Method for separating and recovering nickel and lithium

1. A method for extracting nickel and lithium comprising:

solvent extraction step of using three or more extraction stages to subject a solution containing lithium and nickel to solvent extraction with 2-Ethylhexyl phosphonic acid mono-2-ethylhexyl ester at a pH of 8.0 to 8.5, whereby the nickel and the lithium are co-extracted into a resultant organic phase.

2. The method according to claim 1 , wherein the solution containing lithium and nickel includes 5.0 to 15.0 g/L of nickel, 3.0 to 6.0 g/L of lithium, 0.01 to 0.03 g/L of cobalt, and less than 0.01 g/L of manganese.

3. A method for extracting nickel and lithium comprising:

a solvent extraction step comprising three or more extraction stages, wherein each stage subjects a solution containing lithium and nickel to solvent extraction with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester at a pH of 8.0 to 8.5, whereby the nickel and the lithium are co-extracted into a resultant organic phase, then

the resultant organic phase undergoes a back extraction step wherein the resultant organic phase undergoes back extraction with a sulfuric acid solution, whereby the nickel and the lithium are concentrated into a back extraction liquid.

4. The method according to claim 3 , further comprising a nickel extraction and carbonation process which comprises:

adjusting pH of a water phase obtained by the back extraction step with sodium hydroxide;

subjecting the pH-adjusted liquid to extraction with neodecanoic acid to selectively extract nickel into a resultant oil phase; and

neutralizing the resultant oil phase by adding sodium carbonate to recover nickel in the form of nickel carbonate.

5. The method according to claim 4 , further comprising:

neutralizing a liquid which is not extracted by the nickel extraction and carbonation process with sodium carbonate to recover lithium in the form of lithium carbonate.

6. The method according to claim 5 , further comprising:

adjusting the liquid obtained by the nickel extraction and carbonation process to a pH of 9.5 to 10.5 before the neutralization.

7. The method according to claim 3 , further comprising:

adjusting pH of the back extraction liquid with sodium hydroxide;

subjecting the pH-adjusted liquid to extraction with neodecanoic acid to selectively extract nickel into a resultant oil phase;

adding potassium oxalate to the resultant oil phase to produce a compound of nickel oxalate; and

decomposing the compound thermally and recovering nickel powder.

8. The method according to claim 7 , further comprising:

adding an alkaline agent to keep the resultant oil phase at a pH of 1.5 or more to produce the compound of nickel oxalate.

9. The method according to claim 8 , wherein the decomposing step includes heating the compound at 330 to 370 degrees C.

10. A method for extracting nickel and lithium comprising:

a solvent extraction step comprising three or more extraction stages, wherein each stage subjects a solution containing lithium and nickel to solvent extraction with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester at a pH of 8.0 to 8.5, whereby the nickel and the lithium are co-extracted into a resultant organic phase, and then

the resultant organic phase undergoes a back extraction step wherein the resultant organic phase undergoes back extraction with a sulfuric acid solution, whereby the nickel and the lithium are concentrated into a back extraction liquid, and then

scavenging an oil phase obtained by the back extraction step with a solution having an acid concentration higher than the sulfuric acid solution used in the back extraction step, thereby effusing any nickel and the lithium remaining in the oil phase to a water phase, and then additionally subjecting the resulting oil phase to the solvent extraction step.

11. The method according to claim 10 , further comprising a nickel extraction and carbonation process which comprises:

adjusting pH of a water phase obtained by the back extraction step with sodium hydroxide;

subjecting the pH-adjusted liquid to extraction with neodecanoic acid to selectively extract nickel into a resultant oil phase; and

neutralizing the resultant oil phase by adding sodium carbonate to recover nickel in the form of nickel carbonate.

12. The method according to claim 11 , further comprising:

neutralizing a liquid which is not extracted by the nickel extraction and carbonation process with sodium carbonate to recover lithium in the form of lithium carbonate.