Highly efficient reduction of Cr(VI) from industries sewage using novel biomass-driven carbon dots modified TiO2 under sunlight

Hexavalent chromium (Cr(VI)) pollution poses a significant global environmental challenge, with current photocatalysts exhibiting limited efficiencies under natural sunlight, especially in neutral to alkaline conditions or at high Cr(VI) concentrations. In this study, amine-rich biomass-derived carbon dots (CDs) were synthesized from peanut shells and ethylenediamine via a hydrothermal method, combined with titanium dioxide (TiO2) to form a composite with a narrower band gap. This enhanced the electrostatic interactions with Cr(VI), thus improving photocatalytic performance. The composite (1 % CDs) effectively reduced 50 mg/L of Cr(VI) within 60 min under sunlight irradiation, demonstrating stable performance across various pH levels (3, 5, 7, and 9) and Cr(VI) concentrations (10 to 60 mg/L). Even after five cycles, the reduction efficiency remained high at 96.83 %. The composite also achieved reduction rates of 90.09 % and 89.01 % for domestic and electroplating wastewater, respectively, while exhibiting antibacterial properties. Free-radical scavenging experiments confirmed that electrons and holes were the primary active species driving the reduction. This work highlights the potential of the composites for efficient and stable Cr(VI) reduction in real-world water treatment applications.