Efficient removal of Cr (VI) by modified sodium alginate via synergistic adsorption and photocatalytic reduction

Conventional photocatalytic removal of hexavalent chromium (Cr (VI)) suffers from low metal uptake capacity, expensive photocatalysts, and slow desorption of trivalent chromium from the catalyst surface. In this study, calcium chloride and iron(III) nitrate were used to cross-link with polyethyleneimine grafted sodium alginate (SA) to acquire two materials, named as SPC and SPF, respectively, for the efficient removal of Cr (VI) from aqueous solutions via adsorption and photocatalytic reduction. FT-IR, DFT, and XPS results indicated that polyethyleneimine was successfully grafted onto the SA matrix and could electrostatically attractted hexavalent chromium anions in solution. Fe (III) cross-linking forms a highly porous structure at ambient temperature, which could overcome the polysaccharide collapse in the dehydration process. The UV-vis DRS, EIS, and photocurrent density characterizations of SA, SPC, and SPF suggested that SPF has smaller charge transfer resistance and is conducive to the separation of photogenerated charges, thus SPF exhibited superior performance in the photocatalytic reduction of Cr (VI). As a result, SPF is an efficient photocatalyst for the removal of Cr (VI) and provides new sights on polysaccharide-based photocatalysts applications.