On the adsorption of neodymium species from aqueous solution by beneficiated palygorskite

Abstract

Run-of-mine (ROM) palygorskite (PAL) from Guadalupes (Piauí/Brazil) was prepared, beneficiated and then properly characterized by physical–chemical analyses. Then, the removal of Nd3+ ions by PAL was evaluated as a function of solution pH, adsorbent concentration, and initial metal concentration. The results showed that the maximum sorption capacity was 18 mg/g, and more than 99 % of Nd was remove from the solution at pH 5. The sorption data were analysed by several isotherm models, but the better good of fitness (R2 ≥ 0.97; RMSE ≤ 0.98) was attributed to the Temkin model. It́s suggested that the adsorption process proceeds firstly by the introduction of the Nd ions into the interior and exterior pore of PAL, then the PAL surface acquires a negative charge by deprotonation of PAL actives sites (Me-OH), and then the capture of the Nd3+ ions on its inside and outside surface may take place through electrostatic interaction. Thermodynamic parameters indicated that the sorption process was favourable and endothermic. Thus, the present results pointed out that palygorskite has potential for removing Nd ions, and probable another rare earth elements from aqueous solutions, being a promisor adsorbent to the treatment of effluents containing neodymium, e.g. industry of permanent magnets.