真空紫外/紫外/过硫酸盐工艺降解水中全氟辛酸

Aquatic perfluorooctanoic acid degradation by a vacuum-ultraviolet/ultraviolet/persulfate process

全氟辛酸(PFOA)是一种水中检出频率较高的全氟和多氟烷基物质,常规水处理工艺难以有效去除。紫外(UV)/过硫酸盐(PDS)工艺对PFOA具有较好的处理效果。相对于传统低压汞灯,新型光源真空UV/UV(VUV/UV)汞灯,可在不增加电能输入下,额外输出185 nm VUV光子有效光解PFOA。因此,采用VUV/UV汞灯驱动UV/PDS工艺具有高效降解PFOA的潜力。选用前期研发的配装VUV/UV汞灯的细管流光反应系统开展研究,通过微量过氧化氢生成法和化学感光剂(尿苷)测定VUV和UV辐照强度分别为1.16×10^(-4)einstein·(m^(2)·s)^(-1)和1.39×10^(-3)einstein·(m^(2)·s)^(-1)。结果表明,相对于单独UV和VUV/UV辐照,PDS的投加会生成SO_(4)^(-)·,进而强化PFOA的降解。由于额外的185 nm VUV光子辐照,VUV/UV/PDS工艺相对于UV/PDS工艺具有明显强化降解作用。当PDS浓度在0~0.9 mmol·L^(-1)时,协同因子(R)均低于1,表明尽管VUV/UV汞灯可强化UV/PDS工艺对PFOA的去除,但PDS和VUV/UV的联用并没有明显的协同作用。PDS浓度的提升会增加SO_(4)^(-)·的生成,强化自由基降解的贡献(18%上升为35%),但同时竞争吸收VUV光子导致PFOA的直接VUV降解作用减弱(82%下降为65%),总体PFOA降解的协同效果有所减弱。以上研究结果表明VUV的加入可强化UV/PDS工艺去除PFOA的效率,为VUV/UV/PDS工艺应用于水中PFOA高效去除提供参考。

Perfluorooctanoic acid(PFOA)is a kind of perfluoroalkyl and polyfluoroalkyl substance with high detection frequency in water,which cannot be effectively removed by the conventional water treatment processes.The ultraviolet(UV)/persulfate(PDS)process has a good treatment effect on PFOA.Compared with traditional low-voltage mercury lamps,the new light source of vacuum UV/UV(VUV/UV)mercury lamp can effectively photolyze PFOA by outputting additional 185 nm VUV photons without increasing the electric power input.Therefore,the UV/PDS process driven by VUV/UV mercury lamp has the potential to degrade PFOA efficiently.The mini-fluidic photoreaction system equipped with VUV/UV mercury lamp developed previously was used in this research.The VUV and UV irradiation intensities determined by micro hydrogen peroxide generation method and chemical actinometry(uridine)were 1.16×10^(−4)and 1.39×10^(−3)einstein·m^(−2)·s^(−1),respectively.According to the results of PFOA degradation by different processes,the addition of PDS could generate SO_(4)^(−)·to enhance the degradation of PFOA comparing to individual UV or VUV/UV processes.Because of additional 185 nm VUV photon irradiation,the VUV/UV/PDS process could significantly enhance the PFOA degradation than the UV/PDS process.When the concentrations of PDS were 0~0.9 mmol·L^(−1),the values of synergistic factor R were all below 1,indicating that although the VUV/UV mercury lamp could enhance the removal of PFOA by UV/PDS process,the combination of PDS and UV/UV has no obvious synergistic effect.The increase of PDS concentration could increase the generation of SO_(4)^(−)·and strengthen the contribution of free radical degradation(18%to 35%),but PDS could also absorb VUV photons,which weakened the direct VUV degradation of PFOA(82%to 65%)and the overall synergistic effect of PFOA degradation.This study shows that the addition of VUV strengthens the UV/PDS process and significantly improves the removal efficiency of PFOA,which provides a theoretical reference for the application of the VUV/UV/PDS process to efficiently remove PFOA in water.