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^‒1. DMT was degraded by 97.8% after 10 min of VUV/UV exposure (VUV fluence = 12 mJ cm^‒2), whereas by only 5.2% after 10 min of UV exposure (UV fluence = 156 mJ cm^‒2). 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^‒1. DMT degradation pathways in the VUV/UV process were proposed based on identified organic intermediates and inorganic ions. SO₄^2‒ was first released due to HO^• attack on the S=P bond of DMT, which governed the DMT degradation efficiency; while the release of PO₄^3‒ was pertinent to the DMT mineralization efficiency. DMT solution toxicity was significantly reduced after VUV/UV treatment. An electrical energy-per-order (E_EO) value of 0.57 kWh m^‒3 Order^‒1 demonstrated the economic feasibility of the VUV/UV process for DMT removal in small-scale drinking water treatment.

真空紫外线/紫外线（VUV / UV）工艺近来已应用于水处理，但对其杀虫剂的功效和机理知之甚少。这项研究调查了典型的有机磷农药乐果（DMT）的VUV / UV降解动力学和机理，然后评估了经济可行性。在初始浓度≤5.0 mg L ^‒1时， DMT降解遵循拟一级反应动力学。VMT / UV暴露10分钟（VUV通量= 12 mJ cm ^‒2）后，DMT降解97.8％，而UV暴露10分钟（UV通量= 156 mJ cm ^‒2）后DMT降解仅5.2％。通过VUV / UV降解DMT的表观量子产率确定为0.19，最多包含50.7％的羟基自由基（HO^•水的VUV光解产生的）可用于DMT降解。随着pH从5.0增​​加到9.0，DMT降解速率从0.43降低到0.23 min ^-1。基于已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。SO ₄ ^2‒最初是由于HO ^•攻击DMT的S = P键而释放的，从而决定了DMT的降解效率。PO ₄ ^3‒的释放与DMT的矿化效率有关。VUV / UV处理后，DMT溶液的毒性显着降低。每次电能（E _EO）值为0.57 kWh m ^‒3阶^‒1证明了在小规模饮用水处理中采用VUV / UV工艺去除DMT的经济可行性。