Integrating Life Cycle Assessment and Cost Analysis for a MOF-Based ZnO–Fe3O4/TiO2 Photocatalyst: Toward Sustainable Degradation of Reactive Blue 21 in Textile Wastewater

In this study, a new ZFT-MIL nanohybrid (ZnO-Fe3O4/TiO2 integrated with MIL-125(Ti)) was synthesized via solvothermal/sol-gel/hydrothermal routes (optimized at pH 3) for UV-driven treatment of textile wastewater. Its photocatalytic activity was evaluated for the degradation of Reactive Blue 21 (RB21) under UV light (8 W, 45 °C). Life cycle assessment (LCA) was performed using SimaPro v9.5 (Ecoinvent 3) with ReCiPe 2016 midpoint-endpoint characterization for treating 1 m3 of RB21-contaminated water, alongside a 40-year life cycle cost (LCC) analysis. The ZFT-MIL achieved ∼99% RB21 removal under optimal UV conditions, far exceeding the 82-97% typical of TiO2 catalysts. This exceptional performance stems from synergistic coupling of the MIL-125 framework and ZnO-Fe3O4/TiO2 domains, improving charge separation. The composite enabled facile magnetic recovery and retained > 97% efficiency after five reuse cycles. The LCA revealed that electricity demand during synthesis/operation dominated environmental impacts (>45% of total, driving global warming potential and ecotoxicity). The LCC showed high capital and operational expenditures (CAPEX and OPEX) but a favorable 40-year net present value (≈U.S.$9.8 × 104), indicating economic viability. To improve sustainability, using renewable energy (e.g., solar UV) and greener solvents (reducing dimethylformamide) is recommended to cut carbon and toxicity burdens. Overall, ZFT-MIL achieves high dye abatement (∼99%) with strong durability, suggesting its promise as a scalable platform for sustainable wastewater treatment; future work will target visible-light activation and energy-efficient operation.