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

Abstract

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 •–) were determined at pH 8.8 and T = 20 °C: estrone ((5.3 ± 1.1) × 108 M–1 s–1), bisphenol A ((2.8 ± 0.2) × 108 M–1 s–1), 17α-ethynylestradiol ((1.6 ± 0.3) × 108 M–1 s–1), triclosan ((4.2 ± 1.4) × 107 M–1 s–1), diclofenac ((2.7 ± 0.7) × 107 M–1 s–1), atrazine ((5.7 ± 0.1) × 106 M–1 s–1), carbamazepine ((4.2 ± 0.01) × 106 M–1 s–1), and ibuprofen ((1.2 ± 1.1) × 106 M–1 s–1). Contributions from UV, reactive nitrogen species (RNS), hydroxyl radical (•OH), and CO3 •– 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 –.

Kinetics and pathways of diclofenac degradation by heat-activated persulfate

“…40,41 Although the second-order rate constant of DCF with CO 3 c À (k CO3 À =DCF ¼ ð2:7 AE 0:7Þ Â 10 7 M À1 s À142 ) was lower than those with SO 4 c À (k SO4 À =DCF ¼ ð9:2 AE 0:6Þ Â 10 9 M À1 s À143 ) and HOc (k HOc/DCF ¼ (7.5 AE 1.5) Â 10 9 M À1 s À111 ), its steady-state concentration might be higher in the reaction system due to its selectivity, 44 resulting in a positive effect of CO 3 2À on DCF degradation. Similar nding was also reported by Huang et al 42 in DCF degradation by UV/NO 3 À in the presence of HCO 3…”

Kinetics and reaction mechanism of photochemical degradation of diclofenac by UV-activated peroxymonosulfate

“…This was mainly because NO 3 À could be excited to produce HOc under UV irradiation as shown in eqn (12)-(15). 42 Huang et al 43 also found that compared with UV alone, UV/NO 3 À signicantly promoted the elimination of DCF, which was due to the contribution of HOc. The presence of HCO 3 À enhanced the removal of DCF, and the promotion effect was gradually increased with the increase of HCO 3 À concentration, as presented in Fig.…”

Photochemical Behavior of Some Estrone Aryl and Methyl Sulfonates in Solution: Preparative and Mechanistic Studies

“…The photocatalytic azolylation reaction of estrone methyl ether, a precursor leading to an FDA‐approved oral contraceptive (mestranol), has been reported by Weaver and co‐workers and they were able to isolate the desired estrone derivative in 37% yield as a single regioisomer in which the benzothiazolylation occurred at C 4 position of the estrone 3‐methyl ether (23). Recently, the photodegradation of estrone and 17α‐ethinylestradiol with HCO 3 − , NO 3 − and 254 nm photolysis has been reported (24) because these steroids are considered as toxic contaminants of emerging concerns (CECs) for water reused applications. Estrogens were also photooxidized efficiently with humic acids in the presence of Mn(III) (25) and the application of alkene cyclopropanation with chloromethyl silicate through a visible‐light‐mediated redox neutral catalysis of vinylphosphonate derived from estrone took place efficiently and the photoproduct was isolated in 92% yield (26).…”