Synthesis, characterization and investigation of chitosan-functionalized ZnFe2O4 for the removal of dichlorvos from aqueous solution

Abstract

Chitosan was successfully functionalized with zinc ferrites (Cs-ZnFe2O4), the composite was characterized using powder X-ray Diffraction, (XRD), scanning electron micrograph (SEM) and Fourier transform infrared spectroscopy (FTIR) and used as adsorbent for removal of 2, 2-dichlorovinyl dimethyl phosphate (DDVP) insecticide from aqueous solutions in batch processes. The equilibrium data were subjected to Langmuir, Freundlich, Dubinin-Radushkevich (R-D), Tempkin, Redlich-Peterson and Sips isotherms models. Pseudo-first order, second order, Elovich and intra particle diffusion models were used to analyzed the kinetics data. The composite was able to remove DDVP from aqueous solution by 90.10 to 99.85 % as the pH was increased from 1 to 8, while an increase in removal efficiency from 6.80 to 88.9 % was observed as the dosage was increased 0.01 to 0.1 g/100 mL. Langmuir isotherms best described the adsorption process with maximum capacities of 119.86 mg/g which compared favorably with other adsorbents in the same category. The adsorption process followed pseudo second-order kinetics with correlation coefficient (R2) values > 0.9 and error margin of 0.003 to 0.009% between Qe(cal.) and Qe(exp). The average ΔG, ΔH and ΔS values of −22.65, 84.51 kJ mol-1 and 339.9 J mol-1K-1 respectively obtained revealed that the adsorption process was spontaneous and endothermic with increase entropy at adsorbate surface. Thus, chitosan modified with zinc ferrites is an efficient adsorbent for the removal of DDVP insecticide from aqueous solution