Green innovation: Ascorbate-based polymers demonstrate excellent performance in removing Cr(VI)

The detrimental effects of hexavalent chromium (Cr(VI)) on ecosystems and human health have garnered significant concern. In this study, ascorbic acid (AA), polyvinyl alcohol (PVA), and polyethyleneimine (PEI) were used as raw materials to synthesize bulk-size polymer materials (APP) via a green and straightforward process, and a comprehensive investigation was conducted to evaluate APP's efficacy in eliminating Cr(VI) from wastewater. It was observed that the APP particles (∼3-4 mm) were macroporous material with an average pore size of 96.31 nm and strong mechanical strength and toughness. Notably, the material exhibited stable Cr(VI) removal performance across varying pHs, especially in alkaline environments (100.00 % at pH = 2, 80.40 % at pH = 11). In addition, APP could preferentially reduce and adsorb Cr(VI) in a mixed solution of a variety of heavy metals. In addition, the material exhibited good reusability after elution with deionized water and hydrochloric acid (removal efficiency >80 % after 6 cycles). Possible mechanisms of Cr(VI) removal by the APP include electrostatic attraction, anion exchange, oxidation-reduction, and complexation. This research mainly addressed three major issues compared to previous studies: the difficulty in recycling nanomaterials, the pH limit on their effects, and the poor mechanical strength of gel materials. Therefore, a new idea for treating Cr(VI)-contaminated wastewater using functional and pH-adjustable materials is proposed, providing a prerequisite for its application in a wider range of pH scenarios.