Degradation mechanism of anatoxin-a in UV-C/H2O2 reaction

In this study, the kinetics and removal mechanism of anatoxin-a (C10H15NO) during a UV-C/H2O2 reaction were investigated. The removal of anatoxin-a was more effective during a UV-C/H2O2 reaction than with either UV photolysis or H2O2 alone, due to the effective production of hydroxyl (OH) radicals. The UV-C/H2O2 reaction of anatoxin-a resulted in an approximately 60% decrease in total organic carbon (TOC) within 420 min, while 45% of the carbon in anatoxin-a was converted into acetate, and most of the nitrogen in anatoxin-a was converted into NH4+, NO2-, and NO3- ions. More than 50% of the nitrogen in anatoxin-a was mineralized, mainly into NO3- ions, and complete nitrogen recovery was achieved after 120 min of the UV-C/H2O2 reaction. Using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS), we identified six degradation by-products in the UV-C/H2O2 reaction ([ M+ H](+)= 142, 127, 113, 132, 117, and 124, respectively), which were further degraded as the reaction continued. Using these by-products, we proposed a degradation pathway for anatoxin-a during the UV-C/H2O2 reaction. Our results indicate that anatoxin-a can be effectively removed by a UV-C/H2O2 reaction during water treatment processes.