N-allylthiourea chitosan (ATUCS), a chelating material, was prepared, characterized, and studied for the removal of arsenazo III (As (III)) dye from aqueous solution. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and 1H- and 13C-nuclear magnetic resonance (NMR) were used to characterize the prepared adsorbent and to investigate the adsorption mechanism. Furthermore, the adsorption behavior of chitosan (CS) and ATUCS were studied under various conditions. The equilibrium adsorbed amount of As (III) onto ATUCS was found to be 116.3 mg/g, compared to 87.3 mg/g with respect to CS. The regeneration of the loaded CS and ATUCS were studied using 1:1 solution of H2O2-H2SO4 and reused with certain change in efficiency after the third cycle. The adsorption process was found to fit well with pseudo-second-order kinetic model. The equilibrium data were better described with the Freundlich isotherm. The monolayer adsorption capacity was found to be 204.08 and 90.90 mg/g for the As (III)/ATUCS and As (III)/CS systems, respectively, at 25 °C. The pH of the higher uptake of As (III) onto ATUCS and CS was 4-5 and 8.0, respectively. The results demonstrated improved adsorption of As (III) using ATUCS as compared to the CS.
Keywords: Adsorption; Arsenazo III; Chitosan; Kinetics; Thermodynamics; Thiourea.
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