Influence of pH, inorganic anions, and dissolved organic matter on the photolysis of antimicrobial triclocarban in aqueous systems under simulated sunlight irradiation

Abstract

The photolysis of the antimicrobial triclocarban (TCC) in aqueous systems under simulated sunlight irradiation was studied. The effects of several abiotic parameters, including solution pH, initial TCC concentration, presence of natural organic matter, and most common inorganic anions in surface waters, were investigated. The results show that the photolysis of TCC followed pseudo-first-order kinetics. The TCC photolysis rate constant increased with increasing solution pH and decreasing the initial TCC concentration. Compared with the TCC photolysis in pure water, the presence of aqueous bicarbonate, nitrate, humic acids, and its sodium salt decreased the TCC photolysis rate, but fulvic acid increased the TCC photolysis rate. The electron spin resonance and reactive oxygen species scavenging experiments indicated that TCC may undergo two different types of phototransformation reactions: direct photolysis and energy transfer to generate (1)O2. The main degradation products were tentatively identified by gas chromatography interfaced with mass spectrometry (GC-MS), and a possible degradation pathway was also proposed.

Photodegradation of the azole fungicide climbazole by ultraviolet irradiation under different conditions: Kinetics, mechanism and toxicity evaluation

“…However, an early report pointed out that the photodegradation of CZ (15.8 mg/L) under UV-A and UV-B appeared to be pH-dependent (pH = 5.0, 7.0 and 9.0) with the k values range of 0.0099-0.0165 min −1 [22]. Similarily, this contrast may also explain by the difference of photodegradation conditions [19,31,33].…”

“…A nearest literature reported that the half-life (t 1/2 ) of CZ under UV-254 was 3.95 min [23], slightly lower than present study (9.78 min), which might cause by the different photodegradation conditions, such as light source (), photo-reactor, initial concentration etc. [19,31,33]. When compared to photodegradation, the chlorine oxidation of CZ was very poor (Fig.…”

“…Effect of water quality and coexisting constituents on the photodegradation of CZ It was reported that the water quality and coexisting constituents of natural waters had some influence on the photodegradation of organic pollutants [33][34][35]. So the effects of natural waters, Fe 3+ , NO 3 − and HA on the photodegradation of CZ under UV-254 were investigated (Fig.…”

“…Because the absence of HA could cause the damage of the iron cycle involving in the photo-reaction [37]. While HA scavenged radicals as light-absorbing species and result in a quenching effect on the reaction system [33,38], so the higher of the HA concentration, the more evident of the inhibitory effects, which was consistent with the previous reports [19,39]. In contrast, a promoting effect of 10 mg/L NO 3 − on the photodegradation of CZ was discovered, which might be caused by the generation of nitrogen reactive species (NRS) and ROS from NO 3 − under the UV-254 nm [40,41].…”

Direct and indirect photolysis of triclocarban in the presence of dissolved organic matter

“…It is also a potential carcinogen due to the possibility of carbon-nitrogen bond cleavage, which would generate N-hydroxylated metabolites (Halden and Paull, 2004). In addition, TCC yields mono-and dichloro-anilines as attenuation byproducts in the environment, which are hematotoxic, genotoxic, and persistent (Heidler et al, 2006;Ding et al, 2014).…”