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

Influence of entropy on catalytic performance of high-entropy oxides (NiMgZnCuCoOx) in peroxymonosulfate-mediated acetaminophen degradation

Developing a high-performance activator is crucial for the practical application of peroxymonosulfate-based advanced oxidation processes (PMS-AOPs). High-entropy oxides (HEOs) have attracted increasing attention due to their stable crystal structure, flexible composition and unique functionality. However, research into the mechanisms by which HEOs function as PMS activators for degrading organic pollutants remains insufficient, and the relationship between entropy and the catalytic performance of HEOs has yet to be clarified. In this study, we synthesized NiMgZnCuCoOx with different levels of entropy as PMS activators for acetaminophen (APAP) degradation, and observed a significant effect for entropy on the catalytic performance. Sulfate radicals (SO4•‒) were identified as the primary reactive oxygen species (ROS), while hydroxyl radicals (•OH) and singlet oxygen (1O2) act as secondary ROS during APAP degradation. Both the Co2+ contents and the oxygen vacancy concentration in NiMgZnCuCoOx are found to increase with the entropy. An increase in the Co2+ sites leads to more activation sites for PMS activation, while excessive oxygen vacancies consume PMS, producing weak oxidation species, and affect the electron-donating ability of Co2+. Consequently, the NiMgZnCuCoOx with middle level of entropy exhibits the optimal performance with APAP degradation rate and mineralization rate reaching 100% and 74.22%, respectively. Furthermore, the degradation intermediates and their toxicities were assessed through liquid chromatography-mass spectrometry and quantitative structure-activity relationship analysis. This work is expected to provide critical insight into the impact of the HEOs entropy on the PMS activation and guide the rational design of highly efficient peroxymonosulfate activators for environmental applications.

Unique effect of bromide ion on intensification of advanced oxidation processes for pollutants removal: A systematic review

Advanced oxidation processes (AOPs) have been developed to decompose toxic pollutants to protect the aquatic environment. AOP has been considered an alternative treatment method for wastewater treatment. Bromine is present in natural waters posing toxic effects on human health and hence, its removal from drinking water sources is necessary. Of the many techniques advanced oxidation is covered in this review. This review systematically examines literature published from 1997 to April 2024, sourced from Scopus, PubMed, Science Direct, and Web of Science databases, focusing on the efficacy of AOPs for pollutant removal from aqueous solutions containing bromide ions to investigate the impact of bromide ions on AOPs. Data and information extracted from each article eligible for inclusion in the review include the type of AOP, type of pollutants, and removal efficiency of AOP under the presence and absence of bromide ion. Of the 1784 documents screened, 90 studies met inclusion criteria, providing insights into various AOPs, including UV/chlorine, UV/PS, UV/H2O2, UV/catalyst, and visible light/catalyst processes. The observed impact of bromide ion presence on the efficacy of AOP processes, alongside the AOP method under scrutiny, is contingent upon various factors such as the nature of the target pollutant, catalyst type, and bromide ion concentration. These considerations are crucial in selecting the best method for removing specific pollutants under defined conditions. Challenges were encountered during result analysis included variations in experimental setups, disparities in pollutant types and concentrations, and inconsistencies in reporting AOP performance metrics. Addressing these parameters in research reports will enhance the coherence and utility of subsequent systematic reviews.

Degradation and detoxification of ribavirin by UV/chlorine/Fe(II) process in water treatment system

Ribavirin (RBV), which is extensively used to treat viral diseases such as COVID-19, is considered one of the major emerging contaminants due to its long-term existence and health risk in the aqueous environmental system. However, research on effective removal of RBV still remains insufficient. In this study, we investigated the RBV degradation kinetics and mechanism in UV/chlorine/Fe(II) process. The degradation rate constant kobs-RBV of RBV was 2.52 × 10-4 s-1 in UV/chlorine/Fe(II) process, which increased by 1.6 times and 1.3 times than that in chlorine alone and UV/chlorine process, respectively. Notably, trace amount Fe(II) promoted RBV degradation in UV/chlorine system through Fe2+/Fe3+ cycles, enhancing the yield of reactive species such as HO· and certain species reactive chlorine radicals (RCS). The contributions of HO· and RCS toward RBV degradation were 53.91% and 16.11%, respectively. Specifically, Cl·, ClO·, and Cl2·- were responsible for 8.59%, 2.69%, and 4.83% of RBV removal. The RBV degradation pathway indicated that the reactive species preferentially attacked the amide moiety of RBV, which cleaved the ether bond and the hydroxyl group. The toxicity evaluation of RBV degradation products elucidated that UV/chlorine/Fe(II) process was beneficial for RBV detoxification.

Chlorination of antiviral drug ribavirin: Kinetics, nontargeted identification, and concomitant toxicity evolution

Residual antiviral drugs in wastewater may increase the risk of generating transformation products (TPs) during wastewater treatment. Therefore, chlorination behavior and toxicity evolution are essential to understand the secondary ecological risk associated with their TPs. Herein, chlorination kinetics, transformation pathways, and secondary risks of ribavirin (RBV), one of the most commonly used broad-spectrum antivirals, were investigated. The pH-dependent second-order rate constants k increased from 0.18 M-1·s-1 (pH 5.8) to 1.53 M-1·s-1 (pH 8.0) due to neutral RBV and ClO- as dominant species. 12 TPs were identified using high-resolution mass spectrometry in a nontargeted approach, of which 6 TPs were reported for the first time, and their chlorination pathways were elucidated. The luminescence inhibition rate of Vibrio fischeri exposed to chlorinated RBV solution was positively correlated with initial free active chlorine, probably due to the accumulation of toxic TPs. Quantitative structure-activity relationship prediction identified 7 TPs with elevated toxicity, concentrating on developmental toxicity and bioconcentration factors, which explained the increased toxicity of chlorinated RBV. Overall, this study highlights the urgent need to minimize the discharge of toxic chlorinated TPs into aquatic environments and contributes to environmental risk control in future pandemics and regions with high consumption of antivirals.

The synergistic effect of oxidant-peroxide coupling systems for water and wastewater treatments

With the growing complexity and severity of water pollution, it has become increasingly challenging to effectively remove contaminants or inactivate microorganisms just by traditional chemical oxidants such as O3, chlorine, Fe(VI) and Mn(VII). Up till now, numerous studies have indicated that these oxidants in combination with peroxides (i.e., hydrogen peroxide (H2O2), peroxymonosulfate (PMS), peracetic acid (PAA) and periodate (PI)) exhibited excellent synergistic oxidation. This paper provided a comprehensive review on the combination of aforementioned oxidant-peroxide applied in water and wastewater treatments. From one aspect, the paper thoroughly elucidated the synergy mechanism of each oxidant-peroxide combination in turn. Among these combinations, H2O2 or PMS generally performed as the activator of four traditional oxidants above to accelerate reactive species generation and therein various reaction mechanisms, including electron transfer, O atom abstraction and oxo ligand substitution, were involved. In addition, although neither PAA nor PI was able to directly activate Fe(VI) and Mn(VII), they could act as the stabilizer of intermediate reactive iron/manganese species to improve the latter utilization efficiency. From another aspect, this paper summarized the influence of water quality parameters, such as pH, inorganic ions and natural organic matter (NOM), on the oxidation performance of most combined systems. Finally, this paper highlighted knowledge gaps and identified areas that require further research.

Smart Organic-Inorganic Polyoxomolybdates in Forward Osmosis for Antiviral-Drug Wastewater Treatment and Drug Reclamation

The demand to effectively treat medical wastewater has escalated with the much greater use of antiviral drugs since the COVID-19 pandemic. Forward osmosis (FO) has great potential in wastewater treatment only when appropriate draw solutes are available. Here, we synthesize a series of smart organic-inorganic polyoxomolybdates (POMs), namely, (NH₄)₆[Mo₇O₂₄], (PrNH₃)₆[Mo₇O₂₄], (ⁱPrNH₃)₆[Mo₇O₂₄], and (BuNH₃)₆[Mo₇O₂₄], for FO to treat antiviral-drug wastewater. Influential factors of separation performance have been systematically studied by tailoring the structure, organic characteristics, and cation chain length of POMs. POMs at 0.4 M produce water fluxes ranging from 14.0 to 16.4 LMH with negligible solute losses, at least 116% higher than those of NaCl, NH₄HCO₃, and other draw solutes. (NH₄)₆[Mo₇O₂₄] creates a water flux of 11.2 LMH, increased by more than 200% compared to that of NaCl and NH₄HCO₃ in long-term antiviral-drug wastewater reclamation. Remarkably, the drugs treated with NH₄HCO₃ and NaCl are either contaminated or denatured, while those with (NH₄)₆[Mo₇O₂₄] remain intact. Moreover, these POMs are recovered by sunlight-assisted acidification owing to their light and pH dual sensitivity and reusability for FO. POMs prove their suitability as draw solutes and demonstrate their superiority over the commonly studied draw solutes in wastewater treatment.

Comparison of ribavirin degradation in the UV/H2O2 and UV/PDS systems: Reaction mechanism, operational parameter and toxicity evaluation

Residues in surface water of ribavirin, which used extensively during the COVID-19 pandemic, have become an emerging issue due to its adverse impact on the environment and human health. UV/H2O2 and UV/peroxydisulfate (PDS) have different degradation effects on ribavirin, and the same operational parameter have different effects on the two processes. In this study, the reaction mechanism and degradation efficiency for ribavirin were studied to compare the differences under UV/H2O2 and UV/PDS processes. We calculated the total rate constants of ribavirin with HO• and SO4 •- in the liquid phase as 2.73 × 108 and 9.39 × 105 M-1s-1. The density functional theory (DFT) calculation results showed that HO• and SO4 •- react more readily with ribavirin via H-abstraction (HAA). The nitrogen-containing heterocyclic ring is difficult to undergo ring-opening degradation. The UV/PDS process was more stable and performed better than the UV/H2O2 for the ribavirin degradation when the same molar oxidant dosage was applied. HO• plays an extremely important role in the degradation of ribavirin by UV/PDS. The reason for this phenomenon is the combination of the higher yield of HO• produced in the UV/PDS process and the faster reaction rate of ribavirin with HO•. The UV/H2O2 process is more sensitive to pH than UV/PDS. Alkaline condition can significantly inhibit the ribavirin degradation. The effects of natural organic matter (NOM) and ribavirin concentration were also compared. Eventually, the toxicity prediction of the product showed that the opening-ring products were more toxic than the parent compound.

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.

Environmental impacts of the widespread use of chlorine-based disinfectants during the COVID-19 pandemic

Chlorinated disinfectants are widely used in hospitals, COVID-19 quarantine facilities, households, institutes, and public areas to combat the spread of the novel coronavirus as they are effective against viruses on various surfaces. Medical facilities have enhanced their routine disinfection of indoors, premises, and in-house sewage. Besides questioning the efficiency of these compounds in combating coronavirus, the impacts of these excessive disinfection efforts have not been discussed anywhere. The impacts of chlorine-based disinfectants on both environment and human health are reviewed in this paper. Chlorine in molecular and in compound forms is known to pose many health hazards. Hypochlorite addition to soil can increase chlorine/chloride concentration, which can be fatal to plant species if exposed. When chlorine compounds reach the sewer/drainage system and are exposed to aqueous media such as wastewater, many disinfection by-products (DBPs) can be formed depending on the concentrations of natural organic matter, inorganics, and anthropogenic pollutants present. Chlorination of hospital wastewater can also produce toxic drug-derived disinfection by-products. Many DBPs are carcinogenic to humans, and some of them are cytotoxic, genotoxic, and mutagenic. DBPs can be harmful to the flora and fauna of the receiving water body and may have adverse effects on microorganisms and plankton present in these ecosystems.

Biocatalyst developed with recovered iron-rich minerals enhances the biotransformation of SARS-CoV-2 antiviral drugs in anaerobic bioreactors

The biotransformation of the SARS-CoV-2 antiviral drugs, ribavirin and tenofovir, was studied in methanogenic bioreactors. The role of iron-rich minerals, recovered from a metallurgic effluent, on the biotransformation process was also assessed. Enrichment of anaerobic sludge with recovered minerals promoted superior removal efficiency for both antivirals (97.4 % and 94.7 % for ribavirin and tenofovir, respectively) as compared to the control bioreactor lacking minerals, which achieved 58.5 % and 37.9 % removal for the same drugs, respectively. Further analysis conducted by liquid chromatography coupled to mass spectroscopy revealed several metabolites derived from the biotransformation of both antivirals. Interestingly, tracer analysis with ¹³CH₄ revealed that anaerobic methane oxidation coupled to Fe(III) reduction occurred in the enriched bioreactor, which was reflected in a lower content of methane in the biogas produced from this system, as compared to the control bioreactor. This treatment proposal is suitable within the circular economy concept, in which recovered metals from an industrial wastewater are applied in bioreactors to create a biocatalyst for promoting the biotransformation of emerging pollutants. This strategy may be appropriate for the anaerobic treatment of wastewaters originated from hospitals, as well as from the pharmaceutical and chemical sectors.

Evaluation of degradation performance toward antiviral drug ribavirin using advanced oxidation process and its relations to ecotoxicity evolution

The rapid spread of coronavirus disease 2019 has increased the consumption of some antiviral drugs, wherein these are discharged into wastewater, posing risks to the ecosystem and human health. Therefore, efforts are being made for the development of advanced oxidation processes (AOPs) to remediate water containing these pharmaceuticals. Here, the toxicity evolution of the antiviral drug ribavirin (RBV) was systematically investigated during its degradation via the UV/TiO₂/H₂O₂ advanced oxidation process. Under optimal conditions, RBV was almost completely eliminated within 20 min, although the mineralization rate was inadequate. Zebrafish embryo testing revealed that the ecotoxicity of the treated RBV solutions increased at some stages and decreased as the reaction time increased, which may be attributed to the formation and decomposition of various transformation products (TPs). Liquid chromatography-mass spectrometry analysis along with density functional theory calculations helped identify possible toxicity increase-causing TPs, and quantitative structure activity relationship prediction revealed that most TPs exhibit higher toxicity than the parent compound. The findings of this study suggest that, in addition to the removal rate of organics, the potential ecotoxicity of treated effluents should also be considered when AOPs are applied in wastewater treatment.

The role of trace N-Oxyl compounds as redox mediator in enhancing antiviral ribavirin elimination in UV/Chlorine process

Ribavirin (RBV) is an antiviral drug used for treating COVID-19 infection. Its release into natural waters would threaten the health of aquatic ecosystem. This study reports an effective approach to degrade RBV by the trace N-oxyl compounds (2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) and N-Hydroxyphthalimide (NHPI)) enhanced UV activated free chlorine (UV/Chlorine) process. The results indicated that TEMPO and NHPI at low concentrations (0.1 μM and 1 μM, respectively) could strongly enhance RBV degradation in both deionized water with different pHs and practical surface water. The enhancement was verified to be attributed to the transformation of TEMPO and NHPI into their reactive forms (i.e., TEMPO⁺ and PINO), which generations deeply relied on radicals. The two N-oxyl compounds inhibit ClO• yield by hindering the reaction of free chlorine vs. HO• and Cl•. The analyses on acute toxicities of RBV degradation products indicate that UV/Chlorine/N-oxyl compounds process can detoxify RBV more efficiently than UV/Chlorine process.

SARS-CoV-2 pharmaceutical drugs: a critical review on the environmental impacts, chemical characteristics, and behavior of advanced oxidation processes in water

This review summarizes research data on the pharmaceutical drugs used to treat the novel SARS-CoV-2 virus, their characteristics, environmental impacts, and the advanced oxidation processes (AOP) applied to remove them. A literature survey was conducted using the electronic databases Science Direct, Scopus, Taylor & Francis, Google Scholar, PubMed, and Springer. This complete research includes and discusses relevant studies that involve the introduction, pharmaceutical drugs used in the SARS-CoV-2 pandemic: chemical characteristics and environmental impact, advanced oxidation process (AOP), future trends and discussion, and conclusions. The results show a full approach in the versatility of AOPs as a promising solution to minimize the environmental impact associated with these compounds by the fact that they offer different ways for hydroxyl radical production. Moreover, this article focuses on introducing the fundamentals of each AOP, the main parameters involved, and the concomitance with other sources and modifications over the years. Photocatalysis, sonochemical technologies, electro-oxidation, photolysis, Fenton reaction, ozone, and sulfate radical AOP have been used to mineralize SARS-CoV-2 pharmaceutical compounds, and the efficiencies are greater than 65%. According to the results, photocatalysis is the main technology currently applied to remove these pharmaceuticals. This process has garnered attention because solar energy can be directly utilized; however, low photocatalytic efficiencies and high costs in large-scale practical applications limit its use. Furthermore, pharmaceuticals in the environment are diverse and complex. Finally, the review also provides ideas for further research needs and major concerns.

Occurrence and risk assessment of typical PPCPs and biodegradation pathway of ribavirin in wastewater treatment plants

A large number of pharmaceuticals and personal care products (PPCPs) persist in wastewater, and the consumption of PPCPs for COVID-19 control and prevention has sharply increased during the pandemic. This study investigated the occurrence, removal efficiency, and risk assessment of six typical PPCPs commonly used in China in two wastewater treatment plants (WWTPs). Ribavirin (RBV) is an effective pharmaceutical for severely ill patients with COVID-19, and the possible biodegradation pathway of RBV by activated sludge was discovered. The experimental results showed that PPCPs were detected in two WWTPs with a detection rate of 100% and concentrations ranging between 612 and 2323 ng L^-1. The detection frequency and concentrations of RBV were substantially higher, with a maximum concentration of 314 ng L^-1. Relatively high pollution loads were found for the following PPCPs from influent: ibuprofen > ranitidine hydrochloride > RBV > ampicillin sodium > clozapine > sulfamethoxazole. The removal efficiency of PPCPs was closely related to adsorption and biodegradation in activated sludge, and the moving bed biofilm reactor (MBBR) had a higher removal capacity than the anoxic-anaerobic-anoxic-oxic (AAAO) process. The removal efficiencies of sulfamethoxazole, ampicillin sodium, ibuprofen, and clozapine ranged from 92.21% to 97.86% in MBBR process and were relatively low, from 61.82% to 97.62% in AAAO process, and the removal of RBV and ranitidine hydrochloride were lower than 42.96% in both MBBR and AAAO processes. The discrepancy in removal efficiency is caused by temperature, hydrophilicity, and hydrophobicity of the compound, and acidity and alkalinity. The transformation products of RBV in activated sludge were detected and identified, and the biodegradation process of RBV could be speculated as follows: first breaks into TCONH₂ and an oxygen-containing five-membered heterocyclic ring under the nucleosidase reaction, and then TCONH₂ is finally formed into TCOOH through amide hydrolysis. Aquatic ecological risks based on risk quotient (RQ) assessment showed that PPCPs had high and medium risks in the influent, and the RQ values were all reduced after MBBR and AAAO treatment. Ranitidine hydrochloride and clozapine still showed high and medium risks in the effluent, respectively, and thus presented potential risks to the aquatic ecosystem.

Synergistic effects of ozone/peroxymonosulfate for isothiazolinone biocides degradation: Kinetics, synergistic performance and influencing factors

Synergistic effects of ozone (O₃) and peroxymonosulfate (PMS, HSO₅^-) for isothiazolinone biocides degradation was studied. The synergistic ozonation process (O₃/PMS) increased the efficiency of methyl-isothiazolinone (MIT) and chloro-methyl-isothiazolinone (CMIT) degradation to 91.0% and 81.8%, respectively, within 90 s at pH 7.0. This is 30.6% and 62.5% higher than the corresponding ozonation efficiency, respectively. Total radical formation value (R_ct,R) for the O₃/PMS process was 24.6 times that of ozonation alone. Calculated second-order rate constants for the reactions between isothiazolinone biocides and (k_SO4-,MIT and k_SO4-,CMIT) were 8.15 × 10⁹ and 4.49 × 10⁹ M^-1 s^-1, respectively. Relative contributions of O₃, hydroxyl radical (OH) and oxidation to MIT and CMIT removal were estimated, which were 15%, 45%, and 40% for O₃, OH and oxidation to MIT, and 1%, 67%, and 32% for O₃, OH and oxidation to CMIT at pH 7.0, respectively. Factors influencing the O₃/PMS process, namely the solution pH, chloride ions (Cl^-), and bicarbonate (HCO₃^-), were evaluated. Increasing the solution pH markedly accelerated O₃ decay and OH and formation, thus weakening the relative contribution of O₃ oxidation while enhancing that of OH and . Cl^- had a negligible effect on MIT and CMIT degradation. Under the dual effect of bicarbonate (HCO₃^-) as inhibitor and promoter, low concentrations (1-2 mM) of bicarbonate weakly promoted MIT and CMIT degradation, while high concentrations (10-20 mM) induced strong inhibition. Lastly, oxidation performance of O₃ and O₃/PMS processes for MIT and CMIT degradation in different water matrices was compared.