Isotherm and kinetic studies for the adsorption of chromium and zinc ions from electroplating effluent by mercerized sugarcane bagasse-graft-poly (acrylamide-co-methacrylic acid) copolymer using column leaching experiment

Abstract

Containment of insidious heavy metal ions migrants from anthropogenic sources into the eco-system is imperative for a sustainable environment. This research aimed to evaluate the kinetic and isotherm parameters of a copolymer derived from sugarcane bagasse grafted with binary hydrophilic vinyl monomers, for the preferential remediation of chromium and zinc ions, from electroplating wastewater using column leaching experiment. Characterization of the copolymer adsorbent material showed that the monomers were effectively grafted onto the cellulosic backbone as evidenced by values of 54.11±0.51 %, 66.01±0.32 % and 331.34±0.67 Kgm^-3 for grafting efficiency, grafting percentage and bulk density respectively. The copolymer was stable in acidic and basic media, with optimum sorption at pH 3.5 and 3.0 g adsorbent dosage, with 30 min. equilibrium sorption time for chromium ion. The linear regression (R²) values from kinetic studies present pseudo-second order and film diffusion models as best fit, which affirms chemosorption as the mechanism for the coordination of the adsorbate onto the copolymer surface. The Dubinin-Radushkevich isotherm model with R² values of 0.6821 and 0.5693 for chromium and zinc ions respectively, lower than R² values between 96 to 99 %, for other isotherms studied, indicated a homogeneous and multilayered coverage of the copolymer surface by the adsorbate. The ∆G⁰ values of -8.6 KJmol^-1 and -14.5 KJmol^-1for chromium and zinc ions respectively, revealed that the leaching process was feasible and spontaneous. This study presents the copolymer, as a right for purpose adsorbent material in a column technology, to selectively attenuate these metal ions from electroplating wastewater.