Detoxification of arsenic from contaminated water using chitosan and radiation-induced grafted chitosan: a comparative study

Presence of arsenic in groundwater, eventually in drinking water, has been recognised as a serious community health problem, due to its high toxic nature. Therefore, its removal is highly essential. Chitosan-based adsorbents have been widely used in water treatment in the present scenario due to their abundance and cost-effectiveness. However, there are some problems hindering its practical use, such as low tensile strength and low solubility in acidic mediums. Thus, in this work, to enhance the adsorption capacity of chitosan for the removal of As (V), it has been modified by grafting with monomer HEMA and SSS using gamma radiation. Modified chitosan was characterised by SEM and FTIR spectroscopy. In grafted and ungrafted chitosan, maximum adsorption capacity was found to be (16.8) mg/g and 1.78 (mg/g) using the 0.1 g of adsorbent dose at pH 3–4 in 35 min, and initial As (V) concentration of 60 mg/L. Isotherm study reveals the adsorption process followed by Langmuir isotherm model for both grafted and ungrafted chitosan. Kinetic study suggested that grafted chitosan followed pseudo second order whereas chitosan followed first order kinetics. The thermodynamics indicated that the adsorption process of modified chitosan for As (V) was endothermic and spontaneous in nature.