Radiation crosslinking and grafting of chitosan: Conversion of biowaste to an efficient adsorbent for removal of cationic dyes

By the mutual radiation grafting technique using Co-60 gamma radiation, a novel anionic adsorbent "CRChitosan-g-SSS" was developed where in p-Sodium Styrene Sulphonate was covalently grafted onto crosslinked chitosan backbone. The synthesized radiation-grafted adsorbent was tested for the adsorptive removal of cationic dyes: methylene blue, malachite green and Congo red from aqueous solutions. The adsorbed amount of the respective dyes was 89.12, 73.13, and 29.14 (mg/g) respectively, which could be better described with Langmuir isotherm and pseudo-second-order reaction according to the correlation coefficient values, indicating favorable and feasible adsorption. Various factors influencing the adsorption capacity of"CRChitosan-g-SSS" like initial dye concentration, contact time, solution pH, and temperature were also studied. Different thermodynamic parameters such as standard free energy, standard enthalpy, and standard entropy were calculated which revealed the adsorption process to be exothermic and spontaneous. The radiation-grafted anionic adsorbent showed promising properties for the removal of toxic cationic dyes (i.e. Methylene blue, Malachite green, and Congo red).