Process for Recovery and Purification of Lithium from Dilute Sources

Abstract

A process was studied for recovery and purification of lithium from hot spring water and leachate of coal fly ash in which lithium is present at very low concentration in a mixture of high concentration of less desirable species such as alkali metals, alkaline earth metals and others. Lithium is, as a first step, adsorbed selectively by an ion-sieve type adsorbent, λ-MnO2, which can effect separation by adsorbing lithium alone in its intraparticle spaces while adsorbing most metals on its surface. Stagewise elutions are performed, employing two elutrients : NH4NO3 and then HNO3 solution. The concentration ratio of lithium and sodium is 1/70~1/120 in the original feed stream, and this is upgraded to 300/1 in the pregnant elutrient. Some impurities in the pregnant elutrient is removed by a solvent extraction technique, employing a mixed extractant of a β-diketone (LIX51) and tri-n-octyl-phosphine oxide in kerosene. A lithium solution with an undetectable amount of impurities is obtained by single extraction followed by single scrubbing with dilute hydrochloric acid of carefully controlled concentration. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.