Canadian Journal of Chemical Engineering, Vol.98, No.2, 544-555, 2020
Adsorption of lithium ions on lithium-aluminum hydroxides: Equilibrium and kinetics
The rapid development of rechargeable lithium batteries has promoted the demand of primary lithium products obtained from lithium-bearing resources, especially salt lakes. Layered lithium-aluminum hydroxides connecting with ion exchange resin were used for the adsorption of lithium ions from aqueous resources. Batch experiments were conducted to determine the effects of pH, initial lithium concentration, and contact time on lithium adsorption. The optimal conditions for lithium adsorption were found to be pH = 7, and the equilibrium time is approximately 600 minutes. The selectivity experiment indicated that the adsorbent showed selectivity toward lithium ion, so the adsorbent could be used in the separation of lithium ion with other metal ions, especially the divalent magnesium ions. The experiment showed that the existence of the magnesium chloride enhanced the lithium adsorption onto the adsorbent greatly. The kinetic data were analyzed by several kinetic models, and the best result was achieved with a pseudo-second-order model. The commonly used adsorption isotherms were used to fit the experimental data by nonlinear regression. Both Langmuir and Temkin isotherm models could describe the isotherm well. The thermodynamic parameters (Delta G, Delta S, and Delta H) were also calculated subsequently and the results showed the lithium adsorption process is exothermic with the decrease of randomness. Breakthrough curves demonstrated the cyclic stability of the adsorbent and the influence of the feed flow rate. Lithium ions were effectively adsorbed from the aqueous solution by the adsorbent, demonstrating its feasibility for lithium recovery and providing the fundamental data for further column design.