Method for removing impurities from solvent extraction solutions
A method for regenerating an amine extractant used for recovery of metals involves contacting a liquid organic phase containing an amine complexed with one or more metals with an aqueous solution substantially free of chloride ions to strip the one or more metals from the organic phase. The stripped organic phase is then contacted with a solution of hydrochloric acid to regenerate the amine extractant which can then be recycled in a production process.
1. A process for regenerating metal loading capacity of an amine comprising:
providing a liquid organic phase containing an amine complexed with a metal that loads on the amine as a chloride complex, wherein said metal is selected from the group consisting of Zn and Fe;
contacting said liquid organic phase with an aqueous solution substantially free of chloride ions to strip said metal without formation of a metal precipitate; and
contacting the stripped organic phase with a solution containing chloride ions to hydrochlorinate the amine.
2. A process for regenerating the metal loading capacity of an amine according to claim 1 wherein said amine has the formula R 1 R 2 R 3 N wherein R 1 , R 2 and R 3 may be the same or different and are selected from the group consisting of aliphatic, aryl, aromatic chain and hydrogen atom(s).
3. A process for regenerating the metal loading capacity of an amine according to claim 2 wherein said amine is a tertiary amine selected from the group consisting of triisobutylamine, trihexylamine, triisooctylamine, triisononylamine and triphenylamine.
4. A process for regenerating the metal loading capacity of an amine according to claim 1 wherein said liquid organic phase comprises an aliphatic diluent.
5. A process for regenerating the metal loading capacity of an amine according to claim 4 wherein said aliphatic diluent is a paraffin solvent.
6. A process for regenerating the metal loading capacity of an amine according to claim 5 wherein said paraffin solvent comprises isoparaffins.
7. A process for regenerating the metal loading capacity of an amine according to claim 1 wherein said liquid organic phase comprises an alcohol.
8. A process for regenerating the metal loading capacity of an amine according to claim 7 wherein the alcohol is an alkanol.
9. A process for regenerating the metal loading capacity of an amine according to claim 9 wherein the alkanol is isodecanol.
10. A process for regenerating the metal loading capacity of an amine according to claim 1 wherein said aqueous solution substantially free of chloride ions contains an ion selected from the group consisting of sulfate, nitrate and phosphate.
11. A process for regenerating the metal loading capacity of an amine according to claim 10 wherein the concentration of sulfate, nitrate or phosphate ranges from about 0.01 to about 300 grams per liter.
12. A process for regenerating the metal loading capacity of an amine according to claim 1 wherein said solution containing chloride ions is a hydrochloric acid solution.
13. A process for regenerating the metal loading capacity of an amine according to claim 12 wherein said hydrochloric acid solution ranges from about 0.5N to about 6N.
14. A process for regenerating the metal loading capacity of an amine according to claim 1 further comprising returning the hydrochlorinated amine to a solvent extraction circuit.
15. A process for regenerating the metal loading capacity of an amine according to claim 1 wherein the ratio of liquid organic phase to the aqueous solution (O/A ratio) is about 1.
16. A process for regenerating the metal loading capacity of an amine according to claim 1 wherein the temperature ranges from about 10° C. to about 80° C.