Degradation of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV328) in soil by FeS activated persulfate: Kinetics, mechanism, and theoretical calculations

2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV328) is a commonly used benzotriazole ultraviolet stabilizers (BUVs) with bioaccumulative properties. Since it's stubbornly degraded in the environment, it poses significant environmental risks in soil. However, the removal of UV328 from soil is challenging, and existing treatment methods have low efficiency. This study focuses on UV328 in soil and proposes an efficient method for its removal using persulfate (PS) activated by iron sulfide (FeS). The research demonstrates that with FeS and PS dosages of 20 and 100 mM respectively, and a soil-to-water ratio of 5:1, 12 h-removal efficiency of UV328 with an initial concentration of 12 mg/kg reaches 93.0%. Furthermore, employing electron paramagnetic resonance spectroscopy and quenching experiments, key reactive oxygen species (ROSs) are identified. SO₄^•-, •OH, ¹O₂ and •O₂^- contribute 31.76%, 28.77%, 26.52% and 12.95%, respectively. Four main reaction pathways of amination, hydroxylation, sulfate substitution, and bond cleavage, are identified with 14 transformation products characterized. Calculated energy profiles based on density functional theory (DFT) identify the most susceptible reaction sites for different ROSs. Five different types of agricultural soils were selected to explore the impact of soil characteristics on UV328 removal. The degradation performance of natural mackinawite demonstrates the effectiveness and accessibility of raw materials. Toxicity assessments of transformation products confirm the environmental friendliness of this system. This study proposes an efficient degradation method for UV328-contaminated soil, providing scientific insights and theoretical guidance for addressing environmental removal of BUVs from soil.