The profound review of Fenton process: What's the next step?

Fenton and Fenton-like processes, which could produce highly reactive species to degrade organic contaminants, have been widely used in the field of wastewater treatment. Therein, the chemistry of Fenton process including the nature of active oxidants, the complicated reactions involved, and the behind reason for its strongly pH-dependent performance, is the basis for the application of Fenton and Fenton-like processes in wastewater treatment. Nevertheless, the conflicting views still exist about the mechanism of the Fenton process. For instance, reaching a unanimous consensus on the nature of active oxidants (hydroxyl radical or tetravalent iron) in this process remains challenging. This review comprehensively examined the mechanism of the Fenton process including the debate on the nature of active oxidants, reactions involved in the Fenton process, and the behind reason for the pH-dependent degradation of contaminants in the Fenton process. Then, we summarized several strategies that promote the Fe(II)/Fe(III) cycle, reduce the competitive consumption of active oxidants by side reactions, and replace the Fenton reagent, thus improving the performance of the Fenton process. Furthermore, advances for the future were proposed including the demand for the high-accuracy identification of active oxidants and taking advantages of the characteristic of target contaminants during the degradation of contaminants by the Fenton process.

A review on reactive oxygen species-induced mechanism pathways of pharmaceutical waste degradation: Acetaminophen as a drug waste model.

Innately designed to induce physiological changes, pharmaceuticals are foreknowingly hazardous to the ecosystem. Advanced oxidation processes (AOPs) are recognized as a set of contemporary and highly efficient methods being used as a contrivance for the removal of pharmaceutical residues. Since reactive oxygen species (ROS) are formed in these processes to interact and contribute directly toward the oxidation of target contaminant(s), a profound insight regarding the mechanisms of ROS leading to the degradation of pharmaceuticals is fundamentally significant. The conceptualization of some specific reaction mechanisms allows the design of an effective and safe degradation process that can empirically reduce the environmental impact of the micropollutants. This review mainly deliberates the mechanistic reaction pathways for ROS-mediated degradation of pharmaceuticals often leading to complete mineralization, with a focus on acetaminophen as a drug waste model.

Combination of electrochemical advanced oxidation and biotreatment for wastewater treatment and soil remediation.

The global concern surrounding the advancement of methods for treating wastewater and polluted soil has markedly increased over time. While electrochemical advanced oxidation processes (EAOPs) and biotreatments are commonly employed technologies for remediating wastewater and polluted soil, their widespread adoption is hindered by their limitations, which include high costs associated with EAOPs and prolonged remediation time of biotreatments. In the review, we provided an overview of EAOP technology and biotreatment, emphasizing the critical aspects involved in building a combined system. This review systematically evaluates recent research that combines EAOPs with bioremediation for treating wastewater or contaminated soil as pretreatment or post-treatment process. Research findings suggest that the combined treatment method represents a promising and competitive technology that can overcome some of the limitations of individual treatments. Additionally, we discussed the potential applications of this technology in varying levels of wastewater and soil pollution, as well as the underlying combination mechanisms.

Transformation of dissolved organic matter leached from biodegradable and conventional microplastics under UV/chlorine treatment and the subsequent effect on contaminant removal.

The ultraviolet (UV)/chlorine process has been widely applied for water treatment. However, the transformation of microplastic-leached dissolved organic matter (MP-DOM) in advanced treatment of real wastewater remains unclear. Here, we investigated alterations in the photoproperties of MP-DOM leached from biodegradable and conventional microplastics (MPs) and their subsequent effects on the degradation of sulfamethazine (SMT) by the UV/chlorine process. Spectroscopy was used to assess photophysical properties, focusing on changes in light absorption capacity, functional groups, and fluorescence components, while photochemical properties were determined by calculating the apparent quantum yields of reactive intermediates (ΦRIs). For photophysical properties, our findings revealed that the degree of molecular structure modification, functional group changes, and fluorescence characteristics during UV/chlorine treatment are closely linked to the type of MPs. For photochemical properties, the ΦRIs increased with higher chlorine dosages due to the formation of new functionalities. Both singlet oxygen (1O2) and hydroxyl radicals (•OH) formation were strongly correlated with excited triplet state of DOM (3DOM*) in the UV/chlorine treatment. Additionally, we found that the four types of MP-DOM inhibit the degradation of SMT and elucidated the mechanisms behind this inhibition. We also proposed degradation pathways for SMT and assessed the ecotoxicity of the resulting intermediates. This study provides important insights into how the characteristics and transformation of MP-DOM affect contaminant degradation, which is critical for evaluating the practical application of UV-based advanced oxidation processes (UV-AOPs).

Enhanced mineralization of pharmaceutical residues at circumneutral pH by heterogeneous electro-Fenton-like process with Cu/C catalyst.

Conventional electro-Fenton (EF) process at acidic pH ∼3 is recognized as a highly effective strategy to degrade organic pollutants; however, homogeneous metal catalysts cannot be employed in more alkaline media. To overcome this limitation, pyrolytic derivatives from metal-organic frameworks (MOFs) have emerged as promising heterogeneous catalysts. Cu-based MOFs were prepared using trimesic acid as the organic ligand and different pyrolysis conditions, yielding a set of nano-Cu/C catalysts that were analyzed by conventional methods. Among them, XPS revealed the surface of the Cu/C-A2-Ar/H2 catalyst was slightly oxidized to Cu(I) and, combined with XRD and HRTEM data, it can be concluded that the catalyst presents a core-shell structure where metallic copper is embedded in a carbon layer. The antihistamine diphenhydramine (DPH), spiked into either synthetic Na2SO4 solutions or actual urban wastewater, was treated in an undivided electrolytic cell equipped with a DSA-Cl2 anode and a commercial air-diffusion cathode able to electrogenerate H2O2. Using Cu/C as suspended catalyst, DPH was completely degraded in both media at pH 6-8, outperforming the EF process with Fe2+ catalyst at pH 3 in terms of degradation rate and mineralization degree thanks to the absence of refractory Fe(III)-carboxylate complexes that typically decelerate the TOC abatement. From the by-products detected by GC/MS, a reaction sequence for DPH mineralization is proposed.

Remediation of benzo[α]pyrene contaminated soil using iron naturally bearing in tropical soil: A new frontier in catalyst-free in soil remediation.

Nature iron is considered one of the promising catalysts in advanced oxidation processes (AOPs) that are utilized for soil remediation from polycyclic aromatic hydrocarbons (PAHs). However, the existence of anions, cations, and organic matter in soils considered impurities that restricted the utilization of iron that was harnessed naturally in the soil matrix and reduced the catalytic performance. In this regard, tropical soil naturally containing iron and relatively poor with impurities was artificially contaminated with 100 mg/50 g benzo[α]pyrene (B[α]P) and remediated using a slurry phase reactor supported with persulfate (PS). The results indicated that tropical soil containing iron and relatively poor with impurities capable of activating the oxidants and formation of radicals which successfully degraded B[α]P. The optimum removal result was 86% and obtained under the following conditions airflow = 260 mL/min, temperature 55 °C, pH 7, and [PS]0 = 1.0 g/L, at the same experimental conditions soil organic matter (SOM) mineralization was 48%. After the remediation process, there was a significant reduction in iron and aluminum contents, which considered the drawbacks of this system. Experiments to scavenge reactive species highlighted O2•- and SO4•- as the main radicals that oxidized B[α]P. Additionally, monitoring of by-products post-remediation aimed to assess toxicity and elucidate degradation pathways. Mutagenicity tests yielded positive results for two B[α]P by-products. The toxicity tests considered were the lethal concentration of 50% (LC50 96 h) for fat-head minnows revealed that all B[α]P by-products were less toxic than the parent pollutant itself. This research marks a significant advancement in soil remediation by advancing the use of the AOP method, removing the requirement for additional catalysts in the AOP system for the removal of B[α]P from soil.

Singlet oxygen dominant-activation by hollow structural cobalt-based MOF/peroxymonosulfate system for micropollutant removal.

Despite the keen interest in potentially using the metal-organic framework (MOF) in advanced oxidation processes (AOPs), their application for environmental abatement and the corresponding degradation mechanisms have remained largely elusive. This study explores the use of cobalt-based MOF (CoMOF) for peroxymonosulfate (PMS) activation to remove tetracycline (TC) from water resources. Under optimal conditions, the given catalytic system could achieve a TC removal of 83.3%. Radical quenching tests and EPR analysis revealed that SO4•-, HO•, •O2-, and 1O2 could participate in the catalytic degradation, but the discernible removal mechanism was mainly ascribed to the nonradical pathway induced by 1O2. At only 5 mg/L of CoMOF, the performance of the catalytic system was superior to that of PMS alone for different types of micropollutants. The CoMOF/PMS system could also reliably deal with typical anions in water, such as Cl-, SO42-, HCO3-, and PO43-. The MOF catalyst could last for four cycles with a minor decrease in reactivity of ∼30%. However, the removal performance decreased markedly when aromatic natural organic matter (NOM) were present in the water bodies, and the effectiveness was lower in alkaline or acidic environments. Our work offers insights into the catalytic degradation of CoMOF/PMS applied in contaminated water remediation and serves as a baseline for fabricating an efficient MOF with enhanced catalytic performance and stability.

Recent advances in the removal of psychoactive substances from aquatic environments: A review.

Psychoactive substances (PS) have become emerging contaminants in aquatic environments, characterized by their wide distribution, high persistence, bioaccumulation and toxicity. They are difficult to be completely removed in sewage treatment plants due to their high stability under different conditions. The incomplete removal of PS poses a threat to the aquatic animals and can also lead to human health problems through accumulation in the food chain. PS has become a huge burden on global health systems. Therefore, finding an effective technology to completely remove PS has become a "hot topic" for researchers. The methods for removal PS include physical techniques, chemical methods and biological approaches. However, there is still a lack of comprehensive and systematic exploration of these methods. This review aims to address this gap by providing a comprehensive overview of traditional strategies, highlighting recent advancements, and emphasizing the potential of natural aquatic plants in removing trace PS from water environments. Additionally, the degradation mechanisms that occur during the treatment process were discussed and an evaluation of the strengths and weaknesses associated with each method was provided. This work would help researchers in gaining a deeper understanding of the methodologies employed and serve as a reference point for future research endeavors and promoting the sustainable and large-scale application of PS elimination.

The effect of silica-doped graphene oxide (GO-SiO2) on persulfate activation for the removal of Acid Blue 25.

The release of synthetic dyes into water bodies poses many environmental issues, and their removal is a necessity. Advanced oxidation processes (AOPs) can be employed for removal, in many of which a catalyst is used. graphene oxide (GO) is a viable catalyst due to its distinctive structural properties; however, it is reportedly incapable of effectively activating persulfate. Thus, this study delves for the first time into the influence of doping silica on enhancing GO's catalytic performance to activate persulfate for decolorizing Acid Blue 25 (AB25). Based on the results, an equal weight proportion of GO to silica was selected as the most efficient ratio. In addition, pH had no significant effect on removal efficiency, while temperature had the highest impact. Within 150 min with 0.075 gr/L of GO-SiO2 as the catalyst and 1 gr/L of Na2S2O8 as the oxidant, the investigated process removed Acid Blue 25 up to 82%, which was 9% higher than when GO alone was used as the catalyst. As for COD removal, the contribution of doping silica was more significant and led to 37% COD removal, which was 17% higher than when GO alone was used.

Advances of carbon-based materials for activating peracetic acid in advanced oxidation processes: A review.

In recent years, the peracetic acid (PAA)-based advanced oxidation process (AOPs) has garnered significant attention in the field of water treatment due to rapid response time and environmentally-friendliness. The activation of PAA systems by diverse carbon-based materials plays a crucial role in addressing emerging environmental contaminants, including various types, structures, and modified forms of carbon materials. However, the structural characteristics and structure-activity relationship of carbon-based materials in the activation of PAA are intricate, while the degradation pathways and dominant active species exhibit diversity. Therefore, it is imperative to elucidate the developmental process of the carbon-based materials/PAA system through resource integration and logical categorization, thereby indicating potential avenues for future research. The present paper comprehensively reviews the structural characteristics and action mechanism of carbon-based materials in PAA system, while also analyzing the development, properties, and activation mechanism of heteroatom-doped carbon-based materials in this system. In conclusion, this study has effectively organized the resources pertaining to prominent research direction of comprehensive remediation of environmental water pollution, thereby elucidating the underlying logic and thought process. Consequently, it establishes robust theoretical foundation for future investigations and applications involving carbon-based materials/PAA system.

A multi-analytical approach to evaluate the removal efficiency of Polystyrene nanoparticles in water treatment processes.

The removal of nanoplastics (NP) from water using various treatment processes has gained significant attention recently. This study comprehensively characterizes the degradation of polystyrene nanoparticles (concentration: 200 ppm, diameter: 140 nm) through UVC irradiation. For the first time, we compared four analytical methods to monitor removal efficiency: Py-GCMS, UV-Visible spectroscopy, TOC, and Turbidity. Additionally, DLS, TEM, and SEC were used to understand changes in particle size, morphology, and molecular weight. Results showed that Py-GCMS overestimated the removal rate by a factor of 2 compared to Turbidity and UV-Visible measurements, which were in agreement. Furthermore, after 200 hours of irradiation, the styrene signal disappears from the pyrogram, although the mineralization rate reaches only 50%, as determined by total organic carbon (TOC) analysis. The particle size decreased slowly, reaching 100 nm after 150 hours, while a significant decrease in molecular weight indicated high chain-scission. These findings emphasize the importance of a multi-analytical approach to accurately assess NP removal efficiency and understand degradation mechanisms.

Multiple oxidative modifications on hemoglobin are elevated in breast cancer patients as measured by nanoflow liquid chromatography-tandem mass spectrometry.

Breast cancer is strongly connected with elevated oxidative stress. Oxidative modifications of hemoglobin can serve as biomarkers for monitoring oxidative stress status in vivo. The structure of hemoglobin modifications derived from malondialdehyde (MDA) in human blood hemoglobin exists as N-propenal and dihydropyridine (DHP). This study reports the simultaneous quantification of eleven modified peptides in hemoglobin derived from MDA and advanced histidine oxidation in 16 breast cancer patients and 16 healthy women using nanoflow liquid chromatography nanoelectrospray ionization tandem mass spectrometry. The results reveal statistically significant increases in the formation of MDA-derived N-propenal and DHP of lysine and advanced oxidation of histidine in hemoglobin of breast cancer patients with the Mann-Whitney U-test p values < 0.0001 and the AUC of ROC between 0.9277 and 1.0. Furthermore, the elevation in modified peptides is significant in patients with early stages of breast cancer. By measuring these oxidative modifications in hemoglobin from a drop of blood, the role of lipid peroxidation and oxidative stress in breast cancer can be assessed using this sensitive assay.

Marine toxins in environment: Recent updates on depuration techniques.

Marine toxins pose a significant safety risk, leading to human intoxications and causing substantial economic losses in seafood-producing regions. The development of rapid, cost-effective, efficient, and reliable approaches for the containment of these substances is therefore crucial in order to mitigate the adverse impact of marine toxins. This research conducted a comprehensive review on the toxicity and influencing factors of marine toxins production. Additionally, depuration technologies, including adsorption, advanced oxidation processes, biodegradation, heating treatment, temporary maintenance and purification, and drug inhibition, were systematically summarized. The study also provided a comparative analysis of the advantages and disadvantages of various depuration technologies and proposed strategies for future development.

Electrical breakdown in liquid-phase processing on an enhancement of 7-hydroxymitragynine conversion from mitragynine in Mitragyna speciose (Kratom).

This study investigates the impact of the Electrical Breakdown in Liquid-phase (EBL) process on alkaloid transformation in Mitragyna speciose (Kratom) leaves, focusing on the conversion of mitragynine (MG) to 7-hydroxy mitragynine (7-OH-MG) by using advanced oxidation processes (AOPs). A novel reactor has been developed to enhance plasma exposure to Kratom leaf powdered solutions during the EBL process. Two distinct electrical voltage characteristics, half-positive and negative half-waves, have been utilized for the EBL, with an output voltage of 4.57 kVpeak at a no-load condition and a frequency of 50 Hz. The experimental findings demonstrate a time-dependent enhancement in the transformation process. The highest yield of 7-OH-MG, reaching 2,485 ± 134 µg/g of dried Kratom leaves weight, has been attained with the EBL processing generated by positive half-wave voltage after 20 min of EBL exposure. Notably, the EBL processing generated by positive half-wave voltage has outperformed the one generated by negative half-wave voltage by a significant factor of 2.01.

Combination of oxidative and reductive effects of phenolic compounds on the degradation of aniline disinfection by-products by free radicals.

In this study, we selected 13 phenolic compounds containing -COOH, -CHO, -OH, and -COCH3 functional groups as model compounds for dissolved organic matter (DOM), and explored the redox reactions during the co-degradation of phenolic compounds with aniline disinfection by-products (DBPs) at the molecular level. When phenolic compounds and aniline DBPs were degraded, phenoxy radicals and aniline radicals were the most important intermediates. Phenoxy radicals can degrade aniline DBPs via hydrogen atom abstraction (HAA) reactions, and the reaction rates were related to the reduction potentials of the compounds. Compounds containing electron-withdrawing groups were more likely to oxidize aniline DBPs. Aniline DBPs were more easily degraded by phenoxy radicals when they contained electron-donating groups, and the increase in the number of chlorine atoms inhibited the reaction rates of aniline DBPs degradation by phenoxy radicals. Although phenolic compounds can reduce aniline DBPs, there was no significant correlation between the reaction rates and the reduction potentials of the compounds. Considering the redox effects of phenolic compounds on aniline DBPs, co-degradation simulations showed that phenolics inhibited the degradation efficiency of aniline DBPs. This work provided new insights into the transformation mechanisms and degradation efficiencies of DOM and aniline DBPs when they were co-degraded.

Promoting strategies for biological stability in drinking water distribution system from the perspective of micro-nano bubbles.

Microorganisms thriving in drinking water distribution system (DWDS) reduces biological stability of water, causing numerous threats to residents' drinking water safety. Traditional disinfection methods have intrinsic drawbacks, including microbial reactivation and byproduct formation, leading to waterborne diseases. Thus, effective disinfection techniques are required to ensure the microorganism's inactivation and enhance biological stability. Micro-nano bubbles (MNB) provide a promising result to these issues. This study simulates the hydraulic conditions of the tank of DWDS to investigate the enhancement of biological stability in the tank using MNBs with distinct gas sources. The analysis focused on water quality characteristics, biological stability indicators, and microbial community composition. The results showed that the dissolved gas method could generate abundant bubbles with a particle size below 1000 nm, with a concentration exceeding 106/mL in water. The particle size and Zeta potential of bubbles were crucial factors influencing in situ the ·OH generation; hence, the ·OH concentration was highly sensitive to changes in bubble size. In addition, MNBs inhibited the growth of target bacteria in water, degraded organic matter, and improved the biological stability of drinking water, reaching significant degradation rates for biodegradable dissolved organic carbon (42.74 %), assimilable organic carbon (49.49 %), and total bacteria (51.32 %). MNBs directly degraded organic matter in water by ·OH generation in situ, reducing the microbial nutrient source, thereby inhibiting microbial metabolism and activity, which induced optimum disinfection effects on Proteobacteria, Cyanobacteria, and Planctomycetota in water. In particular, the proposed experiment achieved a 100 % disinfection rate for Acinetobacter in Proteobacteria, disrupting metabolic intermediate functions with the microbial community after MNB treatment. Therefore, this study has demonstrated the potential of MNBs to enhance the biological stability of drinking water, improve water quality, and ensure residents' water health, providing valuable technical support for drinking water safety.

Selective O2-to-H2O2 Electrosynthesis by a High-Performance, Single-Pass Electrofiltration System Using Ibuprofen-Laden CNT Membranes.

Producing H2O2 through a selective, two-electron (2e) oxygen reduction reaction (ORR) is challenging, especially when it serves as an advanced oxidation process (AOP) for cost-effective water decontamination. Herein, we attain a 2e-selectivity H2O2 production using a carbon nanotube electrified membrane with ibuprofen (IBU) molecules laden (IBU@CNT-EM) in an ultrafast, single-pass electrofiltration process. The IBU@CNT-EM can generate H2O2 at a rate of 25.62 mol gCNT-1 h-1 L-1 in the permeate with a residence time of 1.81 s. We demonstrated that an interwoven, hydrophilic-hydrophobic membrane nanostructure offers an excellent air-to-water transport platform for ORR acceleration. The electron transfer number of the ORR for IBU@CNT at neutral pH was confirmed as 2.71, elucidating a near-2e selectivity to H2O2. Density functional theory (DFT) studies validated an exceptional charge distribution of the IBU@CNT for the O2 adsorption. The adsorption energies of the O2 and *OOH intermediates are proportional to the H2O2 selectivity (64.39%), higher than that of the CNT (37.81%). With the simple and durable production of H2O2 by IBU@CNT-EM electrofiltration, the permeate can actuate Fenton oxidation to efficiently decompose emerging pollutants and inactivate bacteria. Our study introduces a new paradigm for developing high-performance H2O2-production membranes for water treatment by reusing environmental functional materials.

Challenges and opportunities for large-scale applications of the electro-Fenton process.

As an electrochemical advanced oxidation process, the electro-Fenton (EF) process has gained significant importance in the treatment of wastewater and persistent organic pollutants in recent years. As recently reported in a bibliometric analysis, the number of scientific publications on EF have increased exponentially since 2002, reaching nearly 500 articles published in 2022 (Deng et al., 2022). The influence of the main operating parameters has been thoroughly investigated for optimization purposes, such as type of electrode materials, reactor design, current density, and type and concentration of catalyst. Even though most of the studies have been conducted at a laboratory scale, focusing on fundamental aspects and their applications to degrade specific pollutants and treat real wastewater, important large-scale attempts have also been made. This review presents and discusses the most recent advances of the EF process with special emphasis on the aspects more closely related to future implementations at the large scale, such as applications to treat real effluents (industrial and municipal wastewaters) and soil remediation, development of large-scale reactors, costs and effectiveness evaluation, and life cycle assessment. Opportunities and perspectives related to the heterogeneous EF process for real applications are also discussed. This review article aims to be a critical and exhaustive overview of the most recent developments for large-scale applications, which seeks to arouse the interest of a large scientific community and boost the development of EF systems in real environments.

Methods for degrading dicloxacillin in water using inorganic peroxides and their combination with UVC- experimental and theoretical aspects.

Antibiotics are currently recognized as environmental pollutants. In this work, the methods involved in the degradation of a ß-lactam antibiotic (i.e., DXC) by treatments based on inorganic peroxides and UVC (e.g., UVC alone, UV-C/H2O2, UVC/peroxymonosulfate, and UVC/peroxydisulfate) are presented. The methodology of computational calculations to obtain frontier orbitals and Fukui indices for DXC, and elucidate the reactive moieties on the target substance is also shown. Finally, the direct oxidation by peroxides and UV-C/H2O2 action to treat DXC in simulated pharmaceutical wastewater are depicted. The chromatographic and theoretical analyses allowed for determining the degrading performance of inorganic peroxides and UVC-based treatments toward the target pollutant in aqueous samples.•Treatments based on inorganic peroxides and UVC as useful methods for degrading the ß-lactam antibiotic dicloxacillin.•Persulfates and UV-C/H2O2 showed high degrading action on the target pharmaceutical.•Methodologies based on theoretical calculations for the identification of reactive moieties on the DXC susceptible to radical attacks are presented.

Nitrogen and magnesium codoped biochar activates periodate to remediate bensulfuron methyl-contaminated water at low temperature: Performance, mechanisms, and phytotoxicity.

Bensulfuron methyl (BSM), a typical sulfonylurea herbicide, has been widely used worldwide for weed suppression and crop protection. Nevertheless, the long-term and prolonged usage led to residues in environment, resulting in the reduction of crop yields and even threatening food security. In this study, the nitrogen/magnesium codoped biochar (NMg-BC) was prepared via two-step pyrolysis method to activate periodate (PI) for BSM degradation. The results demonstrated BSM degradation rate was 87.9 % within 10 min by NMg-BC/PI system at 15 â„ƒ. The system exhibited the favorable tolerance to environmental changes (pH, temperature, anions, and humic acids), presenting high removal efficiency of BSM. Radicals (IO3•) and non-radicals (1O2 and electron transfer) pathways contributed to the degradation of BSM, while the latter performed a crucial role in BSM degradation. Theoretical calculations further confirmed doped of N and Mg changed the electron configuration and electrostatic potential (ESP) distribution of biochar, which was beneficial to provide more active sites for PI activation. Hydroponic experiments showed that NMg-BC/PI system could effectively degrade BSM, and its residue had no significant effect on the length and weight of soybean. The study provides a promising approach for the pollutant remediation in cold regions.