Dyes decolourization and detoxification of methylene blue and methyl orange by TiO 2 /nylon photocatalytic systems

Abstract Synthetic dyes in industrial effluents pose significant environmental risks due to their resistance to conventional degradation and potential toxicity to living organisms. This study investigates the photocatalytic degradation of methylene blue (MB) and methyl orange (MO) using titanium dioxide (TiO 2 –P25) immobilized on nylon meshes via wash‐coating. Under UVC irradiation (254 nm), the system generates reactive oxygen species (ROS), primarily hydroxyl radicals (•OH) and superoxide anions (O 2 •− ), through TiO 2 photoexcitation, leading to dye degradation via oxidative cleavage of chromophores and subsequent mineralization. The immobilized structure achieved dye removal efficiencies of 92.9% for both MB and MO within 2 h, with total organic carbon (TOC) reductions of 51.01% for MO and 53.87% for MB after 6 h, demonstrating effective pollutant mineralization. Pseudo‐first‐order kinetics were observed, with rate constants of 0.021 min −1 for MB and 0.018 min −1 for MO. Ecotoxicological assessments using Lactuca sativa and Artemia salina revealed reduced phytotoxicity (relative growth index increased from 0.11 to 0.70 for MB after 6 h) and cytotoxicity (LC 50 increased to 0.9238 for reaction water), confirming the mitigation of toxicological risks. Catalyst retention exceeded 98.4%, with no detectable TiO 2 leaching, ensuring environmental safety. However, the reliance on energy‐intensive UVC irradiation may limit scalability and environmental sustainability, as it is less viable under natural solar conditions compared to visible‐light‐driven systems. This photocatalytic system offers a robust and sustainable approach for industrial wastewater treatment, though future optimization with visible‐light catalysts could enhance energy efficiency and scalability.