Adsorption of arsenic from aqueous media using lateritic minerals: Equilibrium, kinetic and thermodynamic studies

Abstract

Abstract The sorption behavior of arsenic on minerals from a lateritic weathering has been investigated to evaluate its potential for the decontamination of arsenic ions from aqueous media. Various physicochemical parameters such as pH, equilibration time, adsorbent dose, concentration of adsorbate, effect of diverse ions and temperature were studied in order to simulate the best conditions under which this material can be used as an adsorbent, employing batch method and radiotracer technique. Maximum adsorption was observed in buffer solutions having pH of 2.0 and 8–9, using 0.5 g of adsorbent for 6.674 · 10 –5 mol L –1 arsenic concentration in 10 min equilibration time. The sorption data followed the pseudo-second order reaction kinetics. The adsorption data fit both the Freundlich and Dubinin-Radushkevich isotherm equations over the range of 3.195 · 10 –5 to 3.195 · 10 –3 mol L –1 arsenic concentration. The characteristic Freundlich constants i.e. 1/n = 0.427 ± 0.009 and K = 3.04 × 10−4 ± 1.46 · 10 –5 mol g –1 have been computed for the sorption system. The sorption mean free energy from the Dubinin-Radushkevich isotherm is 12.00 ± 0.38 kJ mol –1 indicating ion-exchange mechanism of chemisorption. The uptake of arsenic increases with the rise in temperature (278.16–323.16 K). Thermodynamic quantities i.e. ΔG, ΔS and ΔH have also been calculated for the system. The sorption process was found to be endothermic.