Adsorptive potential of dispersible chitosan coated iron-oxide nanocomposites toward the elimination of arsenic from aqueous solution

The present study investigates elimination of the arsenic [As(III)] spiked in water via adsorption using chitosan coated iron-oxide nanocomposites (CINs) as a robust adsorbent. The synthesized adsorbent exploits the magnetic nature of iron oxide for the separation of saturated CINs from the aqueous solution upon completion of treatment process. The optimum conditions for adsorption of As (III) using CINs were found to be pH 6.0, adsorbent dosage of 2.0 g/L and contact time of 30 min. The maximum monolayer adsorption capacity (qm) calculated using Langmuir model was found to be 267.2 mg of As(III) per gram of CINs. The separation factor (RL) was found to lie within 0-1, predicting that the adsorption of As(III) onto CINs is a reversible process. Based on the calculated heterogeneity parameter from Freundlich isotherm (n = 2.236), the process is highly favorable physisorption while the kinetics of the process was best explained by pseudo-second order rate equation. The regeneration of the saturated CINs could be performed using a simple acid base treatment using 0.1 N HCl and NaOH. Upon recycling the adsorbent for 5 batches of repeated adsorption studies, only a meagre 13% loss over its initial adsorption capacity was observed. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.