Comparative study of degradation of ketoprofen and paracetamol by ultrasonic irradiation: Mechanism, toxicity and DBP formation.

The present study comparatively investigated the ultrasonic degradation of ketoprofen (KET) and paracetamol (PCT) in water. Ultrasonic irradiation at 555 kHz achieved rapid degradation of KET and PCT in water, the removal efficiencies of KET (2.5-80 µM) and PCT (2.5-80 µM) reached 87.7%-100% and 50.6%-86.9%, respectively, after 10 min of reaction under an ultrasonic power of 60 W. The degradation behaviors of both KET and PCT followed the Langmuir-Hinshelwood model. KET was eliminated faster than PCT because of its higher hydrophobicity. Acidic media favored ultrasonic degradation of KET and PCT. Organic compounds in water matrices exerted a great negative effect on the ultrasonic degradation rates of KET and PCT major by competing with target compounds with the generated radicals at the bubble/water interfacial region. The effects of anions were species dependent. The introduction of ClO4- and Cl- enhanced KET and PCT degradation to different extents, while the introduction of HCO3- posed a negative effect on both KET and PCT. KET and PCT degradation are accompanied by the generation of several transform intermediates, as identified via LC/MS/MS analysis, and corresponding reaction pathways have been proposed. A human umbilical vein endothelial cell (HUVEC) toxicity evaluation indicated that ultrasonic treatment was capable of controlling the toxicity of KET or PCT degradation. Of note, the enhanced formation of disinfection byproducts (DBPs), i.e., trichloromethane (TCM) and trichloronitromethane (TCNM), was found due to chlorination after ultrasonic treatment for both KET and PCT.

Electrochemically activated peroxymonosulfate for the abatement of chloramphenicol in water: performance and mechanism.

In this study, electrochemically activated peroxymonosulfate (EC/PMS) with a sacrificial iron electrode was used for the removal of chloramphenicol (CAP) from water. Compared to electrolysis alone, peroxymonosulfate (PMS) alone, and Fe2+/PMS, EC/PMS significantly enhanced the CAP degradation. Various parameters, such as the applied current, electrolyte concentration, and PMS dose, were investigated to optimize the process. In addition, acidic conditions facilitated the CAP degradation. The presence of Cl- slightly enhanced the CAP degradation, while both HCO3- and NO3- exhibited an inhibitory effect on the CAP degradation. The floccules were also analyzed after the reaction by XPS and XRD. Quenching experiments indicated that both sulfate radicals (SO4●-) and hydroxyl radicals (•OH) were responsible for the CAP degradation. In addition, the degradation products were identified by LC/TOF/MS, and the degradation pathways were proposed accordingly. These results indicated that EC/PMS is a promising treatment process for the remediation of water polluted by CAP.

Persulfate activation by nano zero-valent iron for the degradation of metoprolol in water: influencing factors, degradation pathways and toxicity analysis.

In this study, nano zero-valent iron (nZVI) was utilized to activate persulfate (PS) for the degradation of metoprolol (MTP), a commonly used drug for curing cardiovascular diseases, in water. Quenching tests indicated that both the sulfate radical (SO4˙-) and hydroxyl radical (˙OH) contributed to the degradation of MTP, while SO4˙- seemed to play a large role under natural pH conditions. Batch tests were conducted to investigate the effects of several influencing factors, such as PS concentration, initial MTP concentration, pH, temperature and common anions, on the degradation performance of MTP. Generally, lower MTP concentration and pH values, and higher PS concentration and temperature favoured MTP degradation. HCO3 -, NO3 - and SO4 2- were found to inhibit MTP degradation, while Cl- enhanced MTP degradation. Several corrosion products of nZVI, including Fe3O4, Fe2O3 and FeSO4, were formed during the reaction, which was reflected by the combined XRD and XPS analysis. Degradation pathways of MTP were proposed according to the identified transformation products, and the peak areas of the major products along with the time were also monitored. Finally, the toxicity of the reaction solution was assessed by experiments using Aliivibrio fischeri. Overall, it could be concluded that nZVI/PS might be a promising method for the rapid treatment of MTP-caused water pollution.