Removal of chromium (VI) from aqueous medium using chemically modified banana peels as efficient low-cost adsorbent

Abstract

The adsorptive removal of hexavalent chromium Cr(VI) from aqueous solutions was investigated by acrylonitrile grafted banana peels (GBPs). Banana peels were treated with 10% HCl, followed by alkaline hydrolysis with 10% NaOH, and washed thoroughly. The bleaching of alkali hydrolyzed peels was carried out with sodium chlorate (NaClO3) in the presence of hydrogen peroxide and glacial acetic acid. The grafting co-polymerization of acrylonitrile onto the bleached pulp was initiated by Fenton’s reagent (Fe+2/H2O2). The optimum conditions for adsorption of Cr(VI) were found to be the following: pH 3, adsorbent dose 4g/L, concentration 400mg/L and contact time of 120min. The surface morphology of adsorbent was characterized by scanning electron microscopy (SEM) before and after the adsorption. The adsorption of Cr(VI) onto grafted banana peels (GBPs) was recorded to be 96%. The adsorption data were fully fitted with the Freundlich and Langmuir isotherm model and followed a pseudo-second order kinetic model. Thermodynamic study showed that the adsorption is exothermic and spontaneous. Owing to high efficiency and low cost, grafted banana peels (GBPs) can be used as effective adsorbent for Cr(VI) removal from wastewater.