Modified chitosan for the collection of reactive blue 4, arsenic and mercury from aqueous media

In the present investigation a series of modified chitosan as adsorbents were synthesized free radically at 70 °C using acryloylated chitosan (AC-chitosan) as macromer, 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS), 2-(diethylamino) ethylmethacrylate (DAEMA) as co-monomers and N,N′-methylene bisacrylamide (N-MBA) as a crosslinker for using as adsorbents in effluent remediation. Their structures (1H and 13C NMR), thermal stability (TG/DTG), surface morphology (SEM), reactive blue 4 (RB4), toxic metals such as arsenic (AsO2−) and mercury (Hg2+) uptake, swellability and reusability were evaluated. The adsorption of RB4 (701 mg/g), and the uptake of AsO2− (551 mg/g) and Hg2+ (455 mg/g) showed Langmuir isotherm behavior with pseudo-first-order kinetics. The diffusion of water, RB4, AsO2− and Hg2+ into the matrix followed non-Fickian mechanism. The evaluated changes in Gibbs free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) for adsorption indicated that the process was exothermic.