Effective removal of dichlorvos from aqueous solution using biopolymer modified MMT-CuO composites: Equilibrium, kinetic and thermodynamic studies

In the present study, the adsorption experiments were carried out with dichlorvos (DCV), an organophosphate insecticide using biopolymer modified montmorillonite (MMT)-CuO composites viz. MMT-CuO-Chitosan (Ch), MMT-CuO-Gum ghatti (Gg), and MMT-CuO-Poly Lactic add (PIA) along with control (MMT-CuO). Optimization of parameters viz., pH (3.0-12.0), contact time (1-12 h), temperature (20-50 degrees C), initial DCV concentration (20-100 mg L-1) and composite dosage (0.5-3.0 g L-1) was done during the adsorption process. The DCV removal was found to be maximum in case of MMT-CuO-Ch composite (93.4%) followed by MMT-CuO-Gg (87.8%), MMT-CuO (832%) and MMT-CuO-PIA (633%). Equilibrium data showed the best fit to Freundlich model with the highest adsorption capacity suggesting a heterogenous mode of DCV adsorption. This was further confirmed by SEM analysis. Better applicability of pseudo-first order kinetic model suggested physisorption as the underlying phenomena. Intraparticle diffusion and Boyd plot suggested that film diffusion was not the sole rate limiting process for DCV adsorption onto MMT-CuO-Ch composite. Thermodynamic studies confirmed the spontaneous and endothermic nature of the process. FTIR analysis confirmed the major involvement of amines and alcohol groups during DCV adsorption. EDX analysis confirmed the major participation of carbon atom followed by CuO nanoparticles and Si thereby suggesting the involvement of all the three components in adsorption. AFM analysis confirmed the homogenous distribution of CuO nanoparticles on the surface of the MMT-CuO-Ch composite which validated the potentiality of chitosan modified MMT-CuO composite for the effective removal of DCV from aqueous environment. (C) 2015 Elsevier B.V. All rights reserved.