Simiao Li,Xiuwei Ao,Chen Li,Zedong Lu,Wenfeng Cao,Fangfang Wu,Shuming Liu,Wenjun Sun
The UV/NH 2 Cl process is an emerging advanced oxidation process (AOP) that is greatly effective in degrading pharmaceuticals and personal care products (PPCPs). However, detailed information regarding the process is lacking. The degradation of ibuprofen (IBP, an electron-withdrawing PPCP) and naproxen (NPX, an electron-donating PPCP) in UV/NH 2 Cl and UV/NaClO processes was performed to investigate the applicability and security of the UV/NH 2 Cl process and compare with those of UV/NaClO. UV/NH 2 Cl was effective in degrading both IBP and NPX and the degradation followed pseudo-first order kinetics (k IBP = 0.0037 cm 2 /mJ and k NPX = 0.0044 cm 2 /mJ). This indicated the broad applicability of UV/NH 2 Cl to different kinds of PPCPs. Ranges of values of UV intensity (0.3–1.0 mW/cm 2 ) and pH (6.0–8.0) showed little effect on the degradation of PPCPs by UV/NH 2 Cl based on UV Dose but HCO 3 − (2–8 mM), natural organic matter (NOM, 2–8 mg/L), and the natural water matrixes were inhibitory. Increasing the dosage of NH 2 Cl from 0.15 mM to 0.75 mM, resulted in an even increase of k IBP ; however, k NPX increased slowly after 0.3 mM NH 2 Cl. Mechanism experiments involving nitrobenzene showed that •OH was the major radical involved in degrading IBP and NPX via UV/NH 2 Cl. The electron spin resonance spectroscopy and kinetic modeling results also indicated the larger amount of •OH and weaker reactive chlorine species (mainly ClO• and ClO 2 •) in UV/NH 2 Cl compared with UV/NaClO. Compared to UV/NaClO in synthetic and natural water, UV/NH 2 Cl was a more stable degrader with little pH- and substrate-dependence, while UV/NaClO preferred degrading the electron-donating PPCP and at low pH. The UV/NH 2 Cl produced less halogenated disinfection byproducts (DBPs) (even nitrogenous DBPs) and was less cytotoxic theoretically than UV/NaClO based on the DBPs included in this study. Thus UV/NH 2 Cl process may be an effective AOP for water treatment .
Liu Anchen,Lin Wenting,Ping Senwen,Guan Wenqi,Hu Ningyi,Zheng Sichun,Ren Yuan
Antihistamines (ANTs) are medicines to treat allergic diseases. They have been frequently detected in the natural water environment, posing potential threats to the ecological environment and human health. In this study, the degradation of three common antihistamines, loratadine, fexofenadine, and cetirizine, was estimated under different oxidation methods (NaClO, UV, and UV-NaClO). The results showed that UV-NaClO had the highest degree of degradation on the drugs under most conditions: 100% degradation for fexofenadine within 20 s at pH 7 and 10. Under UV irradiation, the degradation efficiencies of the three drugs during 150 s were all above 77% at a pH of 7. The drugs’ removal by NaClO was much lower than that of the previous two methods. In addition, this study explored the contribution rates of active oxygen species in the photolysis process. Among them, the contribution of 1 O 2 to the fexofenadine and cetirizine removal rate reached 70%. Different aqueous matrices (HCO 3 − , NO 3 − , and humic acid) had varying degrees of influence on the degradation. Acute toxicity tests and ultraviolet scans of the degradation products showed that the drugs were not completely mineralized, and the toxicities of the intermediates were even higher than those of the parent drugs. There were 9, 8, and 10 chloride oxidation products of loratadine, fexofenadine, and cetirizine, respectively, and 8 photolysis products of cetirizine were identified. For cetirizine, it was found that there were three identical intermediates produced by photodegradation and NaClO oxidation. Graphical abstract
Yishu Cai,Fan Chen,Lingfang Yang,Lin Deng,Zhou Shi
Nanoplastics have gradually become a concern due to the wide use of plastics. Nanoplastics in aqueous phase can be exposed to users through water supply networks and cannot be efficiently removed by conventional water treatment processes. This work studied the degradation of polystyrene nanoplastics (PS-NP) by two commonly used advanced oxidation systems: UV/NaClO and UV/peroxymonosulfate (PMS). Results showed that almost no turbidity was detected in the PS-NP solution (5.00 mg/L) after treated by both UV/NaClO and UV/PMS for 360 min, suggesting the excellent turbidity removal ability. Yet, scanning electron microscope (SEM) and total organic carbon (TOC) removal tests demonstrated that PS-NP could not be completely degraded by UV/NaClO. The mineralization rate using UV/NaClO was only 7.00% even when the NaClO concentration increased to 5.00 mM, and many PS-NP particles could still be observed in SEM images. By contrast, the mineralization rate reached 63.90% in the UV/PMS system under the identical experimental conditions, and no spherical particles appeared in the SEM results. Density functional theory (DFT) calculations revealed that the different reaction sites and energy barriers of SO4•−and•Cl on PS-NP resulted in the differences in mineralization rates and degradation intermediates. The degradation pathway of PS-NP by UV/NaClO and UV/PMS was proposed accordingly. Additionally, the intermediates toxicity evaluation by a luminescent bacteria test showed that the inhibition rate in the UV/NaClO system (2.97%) was not markedly different from that in the control group without any treatment (1.98%); while that in UV/PMS system increased sharply to 98.19%. This work demonstrated that UV/PMS was more effective in PS-NP degradation than UV/NaClO, and the chemical risks of degradation intermediates were non-negligible.Keywords:nanoplastics;polystyrene degradation;mechanisms;DFT calculation;toxicity assessment
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