基于细管流紫外反应系统探讨紫外和真空紫外/紫外辐照下水中微量磺胺甲噻二唑的光降解效果

水环境中存在的微量有机污染物可在较低浓度下对人类造成较大的危害.基于细管流紫外反应系统(MFPS)研究了典型微量有机污染物磺胺甲噻二唑(SML)在紫外(UV)和真空紫外/紫外(VUV/UV)辐照下的光降解过程,发现SML在VUV/UV辐照下的降解速率明显快于UV辐照.采用MFPS测定了各光化学动力学参数:UV和VUV/UV辐照下光子剂量基反应速率常数分别为0.88×10~3和4.64×10~3m~2·einstein-1;量子产率分别为0.227和0.379;羟基自由基(HO·)和SML的二级反应速率常数测定为6.59×10~9L·mol~(-1)·s~(-1).探讨了pH值和初始SML浓度对降解效果的影响,结果表明,VUV/UV辐照下pH 7.0时的SML降解速率达到最大,而UV辐照下SML的降解速率随pH增加而逐渐增大;初始SML浓度的增大会降低UV和VUV/UV辐照下的降解速率.此外,本研究表明MFPS作为实验室光反应系统可快速、准确地测量各光反应动力学参数,VUV/UV在去除水中微量有机污染物方面的效果优于UV,可较好的处理水中微量有机污染物.

Photodegradation of trace sulfamethizole in water under UV and VUV/UV irradiation based on a mini-fluidic photoreaction system

The presence of micro-pollutants in water can have harmful or toxic impacts to human beings at very low concentrations. Based on a mini-fluidic photoreaction system (MFPS), the photodegradation of a typical micro-pollutant, sulfamethizole (SML), in water under UV and VUV/UV irradiation was studied. The results indicate that VUV/UV irradiation achieved a much faster SML degradation rate than UV irradiation. The photoreaction parameters were determined by the MFPS as follows:under UV and VUV/UV irradiation, the fluence-based SML degradation rates were 0.88×10³ and 4.64×10³ m²·einstein^-1 and the quantum yields were 0.227 and 0.379, respectively; and the secondary reaction rate constant of hydroxyl radical (HO·) with SML was 6.59×10⁹ L·mol^-1·s^-1.The effects of pH and initial SML concentration were examined. The SML degradation rate reached maximum at pH 7.0 under VUV/UV irradiation, whereas it increased with increasing pH under UV irradiation. Increasing the initial SML concentration reduced its degradation rate under both UV and VUV/UV irradiation. In addition, this study demonstrates that the MFPS, as a bench-scale photoreaction system, can fast and accurately determine the photoreaction kinetic parameters, and VUV/UV irradiation is more effective for micro-pollutant removal in water than UV irradiation.