Thermally-driven ion-exchange process for lithium recovery

Apparatus for producing in cycles, each cycle comprising at least two phases, and from a feed solution containing at least one desirable ion (DI) and at least one undesirable ion (UI), a solution enriched in said at least one DI and a solution impoverished in said at least one DI, said apparatus comprising:

• a source of said feed solution;
• a train through which solution can flow said train having an inlet and an outlet, and including at least one bed of an ion-exchange material having a higher temperature-dependent selectivity for said at least one DI in the solution flowing therethrough at a first temperature different from a second temperature;
• means for introducing said feed solution to the said train;
• temperature control means for controlling the temperature of the solution flowing through the said train to selectively obtain a different one of said first and second temperatures in said train for each one of said two phases during each of a series of cycles;
• the solution flowing through said train during the first phase at said first temperature reaching the outlet of said train being impoverished in said at least one DI;
• part of the DI-impoverished solution being stored and then later re-entering the outlet of the said train as DI-impoverished reflux during said second phase at said second temperature;
• the solution flowing in the opposite direction through said train during the second phase at said second temperature reaching the inlet of said train being enriched in said at least one DI;
• part of the DI-enriched solution being stored and later re-entering the inlet of said train as DI-enriched reflux during the first phase at said first temperature in the next cycle, wherein said DI includes lithium ion, said UI comprises at least one other alkali metal ion and said ion exchange material comprises zeolite X.