Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing, 100085, China; School of Environmental and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang, 212003, China.
Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing, 100085, China; School of Food and Chemical Engineering, Shaoyang University, No. 28, Lane 3, Shaoshui West Road, Shaoyang, 422900, China.
Chemosphere. 2021 Jun;273:129724. doi: 10.1016/j.chemosphere.2021.129724. Epub 2021 Jan 23.
Vacuum ultraviolet/ultraviolet (VUV/UV) process has been applied to water treatment recently, but little is known about its efficacy and mechanism for pesticide degradation. This study investigated the degradation kinetics and mechanism of a typical organophosphorus pesticide, dimethoate (DMT) by VUV/UV, and then the economic feasibility was assessed. DMT degradation followed well the pseudo-first-order reaction kinetics at an initial concentration of ≤5.0 mg L. DMT was degraded by 97.8% after 10 min of VUV/UV exposure (VUV fluence = 12 mJ cm), whereas by only 5.2% after 10 min of UV exposure (UV fluence = 156 mJ cm). The apparent quantum yield of DMT degradation by VUV/UV was determined to be 0.19, and at most 50.7% of hydroxyl radicals (HO) generated from VUV photolysis of water could be utilized for DMT degradation. As the pH increased from 5.0 to 9.0, the DMT degradation rate decreased from 0.43 to 0.23 min. DMT degradation pathways in the VUV/UV process were proposed based on identified organic intermediates and inorganic ions. SO was first released due to HO attack on the SP bond of DMT, which governed the DMT degradation efficiency; while the release of PO was pertinent to the DMT mineralization efficiency. DMT solution toxicity was significantly reduced after VUV/UV treatment. An electrical energy-per-order (E) value of 0.57 kWh m Order demonstrated the economic feasibility of the VUV/UV process for DMT removal in small-scale drinking water treatment.
真空紫外/紫外（VUV/UV）工艺最近已被应用于水处理中，但对于其降解农药的效果和机制知之甚少。本研究考察了典型有机磷农药乐果（DMT）在 VUV/UV 下的降解动力学和机制，然后评估了其经济可行性。在初始浓度≤5.0 mg L 的条件下，DMT 的降解符合准一级反应动力学。在 10 分钟的 VUV/UV 照射（VUV 光强为 12 mJ cm）下，DMT 降解了 97.8%，而在 10 分钟的 UV 照射（UV 光强为 156 mJ cm）下，DMT 仅降解了 5.2%。通过 VUV/UV 降解 DMT 的表观量子产率被确定为 0.19，并且最多只有 50.7%的 VUV 光解水中生成的羟基自由基（HO）可用于 DMT 降解。随着 pH 值从 5.0 增加到 9.0，DMT 的降解速率从 0.43 降至 0.23 min。根据鉴定的有机中间体和无机离子，提出了 VUV/UV 工艺中 DMT 的降解途径。由于 HO 攻击 DMT 的 SP 键，首先释放出 SO，这控制了 DMT 的降解效率；而 PO 的释放与 DMT 的矿化效率有关。VUV/UV 处理后，DMT 溶液的毒性显著降低。电耗每阶（E）值为 0.57 kWh m Order，表明 VUV/UV 工艺在小型饮用水处理中去除 DMT 具有经济可行性。
