Valorization of water hyacinth to biochar-supported copper-doped tungsten trioxide composite for enhanced adsorptive/photocatalytic degradation: Life cycle assessment, techno-economic, and toxicity prediction

While the photodegradation of hazardous contaminants using biochar-based composites has recently been examined, further research should address the associated environmental sustainability, economic feasibility, and by-product toxicity. Therefore, this study presents copper-doped tungsten trioxide anchored onto water hyacinth biochar as an eco-friendly persulfate (PS) activator-composite for the adsorptive/photocatalytic decomposition of methylene blue (MB) under UV–Vis irradiation. The adsorption efficiency of MB dye was 26.92 ± 1.43 % using the water hyacinth biochar (BC). This removal efficiency was improved to 98.79 ± 0.25 % for the combined adsorption/photodegradation mechanism using the as-prepared composite. These enhanced dye removal efficiency and chemical oxygen demand reduction (88.21 ± 1.32 %) were attributed to the synergistic effects of copper ions and BC on PS activation, generating radical species responsible for contaminant detoxification. The proposed system also maintained removal efficiencies of 89.25 ± 1.78 % for tetracycline and 91.72 ± 1.19 % for methyl orange, demonstrating a partial photocatalytic oxidation of other organic compounds. This adsorptive/photocatalytic process was economically feasible, with an internal rate of return of 10 %, positive net present value, and a shorter payback period of 6.27 years. Sensitivity analysis demonstrated that the photocatalyst price was the main contributor responsible for achieving a financially profitable adsorptive/photodegradation process. A cradle-to-gate life cycle assessment approach showed minimum environmental burdens across the toxicity-related midpoint impact categories, which were also validated using a toxicity estimation software tool (i.e., releasing less-toxic degradation by-products). Future studies should assess the catalyst/PS/UV–Vis system's performance for mixed dye stuff degradation under solar radiation conditions, mitigating various environmental contaminants from the textile industries.