化学学报 ›› 2019, Vol. 77 ›› Issue (1): 72-83.DOI: 10.6023/A18090365 上一篇    下一篇

研究论文

溶液制备过程引入的甲醇对阿特拉津UV光氧化速率和降解机理的影响

刘玉灿a, 苏苗苗a, 张岩a, 段晋明b, 李伟b   

  1. a 烟台大学土木工程学院 烟台 264005;
    b 西安建筑科技大学环境与市政工程学院 西安 710055
  • 收稿日期:2018-09-04 出版日期:2019-01-15 发布日期:2018-11-26
  • 通讯作者: 刘玉灿 E-mail:liuyucanfendou@163.com
  • 基金资助:

    项目受山东省自然科学基金(No.ZR2017BEE016)、国家自然科学基金(No.51308437)和烟台大学科技项目(No.TM17B19)资助.

Influence Rule of Organic Solvents Methanol from Sample Preparation on Degradation Rate and Mechanism of Atrazine in UV-based Oxidation Processes

Liu Yucana, Su Miaomiaoa, Zhang Yana, Duan Jinmingb, Li Weib   

  1. a School of Civil Engineering, Yantai University, Yantai 264005;
    b School of Environmental & Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055
  • Received:2018-09-04 Online:2019-01-15 Published:2018-11-26
  • Contact: 10.6023/A18090365 E-mail:liuyucanfendou@163.com
  • Supported by:

    Project supported by the Natural Science Foundation of Shandong Province (No. ZR2017BEE016), the National Natural Science Foundation of China (No. 51308437) and the Science Fund of Yantai University (No. TM17B19).

在低压汞灯(253.7 nm)光照条件下,研究了样品制备过程中引入的有机溶剂甲醇对目标有机物阿特拉津光氧化降解速率的影响规律,并系统地分析了其影响机理.研究结果表明:反应体系中含有低浓度(<0.1%)有机溶剂甲醇时,不会对阿特拉津在单独UV工艺中的降解动力学产生影响;对UV/H2O2工艺中阿特拉津降解动力学的影响较小,但此含量的甲醇却能显著地降低阿特拉津在UV/TiO2工艺中的降解速率.甲醇对阿特拉津在不同光氧化工艺中降解动力学的影响是甲醇与阿特拉津竞争光量子、改变溶液极性和淬灭活性氧化物种等作用的综合结果,但反应体系中甲醇的存在及含量未改变阿特拉津降解产物的种类及降解途径.本研究的结果可为探索溶液制备时引入到反应体系中的有机溶剂对有机目标物光氧化速率的影响提供新的研究视角,同时也能为文献中目标物配制在不同溶剂中的降解速率差异提供合理解释.

关键词: 阿特拉津, 甲醇, 紫外光, 高级氧化工艺, 降解速率, 降解机理

Stock solutions of organic micro-pollutants with low water solubility are commonly prepared using organic solvents in laboratory studies on degradation of these organic compounds. Dilution of the stock solution unavoidably introduces a small amount of organic solvent into the experimental working solutions. This could possibly affect the estimation of the degradation rate constants (kobs) of these organic micro-pollutants by UV-based oxidation processes. To demonstrate this problem, the effect of organic solvents on the degradation rate of atrazine (ATZ) has been investigated in the sole-UV, UV/H2O2 and UV/TiO2 process at the concentration levels that would likely be derived from stock solutions. Organic solvent methanol (MeOH) commonly used for stock-solution preparation was selected. The degradation of ATZ was investigated under ultraviolet irradiation (253.7 nm). The reaction was conducted in an annular photochemical reactor, in the axis of which a low-pressure mercury lamp (LPUV) was installed. The photon flux into the solution from the LPUV was determined to be at 1.18×10-7 Einstein/s. A magnetic stirrer was located at the bottom of the reactor to maintain homogeneity of the reacting solution. A thermostatic water recirculation system was used to control the solution temperature at 20±0.5℃. Prior to irradiation, the mercury lamp was ignited for 30 min for a stable output. UV photo-oxidation was performed with ultrapure water containing an initial 0.1 or 5 mg/L ATZ and different volume ratio of methanol. Solution pH value of 4.0, 7.0 and 10.0 was buffered using phosphate or borate. Determination of ATZ using ultra-performance liquid chromatography-electrospray-triple quadrupole mass spectrometry coupled with an ACQUITYTM UPLC BEH C8 separation column. The results show that the reaction rate of ATZ in UV/TiO2 process could be affected significantly by the presence of MeOH, even at a concentration well below that possibly introduced during the preparation of working solutions from the organic solvent stock solutions (e.g. 0.01%, V/V). With the increase of MeOH concentration, the kobs of ATZ in UV/TiO2 process gradually decreases. The organic solvents having a stronger reaction activity with·OH tend to impose a greater effect on the kobs of ATZ. However, MeOH does not affect kobs of photolysis of ATZ in sole-UV process, and a small effect for the kobs of ATZ in UV/H2O2 process. In addition, MeOH in the reaction system does not affect the speciation and degradation pathway of ATZ under different UV-based oxidation processes. The findings here provide a plausible explanation for the discrepancies in the reaction rate constants reported in the literature for some organic micro-pollutants during the UV-based oxidation processes.

Key words: atrazine, methanol, ultraviolet, advanced oxidation process, degradation rate, degradation mechanism