Fabrication removal method of gallic acid and Pb2+ ions in real samples by a new adsorbent chitosan grafted with a mixture of itaconic acid-methacrylamide

In this study, chitosan (CTS) with medium molecular weight, using a mixture of monomers, itaconic acid (IA) and methacrylamide (MAm) were grafted in the presence of radical initiator, 4,4'-azobis(4-cyanovaleric acid) (ACV) and ethylene glycol dimethacrylate (EGDMA) as cross-linkage. The best graft yield was obtained by gravimetric method (EGDMA = 2 mL, ACV = 0.01 g, IA = 0.01 g, MAm = 0.09 g, t = 45 min, CTS = 0.2 g. The characterization was performed by X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy methods. The composite was used to adsorb Pb 2+ and gallic acid compounds and important adsorption parameters including pH, adsorption time, adsorbate concentration and adsorbent amount were optimized. The best adsorption conditions for Pb 2+ (time = 75 min, pH = 4.0, adsorbent = 0.05 g, adsorbate concentration = 150 mg/L and q max = 276 mg/g) and for gallic acid (time = 60 min, pH = 3.0, adsorbent = 0.02 g, adsorbate concentration = 300 mg/L and q max = 576 mg/g) were recorded. The adsorption data's were fitted by Langmuir isotherm and pseudo-second-order kinetic model, as well. Thermodynamic studies showed that the adsorption process is endothermic and spontaneous and due to the increase in entropy confirms the proper interaction of the adsorbent and adsorbate. Meantime, due to the high adsorption capacity of the adsorbent and good efficiency after several times of adsorption-desorption, it can be used as an industrial adsorbent.