Effective arsenite adsorption from aqueous solution using N- and S-functionalized tetragonal nano-zirconia on chitosan-derived carbon

Abstract

Arsenic pollution in water is a recurring problem for countries where groundwater is the only source of survival. Adsorption is considered as a promising treatment method to abate arsenic pollution in water due to its numerous admirable advantages. In this paper, a facile functionalization of N- and S-rich nano-zirconia (ZrO2) is presented in-conjunction with in situ precipitation using l-cysteine (Cys), a non-essential amino acid, and prepared with a semi-carbonized (500 °C) chitosan biopolymer, ChiC, (ZrO2-Cys@ChiC) by a hydrothermally assisted method. The interaction of Cys on ZrO2 and ChiC moieties in ZrO2-Cys@ChiC was investigated for the adsorption of toxic arsenite (AsO33-) from water by batch and column adsorption methods. The structure of the prepared materials before and after adsorption of arsenite was characterized by a series of techniques such as powder XRD, XPS, BET, SEM, EDAX, mapping, CHN analysis. The adsorption of arsenite on the prepared ZrO2-Cys@ChiC hybrid adsorbent was best described by the Langmuir adsorption isotherm and the pseudo-second-order kinetic models. Apart from the isostructural and isoelectronic nature of the phosphate ions in the selectivity assay, arsenite adsorption is not hindered at basic pH conditions. After adsorption, the stability of the material was maintained without any change in the surfaces and crystalline nature, as shown by XPS, SEM, and powdered XRD. The reusability and column test results confirmed the potential use of the ZrO2-Cys@ChiC adsorbent for the effective removal of arsenite from water. Combining the high removal density and selectivity with fast kinetics, the prepared ZrO2-Cys@ChiC hybrid adsorbent has great potential for the removal of arsenite from aqueous solutions.