Sustainable water treatment using CuO Cocatalyst–loaded Zr-doped Fe₂O₃ nanocomposite for oxidant-free photocatalytic degradation of Orange II dye and E. coli inactivation

Photocatalytic dye degradation and bacterial inactivation are considered potentially effective approaches to mitigate the adverse effects of hazardous pollutants and biohazards on human health. Hence, we aim to investigate the synthesis, kinetics of adsorption and photocatalytic performance of a CuO-cocatalyst-loaded Zr-doped Fe₂O₃ nanocomposite (1-CuO/Zr-HT) in the context of its effectiveness against Orange II dye and E. coli without the addition of an oxidant. Zr-doping was achieved by in-situ hydrothermal and a subsequent wet impregnation method was employed for CuO cocatalyst loading. The maximum adsorption capacity (q_e) was determined to be 8.395 mg/g for the optimized 1-CuO/Zr-HT, which attained a degradation efficiency of 95.9% for Orange II within 150 min. CuO-loading enhanced the specific surface area as well as decreased the pore volume, which are responsible for enhanced active sites for effective photocatalytic reaction. We investigated the orange II dye degradation with varying adsorbent dosage, initial dye concentration and initial pH. The results of the scavenger test and mechanistic evaluation revealed that the degradation of Orange II is attributed to the holes, ^•O₂⁻ and ^•OH produced during the photocatalytic process. The Orange II elimination process by 1-CuO/Zr-HT followed a pseudo-second order (PSO) kinetic parameter with a correlation coefficient (R²) of 0.99972. Furthermore, the 2-CuO/Zr-HT nanocomposite achieved a deactivation rate of 99.1% for E. coli after 120 min of illumination. The results illustrate the effectiveness of the suggested strategy for the decomposition of Orange II dye in water, indicating its potential as a viable and environmentally sustainable solution for the remediation of organic/antibiotic-contaminated water.