Efficient removal of Cr(VI) from aqueous solutions using chitosan/Na-alginate bio-based nanocomposite hydrogel

This research article aimed to assist the works conducted to save water resources, which are rapidly depleted as a result of climate change by eliminating toxic chromium ions Cr(VI) from simulated solution. In this regard, chitosan/Na-alginate/polyacrylic acid (CS/Na-Alg/PAAc) and Ni/chitosan/Na-alginate/polyacrylic acid (Ni@CS/Na-Alg/PAAc) were created as eco-friendly hydrogel composites via gamma radiation. The hydrogel matrix served as a basin for the in-situ formation of Ni nanoparticles. The prepared composites were characterized by the FTIR and XRD analyses. The surface morphology of the nanocomposite was also verified via the SEM. It exhibited a dense packing of the Ni nanoparticles representing about 2.5% of the atomic percentage depicted by the EDX analysis. The swelling performance was investigated versus different pH values and the maximum swelling percent was attained as a non-Fickian character at pH = 13 and 5 for CS/Na-Alg/PAAc and Ni@CS/Na-Alg/PAAc, respectively. Furthermore, the surface topographies of CS/Na-Alg/PAAc and Ni@CS/Na-Alg/PAAc loaded with Cr(VI) were examined by AFM at different pH values. The maximum Cr(VI) removal was top achieved at pH 8 (58.06 and 74.5 mg/g for CS/Na-Alg/PAAc and Ni@CS/Na-Alg/PAAc, respectively) and best fit with the Freundlich isotherm model with calculated R-L values indicated a favorable adsorption.