Freeport Minerals Company

David J Miller

Tadeusz K Wiewiorowski

A process for the selective separation of ferric iron from an aluminum fluoride aqueous solution containing ferric iron is effected by contacting said solution with an organic extractant phase consisting essentially of a mixture of a mono (higher alkyl-substituted phenyl) phosphoric acid and a di(higher alkyl-substituted phenyl) phosphoric acid dissolved in an inert diluent to thereby transfer the ferric iron to said organic extractant phase. The efficiency of the process is further improved by adjusting the aluminum fluoride aqueous feed solution to a temperature in the range of about 140.degree. F. to about 175.degree. F. prior to contacting it with the organic extractant phase, maintaining the temperature within this range throughout the ferric iron extraction stage or stages, then heating the resulting iron-depleted aqueous raffinate to a temperature higher than 195.degree. F., and then crystallizing aluminum fluoride trihydrate out of the raffinate at this higher temperature.

Ferric iron removal from aluminum fluoride solutions

An ammoniacal solution containing nickel and cobalt is contacted with an extractant comprising an oxime or oxine compound dissolved in an organic diluent to selectively extract the nickel into the organic phase while leaving most of the cobalt in the aqueous ammoniacal phase from which it is subsequently recovered. The nickel-loaded organic extract is washed with water and aqueous carbon dioxide to remove and recover ammonia which undesirably transfers to the organic phase during the extraction. The ammonia-free, nickel-loaded extract is then stripped with aqueous sulfuric acid at low temperature to remove the nickel. The ammonia-free nickel sulfate solution produced in the stripping operation is particularly suitable for recovering the nickel by electrolytic deposition. The stripped organic extract is further stripped with aqueous sulfuric acid at high temperature to remove and recover the small amount of cobalt which transfers to the organic phase during extraction and hampers reuse of the organic extractant in the process. Removal of the cobalt permits recycle of the extractant to the process.

Solvent extraction of nickel from ammoniacal solutions

An ammoniacal solution containing nickel and cobalt dissolved as nickel-ammonia complexes and cobalt-ammonia complexes is treated with a material capable of providing free ammonia in the solution, such as gaseous ammonia or aqueous ammonia, in order to increase the proportion of higher nickel-ammonia complexes to lower nickel-ammonia complexes in solution until at least about 85% of the dissolved nickel is in the form of higher nickel-ammonia complexes, i.e., complexes in which the number of NH.sub.3 molecules is greater than 3. The attainment of this high concentration of higher nickel-ammonia complexes is readily determined by various analytical procedures such as, for example, free ammonia electrode measurements and spectrophotometer measurements. The solution is then treated with a sulfiding agent in an amount sufficient to selectively precipitate out the dissolved cobalt as cobalt sulfide. The resulting slurry is separated into a nickel-enriched liquid fraction and a cobalt-enriched solids fraction. Surprisingly, when the dissolved nickel is present as a higher ammonia complex, less tends to undesirably coprecipitate with the cobalt during sulfiding. The highly desirable result is a precipitate containing up to 50% more cobalt and 20% less nickel, and a mother liquor more enriched in nickel, than normally obtained in a conventional selective sulfiding.

Enhanced selectivity in the separation of nickel and cobalt from

An aluminum-containing ore such as a kaolin or montmorillonite clay is treated with a fluorine acid such as HF or H.sub.2 SiF.sub.6 to produce aluminum fluoride (AlF.sub.3) which is recovered from the liquid phase of the reaction mixture by crystallization as AlF.sub.3 . 3H.sub.2 O crystals which are then dried and dehydrated to yield AlF.sub.3. The crystallization mother liquor is recycled to the process to recover its AlF.sub.3 values. The AlF.sub.3 . 3H.sub.2 O crystals and separated solid phase of the reaction mixture are washed to recover AlF.sub.3 values and the wash streams are recycled to the process. To produce alumina, the AlF.sub.3 is pyrohydrolyzed to Al.sub.2 O.sub.3 and HF. The HF is absorbed in the crystallization mother liquor and recycled with the mother liquor to the ore treatment step. All or a part of fluorine acid requirements can also be supplied from any suitable source such as, for example, a wet process phosphoric acid facility which is a plentiful source of inexpensive fluorine. The fluorine acid requirements can be supplied in a recycle stream of the process such as the crystallization mother liquor and/or a fresh make-up stream. The process converts the aluminum values in aluminum-containing ore deposits to a form (Al.sub.2 O.sub.3) useful in the production of aluminum metal.

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Gretna, LA, United States of America

David J Miller