Kinetic mechanism of ozone activated peroxymonosulfate system for enhanced removal of anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) in the environment: Recent updates on the occurrence, fate, hazards and removal technologies

Non-steroidal Anti-inflammatory Drugs (NSAIDs) are extensively utilized pharmaceuticals worldwide. However, owing to the improper discharge and disposal practices, they have emerged as significant contaminants that are widely distributed in water, soils, and sewage sediments. This ubiquity poses a substantial threat to the ecosystem and human health. Consequently, it is imperative to develop rapid, cost-effective, efficient and reliable approaches for containing these substance in order to mitigate the deleterious impact of NSAIDs. This research provides a comprehensive review of the occurrence, fate, and hazards associated with NSAIDs in the general environment. Additionally, various removal technologies, including advanced oxidation processes, biodegradation, and adsorption, were systematically summarized. The study also presents a comparative analysis of the benefits and drawbacks of different removal technologies while interpreting challenges related to NSAIDs' removal and proposing strategies for future development.

Application of O3/PMS Advanced Oxidation Technology in the Treatment of Organic Pollutants in Highly Concentrated Organic Wastewater: A Review

The ozone/peroxymonosulfate (O3/PMS) system has attracted widespread attention from researchers owing to its ability to produce hydroxyl radicals (•OH) and sulfate radicals (SO4•−) simultaneously. The existing research has shown that the O3/PMS system significantly degrades refinery trace organic compounds (TrOCs) in highly concentrated organic wastewater. However, there is still a lack of systematic understanding of the O3/PMS system, which has created a significant loophole in its application in the treatment of highly concentrated organic wastewater. Hence, this paper reviewed the specific degradation effect, toxicity change, reaction mechanism, various influencing factors and the cause of oxidation byproducts (OBPs) of various TrOCs when the O3/PMS system is applied to the degradation of highly concentrated organic wastewater. In addition, the effects of different reaction conditions on the O3/PMS system were comprehensively evaluated. Furthermore, given the limited understanding of the O3/PMS system in the degradation of TrOCs and the formation of OBPs, an outlook on potential future research was presented. Finally, this paper comprehensively evaluated the degradation of TrOCs in highly concentrated organic wastewater by the O3/PMS system, filling the gaps in scale research, operation cost, sustainability and overall feasibility.

Highly stable and efficient calcined γ-Al2O3 catalysts loaded with MnOx-CeOx for the ozonation of oxytetracycline

Catalytic ozonation with supported metal oxides is a promising strategy for addressing refractory pollutants in wastewater. In this study, γ-Al₂O₃ supported MnO_x-CeO_x catalysts (MC₁, MC₂, and MC₃) obtained at different calcination temperatures (400 °C, 550 °C, and 700 °C) were applied as effective catalysts for ozonation and explored the feasibility of the treatment of oxytetracycline (OTC) wastewater. Comparatively, the MC₂ possessed the highest molar ratios of Mn³⁺/Mn⁴⁺ (1.60) and Ce³⁺/Ce⁴⁺ (0.96), the largest surface area (273.8 m² g^-1) with a petal-shaped structure, and most abundant surface hydroxyls (3.78 mmol g^-1). These physicochemical characteristics benefited the surface reaction and resulted in the acceleration of ozone decomposition, electron transfer, and •OH generation, thereby improving the catalyst's adsorption ability and catalytic activity. The combination with MC₂ increased the OTC and COD removal of the ozonation process from 59.1% and 29.0% to 94.7% and 83.3% in 25 min, respectively. By employing electron paramagnetic resonance (EPR) and radical quenching experiments, it was verified that •OH species generation promoted the mineralization of OTC. The possible degradation pathways of OTC were investigated through mass spectrometry, and the route consisted of dehydration, deamination, and demethylation. Moreover, during a 12-day continuous experiment, MC₂ catalyst exhibited excellent reusability and catalytic stability, with COD removal efficiencies above 80%.

Enhanced waste activated sludge dewaterability by the ozone-peroxymonosulfate oxidation process: Performance, sludge characteristics, and implication

Dewatering treatment is an essential step to diminish sludge volume, cut down transportation costs, and improve subsequent disposal efficiency. In this study, ozone-peroxymonosulfate (O₃/PMS) oxidation process was employed to ameliorate sludge dewaterability. Sludge capillary suction time (CST) and water content (Wc) of dewatered sludge cake could reduce from 70.5 s and 81.93% to 26.7 s and 65.65%, respectively, under the optimal dosage of 30 mg/g TS O₃ and 0.4 mmol/g TS PMS. The increased sludge zeta potential, particle size, and fluidity promoted sludge dewatering performance apparently. The decreased hydrophilic, fluorescent EPS components and proteins/peptides-like + Lipids percentage in EPS as well as the ratio of α-helix/(β-sheet + random coil) of treated EPS protein secondary structure was greatly responsible for the enhanced sludge dewaterability. SO₄^- and OH were detected in ozone-peroxymonosulfate process to crack sludge flocs, eliminate hydrophilic substances and liberate bound water. Moreover, the concentrations of both heavy metals and polycyclic aromatic hydrocarbons (PAHs) of sludge after O₃/PMS conditioning were decreased, and the stability and toxicity of heavy metals were also reduced, except Zn. In conclusion, this work offered a comprehensive insight based on ozone-peroxymonosulfate (O₃/PMS) advanced oxidation for improving the sludge dewaterability and environmental implication.

Transformation of antiviral ribavirin during ozone/PMS intensified disinfection amid COVID-19 pandemic

Due to the spread of coronavirus disease 2019 (COVID-19), large amounts of antivirals were consumed and released into wastewater, posing risks to the ecosystem and human health. Ozonation is commonly utilized as pre-oxidation process to enhance the disinfection of hospital wastewater during COVID-19 spread. In this study, the transformation of ribavirin, antiviral for COVID-19, during ozone/PMS‑chlorine intensified disinfection process was investigated. •OH followed by O₃ accounted for the dominant ribavirin degradation in most conditions due to higher reaction rate constant between ribavirin and •OH vs. SO₄•^- (1.9 × 10⁹ vs. 7.9 × 10⁷ M^-1 s^-1, respectively). During the O₃/PMS process, ribavirin was dehydrogenated at the hydroxyl groups first, then lost the amide or the methanol group. Chloride at low concentrations (e.g., 0.5- 2 mg/L) slightly accelerated ribavirin degradation, while bromide, iodide, bicarbonate, and dissolved organic matter all reduced the degradation efficiency. In the presence of bromide, O₃/PMS process resulted in the formation of organic brominated oxidation by-products (OBPs), the concentration of which increased with increasing bromide dosage. However, the formation of halogenated OBPs was negligible when chloride or iodide existed. Compared to the O₃/H₂O₂ process, the concentration of brominated OBPs was significantly higher after ozonation or the O₃/PMS process. This study suggests that the potential risks of the organic brominated OBPs should be taken into consideration when ozonation and ozone-based processes are used to enhance disinfection in the presence of bromide amid COVID-19 pandemic.

The promotions on radical formation and micropollutant degradation by the synergies between ozone and chemical reagents (synergistic ozonation): A review

The combination of ozone (O₃) and chemical reagents (such as H₂O₂) shows synergies on the radical formation and micropollutant degradation. The promoting performance was associated with various parameters including chemical reagents, micropollutants, solution pH, and the water matrix. In this review, we summarized existing knowledge on radical formation pathways, radical yields, and radical oxidation for different synergistic ozonation processes in various water matrices (such as groundwater, surface water, and wastewater). The increase of radical yields by synergistic ozonation processes was positively related to the increase of O₃-decay, with the increase being 1.1-4.4 folds than ozonation alone (0.2). Thus, synergistic ozonation can promote the degradation rate and efficiency of O₃-resistant micropollutants (second order rate constant, k_P,O3 < 200 M^-1 s^-1), but only slightly affects or even minorly inhibits the degradation of O₃-reactive micropollutants (k_P,O3 > 200 M^-1 s^-1). The water matrices^, such as the dissolved organic matters, negatively suppressed the degradation of micropollutant by quenching O₃-oxidation and radical oxidation (i.e. maximum promoting was decreased by 1.3 times), but may positively extend the promoting effects of synergistic ozonation to micropollutants that are more reactive to O₃ (i.e. k_P,O3 was extended from <200 to <2000 M^-1 s^-1). The formation of bromate would be increased through increasing radical oxidation by synergistic ozonation, but can be depressed by relative higher H₂O₂ as the reducing agent of HOBr/OBr^- intermediate. The increase in bromate formation by O₃/permononsulfate is a considerable concern due to permononsulfate cannot reduce the HOBr/OBr^- intermediate.

Effective removal of refractory organic contaminants from reverse osmosis concentrated leachate using PFS-nZVI/PMS/O3 process

Reverse osmosis concentrated leachate (ROCL) from landfill leachate treatment contains high amounts of refractory organics. In this study, a combination of polymerized ferric sulfate (PFS) and nanoscale zero-valent iron/peroxymonosulfate/ozone (nZVI/PMS/O₃) approach was adopted to remove refractory pollutants in ROCL. The effects of coagulant species, dosage and initial pH on the pre-treatment of organics from ROCL during coagulation process were investigated. Moreover, the influences of experimental factors, including initial pH, ozone doses, PMS, and nZVI on the removal of refractory organics in ROCL from coagulation effluent were systematically studied. The characteristics of organics were determined by using microscopic, spectroscopic and electron paramagnetic resonance (EPR) analyses. The batch experimental results indicated that the refractory organic contaminants in ROCL were effectively removed through PFS-nZVI/PMS/O₃ treatment. The maximum removal efficiencies of COD and TOC were 89.1% and 83.2% under the optimum conditions: PFS of 8 g/L, ozone dose of 100 mg/min, PMS dose of 1.5 mM and nZVI dose of 10 mM, and at these conditions, the biodegradability index (BOD₅/COD) was enhanced from 0.02 to 0.32. The excitation-emission matrix fluorescence spectroscopy (EEM) analysis indicated that humic-like and fulvic-like substances in ROCL were effectively removed. According to EPR analysis, hydroxyl and sulfate radicals were the dominant reactive species for the degradation of organics in nZVI/PMS/O₃ system. Overall, the environmental and economic analysis suggested that the PFS-nZVI/PMS/O₃ system was a cost-effective method for cleaning refractory organics from ROCL.

Reactive oxygen species generation in FeOCl nanosheets activated peroxymonosulfate system: Radicals and non-radical pathways

Iron oxychloride (FeOCl) is utilized as a activator of peroxymonosulfate (PMS) for the degradation of paracetamol (APAP) and phenacetin (PNCT) in response to the water pollution by persistent pharmaceuticals. The degradation process was well fitted with a pseudo-first order kinetic pattern, and the excellent catalytic performance towards APAP (100 % removal) and PNCT (86.5 % removal) was obtained in the presence of 0.2 g/L FeOCl and 2.0 mM PMS at pH 7.0 in 30 min. In-situ electron spin resonance (ESR) and scavenging tests revealed the generation of a series of ROS (·OH, SO₄^-, O₂^-, ¹O₂), which was highly dependent on pH. Besides, the non-radical pathways process involved ¹O₂ was dominant in APAP oxidation, while both ·OH and ¹O₂ are significant in PNCT removal. Furthermore, the formation of disinfection by-products (DBPs) during post-chlorination showed neglectable increment at neutral and alkaline condition with FeOCl/PMS pre-oxidation, and the calculated cytotoxicity would experience a continuous deterioration with pH increase. These results displayed high efficiency of FeOCl/PMS system in micropollutants degradation and a relatively comprehensive activation process of PMS, which may promote practical application in environmental remediation.

Anti-inflammatory drugs degradation during LED-UV365 photolysis of free chlorine: roles of reactive oxidative species and formation of disinfection by-products

Light-emitting diode (LED) is environmentally friendly with longer life compared with traditionally mercury lamps. This study investigated the non-steroidal anti-inflammatory drugs (NSAIDs)- phenacetin (PNT) and acetaminophen (ACT)- removal during LED-UV (365 nm) photolysis of free available chlorine (FAC). Degradation of PNT and ACT during LED-UV₃₆₅/FAC treatment at pH 5.5-8.5 followed the pseudo-first order kinetics. The presence of hydroxyl radicals (·OH), reactive chlorine species (RCS), and ozone (O₃, transformed from O (³P)) were screened by using scavengers of ethanol (EtOH), tert-Butanol (TBA), and 3-buten-2ol, and 4-hydroxy-2,2,6,6-tetramethylpiperidine (TEMP), and quantified by competition kinetics with probing compounds of nitrobenzene (NB), benzoate acid (BA), 1,4-dimethoxybenzene (DMOB). Higher pH would lead to decrease of ·OH contribution and an increase of FAC contribution to PNT and ACT degradation. It has been determined that the contribution of O₃ to degradation of PNT and ACT was less than 5% for all pHs, and O³(P) reacts toward EtOH with second-order constant of 1.52 × 10⁹ M^-1s^-1. LED-UV₃₆₅/FAC system reduced the formation of five typical CX₃-R type disinfection by-products (DBPs) as well as the cytotoxicity and genotoxicity of water samples at pH 5.5 and 8.5, compared with FAC alone. The decrease of DBPs formation resulted from fast FAC decomposition upon LED-UV₃₆₅ irradiation. A feasible reaction pathway of DBPs formation in the LED-UV₃₆₅/FAC system was examined with density functional theory (DFT). For FAC decay during LED-UV₃₆₅/FAC with effluent from wastewater, the residual FAC in 15 min was 0.8 mg/L (lower than limit of 0.2 mg/L) once initial FAC was 2.0 mg/L. The results indicate that more tests on the balance of target pollutant removal efficiency, residual FAC and cost should be explored in LED-UV₃₆₅/FAC system for application.