohol, normal aliphatic alcohols, iso-aliphatic alcohols, Ob a certain extent, this might explain the greater ability of the alco­ hols for extraction of cobalt and nickel nitrate. However, it was noted that iso-anyl alcohol extracted more metal than n-anyl alcohol, which disagrees with the above order for bond formation. Methyl ketones show a greater tendency to form hydrogen bonds than do their corresponding analogs. Again the distribution with methyl ethyl ketone m y be explained as being due to hydrogen bonding. HoweverV distribu­ tion measurements with methyl isopropyl ketone seem to dispute the hydrogen bond theory.

Distribution data for cobalt and nickel nitrates with various sol­ vents appear in Table 2. It should be noted that data for solvents with low distribution coefficients may be subject to error on the order of 5 per cent or higher. Analysis for these solvents was necessarily carried out in concentration ranges where instrumental accuracy was poor. However, since these solvents showed such low distribution, the values were important mainly from an order of magnitude standpoint.

Thus, accuracy was of only minor importance where the error values were unknown.

0. Distribution with Additive Data

numerous systems have been reported in the literature where the addition of foreign electrolytes showed highly beneficial effects on extraction and separation of metals. Various reasons have been given 99 to explain the effect of additives on distribution, but each reason

seems to apply only to a specific system. Regardless of the mechanisms

involved, however, it seemed logical to determine the effect of various additives on the extraction of cobalt and nickel.

Literature studies indicated that the most promising additives

should be the nitrate compounds. As a result, distribution data was

determined for extraction of cobalt and nickel nitrates using nitric acid, calcium nitrate, and sodium nitrate as additives. The majority

of these runs were made with n-butanol as the extractant, since n-buta-

nol seemed the most promising of the solvents.

Further runs with additives Included the use of calcium chloride, nitric acid and sodium chloride, ferric nitrate, and cupric nitrate.

Study of chloride additives was made because it was known that

such additives greatly increased extraction of cobalt and nickel chlo­

rides. Iron and copper are two of the most common metals found associ­ ated with cobalt and nickel in ores. Thus, it was of interest to

obtain some data showing the effect of ferric and cupric nitrate on

the extraction of cobalt and nickel nitrate.

Preliminary data showing the effect of additives on distribution

of cobalt and nickel is compiled in Table 3. Data for distribution with additives, using nrbutanol as a solvent, is plotted in Figures 8

and 9. These plots do not include points for nitric acid, since com­

plete curves for this additive are presented later. In Figures 8 and

9 , a line representing the distribution of cobalt or nickel without

additives, taken from Figure 10, is plotted to provide a comparison 1 0 0

JTGUHE 8. DISTRIBUTION IN THE SIS 1234: N-BUTANOL -

NICKEL NITRATE - WATER AT 25.0° C. WITH VARIOUS ADDITIVES 1.0 ADDITIVE CONC. BEFORE EXTRACTION O 66.8 GM. NaN03/LITER n j H P c a (no 3)2/ " P C a CI2 / 98 2 HN03 i 8 0 GM. Na CI/LITER * f e ( n o 3)3 / l i t e r ' A Cu(N0 3)2 / ADDITIVE

0 .0 1 100 150 200 250 Cw , GM. Ni/LITER FIGURE 9. DISTRIBUTION IN THE SYSTEM! N-BUIANOL -

OOBALT NITRATE - WATER AT 25.0° 0. WITH VARIOUS ADDITIVES ) ADDITIVE CONC. BEFORE EXTRACTION O 66.8 6 M. NaN03 / LITER • 117 / “ _ d 117 “ Ca{N03 )2 /" 4 100 100 CaCI2 / q 9 9 8 6 .2 .2 " HN0 3, 80 GM. NACI/LITER ^ 100 F e (N03)3 /LITER A 100 Cu (N03 )2 / ‘ NO ADDITIVE

100 150 200 250 GW, GM. CO/LITER 102 with, additive data,

D. Selection of Solvent and Additive

The solvent selected for detailed study was n-hutanol. The choice of this solvent was comparatively clear-cut. Distribution coefficients using n-hutanol were the highest of any solvent studied. Preliminary measurements also showed that distribution increased with increasing metal concentration when n-hutanol was used as the solvent. This alco­ hol is cheap and is available in tank car lots. It does have a fairly high water solubility, however. On the other hand, solvents with lower water solubility, including the other alcohols, did not show favorable distribution, appreciable separation factors, or other char­ acteristics to recommend them in place of rt-butanol. In addition, it will be shown that the presence of cobalt and nickel nitrates decreases the solubility of n-butanol in water.

Selecting an additive for further study presented considerable difficulty. Hone of the additives used caused any narked change in the distribution of cobalt and nickel nitrates with n-butanol. Most of the additives increased the distribution slightly at low metal con­ centrations. At higher metal concentrations the distribution with these additives approached the value for distribution without additive or fell below It (see Figures 8 and 9). When nickel was equilibrated with both sodium chloride and nitric acid, distribution •was appreciably lowered. The same results were found with cobalt, however, so no sep­ aration was gained with this combination of additives. The highest distribution was gained with cupric nitrate although again no 103 appreciable gain in separation was obtained.

Hitric acid was the additive finally chosen for further study.

.■Distribution with nitric acid showed variation with both metal concen­ tration and acid concentration. Several studies of metal extraction have been reported where the acid counterpart of the metal anion was used as an additive. Thus, a study with nitric acid in this case would be of academic interest at the least. Considering application of extraction with additives to practical processes, nitric acid would have several advantages. It would be the easiest to subject to process control of any of the additives studied. It could be more easily sep­ arated from cobalt and nickel after extraction than other additives.

In addition, it is comparatively low in cost. Prom the above consid­ erations, and from the standpoint that the characteristics of the other additives were not promising, it seemed logical to study the effects of nitric acid on the distribution of cobalt and nickel ni­ trates.

Some data were determined for the distribution of the metals with nitric acids using solvents other than n-butanol. Hitric acid lowered the distribution of both cobalt and nickel using n-ainyl alcohol as a solvent. When a solution of high nickel and high acid concentration was extracted with 4-methyl, 2. pentanone, the green color nickel ni­ trate was not observed in the organic phase, indicating no extraction of nickel. These data are presented in Table 3.

E. Studies with Uormal Butanol

1. Effect of Metal Concentration on Distribution 104

Data showing the variation of distribution coefficient with metal concentration are given in [Cables 4 and 5. [These data are for the equilibration of cobalt or nickel nitrate separately with n—butanol at 25.0° C. Figure 10 is a plot of K versus the aqueous phase metal concentration for both metal nitrates. This is the type of plot used for representation of most of the distribution data. It shows that distribution continuously increases with increasing metal concentra­ tion. The distribution coefficient for cobalt is higher than that for nickel over the entire range of metal concentration.

If distribution is assumed to follow the equation

K = °o/Cwn U ) a log-log plot of C0 versus C^. should be a straight line with slope ‘'n*1 and intercept log K. This can be shown by taking the log of both sides of Equation 1

log K = log 0Q - n log Cw (2)

Rearranging Equation 2 gives

log C0 = n log Cw - log K (3)

Equation 3 is in the standard form for a straight line equation.

Using the data of Tables 4 and 5, a plot of log 0Q versus log 0W liras constructed. It is reproduced in Figure 11. These data for both cobalt and nickel follow straight lines reasonably well. The slopes for these straight lines are 1.69 and 1.82 for cobalt and nickel re­ spectively. The proximity of these values to the integer two would suggest that both cobalt and nickel nitrate are dissociated into two ions in the aqueous phase. It seems reasonable to assume that these 105

FIGURE 10. EFFECT OF METAL CONCENTRATION IN THE SYSTEMS:

METAL NITRATE - WATER - N-BUTANOL AT 25.0° 0. * 1.0

o COBALT NITRATE

• NICKEL NITRATE

0 50 100 150 200 250 CW, GM. METAL/LITER * Cobalt or Nickel Nitrate equilibrated separately. 0.5 0.51 Co, GM. METAL/LITER 100 50 1.0 0 0 0 50 1000 500 100 50 10 PI LOG-LOG OF PLOT DISTBIBUTION INSYSTEMS: CUBE 11. METAL NITBA.TE - WATEH N-BUTANOL- AT ______W G. METAL/LITER GM.CW, i ______NICKEL • COBALT O 50 0. 25.0° -J i 106 107 ions are of the form and (NO^)" where M is either cobalt or nickel. Equation 1 was developed for the case where dissociation or association occurs in the aqueous phase only. Thus it appears that the extracted metal salts are not associated or dissociated in the or­ ganic phase, although slight association or dissociation might account for the deviation of the slope values of Figure 10 from the 2.0 value.

Attempts made to correlate similar data for the sulfate system of cobalt and nickel, as reported by Schlea,* did not meet with success.

However, data for the extraction of the chlorides of cobalt and nickel from aqueous solution by capiyl alcohol* were plotted in the above man­ ner. Figure 12 shows that the data for the chloride system also fell along straight lines. It was found that the slope of the line for cobalt chloride was 7.^ and that for nickel was 7.0. This could not be explained as being due to dissociation of the metal salts, since they could dissociate into no more than three ions. Apparently this method of correlation should be subjected to further experimental in­ vestigation.

2. Effect of Hitric Acid

The effect of nitric acid on the distribution coefficients of the individual metals at 25.0° 0. are tabulated in Tables 6 and 7* Distri­ bution coefficients are plotted against aqueous phase metal concentra­ tion, with acid concentration as a parameter, in Figures 13 and lh.

Figure 15 is a cross plot of Figure 14. It shows a plot of distribution.

* See Literature Be view. 008 WT.% METAL CHLORIDE 0 0 100 50 10 AA F GARWIN OF DATA FI GOES 12. W W. MTL CHLORIDE METAL WT.% CW, N HIXSON09) AND . - WATER METALGHLORU® - CAPEXX ALGOBOL 100-100 HOT T O H OF DISTRIBUTION IN STSTEMS: NICKEL • COBALT O 108

PIGUBE 1 3 . DISTRIBUTION 01 COBALT NITRATE BETWEEN

N-BUTANOL AND AQUEOUS NITRIC ACID AT 25.0° C.

NITRIC ACID CONC. BEFORE EXTRACTION O 0 GM./ LITER • 4 9 5 G M . /L ITE R 6 98.5 GM./LITER f 197 Gta./LITER

_J______I 50 100 150 200 250 Cw* GM. CO/LITER 110

FIGURE 14. DISTRIBUTION OF NICKEL NITRATE BETWEEN

N-BUTANOL AND AQUEOUS NITRIC ACID AT 25 . 0 ° 0.

* 0.1

v

NITRIC ACID CONC. BEFORE EXTRACTION O O GM /LITER 9 4 9 .5 G M /L IT E R fS 9 8 .5 GM./LITER ^ 197 GM./LITER « .01 I______50 100 150 200 250 Cw , GM. Ni/LITER Ill

FIGURE 15. DISTRIBUTION OF NICKEL NITRATE BETWEEN

N-BUTANOL AND AQUEOUS NITRIC ACID AT 25.0° C. (CROSS PLOT) 1.0

Cw, GM. NICKEL/LITER O 20 e 50 d 100 4 150

0.1

.01 0 50 100 150 200 250 Cw , GM. HNO3 /LITER 112 versus acid concentration with aqueous phase metal concentration as a parameter. Figure 13 was not cross plotted since the general trend is the same with "both metals. The acid concentration shown la the aqueous phase concentration before extraction. These figures indicate that dis­ tribution increases slightly with increasing acid concentration at low metal concentrations. As metal concentration increases, the effect is reversed, the distribution coefficient decreases with increasing acid concentration. At high acid and high metal concentrations, the distri­ bution of cobalt and nickel nitrate is lower than that obtained when no acid is present.

The behavior of these systems with nitric acid was generally the same as that with other additives. A reasonable explanation for this behavior cannot be given. At low metal concentrations, additives may increase the aqueous phase activity, which might account for the in­ creased distribution of the metals. However, the reversal of this trend toward lower distribution at higher metal concentrations sug­ gests that two or more competing extraction mechanisms may be present.

The effect of nitric acid on the distribution of cobalt and nickel nitrates was quite different from that encountered when acid solutions of other cobalt and nickel salts were subjected to extrac­ tion. Schlea* found that sulfuric acid increased the distribution of cobalt and nickel sulfates between water and n-butanol almost one-hun­ dred fold at highest acid concentrations. Distribution increased

* See Literature Beview. 113 continuously with increasing sulfuric acid, concentration. Garwin and

Hixson* used hydrochloric acid as an additive in the extraction of cohalt and nickel chlorides "by capiyl alcohol, hydrochloric acid greatly increased the distribution of cohalt chloride, while the dis­ tribution of nickel chloride was increased to a lesser extent. In

Schlea's study, acid addition did not appreciably change the separation of cohalt and nickel by extraction while considerable separation was gained by the addition of hydrochloric acid to the chlorides of cohalt and nickel.

Nitric acid actually lowered the separation factor, /3 , in the extraction of cohalt and nickel nitrates. Separation factors were calculated from the distribution curves of Figures 13 and 14 for the metal nitrates. These separation factors, for the metal equilibrated separately, are tabulated in Table 1^ and plotted in Figure 16. The separation factor was quite low in all ranges of metal and acid con­ centration. The maximum separation factor, about 1.h95> was obtained when the metals were equilibrated without acid.

3» Distribution with Mixtures of Cobalt and Nickel

Several equilibrium runs were made involving the extraction of aqueous mixtures of cobalt and nickel nitrates with n-butanol. The data for these runs at 25.0° C. are given in Table 8. These runs were made with various metal concentrations and various cobalt-to-nickel ratios. One run was made using an Initial aqueous solution of 50

♦See Literature Review. TABLE 14. SEPARATION FACTOR, , WITH 7AHTING HNO^

CONCENTRATIONS

(Metals Equilibrated Separately)

°w» f®- Phases at Equilibrium HN03/1. K Before \ > en. metal/1. Ni Co Extraction V % i

20 4.0 X 10“ 2 4.7 X 10"2 1.175 50 6.4 X 10“2 8.5 X 10-2 1. 328 0 100 1.07 X 10-1 1.6 X 10“1 1.495 150 1.64 X 10“1 2.35 X io”i 1.434 200 2.25 X lO”1 3.04 X lO”1 1.352 10“ 2 25 4.1 X 10"? 4.20 X 1.025 49.5 50 5.4 X lO”*2 6.7 X 10“2 1.240 100 7.44 X 10-2 9.8 X lO"2 1.317 150 1.0 X 10-1 1.39 X lO”1 1.390

25 5.6 X 10”2 6.8 X lO-2 1.215 50 5.4 X 10“2 6.6 X 10“2 1.222 10-2 98.5 100 5.8 X 10-2 7.8 X 1.345 150 6.6 X 10“ 9.4 X lO"2 1.425

25 8.8 X lO”2 1.01 X 10-1 1.148 50 6.5 X 10-2 7.7 X lO-2 1.185 197 100 4.55 X 10-2 5.4 X lO”2 1.187 125 4.1 X 10“2 5.10 X 10“2 1.243 150 4.05 X lO”2 5.05 X 10“ 2 1.245

114 * Kco/KNi -N-BUTANOL AT NITRIC - - WATER NITRATE ACID METAL 2.0 1.2 1.4 1.0 .6 8 IUE1. EAAINFCOSI H SYSTEMS;IN SEPARATION FACTORS THE 16.FIGURE 0 **separately. equilibrated Metals w M HNO GM. Cw w GM. METAL/LITER Gw, 0 0 10 200 150 100 50 .5 9 4 5 .5 8 9 197 3 / LITER / 5 0.* ° 0 25. 115 11.6

grams cobalt, 50 grama nickel, and 98.5 grams nitrate acid per liter

concentration. The purpose of these runs was to determine the depend- an.ce of the distribution of one metal on the presence of the other , metal.

The distribution data for mixtures is plotted in Figures 17 and

18. Figure 17 represents data for cobalt while Figure 18 represents data for nickel In these figures, the distribution coefficient is plotted versus the aqueous phase total (nickel plus cobalt) metal con­ centration. The aqueous phase metal concentration is the concentration

of both cobalt and nickel after extraction. For comparison of the var­ ious runs, two lines are plotted on the graphs along with the data points for the mixtures. Curve A represents the distribution of the particular metal nitrate when it was equilibrated in the absence of

the other metal. Curve £ in each figure represents the distribution

of the particular metal nitrate with an aqueous phase acid concentra­ tion of 98.5 grams per liter before extraction, but in the absence of

the other metal nitrate.

It can be readily seen from the graphs that the data points plot very closely to the comparison curves. This is true for both metals,

for various cobalt-to-nickel ratios, for various metal concentrations, and for equilibration with nitric acid. Thus it can be stated that

the distribution of cobalt nitrate or nickel nitrate in mixtures of

the two depends upon the total metal or total metal salt concentration.

This same type of interdependence phenomena was observed In the extrac­

tion of cobalt and nickel chlorides. It was not found, however, in the 117

FIGURE 17. DISTRIHJTION OF COBALT IN THE SYS TIM s

NICKEL NITRATE - COBALT NITRATE - WATER - N-BUTANOL AT 2 5 . 0 ° C.

1.0 T CONC. .BEFORE EXTRACTION O 20 GM. Co. 20 OM. Mi/1 a a a / a • 5 0 « 5 0 * a a m 100 900 " •/ £ a a ’a m 100 29 * •/ a a 9 ■ 2 5 9 100 * ■ /

^ 8 a a 10 o a 5 0 9 9 9 8 .5 GM HNOft/LITELF

S'*

0.1

o CURVE A - COBALT AL o CURVE B - 98. S BML HMOj PER LITER

.01 ■L 50 100 150 200 250 Gyy, GM. TOTAL METAL/LITCR 1 1 8

FIGURE 18. DISTRIBUTION OF NICKEL IN SYSTB4S NICKEL

NITRATE - COBALT NITRATE - WATER - N-BUTANOL AT 25.0° C. 1.0 I- GONC. BEFORE EXTRACTION

ii II y H 5 0 " » 5 0 " it My 19 100 " i 100 " u My II 100 ■ 9 25 “ M M y M 2 5 “ » 100 “ U 5 0 " 1 5 0 - ' t • , PLUS 9 8 .5 GM. HN03/ L I T E R ^ ^ '

0.1

CURVE A * NICKEL A LOME

CURVE B - * , 98.5 GM. WMOj PER LITER

.01 0 50 100 850 200 250 Cw, GM. TOTAL METAL/LITER 119 extraction of cobalt and nickel sulfates.

Bffect of Temperature on Distribution

The effect of temperature on the distribution coefficients of the separate metal nitrates 1b illustrated hy the data in Tables 9 and 10.

These data are plotted in Figure 19 by means of the van't Hoff corre­ lation. If the van* t Hoff equation

InK = - a 2aS + m RT has been obeyed, both curves of distribution coefficient versus the reciprocal absolute temperature would be essentially straight lines over the range of temperature involved. However, both lines of Figure

19 show appreciable curvature. Seasons for the deviations can be found in the section on theory. Distribution of both cobalt nitrate and nickel nitrate decreased with increasing temperature. The reverse trend of distribution coefficient versus l/T was found by Schlea in the extraction of cobalt and nickel sulfateB with n-butanol. Lines plotted by means of the van't Hoff correlation showed very little cur­ vature in this case.

5« Nitric Acid Distribution

Nitric acid distribution was measured for systems of the metal ni­ trates containing this acid as an additive. The distribution data for nitric acid appear in Tables 6 and 7. Distribution of nitric acid with cobalt nitrate present is plotted in Figure 20. Figure 21 shows the distribution of nitric acid when nickel nitrate is present. In

* See literature Be view. 120

3PIGUHE 19. DISTRIBUTION IK THE ST STEMS; METAL NITRATE *

WATER - K-BUTANOL AT 7ARI0U8 TEMPERATURES * 0.5

Cw AFTER EXTRACTION, 97 GM./LITER OF Co OR Ni

COBALT NITRATE NICKEL NITRATE

0.1

0.05 2.8 3.0 3.2 3.4 3.6 3.8 l/T X I03, (l/K°) X I03

* Metals equilibrated alone. hno 3 0 2 4 3 5 6 WATEE 0. B-BUTANOL 25,0° WATEE AT AND # HIT COBALT PATE PRESEHT FIGURE 20. THE DISTBIBUTIOH OF NITRIC ACID OF NITRIC BETWEEN ACID DISTBIBUTIOH THE 20. FIGURE , 0 5 Cw,

M CO/LITER GM. 100

EOE EXTRACTION BEFORE W HN0 CW, 49. M./LITER GM .5 9 4 O • ' 38.5 150 9 " “ / " 197

/ " / " 3 CONC. CONC. 200 250 121 hno 3 0 3 2 4 5 6 I 0 WATER WATER AND N-BUIANQL AT IUE2. THE DISTRIBUTION OF NITRIC ACID BETWEEN FIGURE 21. 50 W GM. Nl/LITER CW) 100 25.0° EOE EXTRACTION BEFORE w, HNO , Cw 9 "/ * " / 197 b 85 * " / 98.5 • O 49.5 49.5 O 0. ,NICKEL NITRATE PRESENT 150 3 6 CONC. 200 M./LITER 250 122 1 2 3 each case, the nitric acid distribution coefficiente are plotted ver­ sus the metal concentration of the aqueous phase before extraction with the nitric acid concentration before extraction as the parameter.

Distribution coefficients for nitric acid varied from about 0.8 to approximately 5*5 at the highest. The highest distribution coeffi­ cients corresponded to hi^x metal concentrations and low acid concen­ trations. The distribution coefficient approached a constant value at low metal concentrations for all acid concentrations. The behavior described held true for distribution of acid in the presence of either cobalt or nickel.

6. Phase Densities

Densities of the phases at equilibrium appear in Tables Jf, 5» 6, and 7* Aqueous phase densities are plotted in Figure 22 for systems involving various nitric acid concentrations. For simplicity, most of the aqueous phase densities with cobalt present are not plotted, since densities for both cobalt and nickel fall on the same lines. In gen­ eral, densities were as expected. At low metal concentrations, density increased with increasing acid concentration. At high metal concentra­ tions, densities approached a common value for all acid concentrations.

Since organic phase densities varied somewhat with the metal in­ volved, two separate plots were made. Figure 23 represents organic phase values obtained when cobalt was present, while Figure 2k repre­ sents data obtained with nickel present. Densities measured when nitric acid was present showed a marked difference from those obtained when no acid was present. This was particularly true at low metal DENSITY, GM./ML. 1.2 1.0 1.4 1.3 1.5 1.6 1.1

5 10 5 20 250 200 150 100 50 0 EA, HNO METAL, 0 b ♦ <> • IJE2„ CPOSPAEDNIISI YTM METAL ACJPEOUS SYSTEM;IN DENSITIES PHASE 22„ EIOJEE NITRATE - WATER - NITRIC ACID - N-BUTANOL AT AT N-BUTANOL - NITRIC - ACID WATER - NITRATE r N o, C * Metals equilibrated separately. equilibrated Metals * i , Ni M II » , t w G. METAL GM./LITER Gw. 5 8 9 49.5 197 0 0 3 OC BFR EXTRACTiOW BEFORE CONC. 6 M. HNO 3 / / / / /LITER /LITER 2 5 . 0 ° 0. * 0. ° 0 . 5 2 124 - DENSITY, GM./ML. .80 1.05 .90 85 95 1.0 NITBATE - NITBIG ACID - WATBB - N-BUTANOL AT 25.0° 0. 25.0° N-BUTANOL WATBB --AT NITBIG - ACID NITBATE PIGIIHE EOE EXTRACTION BEFORE C 1 W 0 0 10 200 150 100 50 HNO 23 5 .5 8 9 .5 9 4 197 OGNCPABDNIISI TTM COBALT STST5M:IN DENSITIES OBGANIC PBASB . W G. CO/LITER GM.CW, 3 CONC. M./LITER GM 250 5 2 1 DENSITY, GM./ML. 1.05 .80 . — 1.0 NITRATE NITRIC - - WATER N-BUTANQL - ACID AT IUE2. RAI HS ESTE NSSE: NICKEL ORGANICDENSITIESPHASE SYSTEM:IN FIGURE24. w HNO Cw. EOE EXTRACTION BEFORE 0 0 0 • 50 49.5 85M / 98.5 9 / " 197 0 w GM.Cw, Ni/LITER 3 GM./ CONC. / " 100 LITER II

M N 150

200 5 0. ° 0 25. 290 6 2 1 d 12? concentrations. It can be explained as being due to the high extrac­ tion of nitric acid by n-butanol.

7. Solubility Determinations

The data representing the two-liquid region of the phase diagram of the system nitric acid-water-n-butanol at 25.0° 0., are given in

Table 11. The effects of metal nitrates on the solubility of n-butanol in the aqueous solutions containing 100 grams metal per liter on an al­ cohol-free basis were determined by data given in Table 1ZC Data for the effect of nickel nitrate on the solubility of nitric acid solutions in n-butanol at 25.0° 0. are given in Table 13. Tie line data for the nickel nitrate system were calculated from Table 6 and are tabulated in

Table 15.

All of the above data are plotted in Figure Z$ on a metal-free basis. This figure shows that metal nitrates definitely lower both the

solubility of the alcohol in the aqueous phase and the solubility of the aqueous solutions in the alcohol phase. The complete solubility curve with metal nitrates present could not be determined since high acid concentrations caused decomposition of the alcohol.

Schlea* found that cobalt and nickel sulfates had a small salting-

out effect on the solubility of n-butanol in water. Addition of sul­

furic acid to this system caused the salting-out effect to vanish.

Little data could be obtained on the effect of the metal sulfates on the solubility of aqueous acid solutions in n-butanol. The acid caused

* See Literature Eeview. TABLE 15. TIB LINE DATA POR THE ST STEM: NICKEL

NITRATE - NITRIC ACID - WATER - N-BUTANOL AT 25.0° 0.

Phase Composition _ ^ ^ . . at Equilibrium Cone. Before Extraction Wei ht Per 0ent M 0 C*/, Gm. /Liter . ______1 Ni HN03 Water Organic Phase Phase

100 *<9.5 1.32 3.97

100 98.5 2.9^ 7.37

100 197.0 6.59 13.35

128 FIGURE 25. PHASE DIAGRAM FOR THE SYSTEM:

NITRIC ACID - WATER - N-BUTANQL AT 2 5 .O0 C. *

50 a tt a 50 a NO METALS PRESENT • 100 GM. Nl/L., ALCOHOL- f , FREE BASIS o ' 4 i) 100 GM. Co/L., ALCOHOL- ▼ / FREE BASIS & 2 f * -V - TIE LINE DATA

y - *

75 50 25 WATER

* Weight per cent basis. 130 a solid metal sulfate phase to separate from the alcohol solution.

P. Process Application

Calculations were made on the extraction of cohalt and nickel ni­ trateswith n-hutanol to indicate the degree of separation that might he obtained in an actual process. Per the most part ideal conditions were assumed. Metal concentrations in the range of high distribution and selectivity were used. Extraction with fresh solvent in each con­ tact and equilibrium conditions in each contact were also assumed. The effect of one metal on extraction of the other was neglected.

Case I:

Assume (l) Hi/Co ratio as in Iynn Lake* ora =* 4.67 Hi/Co

(2) 0* for Hi = 100 sa./liter before extraction

(3) 0* for Co = 21.4 gm./liter before extraction

(4) Ho additive

(5) Basiss One liter of the aqueous metal solution

To determine equilibrium concentrations, using the relation K « Co/C* trial and error calculations must he made. For example take K ** 0.1, a reasonable value when 0w for nickel is slightly less than 100 grams per liter. Also use one liter of solvent to extract one liter of the aqueous metal salts o.i . 5a 100 ~ °w °w

* See Introduction. I

131

Ow = 9 1 gm. N i / l .

CQ = 9 gm. Ni/l.

Jor this value of Gy, the graph of K versus Gy shows that

K = 0 . 9 3

By assuming the curve value for Z, a new tria l can he made to find a

new C^. and a new E. A few such, tria l and error solutions w ill give an

assumed K equal to the K found. The distribution of cobalt can be cal­

culated in a sim ilar fashion.

Calculations for Case I were made for five extractions of the

aqueous metal solution with one lite r of fresh solvent used for each

extraction. The raffinate from the fifth extraction was evaporated to

a nickel concentration of 100 grams per lite r to take advantage of the

higher distribution values. A fter five more such extractions, the raf-

flnate was again evaporated to a nickel concentration of 100 grams per

lite r. The resulting solution was extracted five more times with equal

amounts of solvent. By this process, calculation showed that €9.9 p e r

cent of the nickel was in the extract, the overall Ni/Co ratio in the

extract was 5«69» and the Ni/Co ratio In the final raffinate was 3.23.

C a se I I :

Assume

(1) The Co/Ni ratio * 4/l

(2) Gy for Co = 100 gm ./liter before extraction

(3) Cw for Ni = 25 gm ./liter before extraction

(4) No additive

(5) Basis: One lite r of the metal solution 1 3 2

In Case III calculations were made for five extractions of the aqueous solution with equal amounts of fresh solvent followed by evaporation of the last raffinate to a cobalt concentration of 100 grams per liter.

This last solution was extracted five more times with equal amounts of fresh solvent. The calculations showed that, after ten extractions and one evaporation, a total of 65.9 per cent of the cobalt would be ex­ tracted into the organic phase. The overall Co/lTi ratio in the extract was la 18 while the Co/Ni ratio in the last raffinate was 0,789.

For the three cases given, calculations show that the maximum sep­ aration of cobalt and nickel is gained in Case II, Seasons for this can be seen if the curves of Figure 10 are consulted. The plot shows that distribution increases with increasing concentration. It also shows that cobalt is the more easily extracted metal. Thus, when the aqueous phase contains appreciably more cobalt than nickel, these two factors combine to give maximum selectivity or separation.

These calculations indicate that large amounts of solvent are re­ quired to obtain any reasonable separation of cobalt and nickel nitrates by extraction with n-butanol. Ideal conditions were assumed for the calculations. In addition, the effect of one metal on the extraction of the other was neglected. In an actual extraction, the distribution of either cobalt or nickel is dependent upon the total concentration of the metals. The selectivity would be lower than that encountered in the above calculations, resulting in a lower separation of the met­ als. Thus, in any practical process it would be difficult to approach the separation of cobalt and nickel calculated for the above cases. CONCLUSIONS

It can l)e concluded that the separation of cohalt and nickel ni­ trates by liquid-liquid extraction is probably not commercially feasi­ ble. This conclusion was reached on the bases of distribution of the metal nitrates between water and a variety of organic solvents. Dis­ tributions in favor of the organic phase were generally low, being on the order of 10“ ^ to 10“-5. jn addition, cobalt and nickel nitrates were extracted to approximately the same degree by all solvents. Nor­ mal butanol did extract the metals to an appreciable degree, but the separation gained was quite poor. Calculations with n-butanol showed that any appreciable separation with n-butanol would require large volumes of solvent. Even low percentage losses of solvent in an actual system would make the cost for separation prohibitive.

Two properties were characteristic of the solvents which showed measurable extraction of cobalt and nickel nitrate. These solvents possessed the ability to form hydrogen bonds and were somewhat water soluble, two generally Interrelated properties. This behavior has been observed in the extraction of other cobalt and nickel salts.

Extraction data with n-butanol showed that distribution of the metal nitrates was dependent on the second power of the aqueous phase metal concentration. No radical changes in distribution were effected by the addition of foreign nitrates. High nitric acid concentrations lowered distribution somewhat when metal concentration was high.

Nitric acid tended to lower the separation of the metals to a small degree. Thus it may be concluded that the extraction of cobalt and

133 13^ nickel nitrates “by n-butanol is due to cation properties of the two salts and that the common-anion effect is not a mechanism of extraction.

If extraction had depended on the anion, nitric acid should have In­ creased extraction in all ranges of concentration. Lowering of metal distribution at high metal and high acid concentrations may have been due to the lowering of the solubility of water in the organic phase.

Differences in the distribution of cobalt and nickel nitrates between water and n-butanol were probably due to chemical differences of the cations. Cobalt and nickel are, however, quite similar chemi­ cally. No evidence was obtained to show that the chemical nature of the metals were affected by solvents or additives. For this reason, the low separation gained by liquid-liquid extraction with n-butanol may be attributed to the small chemical differences of the metals. SUGGESTIONS FOE FUBTHER INVESTIGATION

Thou^i several investigations of the extraction of cobalt and nickel salts have been made, the possibilities for further study have by no means been exhausted. Studies with salts of these and other met- als will provide more information to add to the fundamental knowledge of extraction behavior. Such knowledge could well eliminate some of the confusion concerning liquid phase relationships.

Any further study of the separation of cobalt and nickel by liq­ uid-liquid extraction should first involve a study of factors effecting their chemical nature. For separation of the metals, a system must be found which will enhance the difference in the chemical properties of the two metals. In all cases where appreciable separation of cobalt or nickel was gained by solvent extraction, there was definite evidence that one metal had formed a complex different from that of the other metal. The successful separation of metals by extraction in many cases has involved specific complex formation. Thus, it appears that no further attempts to separate cobalt and nickel nitrates by extraction should be made. This does not necessarily apply to the addition of complexing agents to systems of the metal nitrates.

Ohelating agents provide one possibility for gaining specific complexes with cobalt and nickel. Few such agents are available or low in cost, however. There is the possibility that the reaction of cobalt and nickel with organic amines could offer an advantage for

separation. If solutions of cobalt or nickel were extracted with a non-reacting solvent containing dissolved organic amines, the amines

135 136 might preferentially extract one metal into the organic phase. The amine would have to form a metal complex which was soluble in the or­ ganic phase. Most probable conditions for formation of soluble com­ plexes would seem to be at low organic amine concentrations.

Two possibilities for further research were suggested by data found and correlations encountered in the present study. It was shown that nitric acid is quite readily extracted by n-butanol. Further studies of the extraction of nitric acid might be made. Such studies could determine the feasibility of concentrating nitric acid by extrac­ tion from weak aqueous solutions. Another possibility for research

Involves the uncertainty arising from the correlation of extraction data to determine association or dissociation of solutes. iUrther studies of extraction of cobalt and nickel salts by various solvents could be made with this correlation in mind. It might prove necessary or interesting to study other inorganic salts as well. MOMEHCIATOSB

Absorbance (of light) &r - log T, where T is the per cent transmittance expressed as a decimal.

Concentration.

Equilibrium concentration of solute in organic phase, grams per liter. Metal concentrations are expressed in grams metal per liter (not grams m&tal salt per liter).

Equilibrium concentration of solute in aqueous phase, grams per liter. Metal concentrations are expressed in grams metal per liter (not grams metal salt per liter).

Concentration of solute in aqueous solutions before extrac­ tion, grams per liter. Metal concentrations are expressed in grams metal per liter (not grams metal salt per liter).

Distribution coefficient = Co/0v .

Distribution coefficient for nickel.

Distribution coefficient for cobalt.

A constant.

A constant, molal heat of transfer of solute between two sol­ vent layers.

A constant.

Association or dissociation number.

Gas law constant.

Absolute temperature, degrees Kelvin.

Temperature, degrees centigrade.

Separation factor or selectivity j= Kq c /Kjj^.

Density of organic phase at equilibrium, grams per milliliter.

Density of aqueous phase at equilibrium, grams per milliliter. NOMENCLATURE (Continued)

SUBSCRIPTS

1 = Component of solution.

2 s Component of solution.

397 = Wave length, millimicrons.

518 = Wave length, millimicrons.

530 = Wave length, millimicrons.

650 as Wave length, millimicrons.

o ts Organic phase,

w = Aqueous phase,

x = Wave lengthy millimicrons.

7 ts Wave length, millimicrons. BIBLIOGRAPHY

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Gagnon, J., Chemist-Analyst, No. 1, 15 (1954).

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Welser, R. B. , Dissertation, Ph.D., The Ohio State University (1954). AUTOBIOGBAPHT

I, Edward Jonathan Schsrf, was "born in Portage, Ohio» Decemher

18, 1928. I received my secondary education in the public schools of Bowling Green,, Ohio, and ny undergraduate training at The Ohio

State University, which granted me the Bachelor of Chemical Engineer­ ing degree in June, 1951* I received the Master of Science degree from The Ohio State University in August, 1951. After serving as an officer in the United States A m y for two years, I returned to The

Ohio State University in the Summer Qyaarter of 1953 to start work for the degree Doctor of Philosophy in the Department of Chemical

Engineering. In October, 1953* 1 received the American Qyanamid

Fellowship, which I held for the academic years 1953**5^ and 195^55.

From June, 1955* "to April, 1956, I held the position of instructor part time in the Department of Chemical Engineering at The Ohio State

University.