Application of advanced oxidation processes and toxicity assessment of transformation products

Insight into the generation of toxic by-products during UV/H2O2 degradation of carbamazepine: Mechanisms, N-transformation and toxicity

Carbamazepine (CBZ) is a widely used anticonvulsant drug that has been detected in aquatic environments. This study investigated the toxicity of its by-products (CBZ-BPs), which may surpass CBZ. Unlike the previous studies, this study offered a more systematic approach to identifying toxic BPs and inferring degradation pathways. Furthermore, quadrupole time-of-flight (QTOF) and density functional theory (DFT) calculations were employed to analyze CBZ-BP structures and degradation pathways. Evaluation of total organic carbon (TOC) and total nitrogen (TN) mineralization rates, revealed carbon (C) greater susceptibility to mineralization compared with nitrogen (N). Furthermore, three rules were established for CBZ decarbonization and N removal during degradation, observing the transformation of aromatic compounds into aliphatic hydrocarbons and stable N-containing organic matter over time. Five potentially highly toxic BPs were screened from 14 identified BPs, with toxicity predictions guiding the selection of commercial standards for quantification and true toxicity testing. Additionally, BP207 emerged as the most toxic, supported by the predictive toxicity accumulation model (PTAM). Notably, highly toxic BPs feature an acridine structure, indicating its significant contribution to toxicity. These findings offered valuable insights into the degradation mechanisms of emerging contaminants and the biosafety of aquatic environments during deep oxidation.

What is the role of nitrate/nitrite in trace organic contaminants degradation and transformation during UV-based advanced oxidation processes?

The effectiveness of UV-based advanced oxidation processes (UV-AOPs) in degrading trace organic contaminants (TrOCs) can be significantly influenced by the ubiquitous presence of nitrate (NO3-) and nitrite (NO2-) in water and wastewater. Indeed, NO3-/NO2- can play multiple roles of NO3-/NO2- in UV-AOPs, leading to complexities and conflicting results observed in existing research. They can inhibit the degradation of TrOCs by scavenging reactive species and/or competitively absorbing UV light. Conversely, they can also enhance the elimination of TrOCs by generating additional •OH and reactive nitrogen species (RNS). Furthermore, the presence of NO3-/NO2- during UV-AOP treatment can affect the transformation pathways of TrOCs, potentially resulting in the nitration/nitrosation of TrOCs. The resulting nitro(so)-products are generally more toxic than the parent TrOCs and may become precursors of nitrogenous disinfection byproducts (N-DBPs) upon chlorination. Particularly, since the impact of NO3-/NO2- in UV-AOPs is largely due to the generation of RNS from NO3-/NO2- including NO•, NO2•, and peroxynitrite (ONOO-/ONOOH), this review covers the generation, properties, and detection methods of these RNS. From kinetic, mechanistic, and toxicologic perspectives, future research needs are proposed to advance the understanding of how NO3-/NO2- can be exploited to improve the performance of UV-AOPs treating TrOCs. This critical review provides a comprehensive framework outlining the multifaceted impact of NO3-/NO2- in UV-AOPs, contributing insights for basic research and practical applications of UV-AOPs containing NO3-/NO2-.

Developing a GC-EI-MS/MS method for quantifying warfarin and five hydroxylated metabolites generated by the Fenton reaction

Since the 1950s, Warfarin has been used globally as both a prescription drug and a rodenticide. Research has shown that warfarin and other rodenticides are present in the environment and food chain. However, emerging contaminants are subject to degradation by biotic and abiotic processes and advanced oxidation processes. In some cases, detecting the parent compound may not be possible due to the formation of structurally changed species. This approach aims to identify hydroxylated transformation products of warfarin in a laboratory setting, even after the parent compound has undergone degradation. Therefore, the Fenton reaction is utilized to insert hydroxylation into the parent compound, warfarin, by hydroxyl and hydroperoxyl radicals generated by Fe2+/Fe3+ redox reaction with hydrogen peroxide. Using multiple reaction monitoring, a GC-MS/MS method, incorporating isotopically labeled reference compounds, is used to quantify the expected derivatized species. The analytes are derivatized using trimethyl-3-trifluoromethyl phenyl ammonium hydroxide, and the derivatization yield of warfarin is determined by using isotopically labeled reference compounds. The method has a linear working range of 30 to 1800 ng/mL, with detection limits ranging from 18.7 to 67.0 ng/mL. The analytes are enriched using a C18-SPE step, and the recovery for each compound is calculated. The Fenton reaction generates all preselected hydroxylated transformation products of warfarin. The method successfully identifies that 4'-Me-O-WAR forms preferentially under the specified experimental conditions. By further optimizing the SPE clean-up procedures, this GC-MS-based method will be suitable for detecting transformation products in more complex matrices, such as environmental water samples. Overall, this study provides a better understanding of warfarin's degradation and offers a robust analytical tool for investigating its transformation products.

Combining fungal bioremediation and ozonation for rinse wastewater treatment

In this work, agricultural rinse wastewater, which is produced during the cleaning of agricultural equipment and constitutes a major source of pesticides, was treated by fungal bioremediation and ozonation, both individually and combined in a two-stage treatment train. Three major pesticides (thiacloprid, chlortoluron, and pyrimethanil) were detected in rinse wastewater, with a total concentration of 38.47 mg C L-1. Comparing both technologies, ozonation in a stirred reactor achieved complete removal of these pesticides (720 min) while proving to be a more effective approach for reducing colour, organic matter, and bacteria. However, this technique produced transformation products and increased toxicity. In contrast, fungal bioremediation in a rotating drum bioreactor attenuated toxicity levels and did not produce such metabolites, but only removed approximately 50 % of target pesticide - hydraulic retention time (HRT) of 5 days - and obtained worse results for most of the general quality parameters studied. This work also includes a preliminary economic assessment of both technologies, revealing that fungal bioremediation was 2 times more cost-effective than ozonation. The treatment train, consisting of a first stage of fungal bioremediation followed by ozonation, was found to be a promising approach as it synergistically combines the advantages of both treatments, achieving high removals of pesticides (up to 100 %) and transformation products, while reducing operating costs and producing a biodegradable effluent. This is the first time that fungal bioremediation and ozonation technologies have been compared and combined in a treatment train to deal with pesticides in agricultural rinse wastewater.

In silico ecotoxicity assessment of pharmaceutical residues in wastewater following oxidative treatment

Advanced oxidation processes such as thermal plasma activation and UV-C/H2O2 treatment are considered as applications for the degradation of pharmaceutical residues in wastewater complementary to conventional wastewater treatment. It is supposed that direct oxidative treatment can lower the toxicity of hospital sewage water (HSW). The aim of this study was to predict the ecotoxicity for three aquatic species before and after oxidative treatment of 10 quantified pharmaceuticals in hospital sewage water. With the application of oxidative chemistry, pharmaceuticals are degraded into transformation products before reaching complete mineralization. To estimate the potential ecotoxicity for fish, Daphnia and green algae ECOSAR quantitative structure-activity relationship software was used. Structure information from pristine pharmaceuticals and their oxidative transformation products were calculated separately and in a mixture computed to determine the risk quotient (RQ). Calculated mixture toxicities for 10 compounds found in untreated HSW resulted in moderate-high RQ predictions for all three aquatic species. Compared to untreated HSW, 30-min treatment with thermal plasma activation or UV-C/H2O2 resulted in lowered RQs. For the expected transformation products originating from fluoxetine, cyclophosphamide and acetaminophen increased RQs were predicted. Prolongation of thermal plasma oxidation up to 120 min predicted low-moderate toxicity in all target species. It is anticipated that further degradation of oxidative transformation products will end in less toxic aliphatic and carboxylic acid products. Predicted RQs after UV-C/H2O2 treatment turned out to be still moderate-high. In conclusion, in silico extrapolation of experimental findings can provide useful predicted estimates of mixture toxicity. However due to the complex composition of wastewater this in silico approach is a first step to screen for ecotoxicity. It is recommendable to confirm these predictions with ecotoxic bioassays.

Recent developments on advanced oxidation processes for degradation of pollutants from wastewater with focus on antibiotics and organic dyes

The existence of various pollutants in water environment contributes to global pollution and poses significant threats to humans, wildlife, and other living beings. The emergence of an effective, realistic, cost-effective, and environmentally acceptable technique to treat wastewater generated from different sectors is critical for reducing pollutant accumulation in the environment. The electrochemical advanced oxidation method is a productive technology for treating hazardous effluents because of its potential benefits such as lack of secondary pollutant and high oxidation efficiency. Recent researches on advanced oxidation processes (AOPs) in the period of 2018-2022 are highlighted in this paper. This review emphasizes on recent advances in electro-oxidation (EO), ozone oxidation, sonolysis, radiation, electro-Fenton (EF), photolysis and photocatalysis targeted at treating pharmaceuticals, dyes and pesticides polluted effluents. In the first half of the review, the concept of the AOPs are discussed briefly. Later, the influence of increasing current density, pH, electrode, electrolyte and initial concentration of effluents on degradation are discussed. Lastly, previously reported designs of electrochemical reactors, as well as data on intermediates generated and energy consumption during the electro oxidation and Fenton processes are discussed. According to the literature study, the electro-oxidation technique is more appropriate for organic compounds, whilst the electro-Fenton technique appear to be more appropriate for more complex molecules.

Ecotoxicity and rapid degradation of quaternary ammonium compounds (QACs) subjected to combined vacuum UV and UV-C treatment

Quaternary ammonium compounds (QACs) are active ingredients in a palette of commercially available disinfectants, sanitizers, and biocides. QACs are widely used because of their broad-spectrum antimicrobial properties but the ubiquitous uses have resulted in frequent detection in aquatic and terrestrial matrices including domestic wastewater, surface waters, urban soils and sediments. An increased domestic QACs consumption has increased the environmental occurrence, and investigation of mitigation methods and effects on non-target organisms are in demand. In this study, we examined the potential ecotoxicity of six QACs and investigated the effect of combined vacuum UV (185 nm) and UV-C (254 nm) irradiation (VUV/UVC) on degradation and mitigation of ecotoxicity of QACs. The study showed that combined VUV/UVC irradiation facilitated rapid degradation of benzalkonium chloride, benzethonium chloride, didecyldimethylammonium chloride, dodecyltrimethylammonium chloride, and hexadecyltrimethylammonium chloride. The estimated half-lives varied between 2 and 7 min, and degradation was affected by the initial QAC concentrations, the UV fluence, and the water matrix. The potential ecotoxicity of QACs and VUV/UVC treated QACs was examined using a battery of test organisms that included the luminescent bacterium Aliivibrio fischeri, the gram-negative and gram-positive bacteria Escherichiacoli and Enterococcus faecalis, the freshwater microalga Raphidocelis subcapitata, and the crustacean Daphia magna. The potential for trophic transfer of QACs was investigated in a simplified aquatic food web. Test organisms from different trophic levels were included to assess adverse effects of bioactive compounds in VUV/UVC treated samples including transformation products. The study showed that several QACs were highly toxic to aquatic test organisms with EC50 and/or EC20 values < 1 μM. VUV/UVC treatment of QACs resulted in substantial photolysis of the parent compounds and comprehensive mitigation of the ecotoxicity potential. VUV/UVC represent an attractive oxidation technology for abatement QACs in contaminated water because the process does not require addition of catalysts or precursors.

Multivariate optimization of methylene blue dye degradation using electro-Fenton process with self-doped TiO2 nanotube anode

This paper reports the optimization of the electro-Fenton (EF) process using different anode materials for the degradation of Methylene Blue (MB) dye as a model compound. The cathode used was an air-diffusion PTFE, while three different anode materials (Pt, DSA, and self-doped TiO2 nanotubes - SD-TNT) were tested individually. A full factorial design (FFD) with a central point combined with response surface methodology (RSM) was employed to optimize the experimental variables, including solution pH, applied current, and anode material. The optimized EF conditions involved a pH of 4.0, a current of 100 mA, and an SD-TNT anode for 120 min of electrolysis. Under these conditions, the MB solution achieved complete decolorization and 45% of total organic carbon (TOC) removal after 120 min of EF treatment. The findings indicate that the hydroxyl radical (•OH) plays a crucial role as the primary oxidizing agent in the EF process. The decay of MB followed pseudo-first-order kinetics, reflecting a consistent formation of •OH radicals that effectively attacked the MB dye and its subproducts during mineralization. Moreover, the EF process exhibited superior performance in terms of energy consumption (EC) and mineralization current efficiency (ECM) in the initial treatment stages, while the presence of recalcitrant by-products and loss of anode self-doping impacted performance in the later stages. The optimized EF conditions and the understanding gained from this study contribute to the advancement of sustainable wastewater treatment strategies for the removal of organic dyes.

Trametes versicolor laccase activity modulated by the interaction with gold nanoparticles

In this study, the impact of gold nanoparticles (AuNPs) on the structure and activity of laccase from Trametes versicolor (Lc) was described. Fluorescence experiments revealed that AuNPs efficiently quench Lc's tryptophan fluorescence by a static and dynamic process. By using differential scanning microcalorimetry and circular dichroism spectroscopy, it was determined how the concentration of nanoparticles and the composition of the medium affected the secondary structure of Lc. The data revealed that upon binding with AuNPs, conformational changes take place mainly in presence of high amounts of nanoparticles. The complex kinetic analysis unveiled the Lc activity enhancement at low concentrations of AuNPs as opposed to the concentrated regime, where it can be reduced by up to 55%. The Michaelis-Menten tests highlighted that the activity of the biocatalyst is closely related to the concentration of AuNPs, while the Selwyn analysis demonstrated that even in a concentrated regime of Lc it is not deactivated regardless of the amount of AuNPs added. The thermal parameters improved by twofold in the presence of low AuNPs concentration, whereas the activation energy increased with AuNPs content, implying that not all collisions are beneficial to the enzyme structure. The effect of AuNPs on the decomposition of a recalcitrant dye (naphthol green B, NG) by Lc was also evaluated, and the Michaelis-Menten model revealed that only the high AuNPs content influenced negatively the Lc activity. The isothermal titration calorimetry revealed that hydrogen bonds are the main intermolecular forces between Lc and AuNPs, while electrostatic interactions are responsible for NG adsorption to AuNPs. The results of the docking analysis show the binding of NG near the copper T1 site of Lc with hydrogen bonds, electrostatic and hydrophobic interactions. The findings of this work provide important knowledge for laccase-based bio-nanoconjugates and their use in the field of environmental remediation.

Advanced oxidation process (AOP) combined biological process for wastewater treatment: A review on advancements, feasibility and practicability of combined techniques

Complexity of wastewater is the most challenging phenomenon on successful degradation of pollutant via any wastewater treatment regime. Upon availability of numerous techniques, Advanced Oxidation Processes (AOP) is the most promising technique for treating industrial wastewater. Higher operating cost is the most promising factor that possess challenge for the industrial scale usage of the AOP process. Combination of biological process with AOP helps in achieving sustainable degradation of toxic pollutant in the wastewater. AOP result in complete or partial degradation of toxic emerging pollutants with the help of free radicals like hydroxyl, superoxide, hydroperoxyl and sulphate radicals. In addition to this the presence of bio-enzymes and microorganisms helps in sustainable degradation of pollutant in an economical and environmentally friendly strategy. In this review, a detailed discussion was conducted on various AOP, focusing on catalytic ozonation, electrochemical oxidation, Sono chemical and photocatalytic processes. With the need for sustainable solutions for wastewater treatment, the use of AOP in conjunction with biological process has innumerous opportunities for not only wastewater treatment but also the production of high value by-products. Further, the effect of AOP combined biological processes needs to be analyzed in real time for the different concentration of industrial wastewater and their benefits needs to be explored in future towards achieving SDGs.

Synergy between UV light and trichloroisocyanuric acid on methylisothiazolinone degradation: Performance, kinetics and degradation pathway

Methylisothiazolinone (MIT) is widely used in daily chemicals, fungicides, and other fields and its toxicity has posed a threat to water system and human health. In this study, ultraviolet (UV)/trichloroisocyanuric acid (TCCA), which belongs to advanced oxidation processes (AOP), was adopted to degrade MIT. Total chlorine attenuation detection proved that TCCA has medium UV absorption and a strong quantum yield (0.49 mol E-1). At a pH of 7.0, 93.5% of MIT had been decontaminated after 60 min in UV/TCCA system (kobs = 4.4 × 10-2 min-1, R2 = 0.978), which was much higher than that in the UV alone system and TCCA alone system, at 65% (1.7 × 10-2 min-1, R2 = 0.995) and 10% (1.8 × 10-3 s-1, R2 = 0.915), respectively. This system also behaved well in degrading other five kinds of contaminants. Tert-butanol (TBA) and carbonate (CO32-) were separately used in quenching experiments, and the degradation efficiency of MIT decreased by 39.5% and 46.5% respectively, which confirmed that HO• and reactive chlorine species (RCS) were dominant oxidants in UV/TCCA system. With TCCA dosage increasing in a relatively low concentration range (0.02-0.2 mM) and pH decreasing, the effectiveness of this AOP system would be strengthened. The influences of coexisting substances (Cl-, SO42-, CO32-, NO2- and NO3-) were explored. MIT degradation pathways were proposed and sulfur atom oxidation and carboxylation were considered as the dominant removal mechanisms of MIT. Frontier orbital theory and Fukui indexes of MIT were employed to further explore the degradation mechanism.

Z-scheme MnO2/Mn3O4 heterojunctions with efficient peroxymonosulfate activation for organic pollutant removal

The exploration of efficient heterogeneous catalysts for persistent organic pollutant removal is extremely attractive. In the present work, MnO2/Mn3O4 photo-Fenton catalysts were designed by a facile hydrothermal route to activate peroxymonosulfate (PMS) under visible light irradiation for organic pollutant degradation. The optimized MnO2/Mn3O4 heterojunction shows excellent Rhodamine B (RhB) removal efficiency, whose apparent kinetic constant is 11.9 and 5.36 times as high as the MnO2 and Mn3O4. Meanwhile, there is a neglectable attenuation in catalytic performance after 5 recycling runs. Based on the active species trapping experiments, the non-radical process contributes more than the radical process during RhB degradation. Moreover, factors including the dosage of PMS, initial RhB concentration, initial pH, the presence of various anions, different organic pollutants, and water sources are investigated. Systematical characterizations reveal that the enlarged specific surface areas and the efficient charge separation aroused from the Z-scheme mechanism are attributed to the enhanced photo-Fenton performance. The present work contributes to the construction of the Mn-based photo-Fenton catalyst with efficient PMS activation capacity for environmental remediation.

New insight into the removal process of benzotriazole UV stabilizers by UV/H2O2: Integrating quantum chemical calculation with CFD simulation

Benzotriazole UV stabilizers (BT-UVs) are important UV absorbers. As high-production chemicals and potential hazards, their ubiquitous presence in aquatic environments is of greatly pressing concern. Herein, the removal of six typical BT-UVs by UV/H2O2 was comprehensively investigated by quantum chemistry calculation integrated with CFD simulation. Utilizing such a micro and macro incorporated model in treating contaminants is the first report. From the micro-view, degradation mechanisms of BT-UVs by •OH oxidation were determined, and corresponding rate constants were obtained with values of 109∼1010 M-1s-1. In a macroscopic aspect, combining the established kinetic model and CFD simulation, the effects of UV lamp power (P), volumetric flow rate (Qv), and H2O2 dosage ([H2O2]0) on removal yields of BT-UVs were expounded, increasing P or [H2O2]0 or decreasing Qv are effective in improving removal yields of BT-UVs, but the enhancement was abated when P or [H2O2]0 increased to a certain level. When [H2O2]0 is 5 mg/L and Qv is decreased from 0.1 to 0.05 m3/h, the removal yields of BT-UVs could achieve more than 95% (P = 150 W) and 99% (P = 250 W), respectively. This work provides a new interdisciplinary insight for investigating organic contaminant removal in potential industrial applications of UV/H2O2 systems.

One-step electrodeposition preparation of boron nitride and samarium co-modified Ti/PbO2 anode with ultra-long lifetime: highly efficient degradation of lincomycin wastewater

Lincomycin (LC) is an extensively applied broad-spectrum antibiotic, and its considerable residues in wastewater have caused a series of environmental problems, which makes degradation of LC wastewater extremely urgent. In this work, we have constructed a novel boron nitride (BN) and samarium (Sm) co-modified Ti/PbO2 as anode for high-performance degradation of LC wastewater. Compared with Ti/PbO2, Ti/PbO2-Sm, and Ti/PbO2-BN electrodes, Ti/PbO2-BN-Sm electrode with smaller pyramidal particles possesses higher oxygen evolution potential (2.32 V), excellent accelerated service life (103 h), and outstanding electrocatalytic activity. The single-factor experiments demonstrate that under optimized conditions (current density of 20 mA.cm-2, 6.0 g L-1 Na2SO4, pH 9, and temperature of 30°C), removal rate and COD degradation rate of LC at 3 h have reached 92.85% and 89.11%, respectively. At the same time, degradation of LC is in accordance with the primary kinetic model. Based on the analysis of high-performance liquid chromatography-mass spectrometry (HPLC-MS), four possible degradation pathways are hypothesized. Therefore, efficient electrochemical degradation of LC by using an extremely long-life Ti/PbO2 electrode with high catalytic activity may be a promising method.

Guidance document on the impact of water treatment processes on residues of active substances or their metabolites in water abstracted for the production of drinking water

This guidance document provides a tiered framework for risk assessors and facilitates risk managers in making decisions concerning the approval of active substances (AS) that are chemicals in plant protection products (PPPs) and biocidal products, and authorisation of the products. Based on the approaches presented in this document, a conclusion can be drawn on the impact of water treatment processes on residues of the AS or its metabolites in surface water and/or groundwater abstracted for the production of drinking water, i.e. the formation of transformation products (TPs). This guidance enables the identification of actual public health concerns from exposure to harmful compounds generated during the processing of water for the production of drinking water, and it focuses on water treatment methods commonly used in the European Union (EU). The tiered framework determines whether residues from PPP use or residues from biocidal product use can be present in water at water abstraction locations. Approaches, including experimental methods, are described that can be used to assess whether harmful TPs may form during water treatment and, if so, how to assess the impact of exposure to these water treatment TPs (tTPs) and other residues including environmental TPs (eTPs) on human and domesticated animal health through the consumption of TPs via drinking water. The types of studies or information that would be required are described while avoiding vertebrate testing as much as possible. The framework integrates the use of weight-of-evidence and, when possible alternative (new approach) methods to avoid as far as possible the need for additional testing.

Insights into degradation of pharmaceutical pollutant atenolol via electrochemical advanced oxidation processes with modified Ti4O7 electrode: Efficiency, stability and mechanism

A novel active Ce-doped Ti₄O₇ (Ti/Ti₄O₇-Ce) electrode was prepared and evaluated for improvement of the refractory pollutants degradation efficiency in Electrochemical advanced oxidation processes (EAOPs). The results showed that the addition of Ce in Ti/Ti₄O₇ electrode leading to great impact on •OH generation rate and electrode stability compared to pristine Ti/Ti₄O₇ electrode. Ti/Ti₄O₇-Ce electrode presented efficient oxidation capacity for pharmaceutical pollutant atenolol (ATL) in EAOPs, which could be attributed to the improvement of indirect oxidation mediated by electro-generated •OH, as the amount of •OH production was 16.5% higher than that in Ti/Ti₄O₇ within 120 min. The operational conditions greatly influenced the ATL degradation. The degradation efficiency of ATL increased as the current density, the degradation efficiency reached 100% under pH 4, but it just removed 81% of ATL under pH 10 after 120 min treatment. Results also suggested that the inhibiting effect from the ATL degradation was mostly associated with the decreased oxidation capacity induced by water hardness and natural organic matter (NOM). It displayed a satisfactory durability after 40 cycles of experimental detections in this research. The results of study suggested that Ti/Ti₄O₇-Ce was a promising electrode for the efficient degradation of PPCPs-polluted wastewater and provided constructive suggestion for the refractory pollutants of EAOPs.

A comprehensive review of chlorophenols: Fate, toxicology and its treatment

Chlorophenols represent one of the most abundant families of toxic pollutants emerging from various industrial manufacturing units. The toxicity of these chloroderivatives is proportional to the number and position of chlorine atoms on the benzene ring. In the aquatic environment, these pollutants accumulate in the tissues of living organisms, primarily in fishes, inducing mortality at an early embryonic stage. Contemplating the behaviour of such xenobiotics and their prevalence in different environmental components, it is crucial to understand the methods used to remove/degrade the chlorophenol from contaminated environment. The current review describes the different treatment methods and their mechanism towards the degradation of these pollutants. Both abiotic and biotic methods are investigated for the removal of chlorophenols. Chlorophenols are either degraded through photochemical reactions in the natural environment, or microbes, the most diverse communities on earth, perform various metabolic functions to detoxify the environment. Biological treatment is a slow process because of the more complex and stable structure of pollutants. Advanced Oxidation Processes are effective in degrading such organics with enhanced rate and efficiency. Based on their ability to generate hydroxyl radicals, source of energy, catalyst type, etc., different processes such as sonication, ozonation, photocatalysis, and Fenton's process are discussed for the treatment or remediation efficiency towards the degradation of chlorophenols. The review entails both advantages and limitations of treatment methods. The study also focuses on reclamation of chlorophenol-contaminated sites. Different remediation methods are discussed to restore the degraded ecosystem back in its natural condition.

Efficient removal of endocrine disrupting compounds 17 α-ethynyl estradiol and 17 β-estradiol by Enterobacter sp. strain BHUBP7 and elucidation of the degradation pathway by HRAMS analysis

Owing to the increased population and their overuse, estrogens are being detected in the environment at alarming levels. They act as endocrine disrupting compounds (EDC's) posing adverse effects on animals and humans. In this study, a strain belonging to Enterobacter sp. strain BHUBP7 was recovered from a Sewage Treatment Plant (STP) situated in Varanasi city, U.P., India, and was capable of metabolizing both 17 α-Ethynylestradiol (EE2) and 17 β-Estradiol (E2) separately as a sole carbon source. The strain BHUBP7 exhibited high rates of E2 degradation as compared to EE2 degradation. The degradation of E2 (10 mg/L) was 94.3% after four days of incubation, whereas the degradation of EE2 (10 mg/L) under similar conditions was 98% after seven days of incubation. The kinetics of EE2 and E2 degradation fitted well with the first-order reaction rate. FTIR analysis revealed the involvement of functional groups like C = O, C-C, C-OH during the degradation process. The metabolites generated during degradation of EE2 and E2 were identified using HRAMS and a plausible pathway was elucidated. It was observed that metabolism of both E2 and EE2 proceeded with the formation of estrone, which was then hydroxylated to 4-hydroxy estrone, followed by ring opening at the C4-C5 position, and was further metabolized by the 4,5 seco pathway leading to the formation of 3-(7a-methyl-1,5-dioxooctahydro-1H-inden-4-yl) propanoic acid (HIP). It is the first report on the complete pathway of EE2 and E2 degradation in Enterobacter sp. strain BHUBP7. Moreover, the formation of Reactive Oxygen Species (ROS) during the degradation of EE2 and E2 was observed. It was concluded that both hormones elicited the generation of oxidative stress in the bacterium during the degradation process.

Effective removal of selected pharmaceuticals from sewerage treatment plant effluent using natural clay (Na-montmorillonite)

The consumption of pharmaceuticals has rapidly increased on a global scale due to the serious increase in Covid-19, influenza and respiratuar sinsityal virus, which is called "triple epidemic" in the world. The use of non-prescription analgesic and anti-inflammatory drugs (AAIDs), especially paracetamol, is higher compared to pre-pandemic. This increased the AAIDs load discharged to the aqueous media through sewerage treatment plant (STP). Therefore, simple and effective treatment options for removing AAIDs from STP effluents are needed. The aim of the study was to remove AAIDs (paracetamol, acetylsalicylic acid, codeine, diclofenac, ibuprofen, indomethacin, ketoprofen, mefenamic acid, naproxen, and phenylbutazone) from STP effluents by nearly pure natural clay Na-montmorillonite. The Na-montmorillonite taken from the Ordu region in the northern part of Turkey. Surface area of the Na-montmorillonite is 99.58 m2/g and CEC is 92.40 meq/100 g. The removal efficiencies of AAIDs using Na-montmorillonite were between 82 ± 5% (ibuprofen) and 94 ± 4% (naproxen). Paracetamol was used as a model compound in kinetic and isotherm model studies. Freundlich isotherm model and the pseudo second order kinetic model were the best-fit using the obtained experimental data. Film diffusion governed its rate mechanism. The paracetamol adsorption capacity was acquired as 244 mg/g at 120 min contact time at pH 6.5 at 25 °C. With this study, it could be shown that montmorillonite can be used effectively to eliminate paracetamol from STP effluent. Natural clay can be used as a simple, inexpensive and effective adsorbent for removing AAIDs from STP effluents.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13201-023-01930-5.

Green valorization of end-of-life toner powder to iron oxide-nanographene nanohybrid as a recyclable persulfate activator for degrading emerging micropollutants

The sustainable management of toner waste (T-raw) was performed via carbonization at 500 °C (T-500) and 600 °C (T-600) to produce iron oxide-nanographene nanohybrid (FeO-NG) for activating persulfate (PS) to efficiently degrade dyes (methylene blue, MB), antibiotics (sulfamethazine, SMZ), and pesticides (diazinon, DZN). Morphology, crystallinity, chemical structure, chemical composition, surface area, and pore size distribution of the synthesized materials were investigated using various analyses. High degradation ratios of MB were attained over a wide pH range (2-7), and the optimum operating conditions were determined. The FeO-NG/PS system was tested in different water matrices. MB degradation efficiency dropped from 80.13% to 78.56% after five succeeding experiments, proving the high stability of T-500. Trapping experiments proved the major role of sulfate radicals and the minor contribution of singlet oxygen. The toxicity evaluation of the treated and untreated MB solutions was conducted via measuring the cell viability, showing an increase in cell viability ratio after the degradation of MB. The degradation efficiencies of DZN and SMZ were 97.54% and 83.7%, respectively and the mineralization ratios were 74.08% and 60.37% at initial concentrations of sulfamethazine and diazinon of 50 and 100 mg/L, respectively. The high degradation efficiency of emerging micropollutants as well as the inexpensiveness, and facile synthesis of the catalyst boost the prospect of applying the proposed system on an industrial scale.

Enhanced Plasmonic Photocatalysis of Au-Decorated ZnO Nanocomposites

The rapid development of technological processes in various industrial fields has led to surface water pollution with different organic pollutants, such as dyes, pesticides, and antibiotics. In this context, it is necessary to find modern, environmentally friendly solutions to avoid the hazardous effects on the aquatic environment. The aim of this paper is to improve the photocatalytic performance of zinc oxide (ZnO) nanoparticles by using the plasmonic resonance induced by covering them with gold (Au) nanoparticles. Therefore, we evaluate the charge carriers’ behavior in terms of optical properties and reactive oxygen species (ROS) generation. The ZnO-Au nanocomposites were synthesized through a simple chemical protocol in multiple steps. ZnO nanoparticles (NPs) approximately 20 nm in diameter were prepared by chemical precipitation. ZnO-Au nanocomposites were obtained by decorating the ZnO NPs with Au at different molar ratios through a reduction process. X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) confirmed the simultaneous presence of hexagonal ZnO and cubic Au phases. The optical investigations evidenced the existence of a band-gap absorption peak of ZnO at 372 nm, as well as a surface plasmonic band of Au nanoparticles at 573 nm. The photocatalytic tests indicated increased photocatalytic degradation of the Rhodamine B (RhB) and oxytetracycline (OTC) pollutants under visible light irradiation in the presence of ZnO-Au nanocomposites (60–85%) compared to ZnO NPs (43%). This behavior can be assigned to the plasmonic resonance and the synergetic effects of the individual constituents in the composite nanostructures. The spin-trapping experiments showed the production of ROS while the nanostructures were in contact with the pollutants. This study introduces new strategies to adjust the efficiency of photocatalytic devices by the combination of two types of nanostructures with synergistic functionalities into one single entity. ZnO-Au nanocomposites can be used as stable photocatalysts with excellent reusability and possible industrial applications.

Regeneration of granular activated carbon clogged in the treatment of leachates

Landfill leachates are highly contaminated liquids and complex to treat. Two of the processes which are promising for the treatment are the advanced oxidation and adsorption methods. With the combination of the Fenton and adsorption methods, practically all the organic load of leachates can be removed; however, this combination of processes is limited due to the soon clogging of adsorbent material, which leads to high operation costs. In the present work, the results of the regeneration of clogged activated carbon are shown after the application of the Fenton/adsorption process in leachates. This research consisted of four stages: sampling and leachate characterization, clogging of the carbon through the Fenton/adsorption process, carbon regeneration through the oxidative Fenton process, and lastly, evaluation of regenerated carbon adsorption through jar and column tests. In the experiments, HCl 3 M was used, and different concentration of hydrogen peroxide (0.15 M, 0.2 M, 0.25 M) were tested at different times (16 h and 30 h). The activated carbon regeneration through the Fenton process and the optimal peroxide dosage was 0.15 M for 16 h. The regeneration efficiency was obtained from comparing the adsorption efficiency between regenerated and virgin carbon, reaching 98.27% and can be applied up to 4 times without losing regeneration efficiency. These results prove that it is possible to restore the clogged activated carbon adsorption capacity during the Fenton/adsorption process.

A review on superior advanced oxidation and photocatalytic degradation techniques for perfluorooctanoic acid (PFOA) elimination from wastewater

Perfluorooctanoic acid (PFOA) has been identified as the most toxic specie of the family of perfluorinated carboxylic acids (PFCAs). It has been widely distributed and frequently detected in environmental wastewater. The compound's unique features such as inherent stability, rigidity, and resistance to harsh chemical and thermal conditions, due to its multiple and strong C-F bonds have resulted in its resistance to conventional wastewater remediations. Photolysis and bioremediation methods have been proven to be inefficient in their elimination, hence this article presents intensive literature studies and summarized findings reported on the application of advanced oxidation processes (AOPs) and photocatalytic degradation techniques as the best alternatives for the PFOA elimination from wastewater. Techniques of persulfate, photo-Fenton, electrochemical, photoelectrochemical and photocatalytic degradation have been explored and their mechanisms for the degradation and defluorination of the PFOA have been demonstrated. The major advantage of AOPs techniques has been centralized on the generation of active radicals such as sulfate (SO₄^•-) hydroxyl (•OH). While for the photocatalytic process, photogenerated species (electron (e) and holes (h ⁺ _vb)) initiated the process. These active radicals and photogenerated species possessed potentiality to attack the PFOA molecule and caused the cleavage of the C-C and C-F bonds, resulting in its efficient degradation. Shorter-chain PFCAs have been identified as the major intermediates detected and the final stage entails its complete mineralization to carbon dioxide (CO₂) and fluoride ion (F^-). The prospects and challenges associated with the outlined techniques have been highlighted for better understanding of the subject matter for the PFOA elimination from real wastewaters.

Surface Plasmon Resonance Induced Photocatalysis in 2D/2D Graphene/g-C3N4 Heterostructure for Enhanced Degradation of Amine-Based Pharmaceuticals under Solar Light Illumination

Pharmaceuticals, especially amine-based pharmaceuticals, such as nizatidine and ranitidine, contaminate water and resist water treatment. Here, different amounts of graphene sheets are coupled with g-C3N4 nanosheets (wt% ratio of 0.5, 1, 3 and 5 wt% of graphene) to verify the effect of surface plasmon resonance introduced to the g-C3N4 material. The synthesized materials were systematically examined by advanced analytical techniques. The prepared photocatalysts were used for the degradation of amine-based pharmaceuticals (nizatidine and ranitidine). The results show that by introducing only 3 wt% graphene to g-C3N4, the absorption ability in the visible and near-infrared regions dramatically enhanced. The absorption in the visible range was 50 times higher when compared to the pure sample. These absorption features suggest that the surfaces of the carbon nitride sheet are covered by the graphene nanosheet, which would effectively apply the LSPR properties for catalytic determinations. The enhancement in visible light absorption in the composite was confirmed by PL analysis, which showed greater inhibition of the electron-hole recombination process. The XRD showed a decrease in the (002) plan due to the presence of graphene, which prevents further stacking of carbon nitride layers. Accordingly, the Gr/g-C3N4 composite samples exhibited an enhancement in the photocatalytic performance, specifically for the 5% Gr/g-C3N4 sample, and close to 85% degradation was achieved within 20 min under solar irradiation. Therefore, applying the Gr/g-C3N4 for the degradation of a pharmaceutical can be taken into consideration as an alternative method for the removal of such pollutants during the water treatment process. This enhancement can be attributed to surface plasmon resonance-induced photocatalysis in a 2D/2D graphene/g-C3N4 heterostructure.

Efficient remediation of meropenem using Bacillus tropicus EMB20 β-lactamase immobilized on magnetic nanoparticles

Reducing antibiotic pollution in the environment in essential to preserve the effectiveness of the available antibiotics. In the present study, β-lactamase from Bacillus tropicus EMB20 was immobilized onto magnetic nanoparticles (Fe₃O₄) through covalent coupling method. The nanoconjugate was structurally characterized using SEM, FTIR, UV-spectrometry, and XRD diffraction analyses. The prepared enzyme nanoconjugate was thereafter used for remediation of meropenem (Mer) and showed complete removal of 10 mgL^-1 Mer within 3 h of treatment. Moreover, the immobilized enzyme was successfully recovered and reused for up to 5 cycles with 57% removal efficiency. The immobilized preparation was also observed to be effective in the removal of higher Mer concentrations of 25 and 50 mgL^-1 with 79% and 75% removal efficiency, respectively. The major hydrolyzed product of Mer was found to be opened-lactam ring structure with m/z 402.16. The hydrolyzed product(s) were observed to be non-toxic as revealed through microbial MTT, confocal microscopy, and growth studies. Under the mixed conditions of 50 mgL^-1 ampicillin (Amp), 10 mgL^-1 amoxicillin (Amox) and, Mer, the nanoconjugate showed simultaneous complete removal of Amp and Mer, while 49% Amox removal was detected after 3 h of treatment. Moreover, the nanoconjugates also showed concomitant complete removal of antibiotic mixture with in 2 h from aquaculture wastewater. Overall, the study comes out with an efficient approach for remediation of β-lactam antibiotics from contaminated systems.

Stable isotope labeling for detection of ozonation byproducts in effluent organic matter with FT-ICR-MS

Despite effluent organic matter (EfOM) being a major consumer of ozone during wastewater treatment, little is known about ozonation byproducts (OBPs) produced from EfOM. To unambiguously identify OBPs, heavy ozone was used to ozonate EfOM, resulting in ¹⁸O labeled and unlabeled OBPs. Labeled OBPs mostly represent a single ¹⁸O transfer and were classified as either direct or indirect OBPs based on the ¹⁸O/¹⁶O intensity ratios of the isotopologues. Of the 929 labeled OBPs, 84 were unequivocally classified as direct OBPs. The remainder suggest a major contribution by indirect, hydroxyl radical induced formation of OBPs in EfOM. Overall, labelled OBPs possess a low degree of unsaturation and contributed most to OBP peak intensity - marking them as potential end products. A few direct and indirect OBPs with high peak intensity containing ¹⁸O and heteroatoms (N, S) were fragmented with CID FT-ICR-MS/MS and screened for indicative neutral losses carrying heavy oxygen. The neutral loss screening was used to detect the ¹⁸O location on the OBP and indicate the original functional group in EfOM based on known reaction mechanisms. We identified sulfoxide and sulfonic acid functional groups in selected OBPs - implying the presence of reduced sulfur in EfOM molecules - while no evidence for nitrogen containing functional groups reacting with ozone was found.

Dye mineralization under UV/H2O2 promoted by chloride ion at high concentration and the generation of chlorinated byproducts

Chloride ion (Cl^-) may promote or inhibit the oxidation of specific organic compounds treated by hydroxyl radical based advanced oxidation processes (HR-AOPs) depending on the reactivity of chlorine radicals towards the organics. However, the effects of high contents of Cl^- on the removal of total organic compounds (TOC) in high salinity organic wastewater treated by HR-AOPs were unclear. The removal and mineralization of azo dye Orange II (OrgII) by UV/H₂O₂ process with Cl^- at high contents under various pH conditions were investigated. As the pH conditions increased higher than pH 5, TOC removal rates increased slightly possibly related to the increase of O₂^- production and the reduce of futile decomposition of H₂O₂ into O₂. Cl^- at relative high concentration (1000 and 2000 mM) significantly promoted the mineralization of dyes with TOC removal increasing by 10 %-40 % under both acid and alkaline conditions. The proposed mechanism is that the reaction of Cl^- with OH would decline the decomposition of H₂O₂ into O₂ by inhibiting the reaction between OH and H₂O₂, and the generated chlorine species (Cl and Cl₂^-) could further promote the oxidation of dye molecules into intermediates and be helpful for the subsequent mineralization process. In addition, H₂O₂ and Cl^- can slowly react to give HClO and ClO^-, which may partly contribute to the decolorization and mineralization of OrgII. Meanwhile, an appropriate relative proportion between Cl₂^- and OH depending on Cl^- contents and pH conditions is important to enhance the TOC removal. However, the formation of various chlorinated byproducts especially under alkaline condition may increase the risk of environmental pollution accidents. The results demonstrate the promotion of TOC removal by UV/H₂O₂ under certain high contents of Cl^- and provide new insight into the application of HR-AOPs to the pretreatment of high salinity organic wastewater.

Supercritical Phase Inversion to Produce Photocatalytic Active PVDF-coHFP_TiO2 Composites for the Degradation of Sudan Blue II Dye

TiO2-loaded poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-coHFP) membranes were produced by supercritical CO2-assisted phase inversion. Three different TiO2 loadings were tested: 10, 20, and 30 wt% with respect to the polymer. Increasing the TiO2 amount from 10 wt% to 20 wt% in the starting solution, the transition from leafy-like to leafy-cellular morphology was observed in the section of the membrane. When 30 wt% TiO2 was used, the entire membrane section showed agglomerates of TiO2 nanoparticles. These polymeric membranes were tested to remove Sudan Blue II (SB) dye from aqueous solutions. The adsorption/photocatalytic processes revealed that membrane morphology and TiO2 cluster size were the parameters that mainly affected the dye removal efficiency. Moreover, after five cycles of exposure of these membranes to UV light, SB removal was higher than 85%.

Insights from the genome sequence of Bacillus tropicus EMB20, an efficient β-lactamase-producing bacterium

We report here the whole-genome sequence of β-lactamase-producing bacteria Bacillus tropicus EMB20. The genome sequence of Bacillus tropicus EMB20 has a size of 5.8 Mb (G + C content of 35.52%) with 5593 coding DNA sequences (CDSs), 108 tRNA, and 14 rRNA operons. The bacterium has the unique ability to produce a β-lactamase enzyme with high activity. β-Lactamases are one of the most common causes of antimicrobial resistance as these enzymes inactivate almost all β-lactam antibiotics. The antibiotic susceptibility test showed that the B. tropicus EMB20 is producing β-lactamase and can degrade the β-lactam antibiotics. Further, the antibiotic degradation potential of this bacteria was confirmed by growing the bacteria in the presence of varying concentrations of β-lactam antibiotic, amoxicillin. The bacteria were able to hydrolyze amoxicillin up to 50 mg/L in 4 h. Furthermore, the analyses of the genome revealed the presence of multiple β-lactamase genes, possibly involved in antibiotic degradation. The availability of the genome sequence will provide further insights into the mechanism of antimicrobial resistance by β-lactamase-producing bacteria.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03395-w.

A detailed review on advanced oxidation process in treatment of wastewater: Mechanism, challenges and future outlook

The presence of several contaminants in waterbodies raises global pollution and creates major risks to mankind, wildlife, as well as other living organisms. Development of an effective, feasible, cost-effective and eco-friendly approach for treating wastewater that is discharged from various industries is important for bringing down the deposition of contaminants into environment. Advanced oxidation process is an efficient technique for treating wastewater owing to its advantages such as high oxidation efficacy and does not produce any secondary pollutants. Advanced oxidation process can be performed through various methods such as ozone, Fenton, electrochemical, photolysis, sonolysis, etc. These methods have been widely utilized for degradation of emerging pollutants that cannot be destroyed using conventional approaches. This review focuses on wastewater treatment using advanced oxidation process. A brief discussion on mechanism involved is provided. In addition, various types of advanced oxidation process and their mechanism are explained in detail. Challenges faced during wastewater treatment process using oxidation, electrochemical, Fenton, photocatalysis and sonolysis are discussed elaborately. Advanced oxidation process can be viewed as potential approach for treating wastewater with certain modifications and solving challenges.

Degradation of commercial glyphosate-based herbicide via advanced oxidative processes in aqueous media and phytotoxicity evaluation using maize seeds

Glyphosate is a herbicide that acts as a broad-spectrum, non-selective, post-emergence systemic pest controller. Its continuing, increasing, and excessive use in many countries in recent years poses a significant threat to the environment and human health due to the prevalence of this herbicide in water bodies and its impact on non-target organisms. In this context, it is essential to develop processes aimed at the non-selective degradation of glyphosate and its by-products. In this study, various advanced oxidative processes were applied: Fenton, electro-Fenton, photoelectro-oxidation, and photoelectro-Fenton, with the objective of oxidizing glyphosate in the commercial product Roundup®. The resultant oxidation products and the phytotoxicological effect on maize seed germination were also analyzed. Following each treatment, chemical oxygen demand (COD), total organic carbon (TOC), glyphosate degradation, and oxidation by-product formation were analyzed. The treated solutions were used to germinate maize seeds for 7 days in a germination chamber applying a photoperiod of 12 h at 24 °C. The % of germination, protein and hydrogen peroxide (H2O2) content, lipid peroxidation extent (MDA), and superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities were determined. The photoelectro-Fenton treatment was the most effective in degrading glyphosate, operating synergistically to break glyphosate bonds, thereby generating non-toxic short-chain molecules. Maize seed germination was satisfactory (> 50 %), but the persistent formation of reactive oxygen species (ROS) led to increased antioxidant activities of SOD, CAT, and POD enzymes acting in a compensatory manner against ROS, thus sustaining the photosynthetic apparatus. Hormesis, a stimulatory effect of glyphosate, was also observed in the presence of low concentrations of glyphosate.

Non-target screening of micropollutants and transformation products for assessing AOP-BAC treatment in groundwater

Standard monitoring programs give limited insight into groundwater status, especially transformation products (TPs) formed by natural processes or advanced oxidation processes (AOP), are normally underrepresented. In this study, using suspect and non-target screening, we performed a comprehensive analysis of groundwater before and after AOP by UV/H₂O₂ and consecutively installed biological activated carbon filters (BAC). By non-target screening, up to 413 compounds were detected in the groundwater, with an average 70% removal by AOP. However, a similar number of compounds were formed during the process, shown in groundwater from three waterworks. The most polar compounds were typically the most stable during the AOP. A subsequent BAC filter showed removal of 95% of the TPs, but only 46% removal of the AOP remaining precursors. The BAC removal for polar compounds was highly dependent on the acidic and basic functional groups of the molecules. 49 compounds of a wide polarity range could be identified by supercritical fluid chromatography (SFC) and liquid chromatography (LC) with high resolution mass spectrometry (HRMS); of these, 29 compounds were already present in the groundwater. To the best of our knowledge, five compounds have never been reported before in groundwater (4-chlorobenzenesulfonic acid, dibutylamine, N-phenlybenzenesulfonamide, 2-(methylthio)benzothiazole and benzothiazole-2-sulfonate). A further five rarely reported compounds are reported for the first time in Danish groundwater (2,4,6-trichlorophenol, 2,5-dichlorobenzenesulfonic acid, trifluormethansulfonic acid, pyrimidinol and benzymethylamine). Twenty of the identified compounds were formed by AOP, of which 10 have never been reported before in groundwater. All detected compounds could be related to agricultural and industrial products as well as artificial sweeteners. Whereas dechlorination was a common AOP degradation pathway for chlorophenols, the (ultra-) short chain PFAs showed no removal in our study. We prioritized 11 compounds as of concern, however, the toxicity for many compounds remains unknown, especially for the TPs.

Photocatalysis for arsenic removal from water: considerations for solar photocatalytic reactors

The following work provides a perspective on the potential application of solar heterogeneous photocatalysis, which is a nonselective advanced oxidation process considered as a sustainable technology, to assist in arsenic removal from water, which is a global threat to human health. Heterogeneous photocatalysis can oxidize trivalent arsenic to pentavalent arsenic, decreasing its toxicity and easing its removal with other technologies, such as chemical precipitation and adsorption. Several lab-scale arsenic photocatalytic oxidation and diverse solar heterogeneous photocatalytic operations carried out in different reactor designs are analyzed. It was found out that this technology has not been translated to operational pilot plant scale prototypes. General research on reactors is scarce, comprising a small percentage of the photocatalysis related scientific literature. It was possible to elucidate some operational parameters that a reactor must comply to operate efficiently. Reports on small-scale application shed light that in areas where other water purification technologies are economically and/or technically not suitable, and the solar energy is available, shed light on the fact that solar heterogeneous photocatalysis is highly promissory within a water purification process for removal of arsenic from water.

Visible-Light Driven H2O-to-H2O2 Reaction by Nitrogen-Enriched Resins for Photocatalytic Oxidation of an Organic Pollutant in Wastewater

A photocatalytic H₂O-to-H₂O₂ reaction for sustainable organic wastewater treatment is environmentally attractive. Phenolic resins, inexpensive metal-free photocatalysts, are capable of harvesting visible light. Herein, novel nitrogen-enriched resin photocatalysts with a desired band-gap energy (1.83-1.98 eV) for harvesting visible light were prepared by copolymerization of resorcinol and melem for simultaneous photocatalytic H₂O-to-H₂O₂ and oxidation of methylene blue. Under visible light irradiation for 5 h, very high yields of H₂O₂ (870-975 μM of H₂O₂/g/h) by RFM resin photocatalysts could be achieved. The photocatalytic H₂O₂ for reactive oxygen species (^•OH) and photogenerated h⁺ could account for high conversion (40% conversion under visible light irradiation within 3 h) in oxidation of methylene blue. Such unique low-cost metal-free resins demonstrate the visible light photocatalytic H₂O-to-H₂O₂ reaction which can synergize with the oxidation of organic pollutants in wastewater.

Electrosynthesis of H2O2 through a two-electron oxygen reduction reaction by carbon based catalysts: From mechanism, catalyst design to electrode fabrication

Hydrogen peroxide (H₂O₂) is an efficient oxidant with multiple uses ranging from chemical synthesis to wastewater treatment. The in-situ H₂O₂ production via a two-electron oxygen reduction reaction (ORR) will bring H₂O₂ beyond its current applications. The development of carbon materials offers the hope for obtaining inexpensive and high-performance alternatives to substitute noble-metal catalysts in order to provide a full and comprehensive picture of the current state of the art treatments and inspire new research in this area. Herein, the most up-to-date findings in theoretical predictions, synthetic methodologies, and experimental investigations of carbon-based catalysts are systematically summarized. Various electrode fabrication and modification methods were also introduced and compared, along with our original research on the air-breathing cathode and three-phase interface theory inside a porous electrode. In addition, our current understanding of the challenges, future directions, and suggestions on the carbon-based catalyst designs and electrode fabrication are highlighted.

Solar heterogeneous photocatalytic degradation of phenol on TiO2/quartz and TiO2/calcite: a statistical and kinetic approach on comparative efficiencies towards a TiO2/glass system

Phenol is a widely used synthetic organic compound, which according to global estimations, is discharged into the environment at a rate of 10 tons/year through industrial waste. Phenol is a recalcitrant pollutant, and human exposure to water containing phenolic substances can lead to health issues. It has been found both in drinking water and wastewater. Solar heterogeneous photocatalytic phenol degradation, measured through chemical oxygen demand, was performed on a thin film tilted plate reactor with TiO₂ immobilized onto different support materials. A full factorial experimental design (4 × 3 × 3) was carried out to statistically evaluate if the independent variables' effects were significant. Four advanced oxidation processes (photolysis, photolysis + H₂O₂, heterogeneous photocatalysis, and heterogeneous photocatalysis + H₂O₂), three support materials (quartz, calcite, and glass), and three pH levels (3, 5.4, and 9) were evaluated. Reaction kinetics were fitted to the pseudo-first-order reaction rate and data was analyzed with an ANCOVA and means test, considering solar light intensity as a covariate. Photolysis/calcite at pH 5.4 and heterogeneous photocatalysis + H₂O₂/glass plate at pH 3 gave the best results, with a reaction rate constant k_ph = 3.047 × 10^-3 min^-1 and k_phC = 4.498 × 10^-3 min^-1, respectively. The three independent variables and their interactions had a significant effect in the phenol degradation (p < 0.05).

High efficiency three-dimensional electrochemical treatment of amoxicillin wastewater using Mn-Co/GAC particle electrodes and optimization of operating condition

In this work, Mn-Co/GAC particle electrode was prepared by loading Mn and Co as catalysts on granular activated carbon (GAC) and used in a three-dimensional (3D) electrochemical system for mineralization of amoxicillin wastewater. Observation results by SEM, EDS and XRD confirmed that Mn and Co catalysts were successfully loaded onto GAC. The electrochemical properties were measured using an electrochemical workstation. Mn-Co/GAC had a much higher oxygen evolution potential (1.46V) than GAC (1.1V), which demonstrated that it could effectively reduce the oxygen evolution side reaction. In addition, Mn-Co/GAC had an electrochemically active surface area 1.34 times that of GAC and a much smaller mass transfer resistance than GAC, which could provide favorable conditions for the degradation of pollutants. The investigation of the influences of single operating parameters on total organic carbon (TOC) removal rate and electrical energy consumption (EEC) indicated that current density and treatment time had the greatest effect. In order to maximize TOC removal rate and minimize EEC, optimization of operating parameters was also carried out using response surface method in combination with central composite design. The optimal operating parameters were determined as current density of 5.68 mA/cm², electrolyte concentration of 0.127M, particle electrode dosage of 31.14g and treatment time of 120min. Under this optimum operating condition, TOC removal rate of 85.24% and amoxicillin removal rate of 100% could be achieved with a low EEC of 0.073 kWh/g TOC. In addition, TOC removal rate and EEC were significantly improved compared to the use of bare GAC as particle electrode under the same operating conditions, demonstrating the excellent electrocatalytic ability of the new particle electrode Mn-Co/GAC. A possible mechanism of enhanced amoxicillin and TOC removal was also recommended. In summary, the 3D electrochemical method using Mn-Co/GAC particle electrodes is a suitable choice for amoxicillin wastewater treatment.

Removal of Chloroacetanilide Herbicides from Water Using Heterogeneous Photocatalysis with TiO2/UV-A

Chloroacetanilide herbicides are widely used in the agricultural sector throughout the world. Because of their poor biodegradability, high water solubility, and long persistence, chloroacetanilide herbicides have a high potential to contaminate water, and conventional water treatment processes do not ensure sufficient removal. Therefore, heterogeneous photocatalysis using TiO2/UV-A was investigated for the degradation of alachlor, acetochlor, and metolachlor from water. Two commercially available TiO2 (P25 and AV-01) were used as photocatalysts. Different experimental setups were also tested. In addition, the toxicity of single herbicides and mixtures of their photocatalytic degradation products to the freshwater alga Chlorella kessleri was investigated via a growth inhibition test. The maximum removal efficiency for alachlor, acetochlor, and metolachlor was 97.5%, 93.1%, and 98.2%, respectively. No significant differences in the removal efficiency of chloroacetanilide herbicides were observed for the photocatalysts used. Although the concentrations of all herbicides during photocatalysis decreased, the toxicity of the resulting mixtures of degradation products increased or remained the same, indicating the formation of toxic degradation products.

Potential risks and approaches to reduce the toxicity of disinfection by-product - A review

Water contamination through anthropogenic and industrial activities has led to the emergence and necessity of disinfection methods. Chlorine and bromine gases, often used to disinfect water, resulted in the by-product formation by reacting with organic matter. The Disinfectant by-products (DBP) led to the formation of Trihaloaceticacid (TAA), Trihalomethane (THM), and other minor components. The release of chemicals has also led to the outbreak of diseases like infertility, asthma, stillbirth, and types of cancer. There are new approaches that are found to be useful to compensate for the generation of toxic by-products and involve membrane technologies, namely reverse osmosis, ultrafiltration, and nanofiltration. This review mainly focuses on the toxicology effects of DBPs and various approaches to mitigate the same. The health hazards caused by different DBPs and the various treatment techniques available for the removal are discussed. In addition, a critical comparison of the different removal techniques was discussed.

Catalytic and non-catalytic degradation of acetaminophen in supercritical water

Pharmaceutical industrial wastewater is typical wastewater consisting of complex organic compounds with higher concentration, microbial toxicity, strenuous to deteriorate, and environmental threatening. The present work assesses the degradation of recalcitrant acetaminophen (ACM) by a green technology known as supercritical water oxidation (SCWO). Experiments were carried out in a continuous flow SCWO reactor by altering reaction conditions such as temperature 400-600 °C, oxidant coefficient (OC 0 to 3), and Fe(II) catalyst concentration (0.5 and 1 mg L^-1) to study the technical feasibility of highly concentrated ACM. Liquid product analysis indicated the total organic carbon (TOC) removal efficiency could reach up to 99.5% without catalyst at 600 °C and 99.9% with Fe(II) at 500 °C. The addition of Fe not only suppressed the intermediate ring components but also promoted the formation of permanent gases via decarboxylation and reforming reactions. The reaction between Fe(II) and H₂O₂ in supercritical water is extremely fast, which has a direct impact on the system's operating conditions. The high activity exhibited by Fe(II) catalyst degraded the ACM completely at an operating condition of 500 °C. Maximum H₂ fraction was attained without catalyst at 600 °C, OC 0.5, and with the catalyst at 500 °C, respectively, whereas, CO₂ tends to rise significantly with both temperature and oxidant concentration. The catalytic process is efficient in comparison to the non-catalytic process. A possible reaction pathway was proposed based on the intermediates generated during the degradation.

Electrochemical removal of fluoxetine via three mixed metal oxide anodes and carbonaceous cathodes from contaminated water

In this work, the fluoxetine (FLX) removal has been studied via the anodic oxidation (AO) process. Anode electrodes were Ti/RuO₂, Ti/RuO₂-IrO₂, and Ti/RuO₂-IrO₂-SnO₂, and cathode electrodes were graphite and carbon nanotubes (CNTs). The performances of electrodes were compared in terms of FLX removal efficiency. As a result, Ti/RuO₂-IrO₂-SnO₂ and CNTs were the optimal anode and cathode, respectively. The properties of the optimal electrodes were investigated using scanning electron microscopy, atomic force microscopy and X-ray diffraction spectroscopy. Cyclic voltammetry analysis was performed to study the electrochemical behavior of electrodes. The effect of current intensity (mA), initial pH, initial FLX concentration (mg/L) and process time (min) on the FLX removal efficiency was investigated and the response surface methodology was applied for the optimization of the AO process. The results showed that at current intensity, pH, initial FLX concentration and process time of 500 mA, 6, 25 mg/L and 160 min, maximum FLX removal efficiency was observed, which was 96.25%. Gas Chromatography-Mass Spectrometry (GC-MS), and total organic carbon (TOC) analysis was determined to evaluate the intermediates, and mineralization efficiency. The TOC removal efficiency was reached 81.51% after 6 h under optimal experimental conditions, indicating the successful removal of the FLX.

Preparation of a Heterogeneous Catalyst CuO-Fe2O3/CTS-ATP and Degradation of Methylene Blue and Ciprofloxacin

A heterogeneous particle catalyst (CuO-Fe2O3/CTS-ATP) was synthesized via injection molding and ultrasonic immersion method, which is fast and effective. The particle catalyst applied attapulgite (ATP) wrapped by chitosan (CTS) as support, which was loaded dual metal oxides CuO and Fe2O3 as active components. After a series of characterizations of catalysts, it was found that CuO and Fe2O3 were successfully and evenly loaded on the surface of the CTS-ATP support. The catalyst was used to degrade methylene blue (MB) and ciprofloxacin (CIP), and the experimental results showed that the degradation ratios of MB and CIP can reach 99.29% and 86.2%, respectively, in the optimal conditions. The degradation mechanism of as-prepared catalyst was analyzed according to its synthesis process and ∙OH production, and the double-cycle catalytic mechanism was proposed. The intermediate products of MB and CIP degradation were also identified by HPLC-MS, and the possible degradation pathways were put forward.

An assessment of hospital wastewater and biomedical waste generation, existing legislations, risk assessment, treatment processes, and scenario during COVID-19

Hospitals release significant quantities of wastewater (HWW) and biomedical waste (BMW), which hosts a wide range of contaminants that can adversely affect the environment if left untreated. The COVID-19 outbreak has further increased hospital waste generation over the past two years. In this context, a thorough literature study was carried out to reveal the negative implications of untreated hospital waste and delineate the proper ways to handle them. Conventional treatment methods can remove only 50%-70% of the emerging contaminants (ECs) present in the HWW. Still, many countries have not implemented suitable treatment methods to treat the HWW in-situ. This review presents an overview of worldwide HWW generation, regulations, and guidelines on HWW management and highlights the various treatment techniques for efficiently removing ECs from HWW. When combined with advanced oxidation processes, biological or physical treatment processes could remove around 90% of ECs. Analgesics were found to be more easily removed than antibiotics, β-blockers, and X-ray contrast media. The different environmental implications of BMW have also been highlighted. Mishandling of BMW can spread infections, deadly diseases, and hazardous waste into the environment. Hence, the different steps associated with collection to final disposal of BMW have been delineated to minimize the associated health risks. The paper circumscribes the multiple aspects of efficient hospital waste management and may be instrumental during the COVID-19 pandemic when the waste generation from all hospitals worldwide has increased significantly.

UV/TiO2 Photocatalysis as an Efficient Livestock Wastewater Quaternary Treatment for Antibiotics Removal

Antibiotics are among the most common pharmaceutical compounds, and they have been extensively used for the prevention and treatment of bacterial diseases for more than 50 years. However, merely a small fraction of antibiotics is metabolized in the body, while the rest is discharged into the environment through excretion, which can cause potential ecological problems and human health risks. In this study, the elimination of seventeen antibiotics from real livestock wastewater effluents was investigated by UV/TiO2 advanced oxidation process. The effect of process parameters, such as TiO2 loadings, solution pHs, and antibiotic concentrations, on the efficiency of the UV/TiO2 process was assessed. The degradation efficiency was affected by the solution pH, and higher removal efficiency was observed at pH 5.8 and 9.9, while the catalyst loading had no significant effect on the degradation efficiency. UV photolysis showed a good removal efficiency of the antibiotics. However, the highest removal efficiency was shown by the UV/photocatalyst system due to their synergistic effects. The results showed that more than 90% of antibiotics were removed by UV/TiO2 system during the 60 min illumination, while the corresponding TOC and COD removal was only 10 and 13%, respectively. The results of the current study indicated that UV/TiO2 advanced oxidation processes is a promising method for the elimination of various types of antibiotics from real livestock wastewater effluents.