Researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia engineered a continuous electrically driven membrane process to extract lithium from seawater.

Marine waters contain about 5,000 times more lithium than is found on land and can potentially represent an almost unlimited resource to meet rapid growth in demand for lithium batteries. However, harvesting this metal from seawater is challenging due to its low concentration and an abundance of interfering ions.

The electrochemical cell designed to address these obstacles contains a ceramic membrane made from The electrochemical cell separates lithium ions from seawater. Source: Zhen Li et al./KAUSTlithium lanthanum titanium oxide (LLTO). Holes in its crystal structure are just wide enough to let lithium ions pass through while blocking larger metal ions. Seawater flows into a central feed chamber, where positive lithium ions pass through the membrane into a side compartment containing a buffer solution and a copper cathode coated with platinum and ruthenium. Negative ions exit the feed chamber through a standard anion exchange membrane, passing into another compartment containing a sodium chloride solution and a platinum-ruthenium anode.

When tested with water samples from the Red Sea, the system successfully enriched lithium by 43,000 times. Lithium phosphate with a purity of 99.94% was directly precipitated from the enriched solution, meeting purity requirements for lithium battery industry applications.

A research paper on the economically viable system for harvesting high-purity lithium from seawater is published in Energy and Environmental Science.