Tailoring a photoreactive biomass-based redox coupled material for interaction enhanced removal of Cr(Ⅵ) and As(Ⅲ)

Reduction and complete removal of chromium (VI) and arsenic (III) are crucial for the purification of heavy metal-contaminated wastewater. Here, a photo-responsive eucalyptus-based adsorption-catalytic material was engineered by anchoring polyethyleneimine, porous carbon, and iron oxide onto eucalyptus. The material featured a high density of amino and Fe(Ⅱ)/Fe(Ⅲ), the ability to generate free radicals and heat upon light irradiation. High toxicity Cr(Ⅵ) and As(Ⅲ) in water were adsorbed onto the material while catalytically converted into less toxic Cr(Ⅲ) and As(Ⅴ) under light conditions. Notably, the valence cycling of Fe(Ⅱ) and Fe(Ⅲ) during the adsorption process played a critical role in facilitating the redox reactions converting Cr(Ⅵ) to Cr(Ⅲ) and As(Ⅲ) to As(Ⅴ). Furthermore, the preferential Cr(Ⅵ) adsorption on the material generated reactive sites for As(Ⅲ) oxidation, accelerating arsenic adsorption. Consequently, the eucalyptus-based adsorption-conversion material was capable of completely removing 100.0 mg·L -1 of Cr(Ⅵ) and As(Ⅲ), achieving over 95% conversion to the less toxic forms. This work elucidated the synergistic mechanisms underlying the adsorption-conversion processes of Cr(Ⅵ) and As(Ⅲ), providing novel insights into the material design of substances with synergistic and competing functionalities. The photoreactive biomass-based redox-coupled material constructed from eucalyptus, polyethyleneimine, porous carbon, and iron oxide, which can adsorb highly toxic Cr(Ⅵ) and As(Ⅲ) and convert them with >95% efficiency into less toxic species, enabling comprehensive water purification. • Photoreactive adsorption-redox material was prepared for water purification. • Cr(VI) and As(III) were efficiently adsorbed and converted to Cr(III) and As(V). • Preferentially Cr(VI) adsorption created favorable conditions for As(III)/As(V). • Synergism between Cr(VI) and As(V) enhanced overall adsorption and conversion.