Degradation of 1H-benzotriazole using ultraviolet activating persulfate: Mechanisms, products and toxicological analysis

Benzotriazoles have been widely used as additives in industrial products, and they are released or discharged along with sewage into wastewater treatment plants. Traditional wastewater treatment processes, especially biological methods, cannot completely eliminate BTAs. Developing cost-effective and environmental-friendly treatment methods for the removal of benzotriazoles is in urgent need. This study evaluated the degradation efficiency of 1H-benzotriazole (1H-BTA) with 280 nm ultraviolet activating persulfate (UV/PS). Degradation of 1H-BTA followed pseudo-first order kinetics with a rate constant at 0.226 min(-1) when [1H-BTA](0) = 8.39 mu M, [PS](0) = 420 mu M, UV intensity = 0.023mWcm(-2). Scavenger experiments with ethanol and tert-butyl alcohol proved that both hydroxyl radical and sulfate radical contributed to the degradation of 1H-BTA. Reactions induced by these radicals were affected by pH value, anions and natural organic matters, implying that an incomplete mineralization of 1H-BTA by UV/PS would be ubiquitous in heterogeneous water matrix. As the reaction proceeded, 1H-BTA was transformed to a series of intermediate products. Simple hydroxylated product C6H5N3O was dominating in the initial stage (similar to 10 min), while further open-loop oxidative product C4H3N3O4 had a peak value in the later stage (similar to 45 min). Based on model organism proteomics and metabolic network analyses, down regulation of stress resistance proteins in Escherichia coli exposed to degradation products indicated that the toxicity of 1H-BTA was declined. To summarize, incomplete mineralization of 1H-BTA using UV/PS is likewise effective for its detoxification.