Enhanced Removal of Dichlorvos from Aqueous Solution using zinc-silver Bimetallic Nanoparticles Embedded in Montmorillonite-Biopolymer Nanobiocomposites: Equilibrium, Kinetics and Thermodynamic Studies

Abstract

The present investigation is focused on the application of bimetallic zinc-silver (Zn-Ag) nanoparticles embedded in montmorillonite (MMT)-polysaccharide (chitosan-Ch and gum ghatti-Gg) nanobiocomposites for the removal of dichlorvos (DCV) from aqueous solution. Operating parameters viz., pH (4.0-11.0), contact time (30-360 min), temperature (20-50 °C), initial DCV concentration (20-140 mg/L), composite dosage (0.2-1.2 g/L) were optimized. Zn-Ag/MMT/Ch nanobiocomposite showed the maximum removal of DCV (96.6 %) followed by Zn-Ag/MMT/Gg (85.3 %) nanobiocomposite and Zn-Ag/MMT (64.3 %) nanocomposite. The process followed a heterogenous mode of DCV adsorption by all the composites. The kinetic studies indicated that the DCV adsorption followed pseudo-first order model. Intraparticle diffusion and Boyd plot suggested that the film diffusion was not the sole rate limiting step. The thermodynamic parameters indicated the feasibility and exothermic nature of DCV adsorption. The mechanism of adsorption process was further elucidated by FT-IR, AFM and EDX analysis. Packed bed column studies showed the removal of DCV up to 79.3 % using Zn-Ag/MMT/Ch under 12 cm bed height, 1 ml/min of flow rate and at 0 % dilution. Regeneration studies suggested that the Zn-Ag/MMT/Ch could be reused up to three cycles.