Adsorptive removal of monocrotophos from aqueous solution using biopolymer modified montmorillonite-CuO composites: Equilibrium, kinetic and thermodynamic studies

The present study is focused on the adsorptive removal of monocrotophos (MCP), an organophosphate insecticide onto biopolymer modified montmorillonite (MMT)-CuO composites viz. MMT-CuO-Chitosan (Ch), MMT-CuO-Gum ghatti (Gg), and MMT-CuO poly lactic acid (PLA). Optimization experiments were conducted by varying five parameters viz., pH (3-12), contact time (2-30 h), temperature (10-50 degrees C), initial MCP concentration (20-140 mg L-1) and composite dosage (5-25 gL(-1)). The removal of MCP followed the order: MMT-CuO-PLA (83.99%) > MMT-CuO-Ch (71.6%) > MMT-CuO-Gg (62.1%) > MMT-CuO (40.8%). Equilibrium and kinetic studies revealed a heterogenous and physical mode of adsorption with the highest adsorption capacity 212.23 mg g(-1). This was further confirmed by SEM analysis. Intraparticle diffusion and Boyd plot suggested that film diffusion was not the sole rate limiting process. Thermodynamic studies confirmed the spontaneous and endothermic nature of the process. FTIR analysis confirmed the major involvement of amines and carboxyl groups during MCP adsorption. EDX analysis confirmed the major participation of carbon atom followed by CuO nanoparticles and Si in the process. AFM analysis confirmed the homogenous distribution of CuO nanoparticles on the surface of MMT-CuO-PLA which validated the potentiality of PLA modified MMT-CuO composite for the remediation of MCP from aqueous environment. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.