Patented Oct. 22, 1946 2,409,861

UNITED STATES PATENT office PROCEss AND AGENTs FoR THE REcovERY OF MAGNESUMONS FROM BR NE Melvin J. Hunter and William C. Bauman, Mid land, Mich., assignors to The Dow Chenniea Company,Michigan Midland, Mich., a corporation of No Drawing. Application February 2, 1942, Serial No. 429,303 5 Claims. (C. 23-50) 2 This invention concerns an improved process agents vary considerably as regards the con for the recovery of magnesium ions in relatively venience and economy with which they may be concentrated form from brines containing the employed. Sulphonated organic resins are pre Same. It also concerns certain base exchange ferred, since they have the properties of rapidly agents (also known as cation exchange agents) absorbing magnesium ions from sea water, of rap suitable for use in the process. idly and nearly completely liberating the ab It is well known that the chemical reaction Sorbed magnesium ions upon subsequent treat involved in the use of a base exchange agent is ment with an alkali metal salt solution and of reversible and that the direction in which it pro Swelling or shrinking only moderately during ceeds is dependent to a large extent upon the O use in the process. relative proportions of the reactive positive ions, We have now found that organic resins which e.g. alkali metal ions and alkaline earth metal contain carboxyl groups (which resins are here ions, on the exchange agent and in the liquor inafter referred to generically as “carboxylated in contact with the exchange agent. For in resins') possess cation exchange properties and stance, in usual Water Softening processes the s that when employed in the form of their am water is passed through a bed of a granular monium or other alkali metal salts they are far base exchange agent Such as Sodium aluminum more Selective as regards their ability to absorb silicate, whereby the alkaline earth metal ions in magnesium ions from brines which also contain the water are absorbed by the exchange agent alkali metal salts than are the sulphonated resins, with displacement of alkali metal ions from the 20 i. e. the atomic ratio of magnesium ions to alkali latter so that the water is depleted of alkaline metal ions which may be absorbed from Such earth metal ions and enriched in alkali metal brine by a carboxylated resin is far higher than ions. After becoming saturated with alkaline may be absorbed from a like brine by a sul earth metal ions by Such use in Softening Water, phonated resin. In this connection it may be the exchange agent is reconditioned usually by 25 mentioned that during use for the absorption passage of a dilute, e.g. of about 5 per cent Con of magnesium ions from a brine containing the centration, sodium chloride solution over the same and an equal or larger proportion of alkali same. The absorbed alkaline earth metal ions metal ions no exchange agent is converted en are displaced from the exchange agent by the tirely into its magnesium salt. Instead, the re Sodium ions of the Salt Solution, thus recon 30 action proceeds to a point at which there is verting the exchange agent into its Sodium Salt equilibrium between the magnesium and alkali which may, of course, be used to soften further metal ions on the exchange agent and those quantities of Water. in the brine contacted therewith. The alkali In a co-pending application of John J. Grebe salts of the carboxylated resins usually also pos and William C. Bauman, Serial No. 429,185, filled 35 sess an exceptionally high absorptive capacity for concurrently herewith, and issued October 30, magnesium ions. s 1945, as U. S. Patent 2,387,898, it is disclosed that However, the carboxylated resins have certain base exchange agents may be used to absorb properties which render them inferior to the magnesium ions from sea water, or similar brines sulphonated resins when employed for the ab containing a higher concentration of alkali metal 40 sorption of magnesium ions from brines using than of magnesium ions, and that by thereafter the hereinbefore described preferred procedure of treating the exchange agent with a fairly con the co-pending Grebe and Bauman application, centrated solution of sodium chloride or other Serial No. 429,185. For instance, most carboxyl alkali metal salt, the absorbed magnesium ions ated resins swell or shrink markedly with change may be displaced from the exchange agent with 45 in the salinity of the aqueous liquors contacted formation of a magnesium salt solution which therewith and, although these resins are excep contains the magnesium ions in higher concen tionally selective as regards the absorption of tration than in the initial brine. It is also shown magnesium ions from brines which also contain that although any of a wide variety of base alkali metal salts, they do not satisfactorily re exchange agents may be used in the process, such 50 lease the absorbed magnesium ions upon subse 2,409,861 3. e 4 quent treatment with an aquecus solition of sodius boxylated resins are described in U. S. Patents um chloride or other aikali metal salt, i. e. tile i,945,307, 2,047,398 and 2,230,240, which patents, magnesium sait Solutions tii is regenerated aire however, do not recognize the fact that the resins of undesirably iow concentration. possess properties rendering then useful as base It is an object of this invention to provide a exchange agents. method whereby carboxylated resins may satis in addition to the previously known carboxy factorily be used for the recovery of magnesilim ated resins just mentioned, we have prepared cer. ions in relatively concentrated form from brines tain new carboxylated resins which are especially which also contain alkali metal Saits and where well suited for use in the process. These new by the magnesium sait solution formed by dis carboxylated resins are co-polymers of an alpha placement of the absorbed magnesium ions from beta-unsaturated dicarboxylic acid, a readily the resin may be obtained in unusually high polymerizable vinyl or vinylidene compound concentration and in a form containing not more which contains only a single olefine group in the than a minor amount of other salts. Another molecule, and a polymerizazle organic compound object is to provide certain new carboxylated 5 containing at least two olefine groups in the resins which possess a combination of physical molecule. Examples of alpha-beta-unsaturated and chemical properties rendering them espe acids which may be used in making these resins cially well suited to use in the process. Other are maleic acid, fumaric acid, citraconic acid, ita objects will be apparent from the following de conic acid, etc. In place of these free acids, the . scription of the invention. 20 corresponding acid anhydrides may be used. Ex The present process comprises as its essential amples of vinyl and vinylidene compounds con steps (1) passage of brine containing a magnesium taining a single olefinic group which may be salt and an equimolecular or higher proportion used in making the products are styrene, alpha of an alkali metal salt through a bed of an am methyl-styrene, Ortho-methyl-styrene, meta-me monium or other alkali salt of a carboxylated 25 thyl-styrene, para-methyl-styrene, meta-ethyl resin, whereby the latter absorbs the magnesium styrene, para-isopropyl-styrene, ortho-cloro-sty ions (and other polyvalent metal ions if present) rene, para-chloro-styrene, vinyl chloride, vinyl from the brine; (2) thereafter passing an aque acetate, etc. Among the various polymerizable ous solution of an acid through the bed to dis compounds containing two or more olefinic groups place the absorbed magnesium ions from the car 30 in the naoiecule which may be used in making the boxylated resin to form a relatively concentrated resins are divinyl benzene, butadiene, isoprene, solution of a magnesium Salt and at the same tung oil, oiticica oil, divinyl ether, etc. The pol time convert the resin into its acid form; and (3) yolefinic reactant serves as an agent for de treating the resin with an aqueous solution of an creasing the tendency of the resin product to alkali and a soluble alkali metal salt to form Swell or shrink during use as a base exchange the alkali metal salt of the carboxylated resin so agent. It is believed to function principally as that the latter may be reemployed for the absorp an agent for bonding together, or vulcanizing, the tion of magnesium ions from the brine. In the linear co-polymers of the other reactants and only first of these steps it is important that the resin a very Small proportion thereof, e. g. an amount be used in the salt form specified, since the car 4. corresponding to 0.01 mole or less per mole of the boxylated resins when in their acid form do not unsaturated dicarboxylic acid is required. It Satisfactorily absorb magnesium ions fron brines. nay, of course, be used in much larger propor The use of an acid capable of forming a soluble tions. The alpha-beta-unsaturated dicarboxylic magnesium salt for displacement of the absorbed acid, or its anhydride, is preferably used in magnesium ions from the resin in the Second step 45. armount equai to or exceeding the sum of the is required in order to recover the major portion molecular equivalents of the other polymerizable of the magnesium absorbed by the resin. As reactants So as to obtain a large number of car hereinbefore mentioned, solutions of alkali metal boxyl groups in the resin molecule. The mono salts do not react Satisfactorily to displace the olefinic vinyl or vinylidene compound is used absorbed magnesium ions from the resir and 50 in molecular excess over the polyolefinic reactant the regenerated magnesium Salt solution obtained but in amount not exceeding the molecular equiv by such use of an alkali metal salt is of tandesir alent of the unsaturated dicarboxylic acid. ably low concentration. The presence of a soluble The resin may be formed by heating a mixture of alkali metal salt in the alkali solution employed the reactants to a polymerizing temperature, e.g. in the third of the foregoing steps is required in 55 between 70 and 175 C., until the co-polymeric Order to prevent excessive swelling of the resin. product is a hard glass-like resin at room tem Water alone causes the alkali Salts of the resins perature. If desired, the reaction may be car to Swell greatly. - ried out in the presence of a solvent. The prod Brines from which magnesium ions may ad uct is comminuted, if necessary, and treated as Wantageously be recovered by the present method 80 usual with an alkali, e. g. sodium or potassium are those containing between 0.01 and 0.8 gram hydroxide, to obtain the alkali metal salt there atomic weights of magnesium ions per liter and of. The Salts thus obtained are hard resinuous between 1 and 100 gram atomic weights of alkali water-insoluble bodies having excellent cation metal ions per gram atomic weight of magnesium exchange properties. Examples of such carboxyl ions. Ordinary Sea Or ocean water and also many 65 ated resins are the copolymers of maleic acid, magnesium-containing inland brines, e.g. occur styrene and divinyl benzene; of maleic acid, ring in North America and elsewhere throughout vinyl chloride, and divinyl benzene; and of ita the world, may be used as starting materials in conic acid, Styrene and butadiene; etc., and the the process. - alkali salts thereof. The carboxylated resins which may be used 70 In recovering magnesium ions in relatively as the base exchange agents are the resinous concentrated form from sea water with any of three dimensional polymers of unsaturated acids the foregoing carboxylated resins, sea water is having the linear polymeric molecules bonded passed through a bed of the granular resin in together with a polyfunctional group, e. g. by the form of an alkali salt thereof until the resin reaction with a glycol. A number of such car 75 is nearly saturated with magnesium ions ab 2,409,861 - 5 6 Sorbed from the brine, e. g. as evidenced by an maleic anhydride and 50 parts of acetone was increase in the magnesium ion content of the heated at temperatures varying from 90° to 100° brine flowing away from the bed. C. for 1.5 hours and then cooled. The product. The absorbed magnesium ions are recovered Was a tough resinous solid at room temperature. from the resin by passing over the latter an 5. It was reheated to 135° C. and maintained at said aqueous Solution of an acid capable of reacting temperature for 2 hours, after which it was to form a soluble magnesium salt. The acids cooled and ground. The granular product was employed for this purpose have ionization con reheated to 135° C. at about 25 millimeters abso stants at 25° C. of 1.8X105 or higher. In order lute pressure for approximately 5 hours to vapor to form a magnesium salt Solution of higher con O ize the acetone and any other volatile ingredients centration than in the initial brine, the acid Solu therefrom and again cooled. The product was tion must of course be of higher normality than Screened to eliminate granules of sizes greater the magnesium Salt in said brine. In practice, than 16 mesh and finer than 60 mesh. The re the acids are used in the form of at least 1 maining resin was soaked in an aqueous sodium normal aqueous Solutions thereof. The concen 5 hydroxide Solution of 5 per cent concentration for tration of the regenerated magnesium salt solu about 16 hours, after which it was washed thor tion becomes higher, of course, with increase in oughly, first with distilled water and then with the concentration of the acid used to form the a 5 per cent concentrated aqueous sodium same, but in Some instances, e. g. when using chloride Solution. A glass tube of 1 inch internal sulphuric acid, it is necessary that the acid solu 20 diameter was charged with 25.2 cubic inches of tion be sufficiently dilute to obtain the ionization the resultant sodium salt of the resin and a 0.1 necessary for rapid reaction. Among the Various normal magnesium Sulphate solution was passed acids which may be used in this step of the proc through the tube until the resin had absorbed its ess are hydrochloric acid, hydrobromic acid, capacity of magnesium ions from the liquor (as sulphurous acid, Sulphuric acid, nitric acid, acetic 25 evidenced by an increase in the magnesium con acid, formic acid, etc. Such acids react, of tent of the effluent liquor). It was found that course, to form corresponding magnesium Salts. the resin had absorbed approximately 0.38 gram It should be mentioned that the mid-portion of atomic Weight of magnesium ions. The tube was the regenerated magnesium Salt Solution is usu drained of free-flowing liquor, after which 500 ally more concentrated than the fore and final 30 cubic centimeters of an aqueous hydrochloric portions and may advantageously be collected acid solution of 15 per cent concentration was separately from said other portions. The regen passed into and through the same. The resultant erated magnesium salt solution usually contains magnesium chloride Solution, which contained only minor amounts of free acid or of alkali metal nearly all of the magnesium that had been ab salts. It may be evaporated to crystallize the 35 Sorbed by the resin, was collected in Successive magnesium salt, which may, if desired, be elec portions as it flowed from the tube. 80 per cent trolyzed or otherwise treated to produce metallic of the magnesium which had been absorbed by magnesium. the resin was collected in the richer mid-portions The acid form of the resin which remains after of the regenerated magnesium chloride Solution, the treatment just described is reconditioned by 40 which mid-portions amounted to 200 cubic cen treatment with an aqueous Solution of an alkali timeters of liquor and contained an average of and a corresponding salt of a strong acid, which 147 grams of magnesium chloride per liter. salt serves to prevent excessive SWelling of the resin. The concentration of such salt required Eacomple 2 to prevent excessive Swelling varies somewhat de The procedure of Example 1 was repeated, pending upon the carboxylated resin employed except that instead of using aqueous hydrochloric and the particular salt used, but we usually en acid to displace the absorbed magnesium ions ploy the salt in the form of an at least 0.5 normal from the resin, 500 cubic centimeters of a 12.5 per solution thereof. The concentration of alkali in cent concentrated aqueous sodium chloride solu the solution is of little consequence, i. e. the al 50 tion was employed. Only 45 per cent of the mag kali may be used in dilute or centrated form as nesium ions absorbed by the resin was displaced desired. Examples of alkalies and their salts therefrom and the resultant solution contained which may be used in this treatment are am 18 grams per liter of magnesium chloride. monia, sodium and potassium hydroxides, SOdium Eacample 3 chloride, potassium chloride, ammonium chlo 55 ride, sodium bromide, sodium sulphate, etc. In The purpose of this example is to show the place of the hydroxides just mentioned, corre results obtainable when using a carboxylated resin sponding carbonates may be used, though not as for the absorption of magnesium ions from a brine conveniently as the hydroxides. The treatment as compared with those obtainable when using a with the alkaline solution results in the forma to sulphonated resin for said purpose. Due to the tion of a corresponding salt of the resin and fact that absorbed magnesium ions are best dis thereby renders the latter Suitable for re placed from a carboxylated resin by treatment employment in absorbing magnesium ions from with an acid whereas they are best displaced from brines. a sulphonated resin by treatment with an alkali The following examples describe a number of 65 metal salt solution, the procedure employed in ways in which the principle of the invention has using the two resins was not the same. However, been applied and illustrate certain of its advan the brines employed as starting materials were tages, but they are not to be construed as limiting identical in the two experiments and each resin the invention. was used in the form of its sodium salt for the ab Eacample 1 70 sorption of the magnesium ions from the brines. A solution of 90 parts by Weight of purified Eacperiment Al using a carboacylated resin styrene, 20 parts of divinyl benzene of 65 per cent The sodium salt of the resin described in Ex purity (the remainder being largely ethyl-vinyl ample i was employed. A glass tube of 1 inch benzene along with some styrene), 100 parts of 75 internal diameter was charged with 25.2 cubic 2,409,861 7 8 inches of the finely divided resin and a 0.1 normal magnesium chloride solution was collected in 100 magnesium chloride solution was passed through cubic centimeter portions as it flowed from the the resin bed until the latter had absorbed its bed. The first 500 cubic centimeters of said soul capacity of magnesium ions (as evidenced by the tion to flow from the bed contained 16.31 grams of fact that the liquor then flowing from the tube is magnesium chloride, an amount corresponding to was a 0.1 normal magnesium chloride solution). 93 per cent of the magnesium which had been The effluent liquor was collected and analyzed for absorbed by the resin. The 100 cubic centimeter magnesium chloride, whereby it was found that portion of the solution which was richest in magnesium ions equivalent to 35.95 grams of mag- (magnesium chloride contained 69 grams of mag nesium chloride (MgCl2) had been absorbed by 10 nesium chloride per liter. Eighty per cent of the resin. The absorption of magnesium Corre- the magnesium which had been absorbed by the sponded to 5.4 pounds of magnesium chloride per resin was recovered in mid-portions of the regen cubic foot of resin initially employed. 500 cubic erated magnesium chloride solution having an centimeters of an aqueous hydrochloric acid solu- average magnesium chloride content of 42 grams tion of 15 per cent concentration was then passed 5 per liter. through the resin bed and the resultant regener- The comparative data collected in the fore ated magnesium chloride solution was collected going experiments A and B is summarized in the in portions as it flowed from the bed. All of the following table:

Maximum capace Capacity from sea Maximum conc. MgCls80% ofin regenerrichest ity pounds of water pounds of of regenerated Resin MgCls cubic MgCl, cubic MgCls grams e MgCls solu foot of resin foot of resia per liter E. grams per

Carboxylated.------5.4 4.5 63 147 Sulphonated.------2.1 1.2 69 42 magnesium which had been absorbed by the resin Other modes of applying the principle of the was recovered as magnesium chloride in the efflu- invention may be employed instead of those ent liquor. The highest concentration of mag- 30 explained, change being made as regards the nesium chloride found in any of portions of the method or agents herein disclosed, provided the regenerated magnesium chloride solution was steps or agents stated by any of the following 163 grams per liter. 80 per cent of the regener- claims or the equivalent of such stated steps or ated magnesium chloride was recovered in 200 agents be employed. c. c. mid-portions of the effiuent liquor, which 35 We therefore particularly point out and dis mid-portions contained an average of 147 grams tinctly claim as our invention: of magnesium chloride per liter. An aqueous so- 1. In a method for recovering magnesium ions lution containing 0 per cent by weight of sodium in relatively concentrated form from a brine chloride and 5 per cent of sodium hydroxide was containing the same and an alkali metal salt, passed through the bed of resin to again form the 4 the steps of passing the brine over an alkali salt sodium salt of the latter. A synthetic brine hav- of a carboxylated resin, whereby the latter ab ing approximately the sodium chloride and mag- SOrbS magnesium ions from the brine, thereafter nesium chloride content of sea, Water (i. e. con- passing over the resin an at least 1-normal aque taining 2.5 per cent oy weight of sodium chloride ous Solution of an acid having an ionization con and 0.5 per cent of magnesium chloride) was a stant of at least 1.8 times 10-5 to effect displace passed through the bed of resin until the brine ment of absorbed magnesium ions from the resin flowing from the bed was of the same composition and form a magnesium salt solution of higher as that entering the bed. The effluent liquor was concentration than the initial brine, and subse again collected and analyzed for magnesium quently treating the resin with an aqueous solu chloride, whereby it was found that the resin had 50 tion of an alkalii and an alkali metal salt of a absorbed magnesium ions from the brine in strong acid to form an alkali metal salt of the amount corresponding to 29.68 grams of mag- resin. nesium chloride. The amount of magnesium ab- 2. In a method for recovering magnesium ions sorbed from this. Sodium chloride-containing in relatively concentrated form from a brine con brinehad previously was 82.5 percentabsorbed of from that thewhich solution he rest of is pertaining liter between of the same0.01 andand 0.8at gramleast anatomic equimolec weight magnesium chloride alone. ular proportion of an alkali metal salt, the steps a of passing the brine Over an alkali metal Salt of Eacperiment B using a sulphonated resin a carboxylated resin whereby the latter absorbs magnesium ions from the brine, thereafter pass The finely divided sodium salt of Amberlite 60 ing an at least -normal aqueous hydrohalic acid R-1 (a sulphonated phenol-formaldehyde resin) solution over the resin to displace the absorbed was used in this experiment. A glass tube of 1 magnesium ions and form a magnesium haide inchcubicinches internal of thisdiameter resin andwas a charged0.1 normalaqueous with 31.5 Solution of higher, magnesium ion content than magnesium chloride solution was passed through 65 that of the initial brine, and subsequently treat the bed of resin until the latter had absorbed its ing the resin with an aqueous alkali metal hy capacity of magnesium ions therefron. The droxide solution which contains an alkali metal amount of magnesium absorbed by the resin halide in a concentration of at least 0.5 normal, corresponded to 17.4 grams of magnesium chlor- to again form the alkali metal salt of the resin. ide. The amount of magnesium absorbed cor- 70 3. The method as claimed in claim 2, when responded to 2.1 pounds of magnesium chloride employing a resinous co-polymer of an alpha per cubic foot initial volume of the resin. One beta-unsaturated dicarboxylic acid, a polymer liter of a 12.5 per cent concentrated aqueous so- izable organic compound selected from the class dium chloride solution was then passed through consisting of vinyl and vinylidene compounds the bed of resin and the resultant regenerated 75 containing a single olefine group in the molecule, 2,409,861 O and a polymerizable organic compound contain molecular proportion of an alkali metal salt, per ing at least two olefinic groups in the molecule liter of the brine into contact with an alkali as the carboxylated resin. metal salt of a carboxylated resin, whereby 4. The method as claimed in claim 2, when alkali metalions are displaced by magnesium ions employing a resinous co-polymer of maleic acid, from the alkali metal carboxylated radicals of styrene and divinyl-benzene as the carboxylated the resin with formation of a magnesium salt resin. of the carboxylated resin and magnesium ions 5. The method which comprises passing a brine are thereby withdrawn from the brine. that contains between 0.01 and 0.8 gram atomic MELVN J. HUNTER. weight of magnesium ions, and at least an equi- 0 WAMI C. BAUMAN.