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[Display omitted] • The I-EF system triggers trace iron utilization for simultaneous PBTC degradation and recovery. • The I-EF system coordinates the competition between adsorption and degradation in PBTC treatment (p < 0.001). • The feasibility of I-EF is successfully demonstrated for other OP forms containing C-P and C-O-P bonds. Phosphorus recovery from wastewater has the potential to alleviate both phosphorus scarcity and water pollution. Unlike mineral orthophosphate, organic phosphorus (OP) recovery typically requires multiple steps: oxidation to orthophosphate followed by separation. Electro-Fenton can synchronize these steps in a unified reactor. However, conventional anodic-Fenton (AF) that relies on the direct sacrificial Fe anode, often generates excessive iron sludge. This not only undermines the oxidative capacity but also changes the optimal pH conditions. Herein, we addressed these challenges by developing an induced electro-Fenton (I-EF) system that significantly reduces iron sludge by 94.0 %. The degradation of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC, 5.0 mg P/L) in I-EF reached 76.7 % in 60 min, which is much higher than that (46.0 %) in the conventional AF system. Following PBTC degradation to form PO 4 3-, the I-EF system achieved 88 % PO 4 3- recovery through adsorption onto iron hydroxides. The exceptional performance in simultaneous PBTC degradation and recovery can be attributed to multiple functions of minimal iron utilization in the I-EF system. First, trace iron release can prevent quenching of hydroxyl radicals (·OH) by excessive Fe2+. Second, the absence of strong iron hydrolysis can maintain a stable pH condition (3.0–3.2) for Fenton reaction and avoid PBTC removal through direct coagulation process. The feasibility of I-EF was also successfully demonstrated for other OP forms containing C-P and C-O-P bonds. The degradation efficiency of various OPs was closely related to their bond energy and complexation capacity with iron hydroxides. This study makes use of the I-EF system to innovatively accomplish the degradation of organic phosphorous and simultaneous phosphate recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • An atmospheric-pressure plasma jet with optimal Ar flow degraded dibutyl phthalate (DBP) by 96.6 % in 10 min. • Hydroxyl radicals play a significant role in DBP degradation. • Chemical probing and spectroscopic techniques revealed the liquid- and gas- phase hydroxyl radical concentration. • Cell viability is improved by 40% while dead cell population is substantially reduced, indicating notably reduced toxicity. Phthalate esters such as dibutyl phthalate (DBP) are widely used as plasticizers in various industries and are known to cause water pollution reaching 15.7 mgL -1 in freshwater and 0.01 mgL -1 in seawater. This study investigated the effectiveness of DBP degradation using an atmospheric-pressure plasma jet (APPJ). Variation in the argon (Ar) gas flow rate influenced the spatial distribution of the hydroxyl radicals (∙ O H) as it altered the laminar-to-turbulent flow transition. The highest density of ∙ O H was recorded to be 3.1 × 1016 cm−3 when the Ar flow rate was maintained at 2 standard liters per minute. Additionally, the ∙ O H concentration in plasma-activated water substantially increased to 35.5 μM with prolonged treatment. Similarly, the concentrations of H 2 O 2 , which is formed as a result of the recombination of the ∙ O H , gradually increased to 34.4 μM over 8 min of treatment time, and subsequently reduced to 32.6 μM after an additional 2 min of treatment. A degradation rate of 96.6 % was achieved within 10 min of treatment, as confirmed by a gas chromatography (GC)-flame ionization detector. GC-mass spectrometry was used to identify the intermediate products, and propose possible degradation pathways. However, a decline in the energy efficiency was observed because of reduced initial concentration over the extended treatment time. Furthermore, a 40 % increase in cell viability and a 45 % decrease in the percentage of the dead cell population were observed during the exposure of MRC5, astrocytes, and PC-3 cell lines to APPJ-treated DBP solution, indicating reduced toxicity of the contaminant. Thus, the proposed approach can effectively reduce the contamination of water resources by DBP. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fundamental knowledge on SSPFR are detailed illustrated. • Catalytic mechanism of each step and development of SSPFR are reviewed. • Various strategies aimed at improving the reaction rate are discussed and summarized. • Applications are introduced. • Prospects for the future development of SSPFR are presented. Fenton reaction has gained tremendous attention in the field of non-selective pollutant degradation, as •OH with powerful oxidizing capacity can be produced via H 2 O 2 activation. However, the widespread application is limited by the continuous consumption of commercial H 2 O 2 with high price. As an alternative strategy, self-sufficient photo-Fenton reaction (SSPFR) has been explored, where oxidant H 2 O 2 was in-situ produced inside the system for subsequent Fenton reactions, rather than external addition. Benefiting from the low cost, high H 2 O 2 utilization efficiency, and low risk in H 2 O 2 storage and transportation, SSPFR became a hotpot in scientific research, and developed rapidly in recent years. Herein, we critically reviewed the state-of-the-art development of SSPFR, in which the fundamental mechanism and catalytic process were firstly introduced. Then, SSPFR reaction was divided into three cascade steps: in-situ H 2 O 2 production, H 2 O 2 activation, and reactive oxygen species utilization. This paper reviewed the research progress in every step, and proposes corresponding potential strategies to accelerate the reaction rate. Finally, conclusions and prospects of SSPFR for the removal of organic pollutants were proposed. This study provides a valuable resource for researchers to construct novel and efficient SSPFR systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • The falling-film plasma reactor (FFPR) effectively produces reactive oxygen species. • Reactive oxygen species from FFPR rapidly degrade fenitrothion in aqueous solutions. • Modeling confirms the rapid decomposition of fenitrothion by hydroxyl radicals. • Kinetics and modeling results reveal three major pathways for degradation reactions. The contamination of surface water with organophosphates is an environmental concern due to their acute toxicity to wildlife and humans. This study reports an evaluation of the efficacy of a falling-film plasma reactor (FFPR) for degrading fenitrothion, which is an organophosphate insecticide and a simulant for nerve agents. An FFPR setup was demonstrated to effectively degrade fenitrothion in aqueous solutions. The degradation kinetics of the aqueous fenitrothion was found to follow an exponential decaying function and to have a destruction removal efficiency (DRE) of up to 95% within 60 min. The effectiveness of the FFPR treatment was attributed to its ability to efficiently generate reactive oxygen species, particularly hydroxyl radicals, to oxidize fenitrothion and byproducts. Four transient intermediate products from the fenitrothion degradation reaction were detected and identified. Their concentrations were found to increase in the first ca. 15 min of the reaction and then follow exponential decay patterns. Quantum chemical calculations revealed that hydroxyl radicals react with fenitrothion through three major pathways. The first pathway involves the attack of the hydroxyl radical at the phosphorus atom and the subsequent leaving of the 3-methyl-4-nitrophenol radical, leading to two major products observed in experiments. The second pathway involves the hydrogen abstraction by hydroxyl radicals at the methoxy groups on the phosphorus atom and converts the methoxy groups to hydroxyl groups, resulting in a major product in experiments. The third pathway involves the hydrogen abstraction by hydroxyl radicals at the methyl group on the nitrophenol ring and converts the methyl group to a carboxyl group, resulting in another major product detected in experiments. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel flow-anode, CeO x /CB, was introduced in electro-oxidation. • Ce(IV)/Ce(III) redox cycle accelerated the electron transfer directionally. • The loading of CeO x actuated efficient •OH generation. • Acetaminophen degradation rate was 2.3–2.9 times higher than the control. • CeO x /CB achieved high current efficiency and low energy consumption. Electrochemically active materials can effectively alleviate mass transfer restriction by adding them as flow-anodes into the electrochemical reactor. However, conventional flow-anode materials display a low •OH yield. Here, a novel flow-anode, CeO x /carbon black (CB), demonstrates superior electrocatalytic degradation efficiency of organic pollutants. The acetaminophen degradation kinetic constant of CeO x /CB was calculated to be 2.3–2.9 times higher than that of CB. CeO x /CB achieved a higher current efficiency of 66.4 % and relatively lower energy consumption of 157.8 kWh/kg COD compared with other GAC or γ-Al 2 O 3 -based flow-anodes. The mechanistic analyses demonstrated that rapid electron transfer, strong water adsorption, and low reaction energy barrier of CeO x /CB actuated efficient •OH generation. Moreover, Ce(IV)/Ce(III) redox cycle crucially acted as an "electron porter" to accelerate the electron transfer from adsorbed H 2 O molecules to CB substrate directionally in the electro-oxidation process. This work provides a feasible manner for the development of flow-anodes utilizing the advantage of the Ce(IV)/Ce(III) redox cycle. [ABSTRACT FROM AUTHOR]

• A novel technology was employed to rapidly release carbon source from excess sludge. • Microcurrent can enhance the ratios of C/N and C/P of digestion supernatant. • Hydroxyl radical facilitated the formation of humic substances. • Hydroxyl radical promoted the transformation of soluble microbial products (SMP). • Metabolic pathway of organic matters in synergistic treatment system was proposed. Synergistic treatment via thermophilic microaerobic digestion and microcurrent was adopted to release the internal carbon source from excess sludge, and the effects of the microcurrent on sludge digestion and carbon source release were investigated. Compared with the control group where no current was applied, the digestion supernatant in the tested R1-45 °C reactor maintained a relatively lower phosphate concentration. The optimal technical parameters included a digestion temperature of 45 °C, a current intensity of 175 mA, and a digestion time of 96 h; the concentrations of soluble chemical oxidation demand (SCOD), total nitrogen (TN), and total phosphate (TP) for the test group were 12 189, 903, and 105 mg L−1, respectively, and the ratios of SCOD/TN and SCOD/TP reached 13.5 and 116.1. The sludge flocs were disaggregated into smaller particles upon thermophilic treatment coupled with microcurrent application, and abundant organic matters were released into the digestion supernatant, resulting in a rapid increase in the SCOD. The hydroxyl radicals produced by the microcurrent could directly oxidize fatty acids into end molecules, and it also facilitated regeneration of NAD+ (nicotinamide adenine dinucleotide) through the oxidation of NADH; the orthophosphate in digestion supernatant could be continuously absorbed to synthesize ATP, accompanied by accumulation of acetic and propionic acids. In addition, synergistic treatment accelerated the production of humic acid-like substances and played an important role in the transformation of soluble microbial products. [ABSTRACT FROM AUTHOR]

• CuFe 2 O 4 /CNTs were fabricated and employed as catalysts for electro-peroxone treatment of FLC. • Adsorption combined with catalytic electro-peroxone was efficient for FLC removal. • FLC degradation efficiency was positively related with technique parameters that favor HO production. • The enhancement of oxidation efficiency was attributed to the introduced catalytic ozonation and Fenton-like reactions. Copper ferrite modified carbon nanotubes (CuFe 2 O 4 /CNTs) were synthesized and employed as adsorbents/catalysts to assist electro-peroxone treatment of aqueous emerging pollutant fluconazole (FLC). Results suggest that the synthetic CuFe 2 O 4 /CNTs integrated the CNTs adsorption and ferrite magnetic abilities, showing a fast FLC removal and an excellent recyclability. The pseudo-second-order equation and the Langmuir isotherm model could well elaborate the adsorption of FLC on prepared catalysts. Compared to individual processes, electro-peroxone treatment exhibited a synergetic degradation of FLC. Approximately 89% FLC transformation was observed in the CuFe 2 O 4 /CNTs catalytic electro-peroxone process, 10% higher than that without catalysts, implying that CuFe 2 O 4 /CNTs could enhance the peroxone oxidation. Increasing of inlet gasphase ozone concentration (7.2–29.7 mg/L), catalysts dose (0.1–0.8 g/L), initial solution pH (3–11), and reaction temperature (10–30 °C) could improve the treatment efficiency, while initial FLC concentration (5–40 mg/L) and natural organic matter contents (humic acid, 0–20 mg/L) have opposite effects. The role of cathodic current density (10–60 mA/cm2) was complex, 40 mA/cm2 was observed as the optimal value. Furthermore, the degradation of FLC followed the hydroxyl radicals (HO) oxidation mechanism. The production of HO was mainly via peroxone reactions, and the presence of CuFe 2 O 4 /CNTs could catalytic ozone and H 2 O 2 decomposition, thereby promoting HO generation. Although the magnetic CuFe 2 O 4 /CNTs had not shown obvious microelectrode characteristics, it combined adsorption and catalytic peroxone oxidation, may serve as the catalyst for electro-peroxone process. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Spinel Co 3 O 4 /δ-FeOOH composite was firstly synthesized. • Co 3 O 4 /δ-FeOOH performed dramatic catalytic activity for LOM degradation. • The mechanism of PMS activation by Co 3 O 4 /δ-FeOOH composite was elucidated. • Toxicity test of degraded solution was conducted. • Co 3 O 4 /δ-FeOOH potentially facilitates the application in wastewater treatment. Abstract In the present study, a novel Co 3 O 4 /δ-FeOOH composite was successfully fabricated. Subsequently, we measured its crystal structure, morphology, and surface area. After this, the Co 3 O 4 /δ-FeOOH composite was applied to activate peroxymonosulfate (PMS) for lomefloxacin (LOM, a type of fluoroquinolones) degradation. Compared with pure Co 3 O 4 and δ-FeOOH, Co 3 O 4 /δ-FeOOH composite exhibited the best efficiency towards LOM degradation, in which the removal of LOM (>82%) and first order reaction kinetic rate constant (k app = 0.064 min−1) were achieved after 25 min reaction with 0.25 g·L−1 Co 3 O 4 /δ-FeOOH, 0.49 mM PMS, and 10 mg·L−1 (28.5 μM) LOM at initial pH 6.08. Next, we considered the concentration of catalyst, PMS and the effect of pH on LOM degradation. The results showed that the increase of PMS and catalyst was beneficial for the degradation of LOM. Moreover, the highest degradation efficiency of LOM was achieved under neutral conditions, which was due to the minimum repulsive force between the PMS and the catalyst. In addition, active radical scavenging experiment was performed and it was found that the contribution of hydroxyl radicals was greater than that of sulfate radicals. Subsequently, possible reaction mechanism was proposed. What's more, possible degradation intermediates in Co 3 O 4 /δ-FeOOH system were determined and five decomposition pathways were proposed. Meanwhile, activated sludge inhibition experiment was carried out to evaluate the variation of toxicity of the LOM and its degradation intermediates in the oxidation process. Overall, this work provided a new strategy for the practical application of sulfate radicals-based advanced oxidation processes (SR-AOPs) in wastewater treatment. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel and green cathode modification by electrode polarity reversal was first reported. • Increase in surface oxygen-containing groups and hydrophilic properties were observed. • For modified electrode, low current and neutral pH could support the highest H 2 O 2 yield. • The modified graphite felt cathode exhibited good reproducibility and longevity. • Modified cathode in column reactor supported ibuprofen removal from simulated groundwater. Abstract Electrochemical synthesis of H 2 O 2 offers a great potential for water treatment. However, a significant challenge is the development of efficient cathode materials for the process. Herein, we implement a practical electrochemical cathode modification to support efficient H 2 O 2 electrogeneration via the reduction of dissolved anodic O 2. Graphite felt (GF) is in situ anodically modified by electrode polarity reversal technique in an acid-free, low-conductivity electrolyte. The modified GF exhibits a significantly higher activity towards O 2 reduction. Up to 183.3% higher H 2 O 2 yield is obtained by the anodized GF due to the increased concentrations of oxygen-containing groups and the hydrophilicity of the surface, which facilitates electron and mass transfer between GF and the electrolyte. Another significant finding is the ability to produce H 2 O 2 at a high yield under neutral pH and low current intensity by the modified GF (35% of the charge need to produce the same amount by unmodified GF). Long-term stability testing of the modified GF showed a decay in the electrode's activity for H 2 O 2 production after 30 consecutive applications. However, the electrode regained its optimal activity for H 2 O 2 production after a secondary modification by electrode polarity reversal. Finally, in situ electrochemically modified GF is more effective for removal of reactive blue 19 (RB19, 20 mg/L) and ibuprofen (IBP, 10 mg/L) by the electro-Fenton process. The modified GF removed 62.7% of RB19 compared to only 28.1% by the unmodified GF in batch reactors after 50 min. Similarly, 75.3% IBP is removed by the modified GF compared to 57.6% by the unmodified GF in a flow-through reactor after 100 min. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlight • Studies were carried out towards the HANs degradation by UV/peroxymonosulfate process. • Degradation of HANs followed pseudo first-order degradation kinetics. • radOH was the dominant radicals in the CANs degradation rather than SO 4 −rad. • All of the possible pathways of the CANs degradation were proposed. Abstract Haloacetonitriles (HANs), a specie of new emerging halogenated nitrogenous disinfection by-products (N-DBPs) including trichloroacetonitrile (TCAN), dichloroacetonitrile (DCAN), monochloroacetonitrile (MCAN) and dibromoacetonitrile (DBAN), were more cytotoxic and genotoxic than the conventional DBPs. In this study, kinetics and mechanisms in the oxidization of HANs by UV/peroxymonosulfate (PMS) process were investigated. The degradation of chloroacetonitriles (CANs) in UV/PMS process was more remarkable than UV alone, PMS alone and UV/H 2 O 2 process. And the order of the rates of degradation of HANs was followed: TCAN > DCAN > MCAN, while DBAN was remarkably degraded by UV alone. The degradation of DCAN was accelerated by humic acid and Cl−, while suppressed by bicarbonate. Scavenging experiments showed that hydroxyl radical (radOH) was the predominant species in the reaction. According to the gas chromatography/mass spectrometer (GC/MS) analysis, the breakage of C Cl bond was the dominant pathways in degradation of CANs. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The oxidation capabilities of CaO 2 /Fe(II) and CaO 2 /Fe(III) systems were compared. • Fe(II)/Fe(III), H 2 O 2 , HO, and intermediate products are evaluated in both systems. • An optimal implementation strategy for the CaO 2 application was proposed. • The strategy derived from benzene degradation works for TCE degradation. Abstract This study conducted a comparison of the CaO 2 -based Fenton (CaO 2 /Fe(II)) and Fenton-like (CaO 2 /Fe(III)) systems on their benzene degradation performance. The H 2 O 2 , Fe(II), Fe(III), and HO variations were investigated during the benzene degradation. Although benzene has been totally removed in the two systems, the variation patterns of the investigated parameters were different, leading to different benzene degradation patterns. In terms of the Fe(II)/Fe(III) conversion, the CaO 2 /Fe(II) and CaO 2 /Fe(III) systems were actually inseparable and had the inherent mechanism relationships. For the CaO 2 /Fe(III) system, the initial Fe(III) must be converted to Fe(II), and then the consequent Fenton reaction could be later developed with the regenerated Fe(II). Moreover, some benzene degradation intermediates could have the ability to facilitate the transformation of the Fe(III) to Fe(II) without the classic H 2 O 2 -associated propagation reactions. By varying the Fe(II) dosing method, an effective degradation strategy has been developed to take advantage of the two CaO 2 -based oxidation systems. The proposed strategy was further successfully tested in TCE degradation, therefore extending the potential for the application of this technique. [ABSTRACT FROM AUTHOR]

[Display omitted] • Straw return inhibits the OH and CO 2 production in abiotic processes. • Straw return results in more active Fe(II) species with lower OH production. • Straw return increases the O 2 reduction through a two-electron transfer pathway. • OH oxidizes organic matter through ring-opening and hydroxylation mechanisms. The generation of hydroxyl radicals (OH) mediated by Fe(II) has drawn increasing amounts of attention due to its significant role in the transformation of soil organic carbon (SOM) during redox fluctuations in paddy soil. This study further examined the effect of long-term (since 1984) straw return on Fe(II) on driving OH formation and SOM transformation upon paddy soils oxygenation. We found that long-term straw return could inhibit the OH and CO 2 production in abiotic processes. The OH production decreased from 190.4 to 133.4 µM as the straw return amount increased from 0 to 19.16 t·hm−2·year−1. Moreover, 14.7–38.6 % of the CO 2 production was associated with OH during oxygenation. By combining radical quenching and OM extraction, we determined that straw return could increase O 2 reduction to H 2 O 2 through a two-electron transfer pathway. Based on chemical extraction, Mössbauer spectra and multilinear regression model, we demonstrated that straw return resulted in more active Fe(II) species that controls the OH production. The results of 3DEEMs and FT-ICR MS showed that oxidative transformation can be accomplished by the introduction of OH to aromatic structures or olefins through ring opening and hydroxylation mechanisms. And OM at high straw return concentrations was likely oxidized by OH into bioavailable aliphatic compounds. Therefore, this study highlights the underappreciating effects of long-term straw return on Fe(II) oxidation in driving OH generation and SOM transformation in paddy soil redox fluctuation events. [ABSTRACT FROM AUTHOR]

• Coumarin as probe for data on specific cavitational activity across scale and pressure conditions. • Vortex-diode (d t = 6 and 12-mm) exhibits maximum cavitational activity at 100 kPag inlet pressure. • Data quantified with respect to newly defined parameter – characteristic number of passes (n*) • Data across different scale with respect to n* indicates similar performance at similar n* values. The present work investigates the hydrodynamic cavitation (HC) performance of vortex-diode based devices, which show early inception and superior cavitational performance compared to conventional devices. The study provides novel data on the cavitational efficiency at different operating pressures for two sizes of cavitation devices, addressing a gap in the literature. Using coumarin as a chemical dosimeter in acidic conditions, the study tracked the formation of 7-hydroxycoumarin (7OHC), a hydroxylation product of coumarin, to evaluate cavitational performance. Optimization of solution pH and initial concentration led to selecting pH 3 and a 15 ppm concentration for subsequent experiments with two vortex-diode devices of 12 mm (D 12) and 6 mm (D 6) diameters. These devices were tested under various pressure conditions. The formation of 7OHC was analyzed in relation to process time, number of passes, and a characteristic number of passes (n*) – which correlates device dimensions with operating velocity. The results indicated that the D 6 device outperformed the D 12 in terms of efficiency at inlet pressures ranging from 100 to 400 kPag. Analysis of 7OHC formation trends with respect to n* revealed that while there were variations within different pressures for a given device, the performance was comparable across different scales. By keeping a constant n* across varying pressures (P 1 = 100 to 400 kPag and P 2 = 0 to 300 kPag), the study observed comparable 7OHC formation across different operating conditions and scales. This data is vital for selecting suitable scales and conditions for HC devices and for validating multi-scale models in this field. [ABSTRACT FROM AUTHOR]

[Display omitted] • • A cobalt single-atom (Co 1) electrocatalyst was fabricated to boost •OH production. • • Co 1 was stably anchored on N-doped carbon black to avoid nanoparticle formation. • • •OH generation by Co 1 electrodes was evaluated by electron paramagnetic resonance. • • Cathodic •OH production during electro-oxidation enhanced decontamination. • • Co 1 anode/cathode couple shows high •OH production and synergistic water treatment. Electro-generated hydroxyl radicals (•OH) are of fundamental importance in electrochemical advanced oxidation processes (EAOPs). Herein, a cobalt single-atom (Co 1) dispersed on N-doped carbon black (NCB) was synthesized and used for the first time as a multifunctional electrocatalyst on both the anode and cathode to boost the generation of •OH. Specifically, the Co 1 –NCB anode electrochemically generates •OH through water oxidation reaction (WOR), whereas the Co 1 –NCB cathode generates hydrogen peroxide (H 2 O 2) through oxygen reduction reaction (ORR), followed by its subsequent electrochemical/catalytic activation by Co 1 –NCB, which synergistically promotes the formation of •OH. In an electrochemical system with the optimized coordination structure and operating conditions, the Co 1 –NCB electrode-based EAOP exhibited high phenol-removal efficiency (>95%) over a wide pH range (pH = 3–9). This study provides a new strategy for maximizing radical production and suggests its application in the electrochemical oxidation of recalcitrant organic pollutants. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The in-situ cogeneration effects of OH and H 2 O 2 is examined for the first time using Sb-SnO 2 (SS) and CNT electrocatalysts. • An increase in the potential of SS enhances the OH generation yet decreases the current efficiency (CE) of OH (max. 30%). • The CE of H 2 O 2 with CNT is high at a less negative potential, reaching ∼80% with O 2 purging. • The SS/CNT pair exhibits similar OH generation kinetics and yet significantly enhanced H 2 O 2 generation kinetics. • The simultaneous evolution of O 2 microbubbles leads to a synergistic effect through the production of H 2 O 2. Abstract This study examines the co-generation effect of hydroxyl radicals (OH) via water oxidation and H 2 O 2 via O 2 reduction in electrocatalytic processes with Sb-doped SnO 2 (SS) anode and carbon nanotube (CNT) cathode pairs facing each other as a function of applied SS/CNT cell voltage and purging gas (O 2 vs. N 2). Prior to coupling the electrodes, both electrodes are examined for the generation kinetics and current efficiency of reactive oxygen species as well as the decomposition kinetics and total organic carbon (TOC) removal of phenol, as a function of applied half-potential (E SS or E CNT) and the purging gas. Regardless of the purging gas, a stepwise increase in E SS enhances the OH generation and phenol decomposition, yet inversely decreases the current efficiency of OH (max. ∼30%), owing to competitive O 2 evolution. Similar to this, the current efficiency of H 2 O 2 is high at a less negative E CNT , reaching ∼80% with O 2 purging. However, phenol decomposition with CNT is trivial, owing to the limited reactivity between H 2 O 2 and phenol. With N 2 purging, H 2 O 2 is not produced nor is phenol decomposed. Compared to the sum of the performance of the two half-electrodes, the SS/CNT pair exhibits similar OH generation kinetics regardless of the purging gas, yet significantly enhanced H 2 O 2 generation kinetics. The phenol decomposition and TOC removal with the pair are more than double their sums of the two half-electrodes at all E cell s with O 2 purging, whereas such a synergistic effect is found only at high E cell s when N 2 is purged. The simultaneous evolution of O 2 microbubbles appears to create an in situ oxic environment between the SS and CNT, leading to a synergistic effect through the production of H 2 O 2 , even under anoxic and anoxic-like conditions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Incorporation of F into carbon was beneficial to enhanced electro-Fenton activity. • F-doped porous carbon was fabricated by using waste biomass as precursor. • F-doped porous carbon could efficient decay of organic pollutants. • F-doped porous carbon was capable of treating real secondary effluent of refinery. Abstract Electro-Fenton is an efficient approach to degrade refractory organic pollutants in which electro-generated H 2 O 2 are catalyzed by Fe2+ to produce highly reactive hydroxyl radicals (OH). The properties of H 2 O 2 formation and recovery of Fe2+ are critical factors in electro-Fenton process, which is related to the electronic structure of catalysts. In this work, the electronic structure of carbon was controlled by incorporation of fluorine (F), which facilitated H 2 O 2 generation and accelerated the recycle of Fe2+ from Fe3+, thus enhancing electro-Fenton activity. The resultant F-doped porous carbon exhibited high H 2 O 2 production rate of 22.4–64.5 mmol L−1 at −0.2 to −0.6 V. The kinetic constant of atrazine degradation achieved 0.10–0.31 min−1 at potential of −0.2 to −0.6 V. The real secondary effluent of refinery (COD of 92 mg L−1) was successfully treated to meet the National Standard for the Wastewater Discharge of China (COD < 50 mg L−1) with a low specific energy consumption of 6.38 kW h kg−1 COD−1. This work provides a new insight into design of highly efficient and low-cost catalysts for electro-Fenton treatment of real wastewater. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Electrooxidation of volatile organic compounds were performed in all-solid cell. • Benzene toluene and o-xylene (BTX) were 100% conversion to CO 2 and CO (CO 2 yield >85%). • No gaseous organic byproducts were present in the electro-oxidation of BTX (P cell ≥ 2.0 V). • Benzene oxidation process was mediated by OH generated from water vapor discharge at P cell = 2.0 V. • Electrooxidation of BTX in all-solid cell is a promising method for applications in indoor air purification. Abstract The catalytic elimination of indoor low-concentration gaseous benzene, toluene and o-xylene (BTX) under ambient conditions remains a challenge. Here, we firstly report a facile gas-solid interface electrochemical oxidation method for the mineralization of BTX at ambient temperature. A membrane electrode assembly (MEA) was used in the all-solid cell. An antimony-doped SnO 2 catalyst was coated onto the surface of a porous Ti foam to act as the anode, and reduced graphene oxide/carbon fiber paper-supported Pt (Pt/rGO/CFP) was employed as the cathode. The activity test results showed that 100% BTX conversion to CO 2 (85–99%) and CO (15–1%) was achieved within 4–5 h at the optimal cell voltage of 2.0 V at relative humidity 60%. Proton-transfer-reaction time-of-flight mass spectrometry and Fourier transform infrared spectroscopy results showed that no organic byproducts could be detected in the anodic reservoir. OH generated from water vapor discharge was measured directly by laser-induced fluorescence techniques. The electrochemical behavior of the working electrode in benzene solutions with different concentrations revealed that the benzene oxidation process was mainly mediated by OH at the onset potential of OER (2.0 V vs Ag/AgCl, saturated KCl). Our findings provide evidence that the gas-solid interface electrochemical oxidation method can be a potential method for ambient VOC destruction in indoor air environments. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Catalytic ozonation of atrazine on tourmaline was studied. • Tourmaline exhibited superior catalytic performance even in low temperature (278 K). • Surface properties of tourmaline was characterized in detail. • 31 kinds of intermediates were identified and the degradation pathways of atrazine were proposed. Abstract Tourmaline, an economical and eco-friendly natural mineral, has been widely used during the water treatment processes. In this investigation, the raw tourmaline has been found to be effective as a catalyst for ozonation in the degradation of atrazine (ATZ) under low temperature (278 K). Within typical experimental conditions (tourmaline dosage = 1 g L−1, [ATZ] 0 = 5 μM, [O 3 ] 0 = 3 mg L−1, at pH 7.0 and 278 K), the removal efficiency of ATZ in catalytic ozonation was 98% after 10 min, compared with only 27% ATZ removal in the absence of catalyst. Surface properties and components of tourmaline were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), pyridine-FTIR and energy dispersive X-ray (EDX). The characterization studies showed that metal attached hydroxyl groups (M OH, M = Fe, Al and Si) were the main active sites for ozone adsorption and decomposition. The formation of hydroxyl radicals (OH) as well as hydrogen peroxide (H 2 O 2) led to fast ATZ degradation and 31 kinds of intermediates; meanwhile, possible degradation pathways of ATZ were detected and proposed. The mechanisms of reaction were proposed for tourmaline-catalyzed ozonation based on all the experimental results and material characterizations. [ABSTRACT FROM AUTHOR]

Four sulfonamides, viz. sulfadiazine (SD), sulfamerazine (SM), sulfadimethoxine (SDM) and sulfachloropyridazine (SCP), were selected as model compounds to be degraded in Fe 2+ /S 2 O 8 2− system with a Fe 2+ :S 2 O 8 2− molar ratio of 1:4. The results of degradation kinetics indicate that the rate constants follows the order of SD > SM > SDM > SCP, and the aromatic and heteroaromatic rings of the sulfonamides are relatively low in reaction activity. Both hydroxyl radicals ( OH) and sulfate radicals ( SO 4 − ) are responsible for the degradation of sulfonamides, with the latter playing a more significant role. The theoretical results suggest that OH are majorly involved in the H-abstraction and addition reactions of the sulfonamides. Nonetheless there is single-electron transfer between the SO 4 − and sulfonamides, which results in oxidation of –NH 2 group and Smiles rearrangement. Based on the experimental and theoretical results, the degradation intermediates and degradation pathways are verified. At the initial stage of degradation, there is cleavage of S-N bond, hydroxylation of parent compounds, Smiles rearrangements and oxidation of –NH 2 . It is found that the incomplete mineralization of sulfonamides results in increase of acute toxicity. The study sheds light on the fate and transformation of sulfonamides under the attack of reactive oxygen species in environmental water. [ABSTRACT FROM AUTHOR]

Electro-peroxone process utilizes the in-situ generated H 2 O 2 by electro-reduction of O 2 to react with ozone molecule to produce hydroxyl radical, and achieves high efficiency in the wastewater treatment. However, detailed reaction mechanism in this process is still deficient. In this paper, a three-electrode system was adopted in the electro-peroxone process, and the origin of the synergy was revealed with the aid of the rotating ring disk electrodes. It was found that besides the main reaction between O 3 and H 2 O 2 , O 3 is also electro-reduced to O 3 − and then transformed into OH. Meanwhile, O 3 electro-reduction on the cathode can also possibly generate O 2 and promote H 2 O 2 production. Higher concentration of OH − near the cathode originated from O 2 and O 3 reduction may also react with O 3 to produce H 2 O 2 . These two pathways contributed to the higher amount of H 2 O 2 than the system with O 2 bubbling only, and ultimately contributed to produce more OH. All these reactions are synthetically responsible for the higher degradation rate of sodium oxalate in the electro-peroxone process than those in O 3 -electrolysis and ozonation processes, respectively. Though this system was quite different from normal electro-peroxone process, the conclusions are useful for understanding the practical reactions possibly happened on electrodes in the electro-peoxone process. [ABSTRACT FROM AUTHOR]

The controlled generation of radicals is an effective way to improve the stoichiometric efficiency of oxidants, particularly when treating highly recalcitrant contaminants. In this study, an innovative oxidation system was used to degrade extremely recalcitrant 1,4-dioxane. This system was based on a combination of pyrite, an abundant mineral used as a slow-release source of iron, and peroxymonosulfate (PMS). In addition, other oxidants, including hydrogen peroxide and peroxydisulfate, and their conditions were examined. PMS had the highest degradation performance of the oxidants tested. Near-100% degradation of 1,4-dioxane (50 mg L −1 ) was achieved after 40 min using PMS; the corresponding degradation rates with peroxydisulfate and hydrogen peroxide were around 50% and 15%, respectively. The production of hydroxyl radicals and sulfate radicals by pyrite-activated PMS was confirmed by electron paramagnetic resonance. Neither solid pyrite nor dissolved Fe 2+ or Fe 3+ was directly involved in the degradation. Instead, the Fe 2+ generated from pyrite oxidation activated PMS homogeneously. Quenching tests and the rapid degradation of nitrobenzene show that hydroxyl radicals were the major active species produced by pyrite-PMS. In contrast to the significant scavenging effect of Cl − (3.0 mM) on Co 2+ -PMS, no significant Cl − (≤10 mM) scavenging was observed on pyrite-PMS. These results suggest that the use of pyrite-PMS mitigates the scavenging effects of Fe 2+ and Cl − , and, therefore, may increase the application of iron-based materials and PMS in the water treatment industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mechanism analysis of radical reaction at aromatic ring and side chain of phthalates. • Determination of carbon isotope fractionation factors for H abstraction (HAT) and radical adducts formation (RAF) • Probing radical reactions with phthalates used as plasticizer. • Inverse isotope fractionation characterizes preferential C-H bond cleavage at tertiary carbon. Compound specific isotope analysis (CSIA) has been used to explore the degradation pathways of di-(2-ethylhexyl)-phthalate (DEHP) in photosensitization experiments with H 2 O 2 , TiO 2 , Fe(III) and PMS. The reaction kinetics could be described by first order rate constants [k (h−1)]. The highest degradation rates of DEHP were observed in UV/TiO 2 catalyzed reactions. Carbon isotope fractionation factors (ε C) and metabolite patterns were examined to analyze the radical reaction. Similar carbon isotope fractionation factors have been found in experiments dominated by OH radical reactions (UV/H 2 O 2 , −1.2 ± 0.3‰; UV/TiO 2 , −1.2 ± 0.5‰). An inverse carbon isotope fractionation has been found for UV/Fe(III) (0.8 ± 0.2‰) and SO 4 − (0.6 ± 0.2‰ at pH 3) catalyzed reactions indicating that these reactions preferentially taking place at the H atom bond at tert -butyl carbon of the side chain. This hypothesis is further supported by an experiment with isobutyl acetate (ε C = 1.8 ± 0.2‰ for UV/Fe(III) at pH 7; ε C = -1.1 ± 0.2‰ for UV/PMS at pH 6 and ε C = 0.9 ± 0.3‰ for UV/PMS at pH 3). Quenching experiments in the UV/PMS catalyzed reaction indicated a coexistence of SO 4 − and OH at pH 7. SO 4 − was the predominant radical at pH 3. OH was found to be the predominant radical in UV/H 2 O 2 and UV/TiO 2 reactions. CSIA indicated that the addition of OH to the aromatic ring of DEHP by the RAF pathway is the main reaction mechanism in UV/H 2 O 2 and UV/TiO 2 experiments. The SO 4 − attacks preferentially the C-H bond at the tert -butyl carbon position of the side chain of DEHP which causes an inverse carbon isotope effect. Thus, carbon isotope enrichment factors can be used to distinguish different radical reaction mechanisms with DEHP as a substrate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electronic structure of Fe-Cl-C catalytic sites was tuned to enhance EF reaction. • Fe-Cl 2 C 2 and Fe-Cl 2 C 3 configurations were constructed with Fe2+ and Fe3+ states. • Reactions from O 2 to •OH were verified via 3-electron pathway by two configurations. • FeCl 2 C x /PC showed efficient antibiotics removal from water and structure stability. • •OH as a major ROS contributed on AMX decaying by opening β -lactam ring. Designing heterogeneous catalysts with atomically dispersed active sites is vital to promote electro-Fenton (EF) activity, but how to regulate the electronic structure of metal centers to overcome the rate-limiting step over electron transfer triggered by reduction-/oxidation-state cycle in Fenton still remains a great challenge. Herein, we report a systematic investigation into heteroatom-doped engineering for tuning the electronic structure of iron single-atom sites by integrating electron-acceptor chlorine atoms into MOF-derived carbon substrate, in which the conversion of O 2 toward •OH in EF were enhanced over the electronic structures of Fe-Cl 2 C 2 and Fe-Cl 2 C 3 formed by iron unsaturated coordination with chlorine and carbon atoms via a 3-electron pathway, and overcame the restriction of the rate-limiting step for reducing oxidized metal ions. The resulting accumulative concentration of •OH by FeCl 2 C x /PC surpassed that of iron oxide nanoparticles by almost 2 times. Iron site shielding experiments and density functional theory calculations further demonstrated that the vital effect of Fe-Cl 2 C 3 configuration corresponds to Fe(III) on Fe center contributes to H 2 O 2 production and the dominant role of Fe-Cl 2 C 2 configuration corresponds to Fe(II) in H 2 O 2 activation to form •OH. Meanwhile, FeCl 2 C x /PC exhibited less pH dependence, high stability, and efficient applicability for various antibiotics and wastewater remediation. The above results provide a new perspective into the reaction mechanism of multi-electron oxygen reduction pathway on single-atom catalysts by modulating the electronic structure of chlorine coordination. [ABSTRACT FROM AUTHOR]

The effect of Fe 2+ was evaluated on degradation of cloxacillin (CLX) in the VUV photoreactor and the effect of reaction parameters were optimized for maximum efficiency. The rate of CLX degradation in the VUV photoreactor considerably improved at the presence of a low concentration of Fe 2+ . The reaction with O ̇ H generated from water homolysis and photooxidation of water molecules by VUV photons as well as from photoFenton reaction was the main mechanism of CLX degradation in the VUV/Fe 2+ process. The maximum CLX degradation observed at the acidic solution pH. Over 80% of 50 mg/L CLX was mineralized in the VUV/Fe 2+ process within 60 min under optimum conditions. Over 99% of 50 mg/L CLX was degraded at a hydraulic retention time of 5 min in the continuous flow VUV/Fe 2+ process. Intermediates formed during the degradation was analyzed by LC-MS technique, and the results indicated that C–N, C–S and C–Cl bonds were completely decomposed and the simple aliphatic substances were the main organic by-products of CLX degradation. In addition, VUV/Fe 2+ process was more energy-effective than the VUV process. Accordingly, VUV/Fe 2+ process is a technically efficient and energy-effective for high rate degradation and mineralization of such emerging water contaminants as antibiotics. [ABSTRACT FROM AUTHOR]

The development of efficient, cost-effective, and metal-free activators for the activation of oxidants is important to promote the application of advanced oxidation processes (AOPs) in the wastewater treatment industry. In this study, we propose an innovative AOP that uses a combination of peroxymonosulfate (PMS) and hydroxylamine (HA). The second-order rate constant for this reaction was determined to be 0.34 ± 0.02 M −1 s −1 . Target pollutants, including bisphenol A, phenol, and atrazine, were efficiently degraded by this oxidation, and approximately 100% degradation of the phenol was realized after 6 min. The optimal concentration ratio between HA and PMS was approximately 2.0. Electron paramagnetic resonance confirmed the production of radicals; quenching tests using alcohols, phenol, and nitrobenzene further revealed that sulfate radicals were the dominant species. The unprotonated HA was probably responsible for the activation of PMS. However, because of its reaction with sulfate radicals, the optimal pH of HA-PMS was in the range of 4.0–5.0. Common aqueous constituents such as chloride ions (≤10 mM) and bicarbonate (≤5 mM) had no obvious effects on the HA-PMS, which suggests the important implications of this oxidation. [ABSTRACT FROM AUTHOR]

A comprehensive study on the sonochemical degradation of chlorophene, an emerging pollutant, was performed. The influence of enhancement aids as H -scavenger, different iron forms and supplementary H 2 O 2 was assessed. The addition of tetrachloromethane (CCl 4 ) improved substantially sonochemical degradation of chlorophene due to H -scavenging effect within the cavitation bubble, where CCl 4 interrupted undesirable recombination of H with HO . The resultant increase of HO production was confirmed by an indirect measurement of HO using deoxyribose method. The addition of mere Fe(II) aimed to utilize H 2 O 2 formed in interfacial region of cavitation bubble did not influence the chlorophene degradation efficiency; however, the mineralization was substantially improved. The supplement of Fe(II) and H 2 O 2 (Classical Fenton) to sonolysis showed the highest oxidation and mineralization efficiency. The combination of sonolysis with the ferric oxyhydroxide-mediated Fenton process allowed achieving 25% higher mineralization in 120 min and resulted in faster degradation of chlorophene than that in mere sonolysis. That creates a presumption for the following applicability of the Fenton process residue (ferric sludge) in the enhancement of sonolytic processes. The mechanism of chlorophene degradation by ultrasound involved the sequence of aromatic ring opening reactions, which resulted in formation of carboxylic acids with their following decarboxylation. The studied enhancement aids allowed reducing treatment time and as a result, an energy consumption, which is of a high importance in case of water treatment installations based on sonolysis. The integration of such engineering solutions with conventional sewage treatment plants may serve for the improved degradation of bioresistant contaminants, such as chlorophene. [ABSTRACT FROM AUTHOR]

Iodoform (CHI 3 ) is an emerging disinfection by-product (DBP) that may be formed during pre-oxidation or disinfection processes in drinking water treatment. Degradation kinetics, modeling and mechanism of CHI 3 by combined UV/chlorine advanced oxidation processes (AOPs) were studied in this manuscript. CHI 3 was effectively removed by UV/chlorine process with the reactions followed pseudo-first order kinetics. The contributions of direct UV photolysis as well as indirect photolysis (hydroxyl radicals ( OH ) to CHI 3 degradation during UV/chlorination under different experimental factors were investigated and determined as 20.3% and 79.7% at pH 5 to 97.1% and 2.9% at pH 9, respectively. Chlorine dosage and CHI 3 concentration had slight effects on the contributions of different degradation pathways. NOM and bicarbonate have negative effects on CHI 3 degradation. The degradation model of CHI 3 during UV/chlorine processes was established, and the satisfactory match of the model calculation results and the experimental data were found. The reaction rate constant between CHI 3 and UV light as well as CHI 3 and OH were determined as 3.43 × 10 −3 s −1 and 7.7 × 10 9 M −1 s −1 , respectively. On the basis of the iodine species (such as IO 3 − , HOI, I 2 and I 3 − ) mass balance analysis, the degradation pathways of CHI 3 were proposed and IO 3 − contributed 13.7% of the total liberated iodine species during UV/chlorination. These results demonstrated that UV/chlorination process is a promising AOP technology for the treatment of water containing CHI 3 . [ABSTRACT FROM AUTHOR]

Ultraviolet (UV)-assisted peroxymonosulfate (PMS), persulfate (PS), and hydrogen peroxide (H 2 O 2 ) advanced oxidation processes (AOPs) were investigated by comparing the degradation efficiency for sulfamethoxazole (SMX) on a bench scale. A medium pressure (MP) mercury UV lamp housed in a collimated beam apparatus was used. The effect of operational parameters (initial SMX concentrations, oxidant dosage, solution pH, and common coexisting inorganic anions) on UV/PMS, UV/PS, and UV/H 2 O 2 treatment efficiency on SMX degradation was also examined. It was observed that the direct MPUV photolysis could efficiently remove SMX with the calculated quantum yield 0.176 of SMX photodegradation, moreover, the combination of oxidants especially PMS with UV radiation obviously accelerated the degradation process. The rate of SMX degradation during the three UV-based systems was observed in the following order: UV/PMS > UV/PS > UV/H 2 O 2 . The SMX degradation efficiency decreased with the initially elevated SMX concentrations and increased proportionally to the oxidant dosage. The maximum SMX degradation occurred at pH 11, 5, 3 in UV/PMS, UV/H 2 O 2 and UV/PS system, respectively. It was found that only PMS could be activated by some inorganic anions as compared to PS and H 2 O 2 . Adding Cl − and CO 3 2− into UV/PMS process can differentially raise the degradation rate. SO 4 2− showed no significant effect on UV/PMS and UV/H 2 O 2 system, while the degradation efficiency was improved at a low SO 4 2− concentration in the UV/H 2 O 2 system. The presence of NO 3− could improve the SMX degradation in the three UV-based AOPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Non-thermal plasma used to PS activation for organic pollutants degradation was reviewed. • Factors influencing the degradation of organic compounds by plasma/PS were elaborated. • Plasma-combination for enhanced persulfate activation was summarized. • The mechanism of organic compounds degradation by plasma/PS were cleared. • The conclusion and future prospect of plasma/PS were put forward. Organic pollutants in water bring serious harm to human health and ecological environment. As one of the advanced oxidation technologies, non-thermal plasma technology has attracted extensive research and attention because it can quickly and efficiently treat refractory organic pollutants in the water environment. However, low energy utilization has been the bottleneck of the development of this technology. Plasma coupling catalysis has become the main way to solve this problem. Traditional plasma-catalysis technology was used to produce more OH, but it has an extremely short half-time (2 × 10−8 s) and unable to completely oxidize organic pollutants. Compared to OH, SO 4 − has a longer half-time (3–4 × 10−5 s), which has sufficient reaction time with pollutants. The physical and chemical properties such as ultraviolet light, electrons and free radicals in plasma can be used to activate persulfate for producing double oxidized free radicals (SO 4 − and OH), thus improving the energy utilization efficiency of plasma and removal efficiency of organic pollutants. Hence, this review aims to summarize the development of non-thermal plasma for persulfate activation regards to organic pollutants degradation. Factors influencing pollutants degradation by plasma/persulfate were elaborated in detail. Effect of additives and microbubbles on activation of PS by plasma was summarized. The catalytic effect of persulfate and other additives in plasma system was compared. The mechanism, pathway and toxicity variation of organic compounds degradation by plasma/persulfate were cleared. The in-depth evaluation index includes energy efficiency, TOC, COD and persulfate utilization were recounted. Finally, the conclusion and future prospects were put forward. Although the study of plasma activated persulfate has been very extensive, its mechanism has not been thoroughly studied. For example, the specific activation of persulfate by plasma has not been reported, and the specific dominant pathway of the generated free radicals on pollutants is still unclear. In addition, the impact of sulfate ions generated by activating persulfate on subsequent tail water has always been a problem that needs to be addressed. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D-rGO@nZVI/MnO 2 was fabricated to trigger DO activation. • Complete removal of OTC and 84% TOC removal achieved at natural pH. • Degradation of OTC was caused by the synergism of •OH and 1O 2. • Converting DO into 1O 2 by the redox cycle of Mn(IV)/Mn(III) was explored. This work is dedicated to achieving the high mineralization efficiency of oxytetracycline (OTC) in a dissolved oxygen (DO) activated Fenton-like system by constructing a catalyst with unique catalytic performance. Three-dimensional graphene anchored nZVI hybrid MnO 2 (3D-rGO@nZVI/MnO 2) with layered and porous structures was synthesized and characterized by field emission scanning electron microscopy coupled with an energy dispersive spectrometer (SEM-EDS), Brunner-Emmet-Teller (BET) analysis, X-ray diffraction (XRD) measurement and Raman spectroscopy. The experimental results showed that the removal efficiency of OTC could reach 100.0% with outstanding TOC decrease of 84.0% at natural pH in the 3D-rGO@nZVI/MnO 2 -DO system. Moreover, negligible harmful intermediates were detected by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) after the reaction in the 3D-rGO@nZVI/MnO 2 -DO system. Reactive oxygen species (ROSs) detection, electrochemical measurements and X-ray photoelectron spectroscopy (XPS) analysis confirmed that the elimination mechanism of OTC was the unique catalytic degradation caused by the synergism of •OH and 1O 2. The unprecedented synchronous generation of •OH and 1O 2 by DO activation provides an innovative strategy for further exploration of Fenton-like system toward more effective degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

Endocrine disrupting compounds (EDCs) are a group of hazardous pollutants, generally present in water environments in very low concentrations and causing adverse effects in living organisms. This paper examines the photochemical decomposition of EDCs, including direct photolysis, advanced oxidation processes (AOPs) and photosensitized oxidation (POx). Particular attention was focused on photocatalytic and photosensitized degradation processes. The most important portions of the report concern the photodegradation of six groups of EDCs: natural hormones and steroids, alkylphenols and bisphenol A, polycyclic aromatic hydrocarbon, preservatives, pesticides and phthalates. Two new trends in photocatalytic degradation are the immobilization and modification of photocatalysts, which result in eliminating the problem of removing the photocatalyst slurry from purified water and improving the ability to activate photocatalyst in the visible radiation. Photochemical oxidation, particularly using molecular oxygen, is unquestionably one of the most important photochemical methods because photochemical oxidation does not require additional oxidizers such as ozone or hydrogen peroxide or any additional energy input as are required in cases of ozonation or UV irradiation. The primary reactant formed during photosensitized oxidation is exceptionally reactive species – molecular singlet oxygen. Although AOPs are effective in removing EDCs from aqueous solutions, the costs of these processes are high; therefore, an interesting option among the photochemical processes appears to be immobilization of the photocatalyst or photosensitizer and using these processes in visible light. [ABSTRACT FROM AUTHOR]

Biologically treated cephalosporin pharmaceutical wastewater is a complex industrial wastewater that is toxic and refractory for further biological treatment. For this purpose, a novel sonoelectrochemical catalytic oxidation-driven process using a nanocoated electrode has been developed to treat such wastewater. In the process, the synergy and mechanism of the sonoelectrochemistry using ultrasound enhancement of the nanocoated electrode activity to treat the wastewater was studied. The nanocoated electrode generated more radicals than the traditional coated electrode did; in the presence of ultrasonic waves, the mass-transfer effects on the nanocoated electrode surface were enhanced, resulting in rapid diffusion of the generated hydroxyl radicals into the solution, and quickly reacted with organic pollutants. Compared with the traditional coated electrode, the effect of the nanocoated electrode used on the wastewater treatment process was more enhanced by ultrasound under the same conditions. The biotoxicity of the wastewater in the sonoelectrochemical catalytic oxidation process was monitored and shown as having first increased and then decreased. The optimum operating conditions resulted in a 94% removal efficiency for COD and consisted of a current of density 8 mA/cm 2 and an ultrasound frequency of 45 kHz. All of the results showed that the sonoelectrochemical catalytic oxidation-driven process was found to be a very efficient method for the treatment of non-biodegradable cephalosporin pharmaceutical wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • RRDE was established as an online method to evaluate electrocatalyst performance. • Electrocatalysts active H 2 O 2 to produce •OH and subsequently generate O 2 •−. • Anodic currents on ring electrode due to O 2 •− oxidation were measured. • The RRDE method is verified by terephthalic acid fluorescence detection. One-electron electrochemical reduction of hydrogen peroxide (H 2 O 2) is an effective way to produce hydroxyl radical (•OH), whose yield is greatly dependent on the performance (activity and selectivity) of electrocatalysts. However, the current method to evaluate the performance of electrocatalysts is limited by time-consuming and less sensitive method of •OH detection. Herein, we propose an online rotating ring disk electrode (RRDE) method to evaluate the performance of electrocatalysts in H 2 O 2 activation by rapidly detecting •OH. This method is implemented by determining the current signals on the disk and ring electrodes: the generated •OH from H 2 O 2 reduction on the disk electrode (induce negative disk currents) reacts with H 2 O 2 to produce superoxide radical (O 2 •−), which migrates to and is oxidized on the ring electrode and generates positive ring currents. The relevance of the ring currents to O 2 •− and •OH is proved by radical quenching tests and kinetic analysis. The performance of five electrocatalysts were evaluated by both the RRDE method and the terephthalic acid (TPA) fluorescence method, and the consistent results verify the applicability of the RRDE method. Hence, this work facilitates the development of high-performance electrocatalysts for H 2 O 2 activation and bring insights for RRDE-based electroanalytic chemistry. [ABSTRACT FROM AUTHOR]

[Display omitted] • NO 2 contributes 42.3 % and 69.2 % to aniline transformation in the SO 4 •− and HO• systems, respectively. • Transient intermediates of SO 4 •−, HO• and •NO 2 reacting with aniline are all anilino radicals. • The combination of •NO 2 with anilino radicals results in significant formation of nitroanilines. • Both SO 4 •− and HO• systems with nitrite have high risk in nitrated and coupling product formation from aniline. • Toxicity will increase after the treatment of aniline in nitrite-containing water by SO 4 •− and HO•. Sulfate radicals (SO 4 •−)- and hydroxyl radicals (HO•)-based advanced oxidation processes (AOPs) are efficient for the destruction of contaminants in water treatment, while the ubiquitous presence of nitrite (NO 2 −) in aquatic environments quickly transforms SO 4 •− and HO• to nitrogen dioxide radicals (•NO 2). This study investigated the roles of •NO 2 in the transformation of aniline by SO 4 •− and HO• in the presence of NO 2 −. By laser flash photolysis, aniline radical cations (C 6 H 5 NH 2 •+) were identified to be the primary intermediates by SO 4 •− through electron transfer, while anilino radicals (C 6 H 5 NH•) and HO-adduct radicals were predominant by HO• via hydrogen abstraction and addition, respectively. Also, •NO 2 attacked aniline via electron transfer to form C 6 H 5 NH 2 •+, which contributed 42.3 % and 69.2 % to the overall degradation rates of aniline in the SO 4 •− and HO• systems at the experimental conditions, respectively. C 6 H 5 NH 2 •+ could be reversibly converted to C 6 H 5 NH• with pKa at 7, and HO-adduct radicals could be also quickly transformed to C 6 H 5 NH• via water splitting. Therefore, nitroanilines were comparably generated in the SO 4 •− and HO• systems via the rapid combination of C 6 H 5 NH 2 •+/C 6 H 5 NH• and •NO 2 , which conversion yields from aniline to nitroanilines were 40.0 % and 29.8 % at 20 min, respectively. Additionally, the comparable formation of C 6 H 5 NH 2 •+/C 6 H 5 NH• results in the similar transformation pathways of aniline by SO 4 •− and HO• with the presence of NO 2 −. This study demonstrates the important roles of •NO 2 in the transformation of aniline in SO 4 •−- and HO•-based AOPs with the presence of NO 2 −. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Fe-BiOBr composites with rich surface oxygen vacancies was prepared. • A synergy system of photocatalysis and Fenton degradation was constructed. • This system exhibits excellent remove efficiency for organic pollutants and coking wastewater. • The oxygen vacancies play an important role in promoting synergy degradation performance. Fe-doped three-dimensional flower-like structures BiOBr (Fe-BiOBr) with rich surface oxygen vacancies (OVs) were prepared by a simple microwave method, and the Fe-BiOBr composites completely degraded phenol solution (20 ppm) after 60 min of visible light irradiation in the presence of H 2 O 2. The degradation activity was 12.32 and 1.46 times that of photocatalytic and Fenton reactions, respectively. The catalytic degradation activity was still as high as 90% after five recycles and had good structural stability. Meanwhile, the Fe-BiOBr composites also exhibited good removal efficiency for other phenolics and coking wastewater, and the chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiency of coking wastewater were 63.6% and 53.8%, respectively. Both theoretical calculations and experimental results showed that oxygen vacancies could effectively promote the photocatalytic Fenton synergistic degradation activity, which not only improved the separation efficiency of photogenerated carriers, promoted the transformation of the Fe ion valence state and realized the cycle of the Fenton reaction but also acted as the adsorption and activation site of H 2 O 2 to produce hydroxyl radicals, the most important active species in the synergistic degradation system, which was confirmed by quenching experiments and EPR results. The effects of the Fe doping amount, H 2 O 2 concentration and other factors on the degradation activity were investigated. Based on the results of the experiment and theoretical calculations, the degradation mechanism of the surface oxygen vacancies enhancing the photocatalysis-Fenton degradation activity was proposed. [ABSTRACT FROM AUTHOR]

In this study, the degradation of a widely used non-steroidal anti-inflammatory drug ibuprofen (IBP) by UV/Fe(III)/Oxone was conducted. IBP decomposition by sole-UV, UV/Fe(III), Fe(III)/Oxone and UV/Oxone processes was also carried out to evaluate the isolated effects contributing to IBP degradation. The influence of pH levels, the concentration of Fe(III) and Oxone, and inorganic anions on the performance of UV/Fe(III)/Oxone process was evaluated. SPME (Solid phase microextraction)/GC/MS were used to identify the intermediates for the first time. Nineteen intermediates/byproducts were detected during IBP degradation, among which six escaped from the detection in previous studies. Based on the analysis of intermediates, possible decay pathways of IBP were proposed accordingly. Decarboxylation and hydroxylation were believed to be major reaction mechanisms involved in IBP degradation by UV/Fe(III)/Oxone process. [ABSTRACT FROM AUTHOR]

The addition of a strong reductant, l -ascorbic acid (AA), to Fe 3+ /hydrogen peroxide (H 2 O 2 ) improved alachlor degradation substantially. AA in the form of ascorbate monoanion undergoes a two-step oxidation to yield dehydroascorbic acid through the formation of intermediate semidehydroascorbate and ascorbyl radicals that are responsible for the autocatalytic transformation of Fe 3+ to Fe 2+ . The ability of AA to reduce Fe 3+ to Fe 2+ and propagate the formation of hydroxyl radicals was confirmed by the indirect measuring of hydroxyl radicals. Hydroxyl radicals production and alachlor degradation by H 2 O 2 /AA resulted. Alachlor degradation rate by Fe 3+ /H 2 O 2 /AA was similar to that obtained by Fe 2+ /H 2 O 2 , although a much lower alachlor degradation and mineralization by Fe 3+ /H 2 O 2 was achieved. The kinetics of alachlor removal by Fe 2+ /H 2 O 2 and Fe 3+ /H 2 O 2 /AA were characterized by a rapid decay (0–1 min) because of a higher formation of hydroxyl radicals and then by a slower decay (1–120 min). The determination of a second-order reaction rate constant of hydroxyl radicals with alachlor relied on the competitive reactions of deoxyribose and alachlor with hydroxyl radicals. A rate constant of 6.9 × 10 9 M −1 s −1 (correlation coefficient of 0.997) implies that the reaction rate is close to that of diffusion-controlled reactions in water, and indicates that the hydroxyl radicals play a predominant role during oxidation. Phenylacetamide compounds that were primary by-products of alachlor degradation allowed for the prediction of the general reaction pathway. This study highlights the ability of AA to reduce Fe 3+ making a presumption for non-regenerated ferric oxyhydroxide sludge reuse for activation of H 2 O 2 oxidation in wastewater treatment at acidic pH. [ABSTRACT FROM AUTHOR]

The sonochemical degradation of bisphenol A (BPA) in the presence of sodium persulfate (SPS) was investigated at 20 kHz. Experiments were performed at 110–450 μg/L BPA and 1–100 mg/L SPS concentration and an ultrasound power density between 4 and 60 W/L. The liquid bulk temperature was either kept constant at 30 °C or left uncontrolled and gradually increased up to 80 °C. BPA degradation occurs due to the combined action of hydroxyl radicals generated by the ultrasound and sulfate radicals generated by SPS sonolysis and this was confirmed with experiments with methanol and t-butanol as radical scavengers. Considerable thermal SPS activation can also occur at increased temperatures (60–80 °C) although the enhanced formation of sulfate radicals is compensated by a decrease in sonochemical activity. Kinetics can be approached by a pseudo-first order expression with the apparent rate constant decreasing with increasing BPA concentration; this implies that the actual order is below first. The rate increases with increasing power density and SPS concentration and decreases at alkaline conditions (i.e. pH = 9) and in the presence of inorganic and organic constituents (e.g. bicarbonate, humic acid etc) typically found in environmental matrices. Liquid chromatography time of flight mass spectrometry (LC–TOF–MS) analysis revealed the formation of twelve transformation by-products that accompany BPA sonodegradation in the presence of SPS. Based on their evolution profiles, a reaction mechanism is proposed consisting of two major pathways: (i) hydroxylation that can occur mainly in the aromatic ring through HO , SO 4 − radical attack and to a lesser extent in methyl groups, through hydrogen abstraction by HO radicals, with subsequent O 2 addition, and (ii) scission of the bond between the isopropylidene carbon and the phenyl group. [ABSTRACT FROM AUTHOR]

Multi-carbon volatile organic compounds (VOCs) was oxidized into CO 2 and H 2 O at ambient temperature over a single atom Na-Pt/TiO 2 catalyst. [Display omitted] • Isopropanol degradation was achieved at 35 °C by Na-Pt/TiO 2 catalyst. • Pt-O-Na coordination structures were responsible for the excellent performance. • Hydroxyl radical was proved to be the dominant active specie. • The formation process of hydroxyl radical and degradation processes of isopropanol were revealed by density functional theory. Volatile organic compounds (VOCs) have become the major atmospheric pollutants in many countries. To develop more efficient VOCs catalytic oxidation technologies, in-depth study of degradation mechanism of VOCs is necessary and urgent. Although the catalytic degradation of small-molecule VOCs such as methanol and formaldehyde is relatively well known, the degradation mechanism of multi-carbon VOCs is largely unclear. Here we construct a single atom Pt catalyst supported on Na-doped TiO 2 (Na-Pt/TiO 2) for degrading isopropanol into CO 2 and H 2 O at a temperature as low as 35 °C. We further reveal the promoting effect of Na in the catalyst, the formation process of hydroxyl radicals and, the catalytic degradation mechanism of isopropanol through combination of sophisticated experimental studies and density functional theory (DFT). This work not only devises a new catalyst for the degradation of isopropanol at ambient temperature, but also provides a new insight into the mechanism of catalytic oxidation of multi-carbon VOCs. [ABSTRACT FROM AUTHOR]

Highlights: [•] We investigated the UV/TiO2 process for ballast water treatment. [•] UV/TiO2 treatment had the potential to inhibit plankton regrowth. [•] The advantages of UV/TiO2 at low UV dose (i.e., 75%) were much greater. [•] The concentrations of disinfection by-products formed during UV/TiO2 treatment were very low. [Copyright &y& Elsevier]

[Display omitted] • Cationic radicals can be repaired through single electron transfer reactions. • Reduction rate constants of a cationic radical are related to oxidation potentials. • Nitrogen-center radicals can be repaired through H atom abstraction reactions. • The self-inhibition of N -heterocyclic pollutants was proposed under PS-AOPs. • Adenine inhibits uracil degradation in the adenine-uracil mixture system. Although the inhibitory effect of purines and phenols on the degradation of N -heterocyclic compounds under UV/peroxymonosulfate (PMS) has been reported, the understanding of contaminants' underlying mechanisms and kinetics is still very limited. In this study, five omnipresent nitrogenous bases (adenine, guanine, cytosine, thymine, and uracil) in the aquatic environment were used to study the inhibitory effect of N -heterocyclic compounds under UV/PMS by quantum chemical calculations. We found that HO• and SO 4 •− initiate base degradation with second-order rate constants of (0.11 – 15.6) × 109 M−1 s−1 and (7.25 – 13.5) × 109 M−1 s−1, respectively, and the primary products contain hydroxyl derivatives (HO-P), intermediate radicals (P(-H)•) and cationic radicals (P•+, only for purines). Because of the lower oxidation potentials of HO-P than their parent compounds (P), we first proposed a self-inhibition pathway in which HO-P can revert P(-H)• and P•+ back to P through H atom abstraction and single electron transfer reactions, respectively. A more significant self-inhibition was found in the degradation of uracil than that of adenine under UV/PMS because the former has a higher yield of hydroxylated derivatives. The main hydroxylated product (6-HO-U) of uracil repairs the uracil radical (U(-4H)•) at the reaction rate constants of 1.01 × 109 M−1 s−1. The combined degradation of bases showed that the reduction rate constants of purine cationic radicals have a linear relationship with the oxidation potentials of reductants. In the adenine-uracil mixture system, adenine inhibits uracil degradation by repairing U(-4H)• (2.33 × 105 M−1 s−1). This work revealed the mechanisms and kinetics of self-inhibition and joint-degradation of N -heterocyclic compounds, which is of great significance for understanding the collective removal of contaminants in the real water environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effective desulfurization by acoustic cavitation (AC) lowers environmental pollution. • Application of peracetic acid as source of radical species. • AC forms radical species from acetone and increases mass transfer. • Waste management, green chemistry process for JET / Aviation fuels. • Sustainable development process, with high potential for industrial application. A combination of dual-frequency acoustic cavitation (acoustic cavitation) and UV assisted advanced oxidation processes (AOPs) reaction system was developed for desulfurization of raw naphtha used to produce aviation fuels. Various types of oxidants in hybrid systems including hydrogen peroxide, acetic acid, acetone, air and ozone were compared. At optimum oxidant to sulfur compounds molar ratio (rox) of 5.0, the hybrid process of acoustic cavitation /acetic acid/hydrogen peroxide (acoustic cavitation/peracetic acid) was the most effective treatment process with synergistic index of 7.55 and desulfurization efficiency of 100% (highest reaction rate constant of 0.1337 min-1) for all sulfur compounds present in naphtha within the short reaction time of 30 min. At rox of 0.5 and 1.0, the synergy coefficients of 3.77 and 5.41 corresponding to the desulfurization efficiencies of 93.07 and 95.10% were obtained in 180 min, respectively. Comparatively, at the rox of 5.0, the efficiency of acoustic cavitation combined with hydrogen peroxide alone and acetic acid alone was 63.68 and 47.36%, respectively. Alternative treatment process of acoustic cavitation /UV/acetone/water can be used for the complete desulfurization (100%) of specific sulphur compounds including dibutyl sulfide, di-tert butyl disulfide, 1,4-butanedithiol and benzyl thiol considering the optimum acetone to water ratio of 2:1. All acoustic cavitation-based treatment systems followed the pseudo first order kinetic model. The most expensive process was ozone-aided acoustic cavitation with treatment costs exceeding 100 USD m-3. The peracetic acid-based system was the most economic process with a treatment cost of 15 USD/m3 with electric energy consumption of 100.17 kWh/m3. [ABSTRACT FROM AUTHOR]

Highlights: [•] NSAIDs are among the most widely used drugs. [•] Their occurrence in natural waters has been highlighted. [•] Electrochemical advanced oxidation showed high performance in elimination of NSAIDs. [•] Anodic oxidation with BDD anode exhibited high removal capacity to remove NSAIDs. [•] Electro-Fenton process using BDD/carbon felt cell showed outstanding performances. [Copyright &y& Elsevier]

Abstract: This paper systematically investigated the performance of carbamazepine (CBZ) degradation oxone by UVC (253.7nm) irradiation in the presence of different common oxidants including peroxymonosulfate (PMS), hydrogen peroxide (H2O2) and persulfate (PS). The influence of oxidant dosage, initial CBZ concentrations, solution pH and coexisting inorganic anions was also evaluated. Results revealed that all the CBZ degradation followed the pseudo-first-order kinetics well. The degradation efficiency of the three UV-based processes was in the order of UV/PS>UV/H2O2 >UV/PMS. The rate of CBZ degradation increased as the oxidant dosage increased and decreased as the initial CBZ concentrations increased. The maximum CBZ degradation occurred at pH 11, 3, 5 in UV/PMS, UV/H2O2 and UV/PS system, respectively. Both Cl− and can inhibit the CBZ degradation in UV/H2O2 and UV/PS system. However, adding Cl− and into UV/PMS system can increase CBZ degradation at different degrees. Comprehensively consideration of energy requirements, oxidant costs and affecting factors, UV/PS system was the most efficient and economic process for CBZ degradation and a promising technology for water treatment. [Copyright &y& Elsevier]

Abstract: The study is about pre-treatment of water by O3-based AOPs as O3/UV, O3/ultrasound (O3/US), O3/H2O2, O3/UV/US and O3/US/FeSO4 to remove residuals of anti-inflammatory pharmaceuticals and to propose a simple modification to an existing drinking water treatment plant (WTP) containing a pre-ozonation unit. Experiments were run in ultrapure and raw water (collected from the aeration tank of the WTP) spiked with 30μM Diclofenac-Na (DCF)-the model compound to represent anti-inflammatory medication. The results showed that the most effective test processes were O3/US/UV and O3/US/Fe2+ (at 2–8mgL−1 O3, 861kHz US, 254nm UV irradiation) that were significantly more effective than ozonation alone or other combinations. The outcome was attributed to the synergy of excess mass transfer and OH radical formation rates, and the presence of additional reaction routes and species. As such, 10-min pre-treatment of pure water by O3/UV/US and O3/US/Fe2+ provided nearly 90% DCF conversion; 26% and 46% mineralization, respectively. The efficiency of the processes for conversion in raw water was slightly lower, but that of mineralization was appreciably higher (55% and 58%, respectively) to be attributed to the synergy of combinations causing the interaction of excited NOM fragments with the intermediate products of DCF, followed by oxidative degradation of all to yield CO2. Coagulation/flocculation of the pretreated streams (of raw water) with alum and without chemicals respectively provided DCF-free water and about 65% DOC mineralization. Hence, integration of the existing water treatment facility with either of the above processes is an excellent option to destroy anti-inflammatory pharmaceutical residues such as DCF and to provide appreciable DOC elimination, thus reducing the likelihood of THM formation in the distribution system. An additional benefit offered by the second process using a ferrous salt was that it allowed for a chemical-free coagulation basin. [Copyright &y& Elsevier]