Removal of Cr(VI) from aqueous solutions using EDCC-MCM-41: Isotherm, kinetics and thermodynamic evaluation

Abstract

EDCC-MCM-41, a novel ethylenediamine derivative of MCM-41 was synthesized from a sugar industry waste, bagasse fly ash. Studies were carried out on its ability to remove Cr(VI) from aqueous solution. Its performance was also compared with that of unmodified MCM-41 and an already known derivative NH2-MCM-41 (both also synthesized from bagasse fly ash) at the same experimental conditions. Results show that the novel adsorbent produced a better sorption performance (adsorption capacity of 49.04 mg g−1) than MCM-41 and NH2-MCM-41 which produced adsorption capacities of 13.78 mg g−1 and 25.29 mg g−1 respectively. Thermodynamics, kinetics and isotherm studies confirm that the sorption process involving the novel adsorbent is favorable for Cr(VI) and can best be represented by pseudo-second-order kinetics model. The sorption process was also found to be multistep, involving both film diffusion and intraparticle diffusion into the pores on the adsorbent’s surface.Abbreviations: BFA: Bagasse Fly Ash; MCM-41: Mobil Composition of matter no. 41; NH2-MCM-41: mine functionalized MCM-41; EDCC-MCM-41: Ethylenediamine grafted MCM-41; qe: Mass of material adsorbed at equilibrium per mass of adsorbent; qt: Mass of material adsorbed at any time t per mass of adsorbent; C0: The initial concentration; Ce: The residual concentration at equilibrium; Ct: Residual concentration at any time t; W: The weight of adsorbents; rRMSD: Root mean square deviation; R: Gas constant