Processes for metal ions removal from aqueous solutions
Provided are continuous methods and processes for removing Li ions from an aqueous feed solution.
1. A continuous method of removing Li ions from an aqueous feed solution, comprising the steps of:
(a) contacting said aqueous feed solution with an extracting organic solution comprising an organic diluent, at least one phosphine oxide, and at least one proton donating agent under basic pH to obtain two separate phases: (i) an organic phase comprising extracted Li ions and (ii) an aqueous solution comprising at least a portion of said at least one phosphine oxide;
(b) stripping said separated organic phase (i) comprising extracted Li ions obtained in step (a) to obtain two separated phases: (iii) an aqueous solution comprising Li ions removed from said organic phase and (iv) an organic stripped solution; and
(c) combining the separated aqueous solution (ii) obtained in step (a) and the separated stripped organic solution (iv) obtained in step (b), thereby regenerating said extracting organic solution of step (a) and then recycling said solution in step (a); and
wherein said method is continuous and closed-cycled without adding additional extracting solution before repeating steps (a) and (b).
2. The method of claim 1 , wherein said basic pH in step (a) is in the range of from 7 to 14.
3. The method of claim 1 , wherein said stripping in step (b) is performed at a pH that is lower than the pH of extraction step (a).
4. The method of claim 1 , wherein said at least one phosphine oxide has a general formula (I),
wherein each of R 1 ,R 2 and R 3 is independently selected from straight or branched C 1 -C 10 alkyl, straight or branched C 2 -C 10 alkenyl, straight or branched C 2 -C 10 alkynyl, optionally substituted C 5 -Cl 2 aryl, and optionally substituted C 4 -C 12 heteroaryl.
5. The method of claim 1 , wherein said at least one proton donating agent is selected from the group consisting of straight or branched C 1 -C 10 alcohol, C 1 -C 10 ketone, C 1 -C 10 aldehyde, C 3 -C 20 fatty acid, and any combination thereof.
6. The method of claim 1 , wherein the molar ratio between said phosphine oxide and said at least one proton donating agent in said extracting organic solution is in the range of from about 5:1 to 1:5.
7. The method of claim 1 , further comprising after step (a) purifying the organic phase comprising extracted Li ions prior to step (b).