سنتز هيدروژل نانوكامپوزيت بر پايه كيتوسان براي حذف فلزات سنگين از آب‌هاي آلوده

Water, as an essential resource for sustaining life, is under constant threat from pollution caused by heavy metals. Recently, polysaccharide hydrogels have been extensively studied as adsorbents in drinking water purification an‎d wastewater treatment. In recent years, chitosan has attracted considerable attention as a raw material for polysaccharide-based hydrogels due to its wide availability, biocompatibility, high adsorption capacity, biodegradability, an‎d non-toxic degradation products. The aim of this study was to investigate a chitosan-based hydrogel with favorable adsorption capacity for removing cadmium, nickel, an‎d thallium cations from aqueous solution. In this study, a nanocomposite hydrogel was synthesized using pomegranate shell as a filler, modified Nano silica as a reinforcing agent, a synthetic polymer poly (sodium styrene sulfonate) for covalent graft polymerization on the chitosan substrate, an‎d citric acid as a green crosslinker in a chitosan-based networked polymer, along with carboxymethyl cellulose. The resulting nanocomposite hydrogel was designated as CMC@Per-C3SO3-NH3+CS-g-(PSI)/PP. This hydrogel was characterized using thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), infrared spectroscopy (FT-IR), specific surface area (BET), energy-dispersive X-ray spectroscopy (EDS), an‎d nuclear magnetic resonance (NMR). Optimal component concentrations for preparing the adsorbent an‎d experimental parameters including initial metal ion concentration, contact time, pH, temperature, an‎d selec‎tivity were also investigated. The adsorption capacities of the hydrogel reached, in the optimal conditions, 547.61, 464.35, an‎d 448.52 mg g⁻¹ for Cd²⁺, Ni²⁺, an‎d Tl⁺, respectively. To describe the kinetic an‎d isotherm behavior, the Langmuir an‎d pseudo-second-order models were respectively employed, an‎d thermodynamic studies indicated that adsorption is an endothermic an‎d spontaneous process for all three metals. Furthermore, reuse tests showed that the hydrogel maintained good adsorption capacity for all metal ions after five cycles.

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