Efficient degradation of diuron via photo-assisted electrooxidation and microbial treatment

Abstract

Diuron is a common herbicide for major crops, but its environmental persistence threatens ecosystems and human health. This study presents a hybrid treatment strategy that combines photoelectrochemical oxidation (PECO) and subsequent biodegradation as a sustainable alternative for diuron remediation. A novel laser-fabricated anode composed of Ti/RuO₂–Sb₂O₄–TiO₂ was developed and employed in the PECO process, offering enhanced electron transfer efficiency and stability. The process was conducted under UVC irradiation for 2 h, followed by biological treatment using Pseudomonas sp. 5CR and Micrococcus luteus M9 over 24, 48, and 72 h. Diuron degradation was evaluated through microbial growth using diuron as the sole carbon source, chemical oxygen demand (COD), high-performance liquid chromatography (HPLC), and toxicity assays. The synthesized anode demonstrated high electron transfer efficiency and stability during the PECO process. Sequential PECO-biological treatment resulted in increased microbial growth, suggesting that PECO pretreatment oxidizes diuron, making it more accessible for biodegradation. The combined treatment employing Pseudomonas sp. 5CR resulted in a 92.5 % reduction in COD, whereas M. luteus achieved a 51 % reduction after 72 h, both surpassing the efficiencies observed with either PECO or biodegradation stand-alone processes. HPLC confirmed effective diuron degradation in the sequential treatment. Phytotoxicity tests also showed reduced toxicity in lettuce seeds, especially after treatment with Pseudomonas sp. 5CR. These results highlight the potential of the combined PECO-biological treatment for effective in situ remediation of diuron-contaminated environments.