Vacuum ultraviolet (VUV) process has been regarded as a novel advanced oxidation process for its unique way of generating HOㆍ via direct photolysis of water. This study investigates the kinetics of the VUV process for degradation of a typical pesticide, glyphosate (GLY), by using a photoreactor equipped with a precision sampler. The precision sampler enables us to take samples at distances ranging from 0.1 to 1.5 cm to the irradiation source so that GLY degradation by VUV in different parts of the reaction volume can be evaluated. The results of experiments on H2O2 production from VUV photolysis of water confirmed that there existed an extremely uneven distribution of VUV flux and HOㆍ generated in the VUV process. Enhancing mass transfer by agitation could significantly increase GLY degradation efficiency by improving the distribution of HOㆍ. The initial concentrations of water and GLY governed the reaction kinetics of GLY degradation in the VUV process. As the solution pH increased from 5.0 to 9.0, the overall degradation efficiency of GLY decreased from 97.6% to 77.8%. Depending on their molar absorption coefficients, inorganic anions affected adversely on the degradation of GLY by VUV in the order of NO3 ->HCO3 -(alkalinity)>Cl->SO4 2-. As a strong HOㆍ scavenger, natural organic matter shows a much more adverse impact on GLY degradation than that of inorganic anions. Based on the experimental results, this study has provided insights into the kinetics of VUV process for pollutant degradation.

Vacuum Ultraviolet Glyphosate Degradation Kinetics Flux Distribution

Feizi R, Ahmadi M, Jorfi S, Ghanbari F, Korean J. Chem. Eng., 36(6), 886 (2019)
Sharma K, Talwar S, Verma AK, Choudhury D, Mansouri B, Korean J. Chem. Eng., 37(2), 350 (2020)
Koppenol WH, Liebman JF, J. Phys. Chem., 88, 99 (1984)
Zoschke K, Bornick H, Worch E, Water Res., 52, 131 (2014)
Li MK, Wang C, Yau ML, Bolton JR, Qiang ZM, Water Res., 108, 348 (2017)
Imoberdorf G, Mohseni M, J. Hazard. Mater., 186(1), 240 (2011)
Bagheri M, Mohseni M, Chem. Eng. J., 256, 51 (2014)
Yao H, Pei J, Wang H, Fu J, Chem. Eng. J., 308, 193 (2017)
Dobrovic S, Juretic H, Ruzinski N, Sep. Sci. Technol., 42(7), 1421 (2007)
Li MK, Qiang ZM, Hou P, Bolton JR, Qu JH, Li IP, Wang C, Environ. Sci. Technol., 50, 5849 (2016)
Yang LX, Zhang ZH, Water Res., 161, 439 (2019)
Yang L, Yao G, Huang S, Chem. Eng. J., 388, 124302 (2020)
Legrini O, Oliveros E, Braun AM, Chem. Rev., 93, 671 (1993)
Heit G, Neuner A, Saugy PY, Braun AM, J. Phys. Chem. A, 102(28), 5551 (1998)
Gonzalez MG, Oliveros E, Worner M, Braun AM, J. Photochem. Photobiol. C, 5, 225 (2004)
Weeks JL, Meaburn GMAC, Gordon S, Radiat. Res., 19, 559 (1963)
Imoberdorf G, Mohseni M, Chem. Eng. J., 187, 114 (2012)
Wu Z, Yang L, Tang Y, Qiang Z, Li M, Chemosphere, 273, 129724 (2021)
Bader H, Sturzenegger V, Hoigne J, Water Res., 22, 1109 (1988)
Crapulli F, Santoro D, Sasges MR, Ray AK, Water Res., 64, 209 (2014)
Li MK, Qiang ZM, Pulgarin C, Kiwi J, Appl. Catal. B: Environ., 187, 83 (2016)
Yang LX, Li MK, Li WT, Bolton JR, Qiang ZM, Photochem. Photobiol., 94, 821 (2018)
Huang L, Jing HY, Cheng ZH, Dong WB, J. Photochem. Photobiol. A-Chem., 251, 69 (2013)
Mora AS, Mohseni M, Environ. Sci. Water Res. Technol., 4, 1303 (2018)
Buchanan W, Roddick F, Porter N, Water Res., 42, 3335 (2008)
Buchanan W, Roddick F, Porter N, Chemosphere, 63, 1130 (2006)