High efficiency simultaneous adsorption of rare earth elements from aqueous solutions using carbon xerogel-chitosan composite

This study investigated the simultaneous sorption of rare earth elements (REEs) from acidic media using carbon xerogel functionalised with chitosan. The combined carbon xerogel with chitosan that was synthesised has a sphere-like structure and a larger BET surface area (275 m2 g-1) than pure carbon xerogel alone (228 m2 g-1). To determine the optimal conditions, adsorption of REEs was established under different variables, including pH, contact time, initial concentration, adsorbent wt. and temperature, as well as desorption experiments. The adsorption isotherms showed that both the Freundlich and Langmuir models were followed, in addition to a pseudo-second order kinetic model. The adsorption is likely exothermic, which confirms it is favourable at low temperatures, and a dissociative adsorption process is involved, according to analysis of thermodynamic state functions. Langmuir calculations revealed that the maximum amount of REEs that were adsorbed was 164 mg/g. Because of its superior adsorption capacity and simplicity in using a recycled material following several desorption cycles, carbon xerogel-chitosan is being employed as a novel adsorbent material to remove REEs from aqueous solutions.