Competitive sorption behavior of some metal ions of nuclear and industrial interest in highly acidic solution using chitosan- acrylic acid polymeric resin prepared by gamma radiation.

The current investigation is conducted to evaluate the sorption capability of an environmentally friendly absorbent polymer chitosan acrylic acid (CS-PAA) towards some metal ions such as Sr (II), Gd(III) and Zr(IV). The polymer is prepared by grafting polymerization using gamma ray. It was exposed to 5 kGy/h of absorbed doses of Co-60 radioactive source for γ-radiation. Scanning electron microscopy (SEM), thermos-gravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FT-IR) were utilized to investigate the chemical structure and morphological characterizations of the hydrogel polymer. The FT-IR data demonstrated that grafting the acrylic acid onto the chitosan backbone was accomplished satisfactorily. while the SEM revealed a surface with a homogeneous and interconnected pore structure. The adsorption experiments demonstrated that, the polymer eliminated 92.4%, 84.9%, and 62.8% of Zr (IV), Gd (III) and Sr (II) ions, respectively at pH 4. The hydrogel adsorbent's maximum adsorption capacities for Sr (II), Gd (III), and Zr (IV) were 48.2, 57.6, and 66.7 mg/g, respectively. The utilized adsorbent could be regenerated for further usage and the regenerated adsorbent was still able to maintain adsorption capabilities that were nearly identical to the original after four adsorption-desorption cycles. The most appropriate fit to the kinetic data was pseudo second order (R2 = 0.99 for Zr, 0.98 for Gd, and 0.97 for Sr), suggesting a mechanism driven by chemisorption. Equilibrium isotherm data were fitted and the Sips model best described the adsorption behavior across all metal ions (R2 > 0.98), capturing both homogeneous and heterogeneous site interactions.