Effects of HCO3- on Degradation of Toxic Contaminants of Emerging Concern by UV/NO3-

This study investigated the significant influence of HCO3- on the degradation of contaminants of emerging concern (CECs) during nitrate photolysis at 254 nm for water reuse applications. The second-order rate constants for the reactions between selected contaminants with carbonate radical (CO3 center dot-) were determined at pH 8.8 and T = 20 degrees C: estrone ((5.3 +/- 1.1) x 10(8) M-1 s(-1)), bisphenol A ((2.8 +/- 0.2) x 10(8) M-1 s(-1)), 17 alpha-ethynylestradiol ((1.6 +/- 0.3) x 10(8) M-1 s(-1)), triclosan ((4.2 +/- 1.4) x 10(7) M-1 s(-1)), diclofenac ((2.7 +/- 0.7) x 10(7) M(-)1 s(-1)), atrazine ((5.7 +/- 0.1) x 10(6) M-1 s(-1)), carbamazepine ((4.2 +/- 0.01) x 10(6) M-1 s(-1)), and ibuprofen ((1.2 +/- 1.1) x 10(6) M-1 s(-1)). Contributions from UV, reactive nitrogen species (RNS), hydroxyl radical (center dot OH), and CO3 center dot- to the CEC decomposition in UV/NO3- in the presence and absence of HCO3- were investigated. In addition, possible transformation products and degradation pathways of triclosan, diclofenac, bisphenol A, and estrone in UV/NO3-/HCO3- were proposed based on the mass (MS) and MS2 spectra. Significant reduction in the cytotoxicity of bisphenol A was observed after the treatment with UV/NO3-/HCO3-.