Equilibrium and Kinetic Studies on Lithium Adsorption from Geothermal Water by λ-MnO₂

Abstract

The adsorption equilibria of lithium from geothermal water were investigated by using both powdery and granulated forms of λ-MnO2 derived from spinel-type lithium manganese dioxide. Optimum amounts of adsorbents were 1.0 g adsorbent/L-geothermal water for powdery λ-MnO2 and 6.0 g adsorbent/L-geothermal water for granulated λ-MnO2. The adsorbents exhibited the promising adsorption capacities and their adsorption equilibria of lithium agreed well with the Langmuir adsorption isotherm model. The kinetic data of lithium adsorption have been evaluated using pseudo-first-order, pseudo-second-order kinetics models, as well as Elovich kinetic model. In addition, intra-particle diffusion model has been used for evaluating the kinetic data to evaluate the adsorption mechanism. The adsorption kinetic process was attributed to the gradual adsorption stage where intra-particle diffusion was found as the rate-controlling step.