The electro-peroxone process for the abatement of emerging contaminants: Mechanisms, recent advances, and prospects

A critical review of ozone-based electrochemical advanced oxidation processes for water treatment: Fundamentals, stability evaluation, and application

In recent years, electrochemical advanced oxidation processes (EAOPs) combined with ozonation have been widely utilized in water/wastewater treatment due to their excellent synergistic effect, high treatment efficiency, and low energy consumption. A comprehensive summary of these ozone-based EAOPs is still insufficient, though some reviews have covered these topics but either focused on a specific integrated process or provided synopses of EAOPs or ozone-based AOPs. This review presents an overview of the fundamentals of several ozone-based EAOPs, focusing on process optimization, electrode selection, and typical reactor designs. Additionally, the service life of electrodes and improvement strategies for the stability of ozone-based EAOPs that are ignored by previous reviews are discussed. Furthermore, four main application fields are summarized, including disinfection, emerging contaminants treatment, industrial wastewater treatment, and resource recovery. Finally, the summary and perspective on ozone-based EAOPs are proposed. This review provides an overall summary that would help to gain insight into the ozone-based EAOPs to improve their environmental applications.

E-peroxone with a novel GDE decorated with hydrophobic membrane for the degradation of pyridine: Stability, byproducts and toxicity

E-peroxone process is an emerging electrochemical oxidation process, based on ozone and the in-situ cathodic generation of H2O2, but the stability of cathode is one of the key restraining factors. In this study, we designed a multilayer gas diffusion electrode (GDE) decorated with a commercial hydrophobic membrane for the degradation of pyridine. It was found that a proper control of membrane pore sizes and hot-pressing temperature can significantly promote the GDE stability. Subsequently, key operational parameters of the constructed E-peroxone system were investigated, including the ozone concentration, current density, pH value, electrolyte type and initial concentration of pyridine. The degradation pathways were proposed according to six identified transformation products. The toxicity variation along the degradation progress was evaluated with microbial respiration tests and Toxicity Estimation Software Tool (T.E.S.T.) calculation and an efficient detoxification capacity of E-peroxone was observed. This research provides a theoretical basis and technical support for the development of highly efficient and stable E-peroxone system for the elimination of toxic organic contaminants.

Electrochemical filtration for drinking water purification: A review on membrane materials, mechanisms and roles

Electrochemical filtration can not only enrich low concentrations of pollutants but also produce reactive oxygen species to interact with toxic pollutants with the assistance of a power supply, making it an effective strategy for drinking water purification. In addition, the application of electrochemical filtration facilitates the reduction of pretreatment procedures and the use of chemicals, which has outstanding potential for maximizing process simplicity and reducing operating costs, enabling the production of safe drinking water in smaller installations. In recent years, the research on electrochemical filtration has gradually increased, but there has been a lack of attention on its application in the removal of low concentrations of pollutants from low conductivity water. In this review, membrane substrates and electrocatalysts used to improve the performance of electrochemical membranes are briefly summarized. Meanwhile, the application prospects of emerging single-atom catalysts in electrochemical filtration are also presented. Thereafter, several electrochemical advanced oxidation processes coupled with membrane filtration are described, and the related working mechanisms and their advantages and shortcomings used in drinking water purification are illustrated. Finally, the roles of electrochemical filtration in drinking water purification are presented, and the main problems and future perspectives of electrochemical filtration in the removal of low concentration pollutants are discussed.

The Nexus of Innovation: Electrochemically Synthesizing H2O2 and Its Integration with Downstream Reactions

Hydrogen peroxide (H2O2) represents a chemically significant oxidant that is prized for its diverse applicability across various industrial domains. Recent innovations have shed light on the electrosynthesis of H2O2 through two-electron oxygen reduction reactions (2e- ORR) or two-electron water oxidation reactions (2e- WOR), processes that underscore the attractive possibility for the on-site production of this indispensable oxidizing agent. However, the translation of these methods into practical utilization within chemical manufacturing industries remains an aspiration rather than a realized goal. This Perspective intends to furnish a comprehensive overview of the latest advancements in the domain of coupled chemical reactions with H2O2, critically examining emergent strategies that may pave the way for the development of new reaction pathways. These pathways could enable applications that hinge on the availability and reactivity of H2O2, including, but not limited to the chemical synthesis coupled with H2O2 and waste water treatment byFenton-like reactions. Concurrently, the Perspective acknowledges and elucidates some of the salient challenges and opportunities inherent in the coupling of electrochemically generated H2O2, thereby providing a scholarly analysis that might guide future research.

Degradation of atrazine by electro-peroxone enhanced by Fe and N co-doped carbon nanotubes with simultaneous catalysis of H2O2 and O3

Fe and N co-doped carbon nanotubes (Fe-N-CNT) was synthesized and attempted as efficient heterogeneous catalysts for simultaneous catalysis of H2O2 and O3 to improve electro-peroxone (Fe-N-CNT/EP) process efficiency for atrazine (ATZ) degradation. The removal and mineralization of ATZ was significantly enhanced, obtaining the degradation rate constant (k) by Fe-N-CNT/EP (0.23 min-1) about two times that of EP (0.12 min-1) owing to the formation of Fe0 and Fe-N coordination in Fe-N-CNT catalyst for co-catalysis of H2O2 and O3. The important factors such as applied current and ozone concentration were investigated, demonstrating that the optimized performance could be achieved at current of 30 mA and ozone concentration of 55 mg L-1. The oxidation capacity of Fe-N-CNT/EP maintained stably under wide pH range of 3∼7, obtaining the degradation rate constant 1.23-1.92 times that of EP and overcoming the defect of EP at acidic and neutral conditions. Capture experiments and electron paramagnetic resonance (EPR) experiments verified that .OH, generated by accelerating decomposition of H2O2/O3 and peroxone reaction, was the dominant active specie in Fe-N-CNT/EP. Besides, Fe-N-CNT showed high catalytic activity and good stability during six cycles. This work provides an efficient activator for enhanced EP process, exhibiting a promising prospect for water and wastewater purification.

Treatment of synthetic textile wastewater containing Acid Red 182 by electro-Peroxone process using RSM

The Azo dyes are primarily utilized in textile industries. Treatment of textile wastewater because of the presence of recalcitrant dyes using conventional processes is greatly challenging and ineffective. So far, no experimental work has been conducted on the decolorization of Acid Red 182 (AR182) in aqueous media. Hence, in this novel experimental work, the treatment of AR182 from the Azo dyes family was explored using the electro-Peroxone (EP) process. For the optimization of operating factors, including AR182 concentration, pH, applied current, and O3 flowrate in the decolorization of AR182, Central Composite Design (CCD) was utilized. The statistical optimization presented a highly satisfactory determination coefficient value and a satisfactory second-order model. The expected optimum conditions by the experimental design were as the following: AR182 concentration at 483.12 mg.L-1, applied current at 0.627,113 A, pH at 8.18284 and O3 flowrate at 1.13548 L min-1. The current density is directly proportional to dye removal. However, increasing the amount of applied current beyond a critical value has a contradictory impact on dye removal performance. The dye removal performance in both acidic and highly alkaline environments was negligible. Hence, ascertaining the optimum pH value and conduction of the experiment at that point is critical. At optimum points, the decolorization performance in predicted and experimental conditions for AR182 were 99 and 98.5%, respectively. The outcomes of this work clearly substantiated that the EP can be successfully utilized for the decolorization of AR182 in textile wastewater.

Formation of dichloroacetic acid and dichloroacetamide from phenicol antibiotic abatement during ozonation and post-chlor(am)ination

This study investigated the formation of dichloroacetamide (DCAM) and dichloroacetic acid (DCAA) from the abatement of three phenicol antibiotics (PABs, chloramphenicol, thiamphenicol, and florfenicol) during ozonation and post-chlor(am)ination. Results show that the three PABs have a low ozone reactivity (kO3 = 0.11‒0.12 M-1 s-1), and therefore are mainly abated through the hydrogen abstraction mechanism by hydroxyl radicals (•OH) during ozonation. During PAB degradation, the carboxamide moiety in the parent molecules can be cleaved off by •OH attack and thus gives rise to DCAM. The formed DCAM can then be further oxidized by O3 and/or •OH to DCAA as a more stable transformation product (TP). When the three PABs were adequately abated (abatement efficiency of ∼82 %‒95 %), the molar yields of DCAM and DCAA were determined to be 2.79 %‒4.71 % and 32.9 %‒37.2 %, respectively. Furthermore, post-chloramination of the ozonation effluents increased the yields of DCAM and DCAA slightly to 4.20 %‒6.45 % and 39.0 %‒41.1 %, respectively. In comparison, post-chlorination eliminated DCAM in the solutions, but significantly increased DCAA yields to ∼100 % due to the further conversion of DCAM and other ozonation TPs to DCAA by chlorine oxidation. The results of this study indicate that high yields of DCAM and DCAA can be generated from PAB degradation during ozonation, and post-chlorination and post-chloramination will result in very different fates of DCAM and DCAA in the disinfected effluent. The formation and transformation of DCAM and DCAA during PAB degradation need to be taken into account when selecting multi-barrier treatment processes for the treatment of PAB-containing water.

Mechanisms of interfacial catalysis and mass transfer in a flow-through electro-peroxone process

To investigate the catalytic mechanism and mass transfer efficiency in the removal of amitriptyline using an electro-peroxide process, a CuFe₂O₄-modified carbon cloth cathode was prepared and utilized in a reaction unit. The results demonstrated a remarkable efficacy of the system, achieving 91.0% amitriptyline removal, 68.3% mineralization, 41.2% mineralization current efficiency, and 0.24 kWh/m³ energy consumption within just five minutes of treatment. The study revealed that the exposed Fe atoms of the ferrite nanoparticles, with a size of 22.7 nm and 89.7% crystallinity, functioned as mediators to bind the adsorbed O atoms. The 3d_xy, 3d_xz, and 3d²_z orbitals of Fe atoms interacted with the 2p_z orbital of O atoms of H₂O₂ and O₃ to form σ and π bonds, facilitating the adsorption-activation of H₂O₂ and O₃ into hydroxyl radicals. These hydroxyl radicals (∼ 1.15 × 10¹³ mol/L) were distributed at the cathode-solution interface and rapidly consumed along the direction of liquid flow. The flow-through cathode design improved the mass transfer of aqueous O₃ and in-situ generated H₂O₂, leading to an increased yield of hydroxyl radicals, as well as the contact time and space between hydroxyl radicals and amitriptyline. Ultimately, this resulted in a higher degradation efficiency of the system.

Recent advances in the removal of emerging contaminants from water by novel molecularly imprinted materials in advanced oxidation processes-A review

Recently, there has been a global focus on effectively treating emerging contaminants (ECs) in water bodies. Advanced oxidation processes (AOPs) are the primary technology used for ECs removal. However, the low concentrations of ECs make it difficult to overcome the interference of background substances in complex water quality, which limits the practical application of AOPs. To address this limitation, many researchers are developing new catalysts with preferential adsorption. Molecular imprinting technology (MIT) combined with conventional catalysts has been found to effectively enhance the selectivity of catalysts for the targeted catalytic degradation of pollutants. This review presents a comprehensive summary of the progress made in research on molecularly imprinted polymers (MIPs) in the selective oxidation of ECs in water. The preparation methods, principles, and control points of novel MIP catalysts are discussed. Furthermore, the performance and mechanism of the catalysts in photocatalytic oxidation, electrocatalytic oxidation, and persulfate activation are analyzed with examples. The possible ecotoxicological risks of MIP catalysts are also discussed. Finally, the challenges and prospects of applying MIP catalysts in AOP are presented along with proposed solutions. This review provides a better understanding of using MIP catalysts in AOPs to target the degradation of ECs.

Removal of antibiotic resistant bacteria and plasmid-encoded antibiotic resistance genes in water by ozonation and electro-peroxone process

The electro-peroxone (EP) process is an electricity-based oxidation process enabled by electrochemically generating hydrogen peroxide (H₂O₂) from cathodic oxygen (O₂) reduction during ozonation. In this study, the removal of antibiotic resistant bacteria (ARB) and plasmid-encoded antibiotic resistance genes (ARGs) during groundwater treatment by ozonation alone and the EP process was compared. Owing to the H₂O₂-promoted ozone (O₃) conversion to hydroxyl radicals (•OH), higher •OH exposures, but lower O₃ exposures were obtained during the EP process than ozonation alone. This opposite change of O₃ and •OH exposures decreases the efficiency of ARB inactivation and ARG degradation moderately during the EP process compared with ozonation alone. These results suggest that regarding ARB inactivation and ARG degradation, the reduction of O₃ exposures may not be fully counterbalanced by the rise of •OH exposures when changing ozonation to the EP process. However, due to the rise of •OH exposure, plasmid DNA was more effectively cleaved to shorter fragments during the EP process than ozonation alone, which may decrease the risks of natural transformation of ARGs. These findings highlight that the influence of the EP process on ARB and ARG inactivation needs to be considered when implementing this process in water treatment.

Effects of water constituents on the stability of gas diffusion electrode during electrochemical hydrogen peroxide production for water and wastewater treatment

Electrochemically producing hydrogen peroxide (H₂O₂) from oxygen reduction reaction (ORR) with natural air diffusion electrode (NADE) is an attractive way to supply H₂O₂ for decentralized water treatment. In this study, the stability of NADE during H₂O₂ electroproduction in varying water matrices were evaluated, including synthetic electrolyte solutions (0.05 M Na₂SO₄) with or without calcium ions (Ca²⁺, 200 mg/L) and/or humic acid (HA, 40 mg/L), as well as a selected municipal wastewater (92.7 mg/L Ca²⁺, 3.6 mg/L Mg²⁺, and 23.9 mg/L total organic carbon). The results show that NADEs maintained a good stability during H₂O₂ electroproduction in Na₂SO₄ solutions regardless of the presence of HA. However, Ca²⁺ (and Mg²⁺) could form significant amounts of mineral precipitates on the surface and in the internal pores of NADEs during H₂O₂ electroproduction. These mineral precipitates can negatively influence H₂O₂ production by impeding the oxygen, electron, and proton transfer processes involved in ORR to H₂O₂. Moreover, the mineral precipitates shifted the NADEs from hydrophobic to hydrophilic, which may promote H₂O₂ reduction to H₂O at the NADEs. Consequently, the apparent current efficiencies of H₂O₂ production decreased substantially from initially ∼90% to 50%-70% as the NADEs were continuously used for 60 h in the Ca-containing solutions and selected wastewater. These results indicate that water constituents that are commonly present in real water matrices, especially Ca²⁺, can cause serious deterioration of NADE stability during H₂O₂ electroproduction. Therefore, proper strategies are needed to mitigate electrode fouling during H₂O₂ electroproduction with NADEs in practical water and wastewater treatment.

Challenges and pitfalls in the investigation of the catalytic ozonation mechanism: A critical review

Catalytic ozonation is a promising technology for pollutant abatement in water and wastewater treatment. However, there are many controversies and contradictions regarding the mechanisms of catalytic ozonation in literature, which has seriously confounded the development of the technology towards industrial applications. Herein, a critical review of literature is conducted to reveal possible underlying causes of the controversies and contradictions, and several common pitfalls in the experimental design and data interpretation are identified, e.g., the fundamentally flawed quenching method popularly used for evaluating the role of reactive oxygen species for pollutant abatement in catalytic ozonation and the neglect of monitoring ozone transfer doses in lab-scale experiments. Based on the identified pitfalls, several measures are suggested to improve the experimental design and data interpretation of catalytic ozonation studies. In addition, recent advances in mechanistic understanding of catalytic ozonation by principle-based modelling approaches are described. Finally, additional works that are needed to shrink the gap between academic research and practical applications and the prospect of catalytic ozonation in future water and wastewater treatment systems are analyzed.

An electro-peroxone oxidation-Fe(III) coagulation sequential conditioning process for the enhanced waste activated sludge dewatering: Bound water release and organics multivariate change

As a by-product of wastewater treatment, waste activated sludge (WAS) has complex composition, strong hydrophilic extracellular polymeric substance (EPS), which make it difficult to dewater. In this study, an electro-peroxone oxidation-Fe(III) coagulation (E-peroxone-Fe(III)) sequential conditioning approach was developed to improve WAS dewaterability. At E-peroxone oxidation stage, hydrogen peroxide was generated through 2-electron path on a carbon polytetrafluoroethylene cathode, and reacted with the sparged O₃ to produce hydroxyl radicals. At the subsequent coagulation stage, Fe(III) was dosed to coagulate the small WAS fragments and release water from WAS. Along E-peroxone-Fe(III) subsequent conditioning process, the physicochemical properties of WAS, main components, functional groups and evolution of protein secondary structure, and typical amino acids in EPS, as well as the type and semi-quantitative of elements in WAS, were investigated. The results indicated that under the optimal conditions, the reductions of specific resistance to filterability (SRF) and capillary suction time (CST) for WAS equalled 78.18% and 71.06%, respectively, and its bound water content decreased from 8.87 g/g TSS to 7.67 g/g TSS. After E-peroxone oxidation, part of protein and polysaccharide migrated outside from TB-EPS to slime, the ratio of α-helix/(β-sheet + random coil) declined, even some of organic-N disintegrated to inorganic-N. At Fe(III) coagulation stage, re-coagulation of the dispersed WAS fragments and easy extraction from inner EPS for protein and polysaccharide occurred. Furthermore, the protein secondary structure of β-sheet increased by 13.48%, the contents of hydrophobic and hydrophilic amino acids also increased. In addition, a strong negative correlation between the hydrophobic amino acid content of Met in slime and CST or SRF (R²_CST = -0.999, p < 0.05 or R²_SRF = -0.948, p < 0.05) occurred, while a strong positive correlation between the hydrophilic amino acid content of Cys in TB-EPS and CST or SRF (R²_CST = 0.992, p < 0.05 or R²_SRF = 0.921, p < 0.05) occurred, which could be related to the WAS dewaterability.

Electro-peroxone enables efficient Cr removal and recovery from Cr(III) complexes and inhibits intermediate Cr(VI) generation in wastewater: Performance and mechanism

Available oxidation processes for removing Cr(III) complexes from water/wastewater usually encounter the formation of highly toxic Cr(VI) and the generation of Cr enriched waste sludge, posing challenges on the subsequent disposal. Herein, we achieve efficient removal of Cr(III)-organic complexes and simultaneous recovery of Cr from wastewater with enhanced curtailment of intermediate Cr(VI), by using an electrochemically driven peroxone (i.e., electro-peroxone) process with activated carbon fiber (ACF) electrodes. For Cr(III)-EDTA, electro-peroxone could remove ∼90% total Cr from 11.50 mg/L to 1.20 mg/L and ∼80% total organic carbon, with a strong curtailment of Cr(VI) to less than 0.2 mg/L. Additionally, the process could obtain a complete recovery of the removable Cr, of which 78.3% are enriched at ACF cathode as amorphous Cr(OH)₃ deposits and the remaining 21.7% are adsorbed at the anode, thus avoiding the generation of Cr laden sludge. Mechanism studies show the electro-generated H₂O₂ reacts with O₃ to generate abundant HO· for decomplexation, which sequentially oxidizes Cr(III) to Cr(VI), and degrades the released EDTA via stepwise decarboxylated process, as confirmed by HPLC analysis. Multiple pathways including electro-reduction, H₂O₂ reduction and electro-adsorption synergistically curtail and immobilize the formed intermediate Cr(VI). ACF characterizations and continuous 5-cycle experiments substantiate the excellent reusability of the ACF electrodes. Moreover, this process exhibits satisfactory effectiveness to Cr(III) complexed with other ligands (e.g., citrate and oxalate), and complexed Cr(III) in the real electroplating wastewater. We believe this study would provide an efficient and eco-friendly alternative for Cr(III) complexes removal from wastewater.

Enhancement of E-Peroxone process with waste-tire carbon composite cathode for tinidazole degradation

The cathode is the key component in the electro-peroxone process (E-Peroxone), which is popularly constructed with carbon materials. This study developed an innovative method to fabricate a cathode with waste-tire carbon (WTC) whose performance was evaluated for the degradation of tinidazole (TNZ), an antibiotic frequently detected in water. It was found that the addition of WTC in the cathode can significantly promote the yield of H₂O₂ and the current efficiency: around 2.7 times that of commercial carbon black at the same loading. The critical influencing factors were studied, including the current density, ozone concentration, initial pH value, chlorine ions and initial TNZ concentration. The scavenger tests demonstrated the possible involvement of •OH and O₂^•-. Some transformation products of TNZ were identified with UPLC-MS and the degradation pathway was proposed accordingly. These results demonstrated the potential of WTC for developing E-Peroxone cathodes.

The potential application of bio-based ceramic/organic xerogel derived from the plant sources: A new green adsorbent for removal of antibiotics from pharmaceutical wastewater

A bio-based ceramic/organic xerogel (BCO-xerogel) was obtained from the combination of sugarcane bagasse ash, polyvinyl alcohol, and pine cone-derived tannin extract, which are abundant, non-toxic, and renewable sources. The as-prepared BCO-xerogel was used as a low-cost green adsorbent for the eliminate of four types of the most widely used antibiotics, including amoxicillin (AMX), tetracycline (TC), cefalexin (CLX), and penicillin G (PEN G) residuals from contaminated water. The simultaneous effects conventional variables including adsorbent dosage, antibiotic concentrations, solution pH, and contact time were studied and optimized by central composite design (CCD) under response surface methodology (RSM). Analysis of variance (ANOVA) was employed as a statistical formula to determine the significance of operating environmental conditions and their interactions with 95% confidence limits. Under optimized conditions, the experimental removal efficiencies for AMX, TC, CLX, and PEN G were 98.78 ± 3.25, 99.12 ± 2.52, 98.02 ± 1.98, and 98.42 ± 2.19, respectively. The adsorption isotherms and kinetics were better fitted with Langmuir and pseudo-second-order models, respectively. Thermodynamic studies showed that the adsorption process was endothermic, spontaneous, and occurred by combination of physical and chemical mechanisms. Also, evaluating the ability of BCO-xerogel to adsorptive removal of AMX, TC, CLX, and PEN G antibiotics in real wastewaters showed about 97.4-98.6% adsorption efficiency in river water and about 67.1-71.3% in three hospital effluents. After the adsorption process, the antibiotic-loaded adsorbent was regenerated by NaOH (0.01 mol L^-1), and the reusability tests showed that the removal efficiencies of the antibiotics in the four recovery steps were still above 90%. This work explored the development of green, efficient, and economical bio-adsorbent that can be utilized for the removal of antibiotics from contaminated wastewaters.

Enhancement of H2O2 yield and TOC removal in electro-peroxone process by electrochemically modified graphite felt: Performance, mechanism and stability

Electro-peroxone (EP) is an emerging advanced oxidation process which combines electro-generation H₂O₂ and ozone for removing organic contaminants. In this paper, a platinum plate as anode, a method of electrochemical oxidation is adopted to modify graphite felt (GF) cathode to promote H₂O₂ yield and TOC removal from oxalic acid solution in EP process, its performance, mechanism and stability were discussed. Compared with original GF cathode, 2.6 times H₂O₂ yield can be achieved by the 5 min electrochemically modified GF (GF-5). The high electrochemical activity of the modified GF can be ascribed to introducing numerous surface oxygen-containing functional groups (OGs), which not only decreased the impedance, but also increased the amount of active site of O₂ reduction. The production of H₂O₂ with GF-5 cathode improved with the increased initial pH, cathodic potential and O₂ flow rate, while this promoting effect was not observed in GF cathode. Compared with GF cathode, TOC removal rate was improved by 21.5% with GF-5 cathode due to higher H₂O₂ yield in EP process. The primary pathway of TOC removal is electrochemically-driven peroxone process, and hydroxyl radical (·OH) is the dominant reactive species. Furthermore, GF-5 cathode had a good stability due to the protection of H₂O₂ and free electrons injected. The results indicate that the electrochemically modified GF severed as the cathode of EP processes has significant efficiency and stability in the removal of ozone-refractory organic contaminants.

Effective degradation of azo dye from textile wastewater by electro-peroxone process

Color-producing chemicals emitted from many sources, such as textile or dye manufacturing industries, are a significant concern worldwide. The present study focuses on the electro-peroxone (EP) process for decolorizing a synthetic azo dye, C.I. Reactive Black 5 (RB5). Findings suggest that the EP process is more effective for dye degradation than ozonation and electrolysis. The EP process resulted in 100% decolorization after 60 min of contact time under optimum testing conditions such as pH 7, applied current 300 mA, and sulfate concentration 3.55 g L^-1. Based on the findings of the primary investigation, EP treatment of real textile effluent was carried out and 2 h of EP treatment resulted in 99% decolorization and 74%total organic carbon (TOC) removal. As an outcome, the EP process can treat textile wastewater in a cost-effective and environmentally friendly manner.

Trends in microbial degradation and bioremediation of emerging contaminants

Modernization and modern ways of living demands more improved products from pharmaceuticals, cosmetics, and food processing industries. Moreover, industries like pesticides, fertilizers, dyeing, paints, detergent etc., also needs improvised products as per demand. As the new product emerges, the pollutants from these industries also constitute new type of danger to the environment and serious health risks to the living organisms. These emerging contaminants (ECs) are from different category of sources such as personal care products (PCPs), pharmaceuticals (Phcs), endocrine disrupting chemicals (EDCs), etc. These ECs can easily escape from the conventional water treatment and eventually get discharged in to the surface water and thus enters in to the ground water, soil, sediments, and also into the oceans. When these contaminants emerge we also require progress in tremendous process for preventing these hazardous chemicals by effective removal and treatment. For the past 50 years, both developed and developing countries are working on this treatment process and found that Microbial degradation and bioremediation are very useful for effective treatment to prevent their emissions. This treatment can be designed for any sort of ECs since the microbial members are so versatile to redesign their metabolic pathways when subject to exposure. However, implementing bioremediation is not alone efficient to degrade ECs and hence, combination of bioremediation, nanotechnology and physical treatment method will also provide sustainable, potent and fast degradation process. In this Book Chapter, we discuss in detail about the ECs, sources of microbial degradation process and its usefulness in the bioremediation of these ECs.

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

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

Fighting Antibiotic Resistance in Hospital-Acquired Infections: Current State and Emerging Technologies in Disease Prevention, Diagnostics and Therapy

Rising antibiotic resistance is a global threat that is projected to cause more deaths than all cancers combined by 2050. In this review, we set to summarize the current state of antibiotic resistance, and to give an overview of the emerging technologies aimed to escape the pre-antibiotic era recurrence. We conducted a comprehensive literature survey of >150 original research and review articles indexed in the Web of Science using "antimicrobial resistance," "diagnostics," "therapeutics," "disinfection," "nosocomial infections," "ESKAPE pathogens" as key words. We discuss the impact of nosocomial infections on the spread of multi-drug resistant bacteria, give an overview over existing and developing strategies for faster diagnostics of infectious diseases, review current and novel approaches in therapy of infectious diseases, and finally discuss strategies for hospital disinfection to prevent MDR bacteria spread.

Degradation of Acid Violet 19 textile dye by electro-peroxone in a laboratory flow plant

This paper deals with the degradation of Acid Violet 19 (AV19) textile dye by the electro-peroxone (E-peroxone) process in a laboratory flow plant using a filter press cell fitted with a 3D gas diffusion electrode (3D GDE) containing a graphite felt positioned on carbon-cloth PTFE as cathode, and a Ti|IrSnSb-oxides plate as anode. H₂O₂ was formed by the oxygen reduction reaction (ORR) in the cathode; the air was supplied by an external compressor. The O₃ produced externally by an ozonator was added in the pipeline at the outlet of the electrolyzer to promote the reaction between the H₂O₂ and O₃ to produce OH, which is the responsible for the mineralization of the dye. The effect of electrolyte flow rate (Q), current density (j), and initial concentration of AV19 dye on its degradation was addressed. The best electrolysis in a solution containing 40 mg TOC L^-1, 0.05 M Na₂SO₄, at pH 3, was obtained at j = 20 mA cm^-2, Q = 2.0 L min^-1, using a pressure of the air fed to the 3D GDE of P_GDE = 3 psi, and an ozone inlet mass flow rate of [Formula: see text]  = 14.5 mg L^-1, achieving 100% discoloration, 60% mineralization, with mineralization current efficiency and energy consumption of 36% and 0.085 kWh(gTOC)^-1. The degradation of AV19 dye was also performed by anodic oxidation plus H₂O₂ electrogenerated (AO-H₂O₂) and ozonation. The oxidation power was AO-H₂O₂ < ozonation < E-peroxone. Three carboxylic acids were quantified by chromatography as oxidation end products.

Effects of coagulation-sedimentation-filtration pretreatment on micropollutant abatement by the electro-peroxone process

The electro-peroxone (EP) process has been considered an attractive alternative to conventional ozonation for micropollutant abatement in water treatment. However, how to integrate the EP process into the water treatment trains in water utilities has yet to be investigated. This study compared micropollutant abatement during the EP treatment of potable source water with and without pretreatment of biological oxidation, flocculation, sedimentation, and filtration. Results show that this pretreatment train removed 39% of dissolved organic carbon (DOC) and 28% of the UV₂₅₄ absorbance of the raw water, leading to higher ozone (O₃) stability in the treated water. By electrochemically generating hydrogen peroxide to accelerate O₃ decomposition to hydroxyl radicals (•OH), the EP process considerably shortened the time required for ozone depletion and micropollutant abatement during the treatment of both the raw and pretreated water to ∼1 min, compared to ∼3 and 7.5 min during conventional ozonation of the raw and treated water, respectively. For the same specific ozone dose of 1 mg O₃ mg^-1 DOC (corresponding to 4.3 and 2.8 mg O₃ L^-1 for the raw and treated water, respectively), the abatement efficiencies of micropollutants with moderate and low ozone reactivity were increased by ∼10-15%, while the energy consumption for micropollutant abatement was decreased by ∼24-56% during the EP treatment of the treated water than the raw water. These results indicate that partial removal of DOC and ammonia from the raw water by the pretreatment train has a beneficial effect on enhancing micropollutant abatement and reducing energy consumption of the EP process. Therefore, it is more cost-effective to integrate the EP process after the pretreatment train in water utilities for micropollutant abatement.

Diuron degradation using three-dimensional electro-peroxone (3D/E-peroxone) process in the presence of TiO2/GAC: Application for real wastewater and optimization using RSM-CCD and ANN-GA approaches

The present study investigates the efficiency of a three-dimensional electro-peroxone (3D/E-peroxone) reactor filled with TiO₂-GAC in removing diuron from aqueous solution and in the remediation of real pesticide wastewater. The behavior of the system in terms of the effect of independent variables on diuron was investigated and optimized by RSM-CCD and ANN-GA methods. Both approaches proved to have a very good performance in the modeling of the process and determined the optimum condition of the independent variables as follows: initial pH = 10, applied current = 500 mA, supporting electrolyte = 0.07 M, ozone concentration = 10 mg L^-1, and reaction time = 10 min. The 3D/E-peroxone process achieved a synergistic effect in diuron abatement and reduced significantly energy consumption, as compared to its individual components. H₂O₂ concentration generated in the electrolysis system was notably increased in the presence of TiO₂-GAC microparticles. The BOD₅/COD ratio of the real pesticide wastewater increased from 0.049 to 0.571 within 90 min treatment. Giving to the considerable enhancement of the biodegradability of the wastewater, this study strongly suggests that the 3D/E-peroxone process can be considered as a promising pretreatment step before a biological treatment process to produce intermediates which are more easily degradable by microorganisms.

The synergistic effect of electrocoagulation coupled with E-peroxone process for shale gas fracturing flowback water treatment

Electrocoagulation (EC) coupled with E-peroxone process (ECP) was a promising and cost-effective integrated technology for shale gas fracturing flowback water (SGFFW) treatment. In this study, the ECP process was comprehensively compared with two sequential processes (EC followed by E-peroxone (EC-E-peroxone) and E-peroxone followed by EC (E-peroxone-EC)) to elucidate the synergistic effect of this coupled process. In EC-E-peroxone process, COD decreased by 89.2%, while COD decreased by 82.5% for 180 min in E-peroxone-EC process. However, COD removal efficiency was 82.4% in ECP for only 90 min. Average current efficiency of the ECP process was 29.9%, which was twice than that of the sequential processes. The enhancement factor was calculated to be 1.63, demonstrating the substantial significant synergistic effects for ECP. Only low MW components could be observed for the EC-E-peroxone (average MW = 533 Da with PD ≈ 1) and ECP process (MW = 538 Da with PD ≈ 1). These results suggested that EC-E-peroxone and ECP process had much stronger oxidation ability, demonstrating the enhancement of OH production induced by the Al-based coagulants might be responsible for the significant enhancement of COD removal. These results indicated there could be a synergistic effect between EC and ozone in addition to EC and E-peroxone reactions. Compared to the two sequential processes, ECP was a high efficiency and space-saving electrochemical system with simultaneous coagulation and enhanced OH generation by the products of anode and the cathode.

Anaerobic membrane bioreactors for treatment of emerging contaminants: A review

Emerging contaminants (ECs) are synthetic organic chemicals that released into the environment, which pose a serious threat to the ecosystem and human health. Due to the high costs of physicochemical methods and the possibility of secondary pollution, and conventional biological treatment techniques are not efficient to remove ECs. Thus, there is a need to develop novel technologies to treat ECs. Anaerobic digestion (AD) is reported to degrade most ECs. Anaerobic membrane bioreactor (AnMBR) is an upgraded AD technology that has high system stability and microbial community abundance. The biogas production and EC biodegradation efficiency in the AnMBR system are markedly higher than those in the traditional AD system. In recent years, AnMBR is widely used to remove environmental ECs. This review analyzes the feasibility and challenges of AnMBR in the treatment of ECs and provides useful insights for improving the performance and efficiency of AnMBR to treat ECs.

Hybrid electrocatalytic ozonation treatment of high-salinity organic wastewater using Ni-Ce/OMC particle electrodes

Hybrid electrocatalytic ozonation is an efficient method for degrading high-salinity organic wastewater that has excellent oxidation ability and is environmentally friendly. Furthermore, the high salt content of the wastewater provides electrolyte to support the process, which avoids secondary pollution caused by the addition of electrolyte. In this work, Ni_0.2-Ce_0.2/ordered mesoporous carbon (OMC)/granular active carbon (GAC) particle electrodes with a Ni:Ce weight ratio of 1:1 were synthesized using a simple method. The electrodes were characterized by transmission electron microscopy and electron paramagnetic resonance spectroscopy, as well as other techniques. The catalytic performance was investigated using cyclic voltammetry and AC impedance. Higher reduction and oxidation peak currents were obtained with the Ni_0.2-Ce_0.2/OMC catalyst than with Ni_0.2/OMC or Ce_0.2/OMC, indicating that the bimetallic catalyst has higher activity for the reduction of O₂ to H₂O₂ and the oxidation of O₃ to ·OH. The order of the k values-which represent the mass-transfer rate-was Ni_0.2-Ce_0.2/OMC (0.157) > Ni_0.2/OMC (0.017) > Ce_0.2/OMC (0.014). The results show that cooperation between Ni, Ce, and OMC promoted the dispersion of Ni and Ce and improved the catalytic performance. Ni_0.2-Ce_0.2/OMC enhances the catalytic reduction of O₂ to H₂O₂, and, in addition, Ce is able to rapidly store and release oxygen through Ce³⁺/Ce⁴⁺ conversions and reacting with O₃ to generate ·OH, which increases the oxidation capacity of the material. Under the optimal conditions the chemical oxygen demand removal for high-salinity organic wastewater using Ni_0.2-Ce_0.2/OMC/GAC particle electrodes reached 93.7%.

High-performance of activated biocarbon based on agricultural biomass waste applied for 2,4-D herbicide removing from water: adsorption, kinetic and thermodynamic assessments

Activated biocarbons were prepared using biomass wastes: sugarcane bagasse, coconut shell and endocarp of babassu coconut; as a renewable source of low-cost raw materials and without prior treatments. These activated biocarbons were characterized by textural analysis, solid-state ¹³C nuclear magnetic resonance spectroscopy, X-ray diffraction and scanning electronic microscopy. Textural analysis results revealed that those activated biocarbons were microporous, with specific surface area values of 547, 991 and 1,068 m² g^-1 from sugarcane bagasse, coconut shell and endocarp of babassu coconut, respectively. The innovation of this work was to evaluate which biomass residue was able to offer the best performance in removing 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from water by adsorption. Adsorption process of 2,4-D was investigated and the Langmuir and Redlich-Peterson models described best the adsorption process, with R² values within 0.96-0.99. The 2,4-D removal performance were 97% and 99% for the coconut and babassu biocarbons, respectively. q_M parameter values obtained from Langmuir model were 153.9, 233.0 and 235.5 mg g^-1 using sugarcane bagasse, coconut shell and endocarp of babassu, respectively. In addition, the adsorption kinetics were described nicely by the second-order model and the Gibbs free energy parameter values were negative, pointing to a spontaneous adsorption, as well.

Kinetics and mechanism of thiamethoxam abatement by ozonation and ozone-based advanced oxidation processes

In this study, the abatement of neonicotinoid insecticide, thiamethoxam, by single ozonation, ozone/ultraviolet (O₃/UV) and electro-peroxone (EP) process was evaluated. The second-order rate constants for the reaction of thiamethoxam with O₃ and hydroxyl radical (OH) at pH 7 were determined to be 15.4 M^-1 s^-1 and 3.9 × 10⁹ M^-1 s^-1, respectively. The degradation pathways of thiamethoxam were proposed based on quantum chemical calculations and transformation products were identified using chromatographic and mass-spectrometric techniques. The acute and chronic toxicity of thiamethoxam and its major TPs to various aquatic organisms were assessed. With typical ozone doses applied in water treatment (≤5 mg/L), thiamethoxam was abated by only ∼16-32 % in two real water matrices (groundwater and surface water) during single ozonation, but by ∼100 % and >70 % during the O₃/UV and EP treatment, respectively. The energy demand to abate 90 % thiamethoxam in the two water matrices was generally comparable for single ozonation and the EP process (∼0.14 ± 0.03 kW h/m³), but higher for the O₃/UV process (0.21-0.22 kW h/m³). These results suggest that single ozonation is unable to sufficiently abate thiamethoxam under typical conditions of water treatment. Therefore, ozone-based advanced oxidation processes are needed to enhance thiamethoxam abatement.

Comparison of emerging contaminant abatement by conventional ozonation, catalytic ozonation, O3/H2O2 and electro-peroxone processes

The abatement of several emerging contaminants (ECs) in groundwater by conventional ozonation and three ozone-based advanced oxidation processes (AOPs) - catalytic ozonation with manganese dioxide (MnO₂), conventional peroxone (O₃/H₂O₂), and electro-peroxone (EP) - was compared in this study. The addition of MnO₂, H₂O₂, or electro-generation of H₂O₂ during ozonation enhanced ozone transformation to hydroxyl radicals to different extent. These changes did not considerably influence the abatement of ECs with moderate to high ozone reactivities ( [Formula: see text] ), whose abatements were similar with >90 % during all four processes. In comparison, the abatements of ozone-refractory ECs (k_O3< 15 M^-1s^-1) were lower during conventional ozonation (∼40-85 % abatement), but could be enhanced by ∼10-40 % during the three ozone-based AOPs. Besides enhancing ozone-refractory EC abatement, the three AOPs, especially the O₃/H₂O₂ and EP processes, reduced considerably bromate formation compared to conventional ozonation. These results demonstrate that the EP process performs similarly as catalytic ozonation and O₃/H₂O₂ processes in terms of EC abatement and bromate control. Considering its more convenient, flexible, and safer way of operation, the EP process may provide an attractive alternative to the two more traditional AOPs for water treatment.

Oxidative removal of benzotriazole using peroxymonosulfate/ozone/ultrasound: Synergy, optimization, degradation intermediates and utilizing for real wastewater

This study investigated the degradation efficiency of BTA using combination of ultrasound (US), peroxymonosulfate (PMS), and ozone. The effects of different operational parameters were investigated to optimize the process performance. The results showed that the highest removal efficiency was reached at neutral pH, ozone = 6.8 mg/L, PMS = 1.5 mM and US power = 200 W. Under these conditions, 40 mg/L of BTA was completely degraded within 60 min leading to the almost 85% of chemical oxygen demand removal, 75% of total organic carbon removal and 73.3% of organic nitrogen removal. Based on the scavenging tests, it was found that hydroxyl radical was the main oxidizing agent in the oxidation of BTA by PMS/ozone/US process. The inhibitive effect of anions on BTA removal was under this order NO₂^- > HCO₃^- > Cl^- > NO₃^- > SO₄^2-. Degradation intermediates of BTA were identified and oxidation pathway was proposed. Finally, real samples of saline water, petrochemical wastewater and secondary effluent matrices were investigated for the performance of PMS/ozone/US process and it was found that 54%, 72.3% and 94.6% BTA removal efficiency were reached, respectively. PMS/ozone/US process was compared to US/peroxone (ozone + H₂O₂) and the results showed importance of US irradiation in both systems. Accordingly, PMS/ozone/US process could be considered as an efficient and promising process for BTA degradation in various wastewaters.

2,4-dichlorophenoxyacetic acid (2,4-D) micropollutant herbicide removing from water using granular and powdered activated carbons: a comparison applied for water treatment and health safety

Activated carbons are well-known porous materials as an effective adsorbent used for the removal of emerging contaminants, such as herbicides, which are increasingly present in water bodies. Most water treatment plants, specially in Brazil, are unable to completely remove such contaminants by the conventional process and advanced treatment using activated carbons is required. The aim of this paper was to verify the influence of the activated carbons granulometry and specific surface area on the 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide removal efficiency using distilled-deionized water and filtered water collected from a conventional Water Treatment Plant. Commercial activated carbons samples used in this work were obtained from two different manufacturers. Activated carbons were analyzed by the specific surface area, pore size and volume distribution, nuclear magnetic resonance, infrared and x-ray spectroscopy, moisture, volatile matter and ash contents. Batch adsorption isotherms experiments were used and performed by Langmuir and Freundlich models. Granular and powdered activated carbons removed over 99% of 2,4-D in distilled water and near to 99% using filtered water. The activated carbons evaluated in this work presented high performance and played a key role in water treatment by removing 2,4-D herbicide, ensuring the protection of human health and the ecosystem.

Highly efficient electro-generation of H2O2 by adjusting liquid-gas-solid three phase interfaces of porous carbonaceous cathode during oxygen reduction reaction

Equilibrium of three reactants (oxygen, proton and electron) in oxygen reduction reaction at large current flux is necessary for highly efficient electro-generation of H₂O₂. In this work, we investigated reactants equilibrium and H₂O₂ electrochemical production in liquid-gas-solid three phase interfaces on rolling cathodes with high electroactive area. Electrocatalytic reaction accelerated the electrolyte intrusion into hydrophobic porous catalyst layer for higher electroactive surface area, resulting in a 21% increase of H₂O₂ yield at 15 mA cm^-2. Air aerated cathode submerged in air/O₂ aeration solution was unable to produce H₂O₂ efficiently due to the lack of O₂ in three phase interfaces (TPIs), especially at current density > 2.5 mA cm^-2. For air breathing cathode, stable TPIs inside the active sites was created by addition of gas diffusion layer, to increase H₂O₂ production from 11 ± 2 to 172 ± 11 mg L^-1 h^-1 at 15 mA cm^-2. Pressurized air flow application enhanced both oxygen supply and H₂O₂ departure transfer to obtain a high H₂O₂ production of 461 ± 11 mg L^-1 h^-1 with CE of 89 ± 2% at 35 mA cm^-2, 45% higher than passive gas transfer systems. Our findings provided a new insight of carbonaceous air cathode performance in producing H₂O₂, providing important information for the practical application and amplification of cathodes in the future.

Oxidation of emerging biocides and antibiotics in wastewater by ozonation and the electro-peroxone process

This study investigated the abatement of a number of antimicrobials frequently detected in municipal wastewater by conventional ozonation and a recently developed ozone-based advanced oxidation process, the electro-peroxone (E-peroxone) process. A synthetic water and a real secondary wastewater effluent were spiked with fourteen antimicrobials, including antibiotics and biocides, and then treated by the two processes. The results show that most of the antibiotics investigated (e.g., ofloxacin, trimethoprim, norfloxacin, and ciprofloxacin) readily react with ozone (O₃) and could therefore be efficiently eliminated from the water matrices by direct O₃ oxidation during both processes. In contrast, most of the biocides tested in this study (e.g., clotrimazole, pentamidine, bixafen, propiconazole, and fluconazole) were only moderately reactive, or non-reactive, with O₃. Therefore, these biocides were removed at considerably lower rate than the antibiotics during the two ozone-based processes, with hydroxyl radical (OH) oxidation playing an important role in their abatement mechanisms. When compared with conventional ozonation, the E-peroxone process is defined by the in situ electrogeneration of hydrogen peroxide, which considerably enhances the transformation of O₃ to OH. As a result, the E-peroxone process significantly accelerated the abatement of biocides and required a considerably shorter treatment time to eliminate all of the tested compounds from the water matrices than conventional ozonation. In addition, the E-peroxone process enhanced the contributions of OH fractions to the abatement of moderately ozone reactive benzotriazoles. These results demonstrate that the E-peroxone process holds promise as an effective tertiary treatment option for enhancing the abatement of ozone-resistant antimicrobials in wastewater.