The dissolution of copper from bornite, covellite, and copper concentrates at elevated temperatures and pressures
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Authors Moss, Thomas Austin, 1935-
Publisher The University of Arizona.
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Link to Item http://hdl.handle.net/10150/319689 THE DISSOLUTION OF COPPER FROM BORNITE, COVE LUTE,
AND COPPER CONCENTRATES AT ELEVATED
TEMPERATURES AND PRESSURES
by
Thomas A . Moss
A Thesis Submitted to the Faculty of the
DEPARTMENT OF MINING AND METALLURGICAL ENGINEERING
In Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE
In the Graduate College
UNIVERSITY OF ARIZONA
1 9 5 8 STATEMENT BY AUTHOR
This thesis has been submitted in partial fulfillment of requirements for the advanced degree of Master of Science at the University of Arizona under a cooperative agreement between the University of Arizona and the United States Bureau of Mines. The cooperative agreement provides that the privilege of publishing all or part of the text has been granted to the United States Bureau of Mines. The thesis is deposited in the University of Arizona Library to be made available to borrowers under rules of the Library.
Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgement of the source is made. Requests for permission for extended quotations from or reproduction of this manuscript in part or in whole may be granted jointly by the Dean of the Graduate College and the United States Bureau of Mines when in their judgment the proposed use of the material is in the interests of scholarship. The author hereby accepts the conditions of publication as stated above.
SIGNED:
APPROVAL BY THESIS DIRECTOR
This thesis has been approved on the date shown below:
T. G . CHAPMAN Director of Thesis ■AC KNOW LEDGEMEN T
the author w i^es td; express his fhqntes to: Carl Rampacek of the
UnilM Stettes Bumqu o f Mihesi and ^ f o Ts G 0 Chapman^ Director of lhssisr College of Mihes^ for their guidance and constructive criti-
menfpl w o # « Appreciation is also expressed to all others who # TdblW pf $qh#nts
Chapter :: "z-' : —■ / V " N g e
Acknowledgement
■ _ I Jntrodjjctton ■- ■=* - = — ^ :.<,==-=■ =-■* i=''= — .=(='== «, .. ■=,; , -
II /sAatenals, Equipment^ and Experrmenta| Procedures 9
/• uOlTI i't^© Be ^ :vst' 'f6* :■»>-«=»...e=»: «*:• •.«=•; .«•. < )*»': -«=» W '«=*"'’•»» '*=»' • -
Govellite ^ c=i ^ ^ ■*s ^ ^ ^ « = « => « .c=i' ^ M «. c=». ™ m « »«t=t -»=»,=3 ^=3 _c=* » 10
Commercial Copper ^ncentFdfeS - = - - ^M s1 ~ ~ ^ ~ « j]
-' :.:Cement Coppei'”' '-.I-a-ri-'-a:13
v jPyflfe '*•’ .•**' '•*«•■ -<=* . =q es*"-*/'«•• «s=» •«; :W «==i W 'ear'W mj t=jmm ,t=a :oo; ts> W J=a t=3 W «=a *t=i, W :ea « 13
.:AiGbes$?ory ^ 16>
; Ahdjyticdi^mc ,, ,«::W:CF,;«»„=; »«- »- ■ l^ .,
Standard Test Procedure: ” « «««««-««-' »• .«• -• 17 ,
III Experimentdl Work osl Bornite dnd Coveliite » - - « « « ^ 20
, Bdri^i te ca. -Ba :oa ,.t=p;-yw me t=3 e=3 -=e ,e=l‘ -tso" :me' w mbj t= G3 esi; c=3' -e=l -a »■: e=» teSlf .ibi;-ca tel1 20”
;:: ■; ; ; ;;BerleS':I^s;tnf|ti#ee:of1 l!nev-^ « . 20. ;/)
; Series li^ Effect of Addlfion pf Sulfuric Acid = »='« «= 3- ==■ » 22
Series ilig 0% ct of A^dltlom^^ « ^ ^ _ 23
SeriestV^ Sffect of Time vyfth, Addition rdf Acid^^ 24
Series Vf Effscf of Time with: the Addition of Pyrite ■= = = 26 Chapter . ' :: ' '' v,.>,.
5eri@s V lf feffect of Temperdtum with ^dli-ion of Aclcl = = - . 27
defies VH^ Effect of Degree of Agiiai-ion with Acid - -■ ~ 28
Series VII I f Effecit of portiai A ssure of Oxygen wi th ; . Addition of Pyriie a =■ =• « - = ■ ' > = ' ' fa. =..* := =3; *= == ■=, *>=, « — - 29
Series IX# Effect of Particle Size with Addifion of Acid - ~ 30
Series Effeet of Flow of Ai r wi th the Addi Hon of Pyrife = 31
Se#es Density y/ifti Addition of Sulfate - 32
Series XII^ Effect of Elevated Temperatures dnd f’ressures ~ 35
Chemistry of Leaching Bornite at Eievated Temperatures and , 'PpBSSMlto. Bay**' »'*«-• «.;•«=* w>=*. WV ;w. ;f».••:«■■<** «=»:-=9 '3^,
Aberation ^f Bomite During J^aohing ^ * - - - » == *. = 38
Corrosion of Equipment - - “ —■ - — ^ >=: « 42
IV Dissolution of Copper from Commercial Concentrates and Cement Copper at Elevated Temperatures and Pressures - - = - = - ==--•=-=> 44
Series XI11, Dissolution oiF Copper from Magma Concehfrdte = ^ ^ •'**. •*<* **• .w •*■•••*«■**«■< .*•" 5*e<" 44
; , Series XIVy Dissolution of Copper from Old Dick .*«=»' eai.. 'ittrt:■ -jaar jM: ,W" =» b»'1=3 .c=3 ;,taa~ ■.ca«\;^V taa l=a ea» ca -ca‘ - •
Series XV/ Dissolutionof Copper from Bagdad Concentrate ■==>- = — — = — — ^ = a =. =, .=,= 46
Series XVI/ 0issd|ufion of Copper t e fhelps Dodge . ■ Concentrate ™ « ^ ^ ™ ^ ™ ^ ™ ™ ^ ^ ^ *«> = 47
Series XVI1/ Disspbtion x>f Copper from Various Goncenfrates Employtng Pyip Densities of 33 ^
\ ■ V"n:;.- vV',- ■ ^■ 'v Chapter
Series XVIII,, Dissolution of Copper from Various Concentrates Employing a Continuous FlowofAir - - = - = - 49
Series XIX* 0issolytiqn of Copper from Ceme Coppdr - - - 50
Series XXj, bissoluHon ofCopper from Mixi'ure of Phelps bodge Concenirate and Cemeht Copper - = - - - = =* - 52
V Conclusions anc! Recommendations = - - - ="■=• = = = — = = = » — ■= 53
C6|1lC;I:tJS.rO^$. ^ ^ -|e». -»•>«.• tsT' i=* ea «=, es:, 53
;•» •’ . I'I ^ «=« • a: c=> t=t: .t=l 'C=J !==» =3Tsq B=dr -c 1=1 t=3 .tsa tsa: -t=a ..a=J .ena -e=o- esf t=3 to)' !^!S
OoniM^rcjol ;Cpncehfr<^^^' ^ *-»• •■=» ;>=••••.».•55
t. Cement Copper ^ «=«••• w -:w ^•:>vt=a.■ 57
- - Recdnniii^enclat^ ^ ^ ^ «. w^w.-.*- -ft:-— w w—». &« ^ « 1 57
Bll b l ( Q^rQjpMy^ ” t=a>t«i t eo t=a, :C^i' :z=a ea oo ca o c=% t=» i="t=j — ;t=l t=>" -G=s -ca t=) — taa , 53 Tables
10 influence of time on the dissolution of copper from bomite under oxidizing conditions =' = ^ =, j- . .21
, '2.o Assays of residues and leach soiutions ==. « ~ ■=< - *= ='=. — - —' — — = 2 1
3o Effect of the addition of sulfuric acid on the dissolution of copper from bomi te for a reaction period of one hour - = -■ = - - „ n., - = 22
4 0 Assays of residues and leach liquors - — - - » ----- 22
5 0 . Effect of the addition of pyrite on the dissolution of copper from l^mlfe for a^i^ctron pprlod df ^ne hpur=<;a ” ” ^ w ^ ^ ” =- » ■- 23
. 6.0 Assays of leach liquors and residues = = =• ======™ — — = =' = == ■=■= 24
Effect of time on dissolution of copper with the addition of 0o50 pound of sulfuric acid per pound of bornite - = « ^ 25
B0 Effect of time on dissplufion of copper with the add!tion of 0 o25 : 'pdundvdfpyrite; per'pound of;b 9mite'w,ia:^ «=.=.=-;w25
9 0 , Effect of temperature on dissolution of copper fora reaction P O ^ O ,o n e hour-™ ...... — " ^
lOo Effect of fhe degree o f agitation of the pulp on dissolution
I I o Effect of the pdrtial pressure of oxygen on the ratc of dissolution of copper— “ « - - _ « » » « _ = *=■ =t == « ^ . 29 i2o Efffect of longer reaction periods at an oxygen partial pressure of 25 pounds per square inch gauge on the dissolution of copper - - 29
130 Effect of particle size on dissolution of copper - - - - “ = " 31 Effect of rate of flow of air on the dissolution of copper - = = '=
Effedt of pulp density on the dissolutiori of copper
Solubility of copper sulfate in wafer " ” - = = -= — ■=• = = - - •= -
Effect of elevated temperafures and pressures on the dissolution
Dissolution of copper from the Magma copper concentrate - - ~
Dissolution of eopper frpm the Phelps Dodge concentrate - » ™
Dissolution of copper from various copper concentrates ertiployirig puip densities of 35 per cept solids ^ “ - >■ “ «
Disspfution of copper fom VOflous concentrates using an air flow of 500 liters per hour - .'=* =° =■ =■ =» = — = ■= •=. ™ »='
Dissolution of copper from cement copper when sulfdte ion was provided with pyrite on sulfuric.acid tiddition
Assays of leach liquor and residue from the 7 minute test using 1,23 pounds of sulfuric acid per pound of cement copper =■ ~ - ■=
Dissdlufipn of copper from a synthetic concentrate composed of a mixture of the Phelps Dodge concentrate and cement copper ~ lllusfrdHons
_ ^Asserirtb.lsd dutocloyB " ™ ,*= « w t- ;■=
Priginctl pdjllshed surfticfs d f ibetrficles showing inclusions of chalcocite— = = = - - — == - - = -
Polished surfaces of residue parHeies Ieached for SO mlnufes with: acid and oxygen magnified at lOQX ^ - - =.
The some polished isuffooeS as of Figure 3 mag showing Ihe WidmOn^tofteri sirueture of tha ohaico|yrife =‘ *=• -
Polished su r g e s of residue parHd ie§ aAer being 200 degrees Ceni"igrade for 120 minutes in a niirogen atmosphere JMfi ©iSS^yJXlOK OF C#PER FROM ,BORN!IE, GOVE1LITE, AND COFFER CONCENTRATES AT.E1EVATED TEMPERATURES AND PRESSURES.
CHAPTER | - INTRODUCTION
Ledehing of Copper Ores
Tte<^meiit of ftxyi^edi e 1915, when dcid I each i nig first wtis used ill large scale operations at Chuquicdmata, Chile, Smaller scale leaching operatioris that produced"cemeht copper were ose ; Most Ieachmg operdtioris are carried out on oxidized or native copper ?riihera|s. For Ores of these. types? sulfuric dcid, ammonium carbonate, or cupric- #imoniu#cdrWhdte We u#d a& tbe so dnd type ^ The dissolution of copper from its sulfide miherdis eiSdlls the pridr dxh^ldn df the copper by tiir or by an oxidizing dgent, Ifi the - pdgtr at I east one ledchingoperdtion tredting theirtinerd I chdlcocite^ cuprolJS s&lflde^ used'adidified ferric s u l^ of dxid^i%ing dnd dissolving fhe copper with W 1 ■; y •’ .. .'1\; ■ , , , / • I, ,Rose, C, A,/M etallurgical Operations at the Chile Exploration.Company", Ehglheerlng and Minings February 12, 1916/ pp, 32iui2 a , v ^ ':;.y:'"- 2 ^ When employing ticid ledch'miethods the copper Is recovered irohi the jecich. liquor by medps of electrolysis or by the use of metallic iron. . Ip the electrolytic method thecopper obtainedis in the; pure state and the equivdlenf acid from copper sulfate is regenerated0. Copper precipitated by tnefdllic iron is pot pure dnd must be refined further using pyrometallurgical methods, add furthermore, the equivalent acid is Pot reg^erated:o ; ; , ' ■ ■ ; Recovery of the copper from dlkal ihe ledch liquors eptails an enfire(y different method of operation o The complexed copper ion in the leach solution is decomposed by hoi I ing wi th steam, to reledse ammonia apd. ctirboP dioxide and to precipitate the capper decupric o>c|cle0 Affer sepdratidP of the oxide from the barren so|utiori, the copper compound is treated by pyrometdl (urgical methods to recover the copper, , Commercial Ledchjpg at Eleyated Temperatures dnd. Pressures beaching at elevPted temperatures dnd pressures has been used commercially ip the past for disso Iving alumipum, tungstep, dnd ather metals from ores and con centrates, , Jo ToiMontmsen htis described, the early use of autoclaves for such tpachipg dperdtidnso . v .. vii: i ■: 2 , Mommsen, J= T0, The Dissolution of Chalcopyrite af Eleyated Temperatures and. Pressures, Thesis, University of Arizona, T955, pp, l-ll, ^ beeh # the recovery of metals from, sulphide miherdls „ Plants which; utilize thls method how are operatlngondCommerciaJ basis at the Sherritt-Gordon hickel property at Saskatchewan, Ccfnada,. and. at the Calera, Mining Cornpahy’s cobalf-nickoi-cppper ; _ ' ■ ' .'; ■ : ^ . ’ , , - ' ■ ... ■ - - ' • ^ . . W inery at Garfield,. Utah, The Sherritt-Gordon operatidn employs autoclaves for the dissolution of nickel minerals in ah ammohiacal pulp followed wifk redaction by hydrogeh of the complex nickel compound to produce metallic nickel powder. The Garfield plant pses an oxidizing, acid leach at elevated temperatures tihd pressures to convert cobalt and nickel sulfides into thesulfate form. The leach solution Is fijtered from the residue and is then neutralized using calcium and ammonium hydroxide to prec i pi fate iron and other imparities which are separated |h a S econ d fi ItraHoh step . Copper then is removed from the leach solution by aementdtion pn metdl^ The Garfield plant, origindlJy designed to produce a metdlj 10 coba I Mntcke I pawde r by reduc tion with hydrogen of tha amhW niacql solatioh, now employs a less costly electrowinning process to recover pure .-.aobdiH^ _ - : ; ; '/ 3. "Sherritn-Gordon Uses Ammonia Leach for Lyne Lake Nickel-Copper-Cobalt Sulphides", Mining. Engineering , Juhe 1953, pp.-577-581. 4. Mitchell^ j. S., "Pressure leaching and Reductlon at the Gdrfieid , Refinery", Mining Engineering^ November 1955, pp. 1093-1095. 5. ’'Continuous Recovery Ciits Cost, Boosts Yield"> Chemical Week, January 11, 1958, pp. 68-69. V V ? Experime#di Work Wt Leaching of Copper _ Minerals at EI.evQ.fedl. Temperatures and Pressures jn meehf years consl(fedB.le .experiitiettMl; work:ia *l^ sufphida nfiitiemls empioying’eleyaied teirtpei^tores pmssur^ has beeh conducted :tih tha ^ Experiment Statiori of the Unifed Stofes Bureau of Mines. The studies were initiated Ih, 1954 when J o T0 Momnisen^ studied the dissolution. of Oo^er frorn chalda^rite^, Usirig d Pdrr rockep-type pressure reactor it was found that chalappyrite cou ld he oxidi S e sajyelit generated used to dissolve the copper content.,, Copper extractions of 99 per c e # were obtdihed in ope hour-at 200 degrees Cen;t]grade using; an oxygeh pattiai pressure; of 300 pounds per square inch. The principal operating difficulty wUs corrosion of the eguiprnent in the yic W 'J C «, TVerberg continued fhe experimehtal work:on the pressure ledching of chalcppyriteo Tyerberg:us#d a impeller type auto- aitiYe^t0: itiinitrtlzse the effects of corrosion encountered by Mommsen and to improve agiW^ Copper extraction of 97 per cent wds obtained in 10 Minutes at 200 degrees Cahfigiade Us|ng; dp oxygen parfIdl pressure of 100 pounds per squdre inch with an iMpeiipr speed of 500 f e v p ^ a pefipheral speed of j^ i 97 fuet per minute0 Results of the experiment work using 60 Mommsen^, opo. cit o y pp0 35-37 0 : • 7o Tverberg ^ J0 Co^ The Dissolution of ChOi copy rite at Elevated Temperatures and Pressures^ Part 11, Thesis, University of Arizona, 1956, pp. 71-73. 5 air insfedd of oxygen as ah oxidant at 600 pouhds per square inch'gauge pressure showed that a. retictioh. period of six times, as great wets required as compared to when, <>>^en wds emplc^ed, Rv So Kirby^ cohducfed studies on chdicopyrite and chdlcocite using the •equalized pressure chamber impeller type autoclave tind investigated the influence of such variables as pulp densityr particle size, ahd temperature = The conclusions stated by KiAy dra ds follows: Chdicopyrite I s When using d digestion time of 30 minutes, d pulp density of 7.^ per cent of solids, a ten^erature of ah agitation speed of 1,000 revolutions per minute, and a partial pressure, of oxygeh of 100 pounds per square, inch; the per cent of the copper dissolved incredsed from 18073 to 92o35 as the pdrticle size wds decreased from m i#s 3$ %^% 2» By extending, the digestion time to 45 minutes, a comparable extraction wOs. obtained from minus 100 plus 150 mesh chdlco- pyrite as wOs obtained from minus 325-mesh material when a digestion time of 30 minutes, wds used® 30 When a pulp density of 33.3 per cent df solids, consisting of ‘ a charge of 150 grams of concentrate and 300 milliliters of . wafer was used; dn extraction of 8 0 .TO percent of the copper was obtained usingja digestion time o f 90 minutes, a tempera= ture of 200 degrees Centigrade, d partial pressure of oxygen . • : of TOO pourtds per square inch., and an impeller speed of 1,000 per minute,, 8 . K'rby, R.S., The-Dissolution of Cha I copy rite and Chajcocite at ^leyated Temperatures and Pressures, Thesis, University ol;Arizona., 1957, pp. 61-64. . . . - . 4o , A maximum of 97*31 per cent of fhe copper could he dissolved when usi.hg.c( total pressure of 600 pourids per square irtch gage, a temperdture of 200 degrees. Centigrade^ d digestion, time of 60 mihiites, without usihg a continuous flow of dir through, the ' reaction bomb* When a total pressure of 480 pounds per square inch gtige wtis used. It was necessary to mdirttdin; a flow of dir of 240 liters per hour to obtain a dissolution of 97*92 per cent of the copper* At a totdl pressure, of 360 pounds per square Inch, the maximum, per cent of the copper dissolved wds J1 *90 when d flow of air of 240 liters per hour wds used* Chclcocite - ' t * Using.oxygen, water, and chdlcocite concentrate as the only reactants, d reaction time of ohe hour, a temperdture of 200 degrees Centigrade, d pdrtfd| pressure of oxygert of 100 pounds per square inch, dndgitatfpn speed Of 1,000 revolutions - per min.ute, drtd a pulp density of 4o76 percent of soiids resulted in dn extraction of 35*78.percent of the copper* 2* When sulfuric, acid, wds added to the charge, 99 £,78 per cent of the copper was found to be dissolved when a reaction time of 30 minutes, d temperature, of 200 degrees Centigfctde, d pulp dehsity of 4*76 per cent of solids, d partial pressure of oxygen of 100 pounds per squdre inch, and.an agitation s p e e d o f 1,000 revolutions per minute were used* 3* ^ Cdhsumpfion of the sulfuric acid which was added to the charge was found, to i?e 0*63 pound of sulfuric acid per pouhd of chajcpcife when an extraction of 99*16 per cent of the copper was obtained * The theoretical consumption of acid for pure chalcocite was found to be 0*62 poUnd of sulfuric acid per pound of chdicocife* 4* When pyrite wds added in place of acid, the maximum per cent of the copper extracted was found to be 98*57 per cent wheh 0*67 poundsof pyrite wns ddded per pound of Chalcocite* All of the other variables were the same ds.when acid wds used except that the pulp deMsity wds 8*3 per cehf of sal ids. 7 So When, temperatures of less, thbri ISO degrees Cenfigrtide arid a digest!art. fime of less than 3 hours, were employed using d pulp density of 4 076 per cent of solids, .dhd-an dgitatioh speed of 1,000 revolutions per minufe; the mdximum per tiedt of the copper extracted was found to he 81 *62. Using d. time, of 30. minutes^ 97*80 per cent of the copper wds extrdcted wheWdsigg d; temperature, of 186. degrees Certti- . grdde * Using d digestion time, of 7 tninutes and a temperature of 200 degrees Centigrdda, dn exfrdction of 98*07 per cent of the copper.wds obtaineds. 6 0 As the dgitatioh speed was decredsed helow 650 revolutions per minute, the eXtrdctlon of the copper decreased rapidly from the vicinity of 99 per cent when a time of 30 minutes, a temperature of 200 degrees Centigrade, and. a pulp density of 4.76 per certt of solids were, bsedh 7c . Extinctions in the neighborhood of 99 per cent may he obtained when using a pulp density of 25*9 pdr cent of solids, d time of 45 minutes, d temperature of 200. degrees Centigrade, drt agitation speed of 1,000 revolutions per minute and a partial pressure of oxygen of 100 pounds per squdre inch* Solutions with A copper concentration of 20*34 per certt of copper were formed when a pulp, density of 25*9 per cent of solids was used* 8* The partial, pressure of oxygen, whbrt usihg pure oxygen ds . the reacting gas, had no influence on the dissolution rate of the chalcocite when pdrtial pressures of oxygen greater than 25 pounds per square inch were used* 9* Particle,size in.the rdnge of 35 to minus 325 mesh had very little; influence on the dissolution rate of the chalcocife* The ayerdge oxygert consumed by the reaction wds found to he 0*64 gram,per gram of chalcocite* The consumption varied from 0 *56 fb 0 *73 gram of oxygen per grdm. of chalcocite* Jhp time required to obtain extractions of greater than 99 per cent of the copper wds fourtd to be -approximately six times as lortg when using dir as when using oxygen with, dll dther conditions bdirtg the same* Ii wds # e objec'r of the experimental work described ih this pdper to copper sulfide itiiherals by experimeittdl work.with boitiite qnd covellite. . it was also the objective of this paper to Undertake experimehiai wqrk on the Iedch lng of cemeht copper and commercidl copper .concen trates s m : ' . : v ' - v' Borniie Concentrdtes The wsej;the tests was harid pickedi from speGimeh grdde mdteriai obtdlded from Company, Superior,, Arizona. Thematetial used for most of the tests was dry crushed^ wet ground, and the borllite separated by fiotptWn from analkdline pulp usihg ethyl xanthate col lector and methylisobutyl>= cdrbitiot Wotliere , ^ pdrtlal ehemiddl aiidlysis of S o, eonoehtrate: fblldwss ^Constituent Per Cent Copper ' 54.73 1irors rAn : 9 3 Sulfur . 24.1 Zinc o j Insoluble 0.2 99.03 • si zing ahdfysis of tho^^p^ is given below; Size^ AAesk. - Weight; Per Cent Minus TOO plus 150 3.0' lt 200 " 270 9 .2 -'K / « m * m ra-: Ir 325 « 20*^ 51.2 V /y:; / ':,20^.\: : : " ■ ' : 12.0 : * Microns . ' V . M other opnoeOtrdte o f fh® minerol ajso wds prepared By wet grinding the . ; ■. ■■■ . . ■ , to This Qonceiifrdte was screened to produce different sized fractions befween SS and 270 mesh for tests to determine the influehce of particle size on the dissolution rate of bornite. Assays of the various sized products are giyen below: Size, Mesh ., Assays^ Per Cent I, Copper: Iron Sulfur Zinc insoluble Minus 35 plus 65 i-# . 0 5 ; 9.26 21.9 0 .2 0,5: * 65 A TOO : 63.27 9,30 24.3 0.15 1.0 “ lOO « 200 63.68 19.13 , 24.1 0 .2 ■ 1.0 ,r 200 16 270 63,67 9. IB 23.6 0.3 1.1 L. GoveititeCtihcehtrdfe A smdil specimeh of reNfiv^iy pure cbv'ellite^ obtained from the Geology Department of the University of Arizona^was used for the tests ihvoivi rig cove 11 i te „ The specimert was dry crushed arid dry gound in a porcelaih mortar«, The ground material was sized and the individual sizes were concentrated with a JFrahtz . Isodynamic Magnetic, Separator wblch yielded bomiter pyrites and cdvetlite as separate |>roduatso The individual minerals were separated by makihg use of chdraat^ristic magnetia susQeptibilitieSo The bomite exhibited the highest suscep- tibi li ty or paramagnetism and pyrite the .[east „ The sampie of coveilite thus obtained assayed as fol lows: Constituent . Per Cent Copper : : 66.32 Iron 0 .7 . . . Sulfur . 30 oO ; Msoluble : .: / '-0.5 , . : 97.52 - ■ ' A sizing analysis of the coyellite is giyert he(ow: Size, Mesh______Weight, Per Cent Minus 65 plus TOO ■ t »5 ,l TOO 11 200 59.3 v " 200 " 325 '' - ^y' x., ;39:«2r; -:\; /V ,. .. : Commercial Copper Cdhcehtrates , Typical copper flotdtioh concentrates of Arizoha were obfained from the Magma Copper Company, Superior; the Old Dick Concentrator of the Cyprus Mihes, Incorporated, Bagdad; the Bagdad Copper Corporation, Bagdad; and the Lavender Pit CdhcehMdar o | the Bhejps Dodge Cdrpordtion, Bisbee» A partial chemical ahalysis of edch cohcentrate wds as fol lows; d y : Per Cent Ounces Per Ion Copper^ '-/Iron' :|2ind: 'Su|fdr Thhdlwble:' Ootd.x'j Silyer . ' Magma 24,72 2AM 0 .2 31.1 8.6 | 0.11 : AM Cyprus 26.68 MM- 10.0 32.6 0 .9 ... o:.oid! 3.05 Bagdad 33.63 19.19 0.3 .27.5 15.1 I . - 1 P h e l ps D o dg e 16.09 32.59 41.76 6 .2 A screeYi analysis of each concentrate gave the following results: Size/ Mesh ;V v ' . 1 Wplght/ Per Cent / ; Magma Gyrpus Bagdad Phelps Dodge Pius 65 0.6 6.2 0.4 Minus 65 “ 100 3.0 0.4 13.6 ::2,4 ■-: / " 1 0 0 * 150 4 .9 0.4 ^ 17.8 7.4 n 150 * 200 7.2 ? : 1,4 ! 14.0 10.2 " 200 ■■'A . 7 .6 / ' ; 3.0: 3.6 : ' ' '9.6/ : K 270 « 325 7 .2 17.8 i .7.4 : 13.0 " 325 " 20* ' '.59,7 ,:: 67.4 ; 24.6 ,50.2 ..... ir: - 20 * “ 10.0 : / ;9.6 -u : ' '7:.8: / -': :6.8/ " *Mierdris The qhd(y$!s of the different co ii^ by micro scopic exdmi#f ion of polished Wqueife suffacgs of the c6nc^entrate& wifk ^ reflecting mlcroscoiDe. ' Thb princlpaf cop|^ of fhe Mdgpd cpnesntrate ehdledpyrite which was dssodiate^ with nito dmouhk of pyHte, gutirtz/ bornlte,, siderife^ speculdrite, sphalerite, arid sporadic grains of chdlcocite dnd covellite 0 The Qidrigpe pdirtic ids s f qtiPrfz arid sidprite. Goritaihed numerousinclusions of c ha I copy rite and pyrite which were; dpprcmimatejy 1 te Sf mrcrons diameter o The Cyprus concentrdt^ wds conipdsed predoWWdnfly of chd Icopy with minor of sphdlerite, chd W covell i % pynfdf quarfz} and gdlend . The forger portion of the minerals were free/ huf there was some liiter- locking between the chdlcopyriie and sphalerite in the coarser grains. The; Bagdad concentrate was composed of about equal amounts of chdlco- pyrite and c hti I coc I te- c ovel ii te intergrowth with lesser amounts of pyrite, qudrfz, and. sporadic grains of feldspars, cdlcite, and muscovite» Most of the chalco- pyritergrdins were padly altered to chalco^ p lanes« - :■ . ■ Examinatkpn of the Mshee concentrate showed that it was composed principally of pyrite with some chdfoocite/rcovellite/bornite, c ha I,copy rite, sphalerite, quartz, and aItered feIdspars» Some of ihe pyrite particles were partly rimmed with thin coatings of chalcocite and covel lite. V-;:-; ^ : Cemenf Copper ■ ; A sample, of Ldyehder Pit cemeltt copper precipitate was obtained from the Phelps podge Corporation, Bisbee, Arizona,, A partial chemical analysis of the precipitate follows: ■ Comfitaerif Per Cent ’y.- : ' , y; ' ' 'v'"1"' ::% p er / ' ' ■: ' m m ' ■ • . ■ • , I roh : \ . / 5 ? T6 :''::y , Sulfur 0,58. ' ... V'';. .. . Ledd 0,55 yZihc : ' S,2d : . \ -■y.;yy'- Tin. : y . y .. ' ' Mh kei . : " 0 .03 ;y . v,;,.,.. ‘ ' Size, Mesh Weight, Per Cent ' .. :' 'PW:Y' <' '..'ZM Minus 6 S TOO M . , 11 100 " T5P - $ . 6 ' : . v.,/.-. . V “ 150 " 200 : ' 13,0 ■ ' ^ 200 11 270 6,0 ' -'-': ''270"; A ' ;:325. ' A # ' ' “ 325 11 400 4.0 * 400 A 20* ■ . -to: ■ - so* ■ . -? ^ -to. .yy : .. " ' v r y ^ ;y''-: ::: y y - ' ^ : y y :: ; ; y- y : y "vv '/ pyrite Concentrate A flotdtion .concentrate of pyrite was prepared from d mineral sample obtained from Go Pi, HoseVeare of the Arizona Bureau of Mines, The spebimen wos dry crushodr wet grdurM, dtid the pyri te: as sepcirdted. by flotatIon from ti sJtghfIy alkaline pulp, using;ethyl ^anthate collector artd methylisobutylcarbinol frather» A ckeWcdj analysis of ihe minus 325 plus 20 micron fraction of the product is giyen helow: ■ ;' ' ■ I’erdent Copper ' Oo05 ^ ."IroR ' .46^4 > ' Sulfur S203 ; Zinc . w Insoluble 0oI :.v : WM- . • Autoclave The experimental work was perfprmed in the. autoclave designed by Tverberg vvhick is shown:Th Figure T„ The autoclave was a two-chamber type which equalized the pressure e f the impe 1 lor shaft packing; gland: and therefore minimized, leakage through the packing . The packing consisted of a graphite and oil impregnated asbes= fos material wound aroundthe impelier shaft and pressed between two cones pf the packing: gland,® All components which were subjected fo corrosion were constructed of type 3T6 stainless steel, . The: volume of the .inaction chamber was 2 ,1 lifers and the pulp was agitated by a 2-inch. diameter downward, pitch Impel ler driven by a 1/12 horsepower,, variable speedy electric motor 0 Anelecfric genera tor-tachometer was connected to the motor fp indicate the Speed of the impeller® Both pressure chambers V/pre fitted with valves for the Introduction of compressed gases and. the bleeding of 9 ® Tverberg op ® cit a i pp, 6“40 ® .x tachometer generator upper chamber cooling coils motor valves flexible cowling water packing pressure gage valve: valve reaction chamber Impeller shaft thermocouple well Impeller Figure 1. Assembled Autoclave (jcale 1:3) & " ' V ■ • ■ ' - ' .14 gases from the pressure chambers e Each chamber was equipped wlih a pressure gauge and a safety valve for pmtection against excessive pressures , . A detailed description of the autoc lave was given by Iverberg0 .Accessory equipment to. the autoclave includeda i^d00=watt electrical heating unit, separate rheostats for control IIhg; the heating unit and the impeller motor, fhe temperature of the reaction chamber was measured with an alumel v 0s 0 chrome 1 thermocouple connected to a Wheeleo Model 330 potentiometer0 The thermocouple extended inside the reaction chamber and into the reacting solution» ^ A gas mefenngoylinder was used'to determine the amount of gas introduced Jnto the reaction chambero The cylinder was fifted wifh a pressure gauger "inlet and outlet valves^.and.a thermometer<> BaSy. bled from the reacting chamber^ was measured b y a ^Precision "Wet TestMeter manufactured by the Precision Scientific Company, ' ' : r" " Analytical procedures Standard analytical procedures wer^ used for determining copper, iron., sulfur, nickel, chromium, zinc, gold, silver, lead,and molybdenum, contents of the solutions ahd residues, ' ■ .: TO, Scott, Wo Wo, Standard Methxads of Chemical Analy^ Volume I, ed0 by N-jg A wbdjfled fnethpd o f i was used to determine the suifuric acid con-” tenf of the ledch solutions Q The method was as follows: potassium iodide was added to thesampieunfilthesolutionturned acledr dark brown GO lor and sodium thiosulfate thon was added dropwise until the solution to colorless <>. Several drops of bromo~ phenol blue indiodtor were added and the solution was^^f of sodium hydroxide until the first permanent b|ue color appeared„ The waste, gases were analyzed for oxygen by means of an Orsai apparatus and the pH of the leach solutions we/e measured by an electric Beckman pH meter. ; ^ ' Standard Test Procedure A 20-gram charge of concentrate was placed, into the reaction chamber of the aufoelave wlfh 49^ milliliters of distilled water to form a slurry which had a pulp density of 4 . percent o f sol Ids. , Aiter the autOclavre: wds assernbled oxyge infroduced^df a partial presu to ef 50 pounds per square inch gauge and then dischat^ed to the atmosphere® This purging procedure was repeated, three times to assure a sub stantially pure oxygen atmosphere in the reaction chamber. Wi th a I ( ya | ves c l osed f he autoc laye then was heated to a tempera to re of about 185degrees Centigrade with infermittent agitafion to prevent sintering of the . concentrate. At this temperature oxygen at a partial pressure of 100 pounds per charged into the reacho agitation was I I . Keyes, N 6 A=, Innovations in Copper Leaching Employing Ferric SulfaterSulfuric.Acid, U. S. Bureau of Mines Bulletin 321, 1930, p. 64. Initiated at T,000 revolutions per minute or a peripheral speed of 52306 feei per minute a Immediately after oxidation of the concentrate began, the exothermic nature.of the reaction caused the temperature to rise to the desired temperature of . 200 degrees Centingrade in a peripd of about 2 rriinutes 0 The reaction was allowed to continue for a period of one hour with the temperature being; maintained as nearly as possible at 200 degrees Centigrade and the partial pressure of oxygen at 100 pounds per square in ch ,. After one hour the agitation was stopped and the test considered completed o The autoclave unit was removed from the heater and was cooled by quench- ing in water0 The waste gases then were bled from the reaction chamber through a prec is ion wet test moter and into a col I ec ting bott|e« Analysis of the gases was made;by means o f an Orsat gas analyser =, The consumption of oxygen was calcu lated by subtracting; the Weight of oxj^gen in the waste gases from the weight of oxygen introduced ihto the reaction chamber» The weight of the oxygen introduced Into the reaction chamber was found by the equaHon W = 90 a89 Q(P] " P2)/T where W was the weight of oxygen in giomsy PT aroid^,. the ihitial and final pressures of the gas in the metering cylindei^ T, the absolute temperature; the per cent of oxygen in the gas entering the reaction chamber; and?i3eB9> a constant which was deter mined by considering the universal gas constant^ the volume of the metering cylinder, and necessdry'conversion Wdtoie$ The weighf of oxygen in the waste gases was determined by the equation W = 0.513 PVQ/T where W, Q ,. and T were the. same, as ■ : ':'V" ; : V 19 d^s^n bed; I1 wds th# Mrotnefcle pressure in/ jrilJ I imsters of mercury; Vf the Volume of waste •gdses; 0 b513, a constahf arfived at by 'considering the universal gas eonstaht and the necessary conversion factors0 After the removal of the wasfe gdses fhe autociave was disassemb led and its contents.remoyedo The leach liquor and leach residue were separated by filtra= lion o The volume of the (eaoh I iquor was measured, the pH determi ned, and a sample taken for and lysis 0 The reslduewas washedwifhdlsti lledwater until the oddition of ammonia, to fi ltrate fai led to indScate the presence of copper^ fhe volume o f the wash solufton vms; then medsured and a sampid token^to » The resulting residue wds dried in;ah oven at 100 degrees Cenfigrade, weighed^ sampled, and then assayed o The extractions given in the tables whieh follow have beeh cdiculdted ffom the assays of the heads and residues® : A comparison of the exfrdctions based on the assays of the residues and the extractions based oh the assays of the l iquors has shown agreement within, one per cent of each other® . |n the tests vvhich fol tow dny deyldtlon from the sto as described is noted® ; ■ . : V-: -f; :/■ 1 ' : ' CtiAPTBiii In, the expen mental work involving the dissolution, of copper from bpmite, : eleven series of tests were made to study the affects of time,, additions of acid or pyrite, temperature, degree o f agitation, partial pressure of oxygen, particle size, the sobsfitutldn of air for oxygen, and pulp density. Dueto the difficultyof obtain ing sufficient cove! I ite. only one test was made. Series I - Influence of Time pn the Dissolution of Copper from Bom ite Under Oxidizing Conditions. ^ ; : .' ; This series o f tests was conducted to determine the effect of time on the dissolution pf copper from a slurry of bornite and water using oxygen as the oxidant. The sulfuric acid produced from the oxidation of the bornite supplies the sulfate ion required for disrolutibn; of tho Sppper. The test procedure employed was the same as the standard test procedure preViously described s The reaction period was varied from 15 to 120 minutes, ^ are given in Table l, analysis of the residues and leach solutions a # shown in{Td^ 21 Table 1 o - Ihflueh Ti#ebn flie Copper from Borriii'e under ' Oxidizing CdndifipnSo : . pissoTution. |. . Free acid'^ ' .:' dime>-.' -: ; Copper dissolved, S lb . su ifuric a a ld pH of (each m inutes V;- - 'p e r o e h t. - ; , ' I per lb. borhife |;'Solutions;/ ' ■ _ : . ^ ! ' : ::: % 0.0 56.05 0.0 3 .5 . ■ ■ ■■ m .83 ■ " ;■ 0.0 ; . ' ' - M . 59.79 ‘ ^ 0.0 I 2Q 0.0 Table 2» - Assays of Residues and Leach Solutions. Dissolution > .} Assays V- ■( < ofr ? ■/ leach - liquorr •.* .* ■">' - timer / grams per liter ; Residue assay, per cent ^minutes Copper Iron, Fe" f: Iron, Fe! Copper |roh Sulfur / .: : 15 ' ■ 9.30 v 0.31 0 .0 2 52.22 :V'9.5':';- Td=8 30 17.20 0.03 0.04 41.53 12.7 : 9 .6 ; / : # : - . i7«4i 0.03 0 .0 2 41.64 13.3 8 .0 / ;;■ ■ 90 /- 23.89 0.04 0.03 ' • ,41 ,064 : 13.2 7=2 d m - 19,76 0.00 41.22 13.9 : 7.2: * Cannot be. explained by author. , Interpretation of Results: * ' ^ was expedtedf the sulfur contenf of fh to supply all of the sulfate ion needed for complete dissolution of the copper. . Dissolution of M .05 p # cent of the oopper was obtain 30 Whutes a^ to 120:'rr|inutes the dhsolufioa was incredsed tp' only cent. The consumption of oK^a^ amountedio I pounds per pound of copper dissptved-and, as noted, in Table 2 , Wee acid was riot found in the Teach liquors. The maximum amount of i ron founxi in solution was 2.65 per cent of the total irdn of the bornite. The forger portioh of the Iron formed a hydra fed iron oxide which gave fheresiduea reddish brown color. Series 11 - Effect of the Addition of Sulfuric Acid on the. Dissolution of ' .- .v Copper from Bornite. f y - : fhe use o f suIfuric; acid:fbr suppi)dng:isujfote ion> in addition to that formed by the o>ddation of sojiof in the charj^ if complete dissolution; of the: copper could be otoaihed« The sidhddni/ procedure was followed except &af yorious amounts of acid were added fo the charge. Thespesults of these tesis are syrhnwrlzed iii Tables d Orid ■ 4. WBIe 3 » Effect 6 f the: Addition of So I fbric; AO id on the ^ISissol uti on of ; • Copper fiom; Bornite for a Seec tion . Period of ©fre Hour . Sulfyric acid ' lb o per lb. per cent C a p # ‘.V free acid/ ■ phi ©f Oxygen consumption j ' ; ',of' :' ; : 5 -'o f ,,., dissolved^, (b. sulfuric acid leach lb. per lb. of bprnite soiwtiorj per c e n t, per lb d bornite; liquor copper dissolved c o o c oo 0 . # 0^0 T 58.85 :%4 0.25 ; T.2 ; 90.43 |.2.9 1 O A QO Q-Z ■ A OO U o OU- , A-0-41. Vo A w ]1 °4A ■1 % v oYZ 0.75 3.6 - ; :# 3 5 : ; ' 1:: 0.26 : 1.0 ti oUy. An' Am • OO KQ1 a Ay " yA''' e /, T7" A ■’ ■ ' ::yT;:=:25;; . : ;;W . 99 .75 : : : ■'■0>58 O dd ■ - ;0d82 Table 4 . - Assays of Residues and Leqch Liquors. Sulfuric acid ^ ledcbliqyois, Assays of residues/ per cent odded> IbAper ;;}g;rams^per-v|iter .'n :::' ; | Su lfur as Sulfate |b . of borni te '-Capper' i r o n y # ' j'lron/ Copper Iron sulfide Ian 0 .0 0 1 17.41 0.03 0 .0 2 MM:' 13.3 4 5 .9 1 ; :> 7.02 0 .2 5 ^ : :;A' 28.67 0.07 1.60 * 19.06 36.5 2:o97 . 4.18 0.50: 31.64 ’ 0.08 0.09 'T.6 0 4 7 .4 ;.::To.77!-. 2V30 0-75 35.13 0 .0 2 0.13 : " 0.87 48.0 1.79 2,56 1 1 oVV" Woi 1 d# on V VA 0 AO'^6 , ■ ...U;oOyA EQ: A-U oOV ZA nrQ-o.y.AQ 6 • ■AO oVOQQ' Q AQ T.25:: ' 32^09 0.05 27.2* 3.19 3.11 Snterpretdtion of Results: ; The. addition of sulfuric acid.in the amount of 0,50. pound per pound of bornite was sufficient to give a copper extraction of 98096 per cents This is aboye the 0o20 pound of sulfuric acid per pound of bornite which is theoreticaliy needed and the- difference was dffribufad fe an excess of acfd. needed,for equilibrium and to the unavailable sulfate ion which was absorbed by the residue. were encountered in the tests with acid addifions of f ,00 and T025 pounds per pound of bornite, ffee sulfur was found in the reacfion chamber W . Series l|| ° Effect of Substitution of Pyrite for SulfurieAcid on the Dissolution of Copper from BOrn ife 0 The purpose of this series was to determine |f the sulfur in pyrite could be converted fp the sulfate ion a ^ dlssolutldn of the copper. The standard procedure was used except that various amounts of pyrite were addisd to the charge, Tuhles S and d g iye the resu I ts Of th is series, Table 5® “ Effect of the Addition of fyrite on the Dissolution of Copper from Bornite for a Reaction Period of One Hour® Pyfite'added^: v- ID® perljb® eqoivalent Copper Free acid, . _ Of ^ actd.:;jpe'rvl:b‘,<>;; dissolved® lb. per lb® pH of ,- bomite of bomite ' :3peroeht'- of. bornite leach l i # ■ ' ; ’ 'f/. 0®00 . 0,00 0,00 .v's'1 3,4 . . 0®25 0,41 , 98,33 0 t l30.13 ■ I 0®50 0,82 9 7 3 1 * 0.51 ' 0 3 . lv - 1,00 /■ im 99.00 ' d .13 ‘ : 0 .4 • - 1,25 2,05 99,00 1.23 0 ,2 . * Cannot be explained by author® Table 6 . - Assays of Leach lSquors and Residues, Pyrite added, Assays of ileach liquors IjL per B e '' grams per liter Assays pi ' res idues, per cent bornite . Copper | Iron, Fe‘‘ |ron^ Pe"' Copper | iron Sulfur OM ■ XT [ 0.03 4 v'.-;:A'0.=W MM 1 3 .3 - 8.0 0o25 32.4 i 0.03 6.32 3.26 I 60 . 3 2.6 0»50 1 3 0 4 i 0.03 / 0.27 2.83 1,60.3. ; 2.4 1.00 31.2 0 4 3 2.73 0.80 61,3 2.3 1=25 30.7 0,20 6.37 0.46. :46..9 10.7 interpretation of Results: , The acid produced by the oxidation of the pyrite was util I zed in the disso^ IW The addition of 0 S25 pound of pyrite per pound of borniter which was equivalent to 0 e4l pound of sulfuric acid^ permitted a copper dissoiution comparable to the 0 o50 pound sulfuric acid per pound of bornite tested in Series it ; The Wlurd fhdn 99 per cent wds attributed to soluble copper being absorbed by the residue ® When pprite was addedT of that necessory to provide the acid to dissolve the copper the ferric ipp increased in the teach liquors ^ Series IV - Effect of Time on the Dissolution of Copper from Bomite with the Addition of 0o50 pound of Sulfuric Acid, per Pound of Bdrnlteo The purpose of this series.was to determine the effect of time on the disso- iutipn of the copper when sulfuric acid-was added to supply the deficiency of sulfate ion Q Since the addition of 0 o50 pound of sulfurlc acid per pound of bomite was found to be sufficient to give 90 696 per cent dissolution of the copper in Series 41, the same amount was chosen for this serleSo , The standard procedure was fol lowed excepf that ac id was add* sd to the chai *ge and the reacth >n time was varied from 7 to d i0 minutes „ The results of this serle# dre listed in Tabl e 7 o Table?, ” iffeet of Time < >n Dissolution of CCopper wi th the i kddifion of 0 ,50 P*sund of Sulfui ic Acid per Pound1.of Bornite, Free dcid in. - Added acid bissolution leach solution^ consumption. Iron in leach. liquors fime. dissolyed. lb, per lb, of lb,, |>erTb=> grams per liter minutes percent bornite Of bdrni te .jren,:Fe,:r' Iron, Fe"8 7 ' ' W ' : ■ ■ 0,34 "0,25 0 bT2 rt A QA A AC A AT - " v® 6 o U oOO UoUD U oU I 60 W ,96 | QoS? ' 0t08 0,09 inferpretdfionof Resulfs; Btsspiyj'roirt pf the copper from the bomite wds rapid In the presence of excess dcjd Iphd 9 T ,80 pervcenf of the dissolution of the copper was obfa ined in 7 mi nutes # # tatter increase in djssoiution of copper was probably due to the smali percentage of larger sized particles o f bornite in the charge , Sincethe majar portion of the reaction mu$t'tdke'.pidce. a? tfw suffa particles^ having a smaller area unit volume than the smaller sized, particles, required a longer reaction time, '■ ■ ' ;; ^ ; ■ ■■ ’ ; / ' ' . ■ . ' : v The iarger amount of iroh reported in solution during:the 7=minute test was believediron sulfide of the bornite reacting with the free sulfuric acid wbieh Was present at the beOihning of the test most of the Iron wds found in S e residue; as hydrated Ibbh oxide. Series V - Effect of Time, oh the dissolution of Copperfrom Bomite with the Addition of 0 .25 Pound of Pyrite per pound of Bomite. If was the purpose of this series to investigate the. rate at which sulfate ion obtained from the oxidation of pyritef could be utilized in the dissolution of the . copper. The procedure used/was the same as the standard procedure except that pyrite was added to the charge and the reaction period was varied between 30 arid 120 minutes. The addition of 0,25 pound of pyrite per pound of bomite was shown to be sufficient to give 98,33 per cent dissolution of the copper in Series HI and therefore the same amount was employed.in this series, . This amount of pyrite is equi valent to 0,41 poundofsulfyric acid. Table 8 gives the results of the series, Table 8 , - Effect of Time on Dissolution of Copper with the Addition of 0,25 Pound of Pyrite per Pound of Bomite, ' .' ' " V ■ ; ;:' Dissolution Copper Free sulfuric timer dissolved, acid, lb, per pH of iron In l e a c h 1 iquors minute ; per cent j lb, of bomite leach liquors T , 30 r • ■ 95,16 0 ,0 6 V.. ' J -,d ' : ; ! 0 ,6 s 0,30 ' ■ 98:,i3 0 .8 0,03 <';S,27’ 120 98,82 0 ,7 a . # do 12 interprWdfion of Results: Dissolution of 98,33 per cent of the copper was obtained in a period of 60 minutes, A longer period failed to increase copper extraction or to increase the free sulfuric acid content in the leach, liquor. :/ . : ' 27 . ! - An . increased, reaction' per tod i'dweTedtke: gmount;.'offerric. iron In solution From 0ff30 grom jper in 3Q mmu^i W 0 ® 12gmm j^r liM 1ft 120 Trtiihu*6s0 A ygiue-of 0 =03 grom of lerrouS; iron!per fiter in solution-appears to be fhe equilibrium @mbu# under fke gggdiffphs enpgunW^ Series VS - Effect' of Temperature on the Dissolution of Copper wii,h 0 e50 Pounci ofSutfuricAcidAciciedperPounclof.Bornitee liie purpose of this, series Ws; to d^temtlin% of tetir^eroturo gn fhe djssolufiprt of the copper from bomii-e 0 The standard procedure, was followed;except that the. temperdture was Varied, from 100 Ip- ^0: degrees Gentigrode urid 0 .50 pound of sulfuricracid was added pound of bomite. The results are shown in Table 9 „ Table 9 9 - Effect of Temperature on Dissofution of Copper for a Reaction Period of One Hour & 1' V - Temperaturej. 1 Copper dissolved^ Assays pf ledeh SblufioriS/ degree Centigrade.! per Cent grams t?er (iter Copper Iron/ Fe" Iron/ Fe8" : - ' - TOO W .30 # 5 2 0*01 0*03 150 90,37' 29*43 0.06 0*00 200 9BM 31*|4 0*08 0*09 ■ v":vT"';v ...... _. Interpretation of Results: The results the rate of ditooiufion o f the copper with an increase in the temperature* Tests were not made to determine the posslbiiity pf ipcroasing the dissoiu#^ by employingyan extended reactip^ fWe at 1 # degrees CehtlgWe^ Merles Vti ^ Effect o ff he Peg ree of Ag I fa j-ion ofi-hePuipw? tKO «50 Pound of SuIfuriG:Acid'Addeci per Pound of Bomife» r -.v The Msk this were mjQdent^ pf the speed of agltdtlp# dissoiution of copper from bornite for a reaction period of dO minutes when 0 o50 pound of sulfuric acid per pound, of bornite was added. The procedure used wds ihe. same as the standard procedure, except that acid was added to the charge and the speed of agitation was varied from 250 to 1,000 revolutions perminufe. The results are shown in Tdbje 10 o Table 10. “ Effect of the Degree of Agitation of the P.ulp on Dissolution of Copper 0 Speed 0 ' Agitation Copper dissolved, Assay Of l edch liquors, Revolutions Peripheral speed, per cent grams per liter per minute feet per minufe Copper Iron, Fe” ' iron, Fe:Ht 250 ' -1306:9',' r:,: 99.46 29,49 0,07 0.00 s o o 261,8 98.65 0.04 0.05 1000 523^6: / " 98 S6 31.64j 0.08 ■ 04)9 Interpretation of Results: The results indicated that the speed of agitation did not affect the.dissolution of copper when acid, was added to th ee barge and a reaction period of 60 minutes was used. The environment in the pulp became more oxidizing with increased, agitation as shown by the amount of ferric Ion in solution. Although, the results did not indicate an appreciable difference in the disso^ lution of the coppOr for different degrees of agitation for a period of 60 minutes, it cannot be assumed that a difference wouId not appear in a period o f 30 minutes. Series VIII - The Effect of the Partial Pressure of Oxygen on the.-Dissolution of the Copper with 0.25 Pound of Pyrite. Added per Pound of Bornitel This series had two ob}ecf?Yes| the JTret was to various partial pressures on the rate of dissolution of copper and the second wos to deternflae Jf h igher dfssiolotion o f eopper could hevob^lried at relatively'low oxygen partial pressures if extended reaction periods were employedc The standard procedure was fol lowed for both objectives except that in the first the oxygen partial pressure was varied using: a reaction: periodof 3d miriufes, and id the second the time was varied ahd thd partial pressure of Oxygon was held at 25 pounds per square inch gage 0 An addition of 0.25 pound of pyrite per pound of bornife was made to furnish:needed Sulfatp ion. The results are given in Tables 1 l and 12. fab!e 11 o ” Iffect of the Pdftlal Pressure of Oxygen, on the Rate of Dissolution of Partial pressure of oxygen, Assa)/s of ieaqh llq uors. pounds per square Copper dissolved, gramsper lltei inch gage percent Copper Iron/ Fe" Iron/ Fe' ' ' 33.52 ' ii.oi’i . 0.36 0.21 ioO : 95.14- ' ; 29.90 0.05 0.30 200 98 M 3 2 .# 0.05 0.03 % & lable, T 2^.:'- Effect <)f Longjer Reaction Periods at an Oxygen Partial Ph 1 25 Pounds per Square Inch Gauge on the EXi$solution of Cc>pper. ' ; ■ Assa)A of jepch liq uors ' Tlme^ ; : Copper dissol ved/ ■ : .. . . • 1grdms per life! r- 'd' - . ■ / #inut#. ; per cent Copper Iron/ Fe" Iran/; Fe'" : so 3d. 52 11.11 0.36 0.21 .. "'im- 98.17 - 0.10 0.03 ::- r[ : 120 ' ' 98.25 : 31.96 0.03. 0.10 , y 3 0 - Inf^rpr^tgtT^h of Ftorri the results shown. ih Tlablo I T It wds Wfermtned that till Tnoretise in parttef pi^swe of <3]^ei^ in^mds^ the dissolution of the copper. The author offers three: possible expIqncitions for this effect on the dissolution. First, an increase in the parfla! pressure would: Inorease the amount of oxygen dissolved iri the 'pulp maldpg ^ Second, since the reactions proceeded with a decrease in volume of gases, increased pressure favored the formation of the products duetto an tippiicatloh'of the j^Ghafejiei^ Braun princlpie of mobile equi iihrlum- Third, if during the oxidation of the particles of bornite the unreacted sulfides ; becatne ericlpsed in ah iron oxide envelope through which the oxygen diffused inward to readf With the suifldes, t the oxygen partial pressure would aid the diffusion, process. It seems reasonable to assume that all the factors would apply, each to a va^ The results shown; la W demdnstrgted that 98.25 per cent o f the copper could be dissolved using an oxygen partial pressure.of only 25 pounds per square inch.;gauge and an extended reaction period of 120 minutes. Series IX - Effect of Particle Size on the Dissoluilon of Copper with , 0.50 Pound of Suifuric Acld added per Pound pf Bornite . This series of tests was run to investigate the influence of particle size on the rate: of dissolution of copper from bornite. The standard procedure was followed except sized bornite was used and#.50 pound pf sulfuric acid was added per pound of bbrnita. The results pf W sserieeare g iw 13. 31 Table 13, - Effect of Particle Size on Dissolution of Copper, A s s a y s of leach liquor, p article size/ Copper dissolved, : grams per l i ter , mesh per cent Copper iron, Fe" lion, fe'" Minus 3 5 plus 6 5 ' 95,81 30.09 0,08 - .O .S : " 6 5 " 100 98.04 31.34 0.01 0.10 " TOO " 200 ' V'. 31.84 0.03 0.06 " 200 " 270 , 31.46 0,04 0.03 interpretation pf Resul ts: An ?ncrease in parfiele size causecl a decrease In the disSoly tiori of the copper „ Particles finer than minus 100-mesh showed only ;d: slight change In the dissolution rate: of the copper with a reaction period of 60 minutes. Series X ^ Tho Effect of the l%te of Flew of Air on # of Copper from Born ite w ith 0. 25 Pound of Pyrite Added per Pound of Bornite. the purpose of this series was to determihe the effect of the rate of flow of dir on the dissoiyfion of copper when the oxygen present inair was used as the oxidant. The sfdndard procedure was followed except that a continuous-flow of air at a total ; pressure of 340 pounds per square inch gage was used inthe reacfion chamber and ()»,25 pound of pyrite.per pound of bornite was added to the charge . The results of this series is giyen in the following faWe for a one^hour#gesflon period, tnbi® - ^ Effect of Rate of FlW of Air on the Dissolution of Copper . Air Flow, Copper Assay ^s of leach 11quors Free Acid, pH of ito I liters per dissolved ■ I t • : U S 3r • : lb, per lb . leach hour per cent Copper Iron, Fe" I ron, Fe1" of bornite solutions T60::',v; 95.81 '' ::.;6i,42' 0.T8 0.10 -yam-'. ,,: 320 97.30 73,43 0.20 : 0.41 '"v:.boTt./::::. i . i Interpretation of Results: A dissolution of 97 = 30 per cent of the contained copper was obtained in 60 minutes with an air flow of 320 Htern per hoyr => This compares with 98,33 per cent d issolution of copper pbtairied In Series Y where an ixjienticdi reaction time dnd amount of pyrite were used with an oxygen atmosphere. The 95,81 percent dissolution obtained during, the test using 160 liters of air per hour compares favorably to the 30-minute test of Series V where 95„ l& per cent dissolution of the copper occurred, ^ : : The continuous flow of # r through the reacfion c oxygen concentration at a level which permitted oxidation of the bornite ond pyrite to proceed> Additional heat was r6quired during this series since the air introduced into the reaction charriber was at room temperature and there was evaporation of the water into the unsaturated atmosphere of flowing air. Series XI - Effect of the Puip E)ensity on the Dissolution o f Copper with Additional Sulfur Supplied, ! ~ ■ ' . ■ ' ■ ■ . - The purpose o f fhis series was to determine if complete dissolution of the Copper could be obtained at higher pUIp densities thus allowing better utilization of machine capac i ty and recovery o f copper sulfate crystals from saturated solutions. The tests Were carried out using the standard procedure except fhat the pulp density was yaried, the necessary additiondl sulfate ion was furnished, and the filterihg operation was modified. Upon quenching of the autoclave, copper sulfate crystallized out o f solution and was contaminated with ferric hydroxide which made the separation of the ferric hydroxide by filtration impossible. This obstacle could have been oyer- come by Oiffer reheating die solution or by dflufing iti :A combination of the two was finally used. In the tests of this series, the quenched pulp was diluted with 200 to 800 milliliters of boiling water just prior to filtering which proved to be successful in qi lowing the separation of # hydfWde . ^ recovered, from the di luted filtrate upon cooling. The resultsof this series are given in Table 15 and the solubilities of copper sulfate in wafer at temperatures up to 130 degree? Centlgixade are .givrn in Tdble Table 15. - Effect of Pulp Density on the Dissolution of Copper. Addition of sulfate ion |ulp.denstiy^ Copper Amount, Assays of leach liquors,* per cent dissolved, perjb. of grams per liter solids per cent Methpd r Time bornlfe Copper ;vlrOh>:,Jlel!:r:' Iron, Fe^ ' : 4.8 MM .acid;. start 0.50 31.6 0.1 0.1 10.0 99.63 acid start ! 0.50 ' •. 75:. i 0.0 0 .4 25.0 96.63 acid start 0.50 312.7 3.0 29.4 35.0 99.36 acid start : 0 . 50 476.4; 10.9 27.0 35.0 99.16 acid stage 0.50 475.4 16,2 29.0 3 5 # * 97.30 pyrite Start 0.25 271.2 4 .6 3.5 * Based oh original volume of leach liquors. '** Solids included.bornife.and pyrite. 34 TpdbJe 16o -- Sol ubi I Ityof Copper Sulfa fern Water. • Teniperatufe> Copper sulfdtd, Copper, degrOes C ent# v ■ , grams per liter grams per‘l iter 208 " ■ •' 83 ■ ' ■ c -. ; # : 244 n : '■■■ .. 40. • : 287 ' ■ ' 114 ' ■vr :334 133 ■A-VO: ■ • \ 365.^ • 146 ’ 4" ' ' 60 ' 390 ■v ' 155 . - ; 70 ' 456 . y ■:y 182 so 542 : 216 . ' 90 \ : 673 268 so o .. ' 305 '■ : n o 78a ■: 3 ii ; 120 : v;; 2 9 r - ■ ‘ 317 . ; . 130 323 * Based on calculations from data in International Critical Tables. Interpretation of Results; ■ ' V -' ;: Pulp density failed to produce a pronounced effect on the dissolution of copper fbr reacSon^peffpdis bf oho hour if the deficiency of sulfate ion was furnished by acid. Analysis of the crystals separated from the saturated solutions showed a pure copper sulfate content of 99.52 per cent for the intermittent acid leach and 99.77 12o Bronsted, J. H °r "Solubility of Salts and of Strong Acids and Bases in Water", International Critical Tables^ Vol. IV, ed. by E. Washburn., McGraw-Hill Book:Company, - Inc., Hew York, I928r p^,: 223:.. per cent for the pyriie subsHfytiorio To avoid dilution of the I each l iquors i f was suggested that a heated pressure filter chamber be used for the separation, of the ferric hydroxide from;the pregnant liquor,, |f this equipment were used up to 72 per cent of the copper theoretically cbu Id be recovered. ss the su I fat e when the: filtrate: was cooled to 50 degrees Centigrade as indicated quantitatively in Table 15. As the puIp density wos increased the hMh initiaI adid concentration caysed seyere corrosion whereas the intermittent addition of the acid reduced the Corrosion arid the substitution of pyrite for acid remedied it Comp^ : When fhe def iciency of the su! fate ion was furnished by the oxidation of pyrite the indicated dissolution of the copper was 1.96 per cent lower than when Sulfuric acid was used at the same pulp density. The author believes that the lower extraction when the pyrite was used was partial ly due to fhe time jag in the formation of acid from pyrite and partial ly due to the absorption of soluble copper sulfate by the c omparative ly large; amount of ferric hydiOxlde formed from the pyrite. The high increase of iron |n solution might be explained by the action of the strong initial sulfuric acid upOn the mineral to form sulfates and hydrogen sulfide beforo oxidatiomstarted. - - ‘ '.d Series XII = Effect of EIeyated Temperatures and Pressures of the Dissoiuiion of Copper from Covellite. ~ ~ Although a series of tests was planned for the experimental work on covellite Sufficient pure covellite could not be obtained for more than one test. The test was made with the addition of 0.25 pound of sulfuric,acid per pound of Goyeijite to insure an excess of sulfate ion in solution. The standard procedure was followed except that ■ '\ ^^\ "7 : :-;; " " ' ; ,' "V/":' : , 36 p- the weight of the covellite was of necessity limited to 9 grams and the redction period was 120 mi nates d Theresultsofthe test aregiven.in Table 17. table |7» " Effect of Elevated temperatures and Pressures oh the Dissolution of ■ : • Copper, ■. v ... - - . . Dissolution jAssay ^ rTiquors, time. Copper dissol ved , g ra ms per 1iter- ■ " minutes per cent Copper Iron, Fe" Iron, Fe’" 12,16 0,04 0,04 Interpretation of Results: - r Dissolution of 96,03 per cent of the copper was obtained in 120 minutes thus showihg that coVell ite was susceptible to ieachi% elevated tempomt^ pressures. This dissolution was. achieved in the absence of an appreciable amount of ferric sulfate» . |t is the author's Jbelief that the failure to; produce higher disso lution of copper was due to mechanical losses inherent to a batch operation. It is quite possible that the reaction time of this test was excessive and. the same dissolution ; might haye been obtained in a shorter time . • Chemistry of Leaching Bornite. at Elevated Temperatures and Pressures Based on the eyidehoe: obtained from the expSrimental work, the author concluded that the following principal chemical reactions occurred during the , dissolution period: • - -■ ■ : ' Primary oxidation converted the copper, sulfur, and possibly the iron present in the .bornite to the oxides by the reactions described in equations I, 2 and 3 . The . .. born]te, CugFeS^r was considered as being a mixture of CuS, 2Cu2Sf and. FeS for simplicify; in Writmg;the chemical equations. 37 (1) 2CuS + 302 = 2CuO + 250 2 (2) Cu2S + 2 0 2 = 2CuO + S 0 2 (3) 2FeS + 3 0 2 = 2FeO + 2S 02 Assuming the presence of a catalytic agent the sulfur dioxide was oxidized to sulfur trioxide and reacted with either the cupric oxide or ferrous oxide to form cupric or ferrous sulfate (4) 2502 + 0 2 = 2SO3 (5) CuO + 503 = CuS0 4 (6) FeO + 503 = FeS04 If a deficiency of sulfur trioxide existed in the vicinity of the ferrous oxide, it is possible that the iron would be oxidized to the ferric state and thus account for the presence of ferric oxide in the residue. (7) 4FeO + 0 2 = 2Fe20 3 If sufficient sulfur trioxide was present, the ferrous sulfate formed was oxidized to ferric sulfate by the following equation: (8) 2FeS0 4 + S 0 2 + 0 2 = Fe2(S04)3 The sulfuric acid added also reacted with the cupric oxide to form cupric sulfate. (9) CuO + H2SO4 = CuS04 + H20 The only explanation for the formation of the oxide from ferric or ferrous sulfate is either by decomposition or hydrolysis. A search of the literature failed to reveal any evidence the decomposition proceeded at the temperature of the auto clave or that hydrolysis occurred at the pH of the leach liquors. Furthermore, 38 information pertaining to the influence of pressure on the formation of ferric oxide was not available. The presence of ferric sulfate probably aids in the dissolution process by the mechanisms shown in the following equations: (10) CuO + Fe2(S0 4 )3 = CuS04 + Fe203*2S03 (11) 2Fe2(S04)3 + Cu2S = 2CuS0 4 + 4 FeSC>4 + S (12) Fe2(S0 4 )3 + CuS = CuS04 + 2FeS04 + S (13) 20FeS04 + 5 0 2 = 6Fe2(S04)3 + 4Fe203*2S03 (14) S + 0 2 = S 0 2 The Alteration of Bornite During Leaching Microscopic examination under reflected light of embedded polished surfaces of the residues showed that the particles of bornite, Cu^FeS^, upon being subjected to the environment of the autoclave altered to chalcopyrite, CuFeS2, and covellite, CuS. This method allowed cross sections of the particles to be observed and it could be seen that the covellite had formed around the periphery of the particle leaving the center composed of bornite with chalcopyrite between the covellite and bornite. At a magnification of 400 diameters the field that appeared to be pure chalcopyrite at lower magnification was resolved to show a Widmanstatten structure where the chalcopyrite had formed along certain preferred crystalographic planes of the bornite, as shown in Figures 2, 3,and 4. There could be two possible explanations for this structure. First, that interstitial leaching had taken place altering the bornite to chalcopyrite and covellite. Interstitial leaching, however, would have involved the acid solvents 39 Figure 2 - Original polished surfaces of particles magnified to 400X showing inclusions of chalcocite. B - Bornife ■ - Chalcopyrite VZ& ” Chalcocite K3 - Cove 11 it© Figure 3 - Polished surfaces of residue particles leached for 30 minutes with acid and oxygen magnified at 100X. 40 Figure 4 - The same polished surfaces as of Figure 3 magnified to 400X showing the Vvidmanstdtten structure of the dial copy rite. E==3 - Bornite ■ I - Cha I copy rite TTTZ - Chalcocite - Cove Hite Figure 5 - Polished surfaces of residue particles after being submitted to 200 degrees Centigrade for 120 minutes In a nitrogen atmosphere without the addition of acid solvents. ;;:V ; ' 41 penetrating info fhe infersiitid spaces of the pqrticI esf |eaching preferentially, and the migration of the soluble salts to the periphery of the particles by capillarity and diffusion. Since the minerals before,and Offer ledching appeared equally dense this ; theory wds abandoned o . : , The second explanation involves the diffusion of atoms to form the new minera Is = The evidence revealed by the microscope indicated that copper and su jfur atoms migrdted from fhe interior of the particles to the periphery white iron atoms migrated in the opposite direction. In order to determine the effect of temperature, pressure, oxidation, Ond teaching upon diffusion of fhe atoms as described a test was conducted using distilled water and sized bornite for the pulp and nitrogen as the atmosphere in the autoclave. A temperature of 200 degrees Centigrade and a nitrOgen over pressure of 100 pounds per square Inch gauge were employed and the original bomite was minus 35 plus 65 mesh. After a reaction, period of two hours thepharge v ^ filtered and ho eyidphpe o f oxidation or leachlpS -was found, although the particles,showed sTgns of abrasion aod slight dlscolorafion . The addition of ammonia to the. colorless, filtrate failed to disclose the presence of copper in solution, A microscopic examination of particles from the above residue revealed a structure similar te that found in the leached particles^ The periphery of the particles was composed of chalcocite, Cu^S, and the center was predominately ibOmite with a few lines of chalcopyrite where the Widmanstatten structure had begun to form as shown in Figure 5. The alteration of the bornite to chalcopyrite 4 2 and chalcocii'e was not due to leaching^ bu'r a consequence of the femperafures and pressures generated in the autoclave,, the diffusion of atoms had taken place . The presence of an oxidizing and leaching environment gppeared to increase the fote of diffusion and to a| ter fhe cha! tide i fe to cove t I ite. Corrosion of Equipment The.environment inside the reaction chamber was inherently corrosive since at elevated temperatures and pressures, the presence of free acid, and in some , instandos hydrogen sulfide Impaired bvbral I corrosion resistance. Jt was apparent that there were two types o f corrosion present during the, reaction period; each- attacking the stainless steel of the autoclave by its own method. One type was relatively slow and was noticeable only as pits In the stainless; &tee!. The other type progressed rapidly and was visually noticeable after certain tests as a uniform surface corrosion. Uhlig stated that for stainless steels corrosion pits begin by a breakdown of passivity at favored nucIei on. the metaI surface fol lowed by the formaf ipn of an electrolytic ceil , the anode which is a minute area of active metai and the cathode which is a large area of passive metal. The potential difference characteristics of this cell accounts for a considerable flow of current with the attendant rapid corro sion at the small anode. Increases in temperature, acidity, or oxygen dissolved in the soiyflons accelorafes thet rate of pitting . t o Uhlig also stated that the presence of copper su lfate and ferricisy jfate, both o f which are found in the leach 13. Uhlig, Ho Ho, "Fitting in Stainless Steel sand Other Passive Metals", Corrosion Handbook, ed. by H. Uhlig, John Wiley and Sons, Inc., New York, 1948, pp. 145-173. ' . ' ' : solutions of this investigation,, retarded the pitting of stainless steels. The afore pdragraph probably explained the pits in the 316 stainless steel which were foundbeiowthesolutionline of the reaction chamber,. The author also cone I uded frpm Uh 1% discussion that the pit ting rat# was reduced in the (atter stages of a test since the amount of copper and ferric sulfate in solution increased as the tests progpessedo : The seyere, corrosion encountered in tests which used a high initial concen tration of acid was attributed to hydrogen syIfide 0 The action of the stronger concentrations of sulfuric acid upon sulfide minerals prior to the beginning of oxidation was to produce hydrogeh^sujfide gas and soluble sulfates 0 Binder slated that moist hydrogen sulfide gas will attack sfSnless steel and that the rate of corrosion is increased when the temperature is raised. In one test which he cited the stainless steel sample was totally converted to sulfideo This corrosion by hydrogen sulfide first became noticeable in the experimental work described in this paper at an acid concentration^of 'Sod per centf therefofe the optirnum acid concentrafiony to safely ;a^oid production of hydrogen: sulfidej, appeared tp he between 2.5 and3.(1. 1 4 . Binder, W. O"Chromium-Iron, Austenitic:Chrom?um-NickeI-iron, and Related Heat-Resistant Alloys", Corrosion Handbook, ed. by H. Uhlig, John Wiley and Sons, Inc., New York, 1948, pp. 651-652. CHAPTER IV ’ ■ Since the experimenta| work on the dissoSui-ion of copper at elevated United States Bureafu of Mines in 1954, all work has been, performed; on relatively pure coppdr sulfide minerals. This chapter deals with the appllcation of the past three years experience for the; dissplution of copper from commerc ral copper concen- t^tes and: cemeht coppero ; Sdmples pf copper concerdrdtes^ which am-described in Chapter (I, were pbtained frdrri the Magma Copper Company ai Superior, Arizona, the Old Dick Concentrator of the Cyprus Copper Corporation at Bagdad, Arizona/ the Bagdad Copper Corporation at Bagdad, Arizona, and the Bisbee, Arizond, Branch of the Phelps Dodge . : v % ■ ■ : Series %|l | - Dissolution of Copper from the Magma Concentrate. This series c f tests avos itrn to determh^ the Magma cohcentrate contained sufficient sulfur for a satisfactory dissolution of the copper and,. if so, to determine the Since 45 in previdys experimental work it was also an objecfiye of this series to determine the :'y-clisssolutlohi:.pf yoldl. and silver from the Magma concentral-e * The sfandard procedure was used excepf that the fime was yarled „ The results of this series dre shown, in Tabie |8 «, - Dissolution of Copper fpom the-Magma Copper Goncentrate 0 Goppeir ; • ^sdys of jBach I cjpors^ Assays of residues, Free acid Time,, dissolv edf grams per liter per cent lb . per |b* minutes per eeint -Cdpper' ■ -l.rpn.y ,'Fe ;;. lrgnr le" ■ Copper Iron ; ;.df:cpnc. ;■ 9,8 o o 30 99M 12.18 0.08 44.43 ■H. o o o ..60:;;; 99.07 12.32 0.05 . 45,»li ' O O 1 nterpretai-ion of Resu Its; The Magma copper concentrate contained sufficieni- sulfur for 99014 per cent dissolution of the copper during a reaction period of 30,minutes and extending the time j^dlysk from five tests of one hourciuration disclosed the dissolutions of 4 .6 per cent of the gold and IIJ per cent of the silver present in the concentrate „ Considerably more work shouId be done pm the dissolution -of'gold^ondpifyp# tp:% yef|fx#eso^ : \ ^ j \ \ / - ■ Series XIV " Dissolution of Copper from the C>Id Dick.Concentrate» The object of this series was to determine the behavior of the Old Dick concen trate when subjected to leaching at elevated temperatures and pressures» The standard procedure.was fol lowed except that the time, interval was varied and In the latter two tests an addition of 0.25 pound of sulfuric acid per pound of concentrate was made. Tabj e : 19 shpws^ the resu I ts of th is series. Table 19® - Dissolution of Copper from the Old Dick.Concentrate«, Copper Acid added, Assay s of leach llqwors, Free acid, Time, dissolved, lb. per lb= ' £rams per liter l b . per lb, minutes per cent of cone . Copper Iron, Fe Iron, Fe'"' of cone. / - I S . 58.99 0.00 '■ 9.71 0.18 0.05 0.02 30 84.58 0,00 14,00 0.08 0.02 6 .0 9 60 94.01: 0,00 15.32 0.05 0,08 0.17 120 97.71 0.00 15.52 0.03 0.07 0.24 83.30 0.25 10.17 0.16 0,12 OM ■-MX' 99,f 7 0.25 16.37 0.08 0.37 0.59 |^terpmtat|oh of i%su|ts: ./ : -:- ^ ^ Extended reactson periods without the addition of sulfuric acid ffomj 5 to I 20 mlnuies |nere95 ed the dissolytren; of the copper from 58 099 to 97 J per\ cent® The: longer dissolution period required for this concentrate was explained by the relatively coarse size of the concentrate as shown in Chapter II. |n: order fd increase the:S#o!!u#^^ ! per cent It was necessary to increase the free acid GoncenW accomplished with the addition Of sulfuric acid. The addition.of 0.25 pdund of acid per pound of concentrate increased the dissolution to 99.17 per cent in a 60 minute period. Series XV - Dissolution of Copper from the Bagdad Concentrate. The ob|eet of this series was to determ required for a satisfactory dissolution of the copper from the Bagdad concentrate. The standard procedure was followed except that the time interval was varied. The results of this series are given? in Table 20. \ - y - ' v : 47 tdfcto 2d » ~ Dissoiuiionof Copper from the Bagdad Concentrate. Coppar Assays of leach liquors/ I Assays pf residues, Free acid, j Time,. dissolved/ grams per liter - ■percent, ■' lb. per lb. 1 minufes per cent Copper Iron, Fe" Iron, Fe"' Copper ''■■Iron: y: ..■oPcanc,, ■.■ r :T5 ’ 99 .0 12,95 0.08, 0,17 0,62 55.51" 0 .3 4 ':30 \ " 98.9 I2;59 0 # 0.17 0.71 85,28 0 .3 6 98.9 12,57 0,08 ■ tm' 0.71 56.16 0 ,3 6 interprehaHen Resw Its r ; • ' Ffefeirihg to-the; rote of fo i^ pf the sulfate ion was sufficiently ftiplcl due to the relai-ively fine material io alIow a dissolution of 99,0 per cent of the . copper in a |5 minute period. Extending the time to 60 minutes did not improve the per cent of dissolution, / Series XVI - Dissolution of Copper from the Phelps Dodge Concentrate. The purpose of this series was to determine if the Phelps, Dodge concentrate . wds susceptible to: ieaching ot eleYated The Standard procedure was followed except that the reaction 'time was varied. The results of these tests are shown in- Table 2 l. Table 21, — Dissolution of Copper from the Phelps Dodge Concentrate, Capper Assays ofleach liquors, Assays pf residues, Free acid Time, dissolved grams per liter percent.. lb, per lb. minutes per cent Copper Iron, Fe" iron# Fe'" Copper Ifon of cone. 7 '■ 82,38 M d / : ■■0,40.- ^D.:25 ■ \ 3,94 42.74 * 0.24 98,32 -■& M 0 i6 4 3.68 . 0,59 49.27 0 ,5 9 7m . : : 98.69 7,76 .rO>72. :y 1.71 0,42 52.28 0.71 Snterpretatjon of Results; ; . . . ! - . S. , - Referring; to Table 21, the results showed a dissolution of 82,,38 per cent of the copper in 7 minutes0 The rapid rate of dissolution, for this concentrate wds .believed to. be due to the # fine material and the presence of considerable pyrite» Extending the time to 15 mi notes improved the dissolution, of 98 „ 32. per cent and a. further increase \in;ti:rh(K^ict'.hof''indt^r?dily increase the dissdl#ipn;-.'.. Series XVII - Dissolution of Copper from Various Concentrates Employing Pulp Densities of 35 i?er Cent of Solids. ™ "" It was the object of this series to determine the affect of high pulp density upon . the dissolution of copper from Wi’fouS copper opncentr^ « The standard procedure was fpllowed except that a pulp density -of 35 per cent of solids was employed. Due, to high, cpncentraflpns of copper in the pregnant solution at this high pulp density the pulp was diluted with boiling water prior to filtering to ayoid crystallization, of copper sulfate, A reaction time equal to that which, allowed high dissoluHon of copper from the particular concentrate at 4,76 per cent solids was used in this series. Table 22 contains the results of this series* Table 22, - Dissolution of Copper from Various Copper Concentrates Employing Pulp Densities of 35 Per Cent. Solids, Copper Assays oFleacFvTIcluor*, * , ATimeyA dissolved, . \ • gra(ms per li ter . Concentrate ‘ rriinyfes. percent: Copper Iron, Fe" Irony Fe " 1 Magma 30 ; 93,91 , 172; ' m Old Dick 30 33,41 83 3 ,r 2 2 o5l Bagdad 30 94,69 ' 187 4 ,6 . . 1,5 Phelps Dodge . 15 • 59,82 71 ,48,2 0o6: * Based on volume of original leach liquor. 49 Interpretation of Results: Referring to the results of Table 22, the per cent dissolutions of copper were less by 5 to 40 per cent as compared with equal times of agitation for pulps of 4.76 per cent of solids and also the amount of iron contained in the solutions was considerably higher. It is probable that due to the higher concentration of copper in the leach solutions at the higher pulp densities the speed of the reaction was reduced. It is also probable that with the amount of oxygen constant and a larger amount of material to be oxidized that the time necessary to obtain the higher dissolutions was increased. The results also indicated that the concentrates with the finer sizes of grains yielded higher extractions but these higher extractions were not comparable to those obtained at 4.76 per cent solids. In planning this series of tests consideration was given to maintaining the amount of solid material constant as compared to that used for 4.76 per sent solids. Such charges, however, could not be agitated satisfactorily. This series was run during the last stages of the experimental work and time was not available for additional tests of longer time periods. It appears reasonable however to expect that satisfactory results could be obtained if longer periods were employed. Series XVIII - Dissolution of Copper from Various Concentrates Employing a Continuous Flow of Air as the Atmosphere. The object of this series was to determine if a continuous flow of air could be substituted for commercial oxygen as the oxidizing atmosphere in the autoclave . The standard procedure was followed except that an air flow of 500 liters per hour Univ. of Arizona Library tit 0 pressure of 340 pounds; per square inch gtiugis used» The resulis of this series are giYen iri Tatie 23 = - , - Table 23 - Dissolution of Copper from Various Concentrates Using an Ajr Flow of \ "-j5^0;Ut^rs;|3eriHpurv::i Assays pf leach liquc ^ ■ dissolved. grams per liter Concentrate percent Copper Iron , Fe" Iron, Fe'" Magma ■ 37,69 % 38 i ;:; ::;2;96 ;V ©Id Pick 84,45 , 12,94 0,23 0 ,0 7 : Bagdad ; 99,00 12,81 0,3 8 0 ,5 7 - ; Fh&lps Dodge : 97,73 ■ 18,98 1,55 ■ % #07 , - : / ■ interpretation of Results: The dissolution of 99,00 and 97,73 per cent of the copper from the Bagdad and Phelps Dodge concentrates respectively were obtained in 60 minutes using an air flow of 500 liters per hour whereas similar dissolutions were previously obtained,in one - fourth this time.employing oxygen. The 98,76 and 84,45 per cent dissolutions yielded from the Magma and Old pick concentrates when air was used were similar to.results obtained with oxygen in an agitation period one - half as. long, ; ; Series XIX - Dissolution of Copper from Cement Copper, It wds the purpose of this series to determine if copper present In.cement copper could be dissolved at a rapid rate when, using eleyated temperatures and pressures. Also the behavior of the lead/ zinc, tiny and nickel from the solder used in the manufacture of the cans upon which the copper was precipitated was to be studied. The standard procedtire was i y except that fhe, redc^ varied and thei theoretlcaT 51 amouh# of sulfate ion were proyided by the add}tion of sulfuric acid or resuiS tire shoym iti TWes 24 and 25 0 Table 24o - Dissolution of Copper from Cement Copper when Sulphate Ion Was '■ Copper 1 Reageiiit added Assays o f leach liquors. dissolved., ' :Ai«6unf . • ■v: grams per liter r I f per cent Kind jb= perlb= eemenf copper Copper Iron, Fe" Iron, Fe"' • . ■ • 7 - ' V; 88=85 ; Acid 'v:d:=23-;\ ;: a30;o|b ;’: .;.a=07'' 0=08 ' 15 . 1=27 fyrife 0=75 0 = 13 trace Jfrtice- 60 65=90 Pyrite a 0=75 25=83 0 = 12 0=03 . V:/A; A. ... . ' Table 25« - Assays of Leach Liquor and Residue from the 7 Minute Test Using er= Assays of leach liquor/ ; Assays of Residues, grams per (iter a A ■:v percent , '.LetidA': ... - '.Zinc : .Tin. Nickel lead ■' /.'Zinc XTin - Nickel Trace 0=05 0=02 0=03 1=73 0.16 0=46 Interpretation of Results; The relatively low dissolution of 88=85 per cent of the copper when sulfuric, acid was added - might have been due to the speed of oxidation of the copper or a deficiency in sulfate ion. ^ > Referring to the tests in which pyrife additions were made, the very low dissolution of 1 =27; per cent in 15 minutes and 65 =90 per cent in60minutes were probably due to insufficient time for the oxidation of the pyrite and copper to occur and a deficiency of sul^fe ioh= . v/ : V ' , ■ : it is likely that additional sulfate ion and increased time of tigifation wouId produce; satisfactory di$s0iufiohs= based oh the results of Table 25 ihdrcated that 25 per cent of the lead, 80 per cent,of the. zinc, 75 per cehf of the tin, and 75 per ceht of the nickel presehf in the cemeht copper were dissolved during the reaction period» , Series XX - Dissolution of Copper from a Mixture of Phelps Dodge Concentrate and Cement Copper; ' — ' ; The purpose of this series was to defenhine if a concentrate which contained excess pyrite could be used in conjunction with cement copper to allow a satisfactory dissolution of the copper in both the concentrate and the cemenf copper0 The mixture contained 10 per cent of cement copper by weight. The tests were carried out using the sfandard procedure except the reacdon time was yaried „ The results of these tests are ^ho#n in Table 2d. , Table 26. - Dissolution of Copper from a Synthetic Concentrate Composed of a Mixture of the Phelps Dodge,Concentrate and Cement Copper. Copper Assays of leach liquors, . dissolyed, grams per liter minutes perednt Copper Iron, Fe" Iron, Fe1" 94.33 10.47 0 .2 7 0.21 97.89 ;:;iT,48: 0,27 ■ O.o93; ' Iriterprefatlon of Results; ■ / . ' \ :' ■ A dissolution of 94.33 per cent of the copper was obtained in 15 minutes: and by increasing the time to 30 minutes a dissolution of 97.89 per cent was obtained. chapter V :: ; ;; ■■■■ CONCLUSIONS AND RECOMMENDATIONS The impori-anf results of the experimental work which have been described herein . haye been summarized as fpllowss \ . ■' .. oBprnite. ' I «'i' Withduf the addition of acid as a. solvent and employing a temperature of 200 degrees Centigrade, a. pulp density pf 4 =,76 per cent of solids, an impeller peripheral spped pf 524 feet per minute, and a pdrtiai pressure of oxygen of 100 pounds per square inch gauge? co^erinci^ased frpB 2^^ the peri bd pi’ dgitptlon was Incregsed from: 15 to; 120 min 20 With the addition of sulfuric acid as the solvent and varying the amounts of sulfuric acid added to the charge up to a maximum of („25 pounds of sulfuric acid per pound of bpmfte The pen&entpge disspW^ pf fhe popper inbrWse&Trbin 58,85 to 99,75 when an agitation, period of one hour, a pulp density of 4,76 per cent of solids, a temperature of 200 degrees Centigrade, a partial pressure pf oxygen of 100 pounds per square Inch gauge, and an impeller speed-pf 524 feet per minute were employed„ 3, By substi tut i ng: pyri te ipr ac id in amounts Ydiryl hg up to a maxi mum of 1.25 pounds per pound of bomite and keeping the other conditions constant the dissolution of coppet Inoteased from 58 4 . By varying the reaction time from 7 to 60 m1nutes and employing the addition of 0.50 pound of sulfuric acid per pound of bornite while Maintaining the other condi - fidns constant, the per cent pf dissolution of the copper increased from 91.80 to 98 ,96. 5o Employing 0,25 pound of pyriie per poundpf bomlteandmairitaining the of her variables constant, the percentage of dissolution of copper ranged from 95,16 to 98,32 as the reaction time y/as vaned from 30 to 120 minutes, Maintaining a puip density of 4 076 per cent of solids, an oxygen partiai pressure of TOO pounds per square inch gauge, an impeller speed of 524 feet per minute, a reactipn period of 60 m|n0^ of 0,50 pound of suifuric acid; the disso!wfion of the copper inqreased from 34=30 to 98,96 per cent when the temperature was raised from 100 td 2Q0 Centigrade, 7, Within the range of Impeller speeds from T3T to 524 feet per minute the degree of dgi tdtlon did not qppeqr to affec t the percentage of dissolution of the copper when using 0,50 poundof suIfuric acld per pound of bornite, a temperature of 200 degrees Cenfigrade^ and maintaining the dther conditions Constant. 8 , The dissolution of the copper increased from 33.52 to 98.96 per cent as the partiqI ptesSy re of oxygen wds raised from 25f to 200 pounds per square inch gauge when using O'.25 pound of pyrife per pound of hormte and W in t^ the other conditions constant. A dissolution of 98 .25 per cent of the coppe r was obfa ined by increasing the time to 120 minutes and using an oxygen partial pressure of only 25 pounds per square inch gauge. 9, Particles coarser than lOO-mesh size decreased the rate of dissolution when uslng ,0,50 pound Of sulfuric acid per pound o f bgrn|te> a parfial pressure of oxygen of TOO pounds per Inch gauge/ a temperqt^ of S)0 degrees Gentigrade> an Impeller speed of 524 feet per mlhufey and a reaction period of 60 minutes. 10, . When air additions of 160 and 320 liters per hour at a total pressure of 340 pounds per square inch gauge were substituted for oxygen during tests employing 0,25 pound of pyrite per pound of bqrnite grid the ofher conditions held constant; dissolutions of :95 e81 and 97« 30 per cent of the copper were: obtained respectively, . Similar extrac - tiohs iyere 41 o Increases of pulp density up to 35 per cent of solids, failed to produce a pro nounced affect on the dissolution of the copper for reaction periods of onO hour ifthe deficiency of Suifdte ion was furhishW by #,50 pound boWte and the other conditm held cohsfaht, Covellite, 12» A copper dissolution amounting to 96 .03 per cent was obtained in 120 minutes when; empioying a pulp density of 2.2 per cent o f solids, a temperature of 200 degrees Centigrade^ a partial pressure of oxygen of 100 pounds per square Inch gguge> an im peller speed o f 524 feetjper minute# and the addition of 0 o25 pound of sulfuric acid per pound of cove!!iteo As preyiously mentioned,, the difficulty of obtaining, more coyel lite did not permit dddttional tests,, Commerc la I Concentrates „ f 13, A dissolution of 99,14 per cent of the copper contained in the Magma concen - trate was dbtgined in 30 minutes when using a temperature of 200 degrees Centigrade, o putjp density of 4,7d:per cent of solids, an impeller speed of 524 feet per minute, and a partial pressure of o x ^ e n o f 100pounds per squaie lneb gauge, l4o When the time was increased from 15 to 120 minutes, the dissolution of copper from the Ctld pick concenfrafe: increased from 5B =?9' tO: 97„71 per cent when the other yariables were held constant. Using a 60-minute period and the additiort gf 0,25 pound of $u(furic acid per pound of concenirgie the dissoIution incredsed td 99.17 per cent. This concentrate wds more refractory than the others tested due to the coarseness of the material. . ' 15 c The Bagdad concentrate yielded a dissolution of copper of 99,0 per cent in IS minutes without the addition of dcid gnd with other conditions maintained constant. 16, During a reaction period of 15 minutes the Phelps Dodge concentrate allowed the dissolufion of 98c32 per cent of the copper with other conditions constant, 17. ;At a pulp density of 35 per cent of solids/ a reaction period of 30 minutes, and the other conditions constant the Magma, Old Dick, and Bagdad concentrates yielded, per cent dissolutions of 93.91, 33,41, and 94.69, respectively. The Phelps Dodge concentrate gave a dissolution of 59.82 per cent in IS minutes. |t is quite probable thaf these dissolutions couId be increased by changing yaridbies, especiaily >'me. : : ' . .18 o, When a flow: of dir of 500 l iters per hour at d total pressure of 340 pounds per square inOh yras substituted for oxygen the Bagdad and Phelps Dodge concentrates required a time period four fold as long to achieve dissolutions comparable to those employing oxygen. The Magma and Old Dick required only twice as long a period. Cemont Copper ■ . 19 , Employing the addition of lUSSt pounds of sulfuric acid per pound of cement copper, a temperature of 200 degrees Centigrade, a speed of agitation of 524 feet per minute, a puip:density of 4-.76 per cent of solids, and a partial pressure of oxygen of 100 pounds; 88;.85 per cent of the copper in the cement copper was dissolved in 7 minutest When 0 ,75 pound of pyrite per pound of cement copper was uSed, 65 .90 per cent of , . - 2Qo . A mixture of 80 per cent of Phelps Dodge concentrate and 20 per cent of cement copper yielded copper dissolutions of 94,33 and 97,89 per cent in periods of 15 and 30 minutes, respectively, when the other conditipns were held constant. The author believes that the following recommendations will be helpful if further eXperi^ coppet sulfide minetols is planned. I „ ■ , Since the development and use of the new packing;gland composed of graphite and oil impregnated asbestos material which wa's sold under the trade pame, SARLGCK number i 17/ prayed to be successful^ Consideration should begiven to the elimination of; the upper chamber of the au toe I aye for ease of operation, The Parr modified auto- claye> which didimt have the equalized pressure chamber, operated satisfqetorily with this packirig at piossures o f 1/000 pounds par square inch gau@e. 2, - . For the filteringof high copper content pregndnt solutions consideration should be given to the design:and.oOnStrucf|on of an accessory pressure filter chamber to permit filtration before crystallization,of copper sulfate takes place. 58 BiBLiOGRAPWY B!iider> We 0 = / "Chromium - Iron, Austen $ fie Chromium - N ickel.- Iron, and Reidted Heat Resistanf Alloys ", Corrosion Handbook^ ed. by H. Uhlig,. ■■.jiptiiiA^ll'ey'dnd'Spns./;' inCo, New Ybrk# i948„ • 2 cBrohsfed, J . N ., "Solubility of Sdlts and of Strong Acid and Bases in Water" , jnfdrndtibnal Orifical TdNes, Vol . IV, ec 1. by Washburn;,; Me Grow- Hill Bobk Company^ Inc =,, New York, 1928, Editor?, "Continuous Recovery Cuts Cost, Boasts Yield", Chemical Week, janUary 11; 1957. 4o Editors, "Sherritf a Gordon Uses Ammonid Leaoh for Lyne lake Nickel —' Copper = Cobalt Sulfides", Mining Engine iering, June 1953 . Keyes, N . A ., Innovation in Copper Leo chlng Employing Ferric Sulfdte>- Sulfuric A cid ,# . S'. Bureau of Mines Bui!1etin 32i> 1930. 6 = Kirby, R. S., The Dissolution of Chalcop; yrite and Chalcocite at Elevated Temperdfures and Pressures, Thesis, Uniys Wty of Arizond, 1957. . 7. Mitchell, J..S., "Pressure leaching and Reduction at the Garfield Refinery", Mining Engineering, November 1955 . 8o Mommsen, J. T. , The Dissolution of Chalcopyr'lte at Elevdted Temperatures and Pressures^ Part 1, Thesis, University cyf Arizona, 1955. 9> Rose, C . A ,, "Metallurgica 1 ©peratiohs ( at the Chi le Exploration Compdny" , Engineering ond Mining journal, February 12, 1916. . . ; , , ,0 . ScOtf, W. WStandard Methods of Chenrfedi Analysis, Volume I, ed. by N ., H. Furman, D . Van Nosfrand Cdmpdny, In c., 1939. Tverberg, J. C=, The Dissolution of Chalicopyrlte at Elevdted Temperatures and Pressures, Part f I, Thesis, University of Arizond, 1956 = 12. Uhlig, H. H ., "pitting in Stainless Steels bnd Other Passive Metals", Corro - sion Handbook, ed. by H. Uhlig, John Wiley and Sons, Inc., New York, 19’