Structural and compositional variation of zeolite 13X in lithium sorption experiments using synthetic solutions and geothermal brine

This study provides insight into the potential application of zeolite 13X powder and beads for direct lithium extraction. The impact of variable stirring time, pH and temperature is investigated. The major ion-exchange process is found to be Li+ vs. Na+ or H+, reaching a maximum sorption capacity of 20.3 mg/g using 13X powder whereas only 8.6 mg/g Li is sorbed to 13X beads. Equilibrium between sorbent and fluid is reached within 1 min and 9 h contact time for powder and beads, respectively. The temperature effect on Li sorption is negligible, whereas pH adjustment to more acidic conditions decreases the Li sorption capacity by up to 68% compared to non-adjusted conditions. Chemical data fits well with changes in crystal parameters confirming the data's significance. Different sorption processes like physisorption, ion exchange of Na+ and H+ with Li+, and different Li sorption sites on zeolite 13X sorbent are indicated. Solutions of different concentrations have been tested for desorption. Lithium recovery from the previously loaded sorbent reaches 94–100%. Aiming at a direct Li extraction technique from geothermal brines in the future, this study shows that zeolite 13X is a promising sorbent although challenges regarding higher selectivity for Ca, K, Mn, Ba, and As need to be resolved for its application in a high saline environment.