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With the misuse of antiviral drugs, the residual levels of ritonavir (RTV) in aquatic environments continue to increase, potentially posing threats to ecosystems and human health. However, the current understanding of the photochemical behavior of RTV in water, especially the mechanism by which dissolved organic matter (DOM) from different sources affects the indirect photolysis of RTV, remains limited. This study systematically investigated the effects of DOM from different sources (including sludge, algae, dustfall, and soil, namely SL-DOM, AL-DOM, DF-DOM, and SO-DOM, respectively) on the photodegradation of RTV for the first time. DOM exhibited a dual role in RTV degradation, with SL-DOM and AL-DOM accelerating the degradation process, while DF-DOM and SO-DOM inhibited it. Direct photolysis accounted for 40–53% of the overall photodegradation, underscoring its significant contribution to the degradation process. Quenching and competitive kinetics experiments revealed that 3DOM⁎ is the dominant contributor to the indirect photolysis of RTV. Exogenous DOM (DF-DOM, SO-DOM) exhibited higher generation rate and steady-state concentraiton of 3DOM⁎, while endogenous DOM (SL-DOM, AL-DOM) exhibited higher quantum yields of 3DOM⁎ and reactivity, leading to distinct mechanisms for the indirect photodegradation of RTV. This study explored the effects of DOM from different sources on the photodegradation of RTV, providing important insights into how DOM affects the photochemical behavior and ecological risk of RTV. It also provides a reference for exploring the photochemical behavior of other drugs. [Display omitted] • First study on the effect of DOM from different sources on RTV photolysis. • The contributions of RIs to indirect photolysis of RTV are: ·OH > 3DOM⁎>1O 2. • Endogenous DOM enhances RTV indirect photolysis more than exogenous DOM. [ABSTRACT FROM AUTHOR]

Although dissolved oxygen plays an important role in electro-Fenton-like processes, few investigations have revealed its underlying effects in such processes. Herein, the effect of dissolved oxygen on peroxide activation in an electro-Fenton-like system comprising electrochemical cells and peroxymonosulfate (PMS) was investigated. Cobalt phosphide-modified carbon aerogel (Co/P/CA) was used as the cathode material owing to the high conductivity and catalytic activity of Co/P/CA. Several free radicals and their effects on organic pollutant removal were observed using electron paramagnetic resonance spectrometry and quenching experiments, respectively. The observations revealed that in the presence of O 2 , hydroxyl radical (·OH), superoxide (O 2 − ·), and singlet oxygen (1O 2) served as the primary active species in the PMS activation process, while in the presence of N 2 , ·OH and sulfate radical (SO 4 −·) served as the dominant active species in this process. The factor responsible for the difference in the PMS activation pathways available under O 2 and N 2 conditions was investigated using rotating disk electrode tests and free energy calculations. The tests indicated that O 2 facilitates PMS activation to form ·OH instead of SO 4 −·. The dissolved oxygen subsequently underwent a single-electron-reduction reaction and was converted into O 2 −·, which could serve as a source of 1O 2. When N 2 was introduced, Co species, particularly Co(II), played a key role in activating PMS. The free radicals · OH and SO 4 − · were generated during the PMS activation process. This study clearly demonstrates the mediating catalysis role of dissolved oxygen in electro-Fenton-like system through experimental data and theoretical calculations, thereby positively contributing to future studies regarding the continuous activation of peroxides in composite systems and improvement of the efficiency of waterbody remediation. [Display omitted] • O 2 − · can be generated from the single-electron reduction reaction of O 2 by the Co/P/CA cathode. • In presence of O 2 , PMS activation is enhanced, leading to the generation of ·OH instead of SO 4 −. • The Co/P/CA cathode exhibits high catalytic activity for O 2 reduction, transition metal reduction, and PMS activation. [ABSTRACT FROM AUTHOR]

E-peroxone process is an emerging electrochemical oxidation process, based on ozone and the in-situ cathodic generation of H 2 O 2 , 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. [Display omitted] • The multilayer gas diffusion electrode decorated with PP membrane (0.45μm) shows a stable performance generating H 2 O 2. • The reaction parameters of gas diffusion electrode (GDE) on pyridine degradation were investigated. • The degradation pathways were proposed according to the six identified transformation products. • The acute toxicity of the transformation products was evaluated by the microbial respiration and T.E.S.T. calculation. [ABSTRACT FROM AUTHOR]

This study proposes a novel and eco-friendly approach for wastewater treatment using plasma jet technology under bubble condition. This method allows for the controlled production of highly reactive hydroxyl radicals (O H •) while minimizing unwanted interactions with nitrogen in the air. The presence of bubbles in liquid significantly boosts the diffusion of O H • within the wastewater, leading to a two-fold increase in degradation rate compared to normal condition. The effectiveness of the treatment was confirmed through ultraviolet-visible spectroscopy, which showed a significant decrease in rhodamine B and methyl orange absorbance peaks. Raman spectroscopy further revealed structural changes in both pollutants, indicating successful degradation. Additionally, plasma characteristics like power, electron temperature, and density were monitored to gain deeper insights into the underlying mechanism. Importantly, the process minimizes the formation of harmful secondary pollutants such as ozone and nitrogen oxides. These pollutants were found under concentration of 0.14 mg m−3 which is below established safety thresholds, adhering to World Health Organization guidelines. This research demonstrates that plasma jet treatment in bubble condition not only enhances the degradation efficiency of pollutants in wastewater but also minimizes the formation of harmful byproducts. This represents a significant breakthrough in developing sustainable wastewater treatment technologies. [Display omitted] • Plasma bubbles enhance degradation rate about double for dye-wastewater treatment. • Bubbles increase •OH diffusion and utilization, bypassing nitrogen interference. • In bubble condition, O 3 (g) and NO x (g) are produced under WHO guidelines. [ABSTRACT FROM AUTHOR]

The contamination of water bodies by synthetic organic compounds coupled with climate change and the growing demand for water supply calls for new approaches to water management and treatment. To tackle the decontamination issue, the activation of peroxymonosulfate (PMS) using copper magnetic ferrite (CuMF) nanoparticles prepared under distinct synthesis conditions was assessed to oxidize imidacloprid (IMD) insecticide. After optimization of some operational variables, such as CuMF load (62.5–250 mg L−1), PMS concentration (250–1000 μM), and solution pH (3-10), IMD was completely oxidized in 2 h without interferences from leached metal ions. Such performance was also achieved when using tap water but was inhibited by a simulated municipal wastewater due to scavenging effects promoted by inorganic and organic species. Although there was evidence of the presence of sulfate radicals and singlet oxygen oxidizing species, only four intermediate compounds were detected by liquid chromatography coupled to mass spectrometry analysis, mainly due to hydroxyl addition reactions. Concerning the changes in surface properties of CuMF after use, no morphological or structural changes were observed except a small increase in the charge transfer resistance. Based on the changes of terminal surface groups, PMS activation occurred on Fe sites. [Display omitted] • CuFe 2 O 4 nanoparticles (CuMF-NP) was synthesized using sol-gel and co-precipitation methods. • CuMF-NP activated peroxymonosulfate (PMS) to produce radical and non-radical species. • Imidacloprid insecticide was promptly oxidized using CuMF-NP/PMS system. • Dissolved Cu(II) and Fe(III) ions had no influence on IMD oxidation. • Fe sites on the CuMP-NP seem to be involved in the PMS activation. [ABSTRACT FROM AUTHOR]

Titanium dioxide nanoparticles (TiO 2 -NP) present in wastewater effluent are discharged into freshwater and saltwater (i.e., marine) systems. TiO 2 -NP can be solar-driven photoactivated by ultraviolet (UV)-light producing reactive oxygen species including hydroxyl radicals (·OH). ·OH are non-selective and react with a broad range of species in water. In other studies, photoactivation of TiO 2 -NP has been correlated with oxidative stress and ecotoxicological impacts on plant and animal biota. This study examined the photoactivation of TiO 2 -NP in freshwater and saltwater systems, and contrasted the oxidation potential in both systems using methylene blue (MB) as a reaction probe. Maximum MB loss (51.9%, n = 4; 95% confidence interval 49.4–54.5) was measured in salt-free, deionized water where ·OH scavenging was negligible; minimum MB loss (1%) was measured in saltwater due to significant ·OH scavenging, indicating the inverse correlation between MB loss and radical scavenging. A kinetic analysis of scavenging by seawater constituents indicated Cl− had the greatest impact due to high concentration and high reaction rate constant. Significant loss of MB occurred in the presence of Br− relative to other less aggressive scavengers present in seawater (i.e., HCO 3 −, HSO 4 −). This result is consistent with the formation of Bromate, a strong oxidant that subsequently reacts with MB. In freshwater samples collected from different water bodies in Oklahoma (n = 12), the average MB loss was 13.4%. Greater MB loss in freshwater systems relative to marine systems was due to lower ·OH scavenging by various water quality parameters. Overall, TiO 2 -NP photoactivation in freshwater systems has the potential to cause greater oxidative stress and ecotoxicological impacts than in marine systems where ·OH scavenging is a dominant reaction. [Display omitted] • TiO 2 -NP photoactivation yields strong, non-selective hydroxyl radicals (·OH). • Probe oxidation in seawater < in fresh water body samples (n = 12). • ·OH scavenging in seawater is attributed primarily to Cl−. • Seawater: OH scavenging rate/probe oxidation rate ∼11,400. • Oxidative stress effects in freshwater systems > marine systems. [ABSTRACT FROM AUTHOR]

Bisphenol A (BPA) in seawater tends to be deposited in coastal sediments. However, its degradation under tidal oscillations has not been explored comprehensively. Hydroxyl radicals (·OH) can be generated through Fe cycling under redox oscillations, which have a strong oxidizing capacity. This study focused on the contribution of Fe-mediated production of ·OH in BPA degradation under darkness. The removal of BPA was investigated by reoxygenating six natural coastal sediments, and three redox cycles were applied to prove the sustainability of the process. The importance of low reactivity Fe(II) in the production of ·OH was investigated, specifically, Fe(II) with carbonate and Fe(II) within goethite, hematite and magnetite. The degradation efficiency of BPA during reoxygenation of sediments was 76.78–94.82%, and the contribution of ·OH ranged from 36.74% to 74.51%. The path coefficient of ·OH on BPA degradation reached 0.6985 and the indirect effect of low reactivity Fe(II) on BPA degradation by mediating ·OH production reached 0.5240 obtained via partial least squares path modeling (PLS-PM). This study emphasizes the importance of low reactivity Fe(II) in ·OH production and provides a new perspective for the role of tidal-induced ·OH on the fate of refractory organic pollutants under darkness. [Display omitted] • Redox oscillations of coastal sediments promoted the production of ·OH. • The tidal-induced production of ·OH was rhythmic and sustainable in three cycles. • Fe(II) low reactivity could serve as an electron pool to facilitate ·OH production. • Fe(II) within the Fe NaAC and Fe AAO fraction could regenerate reactive Fe(II). • The contribution of ·OH in BPA degradation was 36.74–74.51 %. [ABSTRACT FROM AUTHOR]

Nanometric cobalt magnetic ferrite (CoFe 2 O 4) synthesized by distinct methods was used for in situ chemical activation of peroxymonosulfate (PMS) under neutral conditions to oxidize imidacloprid (IMD) insecticide. The effect of CoFe 2 O 4 load (0.125–1.0 g L−1) and PMS concentration (250–1000 μM) was investigated as well as the influence of phosphate buffer and Co(II) ions. PMS activation by Co(II) ions, including those leached from CoFe 2 O 4 (>50 μg L−1), exhibited a strong influence on IMD oxidation and, apparently, without substantial contributions from the solid phase. Within the prepared solid materials (i.e. , using sol-gel and co-precipitation methods), high oxidation rates (ca. 0.5 min−1) of IMD were attained in ultrapure water. Phosphate buffer had no significant influence on the IMD oxidation rate and level, however, its use and solution pH have shown to be important parameters, since higher PMS consumption was observed in the presence of buffered solutions at pH 7. IMD byproducts resulting from hydroxylation reactions and rupture of the imidazolidine ring were detected by mass spectrometry. At optimum conditions (0.125 g L−1 of CoFe 2 O 4 and 500 μM of PMS), the CoFe 2 O 4 nanoparticles exhibited an increase in the charge transfer resistance and an enhancement in the surface hydroxylation after PMS activation, which led to radical (HO● and SO 4 ●–) and nonradical (1O 2) species. The latter specie led to high levels of IMD oxidation, even in a complex water matrix, such as simulated municipal wastewater at the expense of one-order decrease in the IMD oxidation rate. [Display omitted] • Peroxymonosulfate (PMS) was activated by Co(II) ions leached from CoFe 2 O 4. • CoFe 2 O 4 nanoparticles increased charge transfer resistance after use. • Radical (HO.● and SO 4 ●–) and nonradical (1O 2) are the main oxidizing species detected • 1O 2 led to high IMD oxidation levels even in a complex water matrix. • Few IMD intermediates detected by liquid chromatography tandem mass spectrometry. [ABSTRACT FROM AUTHOR]

Tetrabromobisphenol S (TBBPS) is a widely used brominated flame retardant that has attracted environmental concern due to its abundant presence in water. The objective of this study is to systematically analyze the direct photolysis and degradation mechanisms of TBBPS in two different dissociation forms in water, as well as to evaluate their toxicological effects induced by •OH, 1O 2 , and •NO 2 radicals. The degradation mechanism of TBBPS is investigated with density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, and the toxicity of the degradation products is assessed through toxicological studies. The results of the study indicate that the OH-addition and H-abstraction reactions are favorable pathways for •OH-induced TBBPS degradation. The H-abstraction reaction of TBBPS0 with •OH was more favorable than the •OH addition reaction. However, in the degradation of TBBPS−, the •OH addition reaction was favored over the H-abstraction reaction. Additionally, the indirect photolysis of TBBPS by 1O 2 and •NO 2 in water was found to be easier for TBBPS− compared to TBBPS0, with degradation mechanisms involving Br-substitution and NO 2 -addition reactions. The higher E a values calculated indicate that the degradation of TBBPS by 1O 2 and •NO 2 in water has been a secondary reaction. The direct photolysis reaction pathway of TBBPS in water has involved the cleavage of the S1–C7 and S1–C16 bonds. For TBBPS0 in the S 1 /T 1 states, the primary reaction pathway is the cleavage of the S1–C16 bond, while for TBBPS−, the primary reaction pathway is the cleavage of the S1–C7 bond. Furthermore, the computational toxicology results indicate a slight increase in the toxicity levels of most products, highlighting the significance of investigating the degradation byproducts of TBBPS in greater detail. [Display omitted] • The cleavage of S1–C16 bond is the primary reaction path of TBBPS0 in S 0 /T 1 state. • The H-abstraction reaction of.•OH is easier to occur than the OH-addition reaction • 1O 2 and.•NO 2 plays a secondary role in the photodegradation of TBBPS • Most of the TBBPS degradation products are at a harmful level. [ABSTRACT FROM AUTHOR]

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 (O 3) and could therefore be efficiently eliminated from the water matrices by direct O 3 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 O 3. 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 O 3 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. Image 1 • Oxidation of structurally diverse antimicrobials by ozonation and E -peroxone is evaluated. • Most of the biocides studied are moderately reactive or non-reactive with O 3. • E -peroxone accelerates the removal of O 3 -refractory antimicrobials than ozonation. • Water matrix has a significant effect on the kinetics of antimicrobial abatement. • E -peroxone increased. OH exposure at the expense of decreased O 3 exposure compared to ozonation. [ABSTRACT FROM AUTHOR]

Phenolic compounds are problematic byproducts generated from lignocellulose pretreatment. In this study, the feasibility degradation of syringic acid (SA), vanillic acid (VA), and 4-hydroxybenzoic acid (HBA) by Bio-Electro-Fenton (BEF) system with a novel Fe–Mn/graphite felt (Fe–Mn/GF) composite cathode were investigated. The nano-scale Fe–Mn multivalent composite catalyst with core shell structure distributed more evenly on GF surface to form a catalyst layer with higher oxygen reduction reaction performance. Accordingly, the maximum power density generated with Fe–Mn/GF cathode was 48.1% and 238.9% higher than Fe/GF and GF respectively, which further enhanced the in situ generation of H 2 O 2 due to the superiority of nano-scale core shell structure and synergistic effect of Fe and Mn species. The degradation efficiency of the three phenolic compounds in the BEF system could reached 100% after optimization of influencing parameters. Furthermore, a possible SA degradation pathway by BEF process in the present system was proposed based on the detected intermediates. These results demonstrated an efficient approach for the degradation of phenolic compounds derived from lignocellulose hydrolysates. • A novel Fe-Mn/graphite felt composite cathode was simply developed by a one-step approach. • Core shell Fe-Mn multivalent catalyst evenly distributed on the surface of GF cathode to enhance OH generation. • Complete removal of phenolic compounds was achieved due to the excellent catalytic activity of composite cathode. • The possible degradation pathway of syringic acid by Bio-Electro-Fenton process was proposed. [ABSTRACT FROM AUTHOR]

Perturbation of Fe(III)-bearing oxic environments by reduced species such as sulfide occurs widely in natural and engineered systems. However, whether hydroxyl radicals (OH) can be produced in these environments remains unexplored. Here we show that sulfide drives OH production in Fe(III) oxyhydroxides suspensions under neutral and oxic conditions. For lepidocrocite, ferrihydrite and goethite suspensions at 11.2 mM Fe, the addition of 0.5 mM sulfide produced 14.2, 14.3 and 22.4 μM OH within 120 min, respectively. With addition of sulfide to lepidocrocite suspensions at 11.2 mM Fe, the cumulative OH concentration within 120 min increased from 0 to 14.2, 25.2, 52.6 and 63.1 μM when sulfide dosage increased from 0 to 0.5, 2.5, 5 and 7.5 mM, respectively. At a fixed sulfide dosage of 5 mM, the cumulative OH concentration increased with increasing the number of sulfide additions. The mechanisms of OH production were attributed to the generation of surface-bound Fe(II), most likely in the form of >FeIIOH 2 +, and Fe(II) in the solid phase or FeS from the reactions between sulfide and Fe(III), followed by O 2 activation. OH production could take place until depletion of sulfide. Finally, we found that the generated OH could oxidize the coexisting redox-active substances like phenol under neutral and oxic conditions. Our findings reveal that sulfide perturbation of Fe(III)-bearing oxic environments is a new source of OH, and contaminants oxidation by OH necessitates consideration in these environments. A new abiotic pathway of dark OH production. Image 1 •. OH can be produced in oxic Fe(III)-bearing environments perturbed by sulfide. • Surface-bound Fe(II) and Fe(II) in the solid phase or FeS were produced in sulfide/Fe(III)/O 2 systems. • O 2 activation by surface-bound Fe(II) and/or Fe(II) in the solid phase or FeS was responsible for. OH production. • The produced. OH could oxidize organic contaminants. • A new abiotic pathway was proposed for dark. OH production in the environment. [ABSTRACT FROM AUTHOR]

Because of the influence of hydrolysed species from Al-based coagulants on coagulation performance, the performance and mechanism of the developed hybrid ozonation-coagulation (HOC) process using AlCl 3 ·6H 2 O and preformed Al 13 as coagulants were investigated in this study, in which ozonation and coagulation occurred simultaneously within a single unit. It was found that the HOC process exhibited higher organic matter removal performance compared with coagulation and the pre-ozonation-coagulation process. It was found that the high ibuprofen (IBP) removal efficiency in the HOC process was mainly attributed to OH oxidation promoted by in situ formed hydrolysed aluminium species from AlCl 3 ·6H 2 O and preformed Al 13. Furthermore, the surface hydroxyl groups were determined to be the active reaction sites for the HOC process. Due to the higher proportion of surface hydroxyl groups for Al 13 , the HOC process with preformed Al 13 as coagulants (Al 13 -HOC) exhibited a higher removal performance than that with AlCl 3 ·6H 2 O as the coagulant (AlCl 3 -HOC). It was revealed that most of the generated O 2 − in the Al 13 -HOC was adsorbed on the surface of Al 13 at different pH values, while a considerably lower proportion of adsorbed O 2 − was observed on the surface of in situ formed Al species from AlCl 3 ·6H 2 O. Nevertheless, low proportions of adsorbed OH were found on the surfaces of both preformed Al 13 and in situ formed Al species, indicating that the OH oxidation for the removal of organic pollutants occurred primarily in the aqueous phase. Image 1 • Al 13 -HOC process exhibited higher removal performance than AlCl 3 -HOC process. • Surface hydroxyl groups were determined to be the active reaction sites in the HOC. • Preformed Al 13 had a higher proportion of surface hydroxyl groups than AlCl 3 ·6H 2 O. • Most of the generated O 2 − in the Al 13 -HOC was adsorbed on the Al 13 surface. • OH oxidation occurred primarily in the aqueous phase during the HOC process. [ABSTRACT FROM AUTHOR]

This work investigated the feasibility and mechanisms of solar/chlorine process in the removal of a kind of emerging contaminants, lipid regulators (gemfibrozil (GFRZ), benzafibrate (BZF), and clofibric acid (CA)), in simulated and real waters. These lipid regulators could be effectively removed by solar/chlorine treatment, and their corresponding pseudo-first-order rate constants (k ′) increased with increasing chlorine dosage. The degradation of GFRZ and BZF was primarily ascribed to reactive chlorine species (RCS) and ozone, while that of CA was mainly attributable to hydroxyl radical (HO) and ozone. As pH rose from 5.0 to 8.4, k ozone ′ of GFRZ and BZF increased, while k HO ′ decreased. However, k RCS ′ of GFRZ increased by 130%, while that of BZF decreased by 43.3%. These changes resulted in slight changes in the overall k ′s with increasing pH. k ′s of GFRZ, BZF, and CA by solar/chorine treatment were inhibited by natural organic matter (NOM) while the presence of bromide enhanced the degradation of GFRZ by solar/chlorine process. The degradation of lipid regulators was still effective in a secondary wastewater effluent sample and a sand-filtered water sample, although that was inhibited due to the dissolve organic matter (DOM) contained in real waters. The acute toxicity during the degradation of GFRZ by solar/chlorine treatment was comparable to that by treatment with chlorine alone. This study demonstrated that RCS played an important role in the degradation of micropollutants by the solar/chlorine treatment and the feasibility of solar/chlorine process in the application for the degradation of organic compounds in real waters. Image 1 • Lipid regulators could be effectively degraded by the solar/chlorine treatment. • RCS and O 3 were predominant reactive species for GFRZ and BZF degradation. • The k ′s of GFRZ and BZF were affected by chlorine dosage rather than pH. • The acute toxicity in the solar/chlorine process was comparable to that of chlorination alone. • The solar/chlorine treatment was also efficient for the removal of lipid regulator in real waters. [ABSTRACT FROM AUTHOR]

Abstract Diclofenac (DIC) is a new type of contaminant that has been widely detected in the water environment, posing threats to the ecological environment and human health. However, the conventional wastewater treatment process has a very limited ability to reduce DIC. In this research, persulfate is added to electro-Fenton with the three-dimensional particle electrode (TDE) process whose particle electrodes were formed from manganese slag with loaded active substance (Cu: Fe = 1:1) to construct a three-dimensional electro-Fenton-persulfate (3D electro-Fenton-PS) process to investigate the removal rate of DIC under the optimum working conditions. The effects of different persulfate addition, activator addition and different activators on the removal rate of DIC were researched, respectively. The removal rate of DIC reached 96.3% when the persulfate and the Fe0 addition were 1.50 mM and 3.00 mM, respectively. The results showed that and OH existed simultaneously in the reaction system, and the removal of DIC was the result of the two free radicals. Moreover, degradation pathways and mechanism of DIC were also discussed. The study may provide a new theoretical basis and technical support for the treatment of DIC in municipal wastewater. Highlights • 3D electro-Fenton-PS reactor could effectively remove DIC. • Fe0 was more suitable as an activator of persulfate than Fe2+. • The removal of DIC was the result of a combination of and OH. • The degradation pathways of DIC probably were decarboxylation and dechlorination. [ABSTRACT FROM AUTHOR]

Abstract The pharmaceutical valsartan is classified as a trace organic compound and is released into wastewater from human consumption. Trace organic compounds are not completely removed during conventional wastewater treatment. In order to prevent their release into the aquatic environment, advanced wastewater treatment technologies such as ozonation are currently implemented. Ozonation leads to the formation of transformation products (TPs), which then enter the receiving waters. In the present work, laboratory-scale ozonation experiments of valsartan solutions were performed. The resulting TPs were analyzed by HPLC-MS and searched for using a non-targeted approach. Of the 51 compounds detected, 27 have tentative structural suggestions based on MS/MS experiments. Ozonation of valsartan does not lead to the formation of TPs with higher toxicity towards A. fischeri than the parent compound. According to QSAR-based environmental behavior estimations, most TPs reveal lower lipophilicity, increased biodegradability as well as decreased acute and chronic toxicities concerning fish, daphnia and algae compared to their parent compound valsartan. Graphical abstract Image 1 Highlights • TPs of valsartan during ozonation were identified for the first time. • Structural elucidation of numerous TPs was performed. • Reactions with OH radicals were identified as main degradation pathways. • Acute and chronic tests with luminescent bacteria showed no effects. • Lipophilicity, biodegradability and ecotoxicity of TPs were estimated via QSAR models. [ABSTRACT FROM AUTHOR]

Free chlorine sunlight photolysis (sunlight/FC) markedly enhances the degradation rate of methadone, a synthetic opioid used medically, over that obtained using sunlight alone. The pseudo-first-order rate constants of methadone degradation under acidic conditions ([methadone] = 0.2 μM, [free chlorine] = 4 μM, and pH = 4) for sunlight/FC and sunlight photolysis are 7.0 ± 1.1 × 10 −2  min −1 and 1.4 ± 0.2 × 10 −2  min −1 , respectively. The improved methadone degradation can be attributed to the production of HO and reactive chlorine species (RCS) during sunlight/FC photolysis. HO and RCS predominantly accounted for degradation during sunlight/FC photolysis under acidic and neutral conditions, while direct photolysis was the major contributor towards methadone degradation in alkaline conditions. The initial pH (pH 4–11) and free chlorine concentration (1–6 μM) significantly influenced the overall degradation efficiency of methadone. The presence of HCO 3 − , Cl − and dissolved organic matters, which may competitively react with HO and RCS, retard the degradation of methadone in synthetic wastewater. Consequently, a 50% lower methadone degradation rate was observed when deionized (DI) water was replaced with tap water. These results emphasize the need to consider different water matrices when applying sunlight/FC photolysis for water treatment. [ABSTRACT FROM AUTHOR]

A hydroxyl radical ( OH) ballast water treatment system (BWTS) was developed and applied to inactivate entrained organisms in a 10,000-ton oceanic ship, where OH was produced by a strong ionization discharge combined with a water jet cavitation effect. The calculated OH generation rate was 1373.4 μM min −1 in ballast water, which is much higher than that in other advanced oxidative processes such as photocatalysis. As a result, non-indigenous red tide algae were inactivated to meet the ballast water discharge standards (<10 cells mL −1 ) of the International Maritime Organization. The ratio of variable fluorescence to maximum fluorescence (F v /F m ) for algal chlorophyll rapidly decreased to zero within a contact time of only 6 s, indicating complete inactivation of algae. Observation under a scanning electron microscope showed no cellular materials were released by algal cells upon OH inactivation. A risk assessment of the OH treatment system was conducted, and the ratios of predicted environmental concentrations to predicted no effect concentrations of all detected disinfection byproducts were less than 1, even at a worst-case oxidant concentration of 2.41 mg L −1 . Ship ballast water treated using OH inactivation is safe for marine environments. Finally, the energy consumption and operational costs of the OH BWTS were found to be 0.033 kWh m −3 and CNY 0.03 m -3 , respectively. [ABSTRACT FROM AUTHOR]

Wastewater containing dyes are one of the major threats to our environment. Conventional methods are insufficient for the removal of these persistent organic pollutants. Recently much attention has been received for the oxidative removal of various organic pollutants by electrochemically generated hydroxyl radical. This review article aims to provide the recent trends in the field of various Electrochemical Advanced Oxidation Processes (EAOPs) used for removing dyes from water medium. The characteristics, fundamentals and recent advances in each processes namely anodic oxidation, electro-Fenton, peroxicoagulation, fered Fenton, anodic Fenton, photoelectro-Fenton, sonoelectro-Fenton, bioelectro-Fenton etc. have been examined in detail. These processes have great potential to destroy persistent organic pollutants in aqueous medium and most of the studies reported complete removal of dyes from water. The great capacity of these processes indicates that EAOPs constitute a promising technology for the treatment of the dye contaminated effluents. [ABSTRACT FROM AUTHOR]

An Fe-based catalyst was used as a heterogeneous catalyst for the ozonation of industrial wastewater, and key operational parameters (pH and catalyst dosage) were studied. The results indicated that the Fe-based catalyst significantly improved the mineralization of organic pollutants in wastewater. TOC (total organic carbon) removal was high, at 78.7%, with a catalyst concentration of 200 g/L, but only 31.6% with ozonation alone. The Fe-based catalyst significantly promoted ozone decomposition by 70% in aqueous solution. Hydroxyl radicals (·OH) were confirmed to be existed directly via EPR (electron paramagnetic resonance) experiments, and ·OH were verified to account for about 34.4% of TOC removal with NaHCO 3 as a radical scavenger. Through characterization by SEM-EDS (field emission scanning electron microscope with energy-dispersive spectrometer), XRD (X-ray powder diffraction) and XPS (X-ray photoelectron spectroscopy), it was deduced that FeOOH on the surface of the catalyst was the dominant contributor to the catalytic efficiency. The catalyst was certified as having good stability and excellent reusability based on 50 successive operations and could be used as a filler simultaneously. Thereby, it is a promising catalyst for practical industrial wastewater advanced treatment. [ABSTRACT FROM AUTHOR]

A novel vibration-catalytic performance based on piezo-electro-chemical coupling of zinc oxide (ZnO) nanorods for wastewater decolorization was characterized through the product of piezoelectric performance and electrochemical process. The vibration-catalytic decolorization ratio for acid orange 7 (AO7) solution (5 μM) was up to ∼ 80%. The oxidizing hydroxyl radical ( OH) of the intermediates of the vibration-catalytic reactions is observed, indicating the production of piezoelectrically-induced electric charges. The dependence of ZnO addition mass, initial dye concentration and the recycling utilization times of ZnO on dye decolorization ratio were systematically studied. The vibration-catalysis mediated by ZnO, with the advantages of high efficiency and recycling utilization, is potential for dye wastewater decolorization treatment. [ABSTRACT FROM AUTHOR]

The degradation of acrylamide (AA) during UV/chlorine advanced oxidation process (AOP) was investigated in this study. The degradation of AA was negligible during UV irradiation alone. However, AA could be effectively degraded and mineralized during UV/chlorination due to the generation of hydroxyl radicals ( OH). The degradation kinetics of AA during UV/chlorination fitted the pseudo-first order kinetics with the rate constant between AA and OH radicals being determined as 2.11 × 10 9 M −1 s −1 . The degradation rate and mineralization of AA during UV/chlorination were significantly promoted at acidic conditions as well as increasing chlorine dosage. The volatile degradation products of AA during UV/chlorination were identified using gas chromatography-mass spectrometry and the degradation pathways were then proposed accordingly. The formation of disinfection by-products (DBPs) in Milli-Q water and tap water during UV/chlorination of AA was also investigated. The DBPs included chloroform, dichloroacetonitrile, trichloroacetonitrile, 2,2-dichloroacetamide and 2,2,2-trichloroacetamide. Furthermore, the variations of AA degradation during UV/chlorination in different real water samples were evaluated. [ABSTRACT FROM AUTHOR]

Despite the high toxicity and resistance to conventional water treatments exhibited by methiocarb (MC), there are no reports regarding the degradation of this priority pesticide by means of alternative purification technologies. In this work, the removal of MC by means of ozonation was studied for the first time, employing a multi-reactor methodology and neutral pH conditions. The second-order rate constants of MC reaction with molecular ozone (O 3 ) and formed hydroxyl radicals (OH·) were determined to be 1.7·10 6 and 8.2·10 9 M −1 s −1 , respectively. During degradation experiments, direct ozone reaction was observed to effectively remove MC, but not its formed intermediates, whereas OH· could oxidize all species. The major identified TPs were methiocarb sulfoxide (MCX), methiocarb sulfoxide phenol (MCXP) and methiocarb sulfone phenol (MCNP), all of them formed through MC oxidation by O 3 or OH· in combination with hydrolysis. A toxicity assessment evidenced a strong dependence on MCX concentration, even at very low values. Despite the OH· capability to degrade MC and its main metabolites, the relative resistance of TPs towards ozone attack enlarged the oxidant dosage (2.5 mg O 3 /mg DOC) necessary to achieve a relatively low toxicity of the medium. Even though ozonation could be a suitable technique for MC removal from water compartments, strategies aimed to further promote the indirect contribution of hydroxyl radicals during this process should be explored. [ABSTRACT FROM AUTHOR]

This study suggested the amount of hydroxyl radicals ( OH) reacting with organics as a new index to evaluate the reaction efficiency (RE) of Fenton process, and used it to investigate the degradation mechanism of target pollution, Acid Orange 7 (AO7). The effects of initial concentrations of Fe(II), H 2 O 2 , and AO7 on RE were quantified by using response surface methodology (RSM). The main factors affecting RE were Fe(II), H 2 O 2 , and their interaction, and their percentage effects were 65.75, 11.99 and 22.23%, respectively. Moreover, based on the analysis result of RSM, a condition for good RE was proposed that it should ensure a higher amount of OH reacted with organics, and reduce the amount of OH scavenged by Fe(II). Liquid chromatography–mass spectrometry (LC/MS) analysis was used to identify the products of AO7 degradation in Fenton process, and there were three possible mechanisms to be observed, such as azo bond cleavage, hydroxylation, and oxidation of naphthalene ring. The trend of mechanisms might vary with the amount of OH attacks, and therefore the use of estimated RE could provide more particular information to better understand the relationship between organic degradation and OH attacks. [ABSTRACT FROM AUTHOR]

Unsaturated ethers are oxygenated volatile organic compounds (OVOCs) emitted by anthropogenic sources. Potential removal processes in the troposphere are initiated by hydroxyl (OH) radicals and photochemistry. In this work, we report for the first time the rate coefficients of the gas-phase reaction with OH radicals ( k OH ) of 2-chloroethyl vinyl ether (2ClEVE), allyl ether (AE), and allyl ethyl ether (AEE) as a function of temperature in the 263–358 K range, measured by the pulsed laser photolysis–laser induced fluorescence technique. No pressure dependence of k OH was observed in the 50–500 Torr range in He as bath gas, while a slightly negative T -dependence was observed. The temperature dependent expressions for the rate coefficients determined in this work are: k OH , 2 ClEVE ( T ) = ( 9.0 ± 2.0 ) × 10 − 12 exp ( 478 ± 72 T ) c m 3 molecul e − 1 s − 1 , k OH , AE ( T ) = ( 1.3 ± 0.4 ) × 10 − 11 exp ( 442 ± 91 T ) c m 3 molecul e − 1 s − 1 , k OH , AEE ( T ) = ( 5.8 ± 1.3 ) × 10 − 12 exp ( 563 ± 62 T ) cm 3 molecule − 1 s − 1 , The estimated atmospheric lifetimes (τ OH ) assuming k OH at 288 K were 3, 2, and 4 h for 2ClEVE, AE and AEE, respectively. The kinetic results are discussed in terms of the chemical structure of the unsaturated ethers by comparison with similar compounds. We also report ultraviolet (UV) and infrared (IR) absorption cross sections (σ λ and σ ( ν ˜ ) , respectively). We estimate the photolysis rate coefficients in the solar UV actinic region to be less than 10 −7 s −1 , implying that these compounds are not removed from the atmosphere by this process. In addition, from σ ( ν ˜ ) and τ OH , the global warming potential of each unsaturated ether was calculated to be almost zero. A discussion on the atmospheric implications of the titled compounds is presented. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) have been reported to have antibacterial activities and cytotoxicity, resulting from the dissolved silver cation (Ag + ) and its soluble complexes. However, to our knowledge, little has been reported about their potential use in degrading organic contaminants such as endocrine-disrupting compounds in aqueous solution. In this first report on the subject, we examined the effectiveness of the oxidative degradation of bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) in water by reactive oxygen species formed during the decomposition of H 2 O 2 , assisted by polyvinylpyrrolidone (PVP)-stabilized AgNPs. The dissolution of AgNPs accompanied generation of OH at low pH. The fully dispersed PVP-AgNPs in the presence of H 2 O 2 exhibited fast degradation kinetics for EE2 at a typical aquatic condition of pH (6–7). The oxidation kinetics of BPA and EE2 by PVP-AgNPs can be interpreted using three different modeling approaches: an initial pseudo-first-order, a retarded first-order rate, and Behnajady-Modirshahla-Ghanbery kinetic equation. The findings showed that AgNPs may have potential to facilitate the in situ oxidation for emerging contaminants in the aqueous environment. [ABSTRACT FROM AUTHOR]

Table olive processing wastewater (TOW) is a notoriously polluting due to its high organic and phenol content. To reduce them, an electrochemical process has been studied for the treatment of this effluent. Experiments were performed with a cell equipped with lead dioxide (PbO 2 ) or boron-doped diamond (BDD) as anode and platinum as cathode, where Table Olive Wastewater (TOW) were destroyed by hydroxyl radicals formed at the anode surface from water oxidation. The comparative study of both systems shows the performance of the BDD anode compared to PbO 2 , explained by the large amounts of hydroxyl radicals generated effective at BDD anode and its synthesis characteristics. Using LC/MS analysis, it was possible to determine hydroxytyrosol, as major phenolic compounds, in table olive processing wastewater and its concentration reach 890 mg L −1 . A possible reaction mechanism oxidation for hydroxytyrosol was proposed. The kinetics decays for hydroxytyrosol degradation on PbO 2 anode follows a pseudo-first order reaction with a rate constant 0.9 h −1 for j app value 20 mA cm −2 . [ABSTRACT FROM AUTHOR]

The photo-decomposition of organic phosphorus is an important route for the phosphorus cycle by which phosphate is regenerated in the aquatic environment. In this study, the role of Fe 3+ as a natural photosensitizer toward the decomposition of organic phosphorus to release phosphate was examined in deionized and natural waters under UV and sunlight irradiation using glyphosate as the organic phosphorus model. The results showed that the concentration of glyphosate decreased with irradiation time in the Fe 3+ /UV and Fe 3+ /sunlight systems and TOC gradually decreased, which confirmed that glyphosate was degraded by Fe 3+ . The amount of phosphate released from the photo-decomposition of glyphosate was higher in the presence of Fe 3+ than that of the control experiment under UV and sunlight irradiation conditions, and the generation rate of phosphate also increased with increasing Fe 3+ concentrations. The formation of hydroxyl radicals (·OH) in the Fe 3+ /UV and Fe 3+ /sunlight systems was identified according to the photoluminescence spectra (PL) using coumarin as the trapping molecule, and the steady-state concentrations of ·OH for the Fe 3+ /UV and Fe 3+ /sunlight systems were 1.06 × 10 −14 M and 0.09 × 10 −14 M, respectively. When natural water was spiked with glyphosate and Fe 3+ , the phosphate that was released in the Fe 3+ was higher than that of the control, and the phosphate that was released was inhibited when isopropanol was added to the reaction. All of these results demonstrate that the photochemical activity of Fe 3+ has significantly impact in the release of phosphate from the photo-decomposition of organic phosphorus. [ABSTRACT FROM AUTHOR]

Submerged plasma irradiation (SPI)-based advanced oxidation processes have been studied for the oxidation of recalcitrant organic compounds because of their various physical and chemical properties. However, SPI technologies still have a few drawbacks such as relatively low efficiency for wastewater treatment and high energy consumption. In order to overcome these drawbacks, in this study, we proposed the combination of SPI and the Cu(II)-catalyzed Fenton-like system. The removal of methylene blue (MB) by the SPI system was significantly enhanced upon the addition of H 2 O 2 . The pseudo-first-order rate constants of MB removal increased with the increase of applied voltage. In addition, the optimum H 2 O 2 dose and initial solution pH were 100 mM and 9, respectively. The reactive oxidants responsible for MB removal in copper electrode-based SPI/H 2 O 2 systems are likely to be hydroxyl radicals ( OH) or cupryl ion (Cu(III)), wherein Cu(III) is especially important. Furthermore, the copper electrode-based SPI/H 2 O 2 system is a novel advanced oxidation process capable of oxidizing water recalcitrant and toxic organic pollutants at neutral pH. [ABSTRACT FROM AUTHOR]

N-Nitrosopyrrolidine (NPYR) is an emerging contaminant in drinking water and wastewater. The degradation kinetics and mechanisms of NPYR degradation by the O 3 /UV process were investigated and compared with those of UV direct photolysis and ozonation. A synergistic effect of ozone and UV was observed in the degradation of NPYR due to the accelerated production of OH• by ozone photolysis. This effect was more pronounced at higher ozone dosages. The second-order rate constants of NPYR reacting with OH• and ozone was determined to be 1.38 (± 0.05) × 10 9 M -1 s -1 and 0.31 (± 0.02) M -1 s -1 , respectively. The quantum yield by direct UV photolysis was 0.3 (± 0.01). An empirical model using Rct (the ratio of the exposure of OH• to that of ozone) was established for NPYR degradation in treated drinking water and showed that the contributions of direct UV photolysis and OH• oxidation on NPYR degradation were both significant. As the reaction proceeded, the contribution by OH• became less important due to the exhausting of ozone. Nitrate was the major product in the O 3 /UV process by two possible pathways. One is through the cleavage of nitroso group to form NO• followed by hydrolysis, and the other is the oxidation of the intermediates of amines by ozonation. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) are a major contributor to the toxicity in oil sands process-affected water (OSPW), which is produced by hot water extraction of bitumen. NAs are extremely difficult to be degraded due to its complex ring and side chain structure. Photocatalysis is recognized as a promising technology in the removal of refractory organic pollutants. In this work, TiO 2 -graphene (P25-GR) composites were synthesized by means of solvothermal method. The results showed that P25-GR composite exhibited better photocatalytic activity than pure P25. The removal efficiency of naphthenic acids in acid solution was higher than that in neutral and alkaline solutions. It was the first report ever known on the photodegradation of NAs based on graphene, and this process achieved a higher removal rate than other photocatalysis degradation of NAs in a shorter reaction time. LC/MS analysis showed that macromolecular NAs (carbon number 17–22, z value −2) were easy to be degraded than the micromolecular ones (carbon number 11–16, z value −2). Furthermore, the reactive oxygen species that play the main role in the photocatalysis system were studied. It was found that holes and ·OH were the main reactive species in the UV/P25-GR photocatalysis system. Given the high removal efficiency of refractory organic pollutants and the short degradation time, photodegradation based on composite catalysts has a broad and practical prospect. The study on the photodegradation of commercially sourced NAs may provide a guidance for the degradation of OSPW NAs by this method. [ABSTRACT FROM AUTHOR]

Many modern techniques exist for the degradation of organic pollutants in water. Numerous treatment processes which utilize the formation of hydroxyl radicals for oxidation of pollutants have been studied thoroughly. In this study, a three pronged approach has been used to characterize and understand the effect of two distinct acoustic frequencies (37 kHz and 1 MHz) on cavitation behavior. Correlation of this behavior with sonolysis of a target phenol pollutant is described. Hydroxyl radical capture, hydrophone, and microelectrode studies in this work show that megasonic frequencies are more effective for generation of hydroxyl radicals and stable cavitation events than ultrasonic frequencies. UV absorption and fluorescence measurements confirm that the combination of ultrasonic sonolysis with a Fenton reagent achieved complete degradation of p-cresol at 50 mg/L in about 30 min. Cost estimates have been made for different sonication processes and compared with traditional advanced oxidation processes. [ABSTRACT FROM AUTHOR]

Among various plastic additives, di-2-ethylhexyl phthalate (DEHP) has been a great concern due to its high leaching potential and harmful effects on both human and the ecosystem. For the effective oxidation and mineralization of DEHP by ozone in the existing TiO 2 catalytic processes, the heterogeneous catalyst, vanadium oxide (V 2 O 5)-incorporated TiO 2 (V 2 O 5 /TiO 2), was synthesized. The generation of hydroxyl radicals was promoted by cyclic redox reactions of vanadium atoms in V 2 O 5 /TiO 2 via the increase of surface oxygen vacancies by the replacement of V5+ species in the lattice of TiO 2. The catalytic ozonation in the presence of V 2 O 5 /TiO 2 exhibited the significantly higher degradation of DEHP with the pseudo-second-order kinetic constant of 1.7 × 105 mM−1min−1 and the removal efficiency of 58.7% after 60 s in 2 mg/L of ozone. The degradation of DEHP was initiated by the shortening of the alkyl-side chain followed by the opening of esterified benzene moieties. [Display omitted] • The V 2 O 5 /TiO 2 catalyst was successfully applied with O 3 for DEHP removal. • The enhanced yield of.•OH generation happened at V 2 O 5 /TiO 2. • The enhanced performance of O 3 –V 2 O 5 /TiO 2 was explained by the MvK mechanism. [ABSTRACT FROM AUTHOR]

The application of waste biomass-derived hydrochar to soil may cause extremely intensive nitrous oxide (N 2 O) fluxes that can challenge our current mechanistic understanding of the global nitrogen cycle in the biosphere. In this study, two waste biomasses were used to prepare cyanobacterial biomas-derived hydrochar (CHC) and wheat straw-derived hydrochar (SHC) for short-term incubation experiments to identify their effects and mechanisms of waste biomass-derived hydrochar on soil N 2 O efflux, with time-series samples collected for N 2 O efflux and soil analysis. The results showed that CHC and SHC caused short-term bursts of N 2 O effluxes without nitrogen inputs. Moreover, the enrichment of exogenous organics and nutrients at the hydrochar-soil interface was identified as the key factor for enhancing N 2 O fluxes, which stimulated microbial nitrification (i.e. , increased gene copy number of ammonia oxidizing bacteria) and denitrification (i.e. , increased gene copy number of nitrate and N 2 O reducing bacteria) processes. The concentrations of Fe (II) and hydroxyl radicals (HO•) were 6.49 and 5.63 times higher, respectively, in the hydrochar layer of CHC than SHC amendment. Furthermore, structural equation models demonstrated that HO•, as well as soil microbiomes, played an important role in driving N 2 O fluxes. Together, our findings provide a deeper insight into the assessment and prognosis of the short-term environmental risk arising from agricultural waste management in integrated agriculture. Further studies under practical field application conditions are warranted to verify the findings. [Display omitted] • Exogenous organics and nutrients primarily accumulated at hydrochar-soil interface. • Microbial nitrification and denitrification were stimulated for N 2 O fluxes. • HO.•, as well as soil microbiomes, played a crucial role in promoting N 2 O fluxes. • HO.• inhibited N 2 O reduction through the inhibition of nosZ genes. [ABSTRACT FROM AUTHOR]

The Cr(VI) reducing capability of growing cells of the environmental A. tubingensis Ed8 strain is remarkably efficient compared to reference strains A. niger FGSC322 and A. tubingensis NRRL593. Extracellular glucose oxidase (GOX) activity levels were clearly higher in colonies developed in solid medium and in concentrated extracts of the spent medium of liquid cultures of the Ed8 strain in comparison with the reference strains. In addition, concentrated extracts of the spent medium of A. tubingensis Ed8, but not those of the reference strains, exhibited the ability to reduce Cr(VI). In line with this observation, it was found that A. niger purified GOX is capable of mediating the conversion of Cr(VI) to Cr(III) in a reaction dependent on the presence of glucose that is stimulated by organic acids. Furthermore, it was found that a decrease in Cr(VI) may occur in the absence of the GOX enzyme, as long as the reaction products gluconolactone and hydrogen peroxide are present; this conversion of Cr(VI) is stimulated by organic acids in a reaction that generates hydroxyl radicals, which may involve the formation of an intermediate peroxichromate(V) complex. These findings indicated that fungal glucose oxidase acts an indirect chromate reductase through the formation of Cr(VI) reducing molecules, which interact cooperatively with other fungal metabolites in the biotransformation of Cr(VI). [ABSTRACT FROM AUTHOR]

This work deals with the electrochemical degradation and mineralization of perfluorooctanoic acid (PFOA). Model aqueous solutions of PFOA (100 mg/L) were electro-oxidized under galvanostatic conditions in a flow-by undivided cell provided with a tungsten cathode and an anode formed by a commercial ultrananocrystalline boron doped diamond (BDD) coating on a niobium substrate. A systematic experimental study was conducted in order to analyze the influence of the following operation variables: (i) the supporting electrolyte, NaClO 4 (1.4 and 8.4 g/L) and Na 2 SO 4 (5 g/L); (ii) the applied current density , j app , in the range 50–200 A/m 2 and (iii) the hydrodynamic conditions, in terms of flowrate in the range 0.4 × 10 −4 –1.7 × 10 −4 m 3 /s and temperature in the range 293–313 K. After 6 h of treatment and at j app 200 A/m 2 , PFOA removal was higher than 93% and the mineralization ratio, obtained from the decrease of the total organic carbon (TOC) was 95%. The electrochemical generation of hydroxyl radicals in the supporting electrolyte was experimentally measured based on their reaction with dimethyl sulfoxide. The enhanced formation of hydroxyl radicals at higher j app was related to the faster kinetics of PFOA removal. The fitting of experimental data to the proposed kinetic model provided the first order rate constants of PFOA degradation, k c 1 that moved from 2.06 × 10 −4 to 15.58 × 10 −4 s −1 , when j app varied from 50 to 200 A/m 2 . [ABSTRACT FROM AUTHOR]

Oxidative degradation of the antimicrobial agent ciprofloxacin hydrochloride (CIP) has been investigated using electro-Fenton (EF) treatment with a constant current in the range 60–500 mA. The process generates highly oxidant species OH in situ via electrochemically monitored Fenton reaction. The EF experiments were performed using cells with a carbon felt cathode and Pt anode. Effect of applied current and catalyst concentration on the kinetics of oxidative degradation and mineralization efficiency have been investigated. Degradation of CIP followed pseudo-first order reaction kinetics. The rate constant of the oxidation of CIP by OH has been determined to be (1.01 ± 0.14) × 10 10 M −1 s −1 by using competitive kinetics method. An optimum current of 400 mA and a catalyst concentration of Fe 2+ at 0.1 mM are found to be optimal for an effective degradation of CIP under our operating conditions. A remarkably high degree of mineralization (>94%) was obtained at 6 h of treatment under these conditions. A number of stable intermediate products have been identified using HPLC and LC-MS/MS analyses. Based on the identified reaction intermediates, a plausible reaction pathway was proposed for the mineralization process. The high degree of mineralization obtained in this work highlights the potential application of EF process in the efficient removal of fluoroquinolone based drugs in aqueous medium. [ABSTRACT FROM AUTHOR]

In the present work, a three-dimensional electrode reactor (3Der) using pallet activated carbon (PAC), as particle electrodes, was investigated to degrade non-biodegradable organic pollutants in pharmaceutical wastewater and steel industry wastewater. The effect of operating parameters, such as pH, electrode distance, O 2 flow rate, and current density was investigated. The TOC removal efficiency in 3Der was achieved at the highest mineralization yield of 94.1% after 180 min electrolysis, which was 10–19% higher than the two-dimensional electrode reactor (2Der). The higher performance of the 3Der can be attributed to the indirect and direct oxidation mechanisms. The impact of supporting electrolytes was decreased in order as chloride > nitrate > sulfate. The morphology of sludge and the presence of Fe(OH) 3 after Fenton-oxidation were investigated. 3Der system improved biodegradability of pharmaceutical wastewater after electro-Fenton treatment at a PW/SIW ratio of 3:1 (BOD 5 /COD = 0.6). Hence, the mechanism of 3Der/PAC, as particle electrodes was also proposed. 3Der with PAC particle electrodes using steel industry wastewater as a catalyst is an exciting technique for remediation of organic contaminated pharmaceutical wastewater. [Display omitted] • Three-dimensional Electro-Fenton system with PAC particle electrodes was developed. • A comparison of 3Der, 2Der and simple adsorption by different systems was performed. • A combined pharmaceutical wastewater and steel industrial wastewater as catalyst was testified. • Mechanism of three-dimensional electrode was proposed. [ABSTRACT FROM AUTHOR]

The interlayer of Sb-doped SnO2 (SnO2-Sb) and TiO2 nanotubes (TiO2-NTs) on Ti has been introduced into the PbO2 electrode system with the aim to reveal the mechanism of enhanced electrochemical performance of TiO2-NTs/SnO2-Sb/PbO2 electrode. In contrast with the traditional Ti/SnO2-Sb/PbO2 electrode, the constructed PbO2 electrode has a more regular and compact morphology with better oriented crystals of lower size. The TiO2-NTs/SnO2-Sb interlayer prepared by electrodeposition process improves PbO2 coating structure effectively, and enhances the electrochemical performance of PbO2 electrode. Kinetic analyses indicated that the electrochemical oxidation of nitrobenzene on the PbO2 electrodes followed pseudo-first-order reaction, and mass transport was enhanced at the constructed electrode. The accumulation of nitrocompounds of degradation intermediates on constructed electrode was lower, and almost all of the nitro groups were eliminated from aromatic rings after 6h of electrolysis. Higher combustion efficiency was obtained on the constructed TiO2-NTs/SnO2-Sb/PbO2 electrode. The intermediates of nitrobenzene oxidation were confirmed by IC and GC/MS. [ABSTRACT FROM AUTHOR]

Highlights: [•] Organic matter was extracted by pure water from two black soils and IHSS Elliott soil. [•] Reactive species generated upon irradiation of these WEOMs were quantified. [•] The quantum yields are comparable to those of IHSS humic substances or even higher. [•] WEOMs photosensitized the degradation of bisphenol A. [ABSTRACT FROM AUTHOR]

Fe-MCM-41 had been widely used as ozonation catalyst, however, the existence of large amount of hydrophilic silanol hindered its interfacial reaction with O 3 and pollutants. To solve this problem, F–Fe-MCM-41 was synthesized by co-doping F and Fe into the framework of MCM-41 to replace silanol with Si–F groups through a one-step hydrothermal method. F introduced hydrophobic sites which contributed to more ibuprofen (IBP) chemisorption on the surface of F–Fe-MCM-41. Moreover, doping F also enhanced the acidity, which accelerated O 3 decomposition into •OH. F–Fe-MCM-41/O 3 exhibited notably activity with 96.6% IBP removal efficiency within 120 min, while only 78.5% and 80.9% in O 3 alone and Fe-MCM-41/O 3 , respectively. Surface Lewis acid sites and metal hydroxyl groups were considered as important factors for O 3 activation and •OH generation. F–Fe-MCM-41 exhibited excellent catalytic performance under acidic and alkaline conditions. Comparative experiments revealed that F doping improved the interfacial reaction, especially the interfacial electron transfer, which resulted in the high catalytic activity of F–Fe-MCM-41. F–Fe-MCM-41 possessed good stability and reusability, with only 5.7% decline for IBP removal in five successive cycles. Furthermore, the possible degradation path of IBP was proposed according to DFT calculation and GC-MS analysis. [Display omitted] • F–Fe-MCM-41 exhibited a good activity in catalytic ozonation for IBP. • Si–F bond successfully replaced silanol in the framework of Fe-MCM-41. • Hydrophobicity of F–Fe-MCM-41 contributed to more IBP chemisorption. • Strong Lewis acidity accelerated ozone decomposition to produce more.•OH; • The interfacial reaction played a dominant role in the catalytic ozonation process. [ABSTRACT FROM AUTHOR]

The treatment and disposal of spent radioactive organic solvents, i.e., tributyl phosphate (TBP) and diluent (such as kerosene, n -dodecane, etc.), produced in the reprocessing of spent fuel in the closed cycle are crucial for the sustainable development of the nuclear industry. In this study, the synthesized nanoscale zero-valent iron (nZVI) was used as the heterogeneous Fenton-like catalyst to promote the generation of hydroxyl radicals (•OH) by reacting with H 2 O 2 to degrade the mixed organic solvents of TBP and n -dodecane. nZVI was characterized by scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, and X-ray photoelectron spectroscopy (XPS) to investigate the micro-morphology, nano-particle size, and surface valence state. The change of Fe2+/Fe3+ concentration ratio during the reaction was measured to clarify the performance of nZVI. The effects of temperature, catalyst dosage, H 2 O 2 dosage, and acidifier concentration on the degradation of TBP and n -dodecane were studied, and the results were complemented by the COD of the aqueous solution and the volume reduction rate of the organic phase. The mixed organic solvents of TBP and n -dodecane containing Co2+ were used to simulate the spent radioactive organic solvents and to study the distribution of nuclides after the reaction. The results showed that most of the radioactivity was in the residual solution, and the condensate contained almost no radioactivity. The degradation of TBP and n -dodecane was carried out separately, which showed that n -dodecane was more difficult to degrade. Density functional theory (DFT) calculations were applied to determine the adsorption energy of organic solvents and nZVI. According to the Fourier transform infrared spectra (FTIR) and their corresponding DFT calculations, liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) of the sample after the reaction, the possible intermediates were analyzed, and the degradation mechanism was speculated. [Display omitted] • Organic solvents of tributyl phosphate and n -dodecane were degraded by nZVI/H 2 O 2. • TBP was more easily oxidized than n -dodecane because of the shorter lengths and lower adsorption energy of TBP on the surface of nZVI. • The distribution of nuclides was studied. • The degradation mechanisms were originally proposed. • New insights advance the treatment of organic solvents. [ABSTRACT FROM AUTHOR]

Bio-Fenton reaction supported by glucose oxidase (GOx) for producing H 2 O 2 was applied to degrade persistent chloroacetanilide herbicides in the presence of Fe (Ⅲ)-citrate at pH 5.5. There were pH decrease to 4.3, the production of 8 mM H 2 O 2 and simultaneous consumption to produce •OH radicals which non-specifically degraded the herbicides. The degradation rates followed the order acetochlor ≈ alachlor ≈ metolachlor > propachlor ≈ butachlor with the degradation percent of 72.8%, 73.4%, 74.0%, 47.4%, and 43.8%, respectively. During the Bio-Fenton degradation, alachlor was dechlorinated and filtered into catechol via the production of intermediates formed through a series of hydrogen atom abstraction and hydrogen oxide radical addition reactions. The current Bio-Fenton reaction leading to the production of •OH radicals could be applied for non-specific oxidative degradation to various persistent organic pollutants under in - situ environmental conditions, considering diverse microbial metabolic systems able to continuously supply H 2 O 2 with ubiquitous Fe(II) and Fe(III) and citrate. [Display omitted] • In - situ generation of H 2 O 2 using glucose oxidase (GOx) was achieved. • Bio-Fenton reaction non-specifically degraded various chloroacetanilide herbicides. • Use of Fe (Ⅲ)-citrate enables Bio-Fenton reaction at pH 5.5. • Alachlor was dechlorinated and degraded mainly into oxidized intermediates. • Hydrogen atom abstraction was the key mechanism for the degradation of alachlor. [ABSTRACT FROM AUTHOR]

Polar stratospheric clouds (PSCs), of which the surface is a dynamic liquid water layer and might consist of aqueous HNO 3 and H 2 O 2 , is a well-known key meteorological condition contributing to the ozone hole in the polar stratosphere. PSCs has been considered to provide abundant surface for the heterogeneous reactions causing the formation of the Cl 2 and HOCl, which are further photolyzed into Cl and ClO radicals leading to the ozone destruction. Here we demonstrated that the sunlight drives the massive and stable production of OH radicals in aqueous HNO 3 and its main photo-induced byproduct HNO 2. We also found that the photo-generated OH radicals in aqueous HNO 3 , HNO 2 and H 2 O 2 have the remarkable capability to react with the dissolved HCl, Cl− and Br− to form halogen radicals. In addition, we observed that the H 2 O 2 can react with dissolved HCl and Br− in darkness to form and release Cl 2 and Br 2 gases, which could further be photolyzed into reactive halogen radicals whenever sunlight is available. All these findings suggest that, except for the well-known heterogeneous reactions, photochemical reactions involving the aqueous HNO 3 and H 2 O 2 on and within PSCs surface might constitute another important halogen activation pathway for ozone destruction. This study may shed deeper insights into the mechanism of halogen radicals resulting in ozone depletion in polar stratosphere. [Display omitted] • Photo-generated OH radicals were determined in sunlight-irradiated HNO 3 and HNO 2. • The OH radicals react with dissolved inorganic halides to form halogen radicals. • The H 2 O 2 reacts with HCl and Br− to form and release Cl 2 and Br 2 gases in darkness. • Mechanism on photo-generation of halogen radicals on/within PSCs surface were proposed. [ABSTRACT FROM AUTHOR]

Improper disposal of chlorinated solvents such as trichloroethylene (TCE) and its stabilizer 1,4-dioxane has resulted in extensive contamination in soils and groundwater. Oxidative degradation of these contaminants by strong oxidants has been proposed recently as a remediation strategy, but specific mechanisms and degradation efficiencies are still poorly understood, especially in commingled systems. In this study, a reduced iron-bearing clay (RIC), nontronite (rNAu-2), was oxygenated to produce hydroxyl radicals (•OH) for degradation of TCE and 1,4-dioxane under circumneutral and dark conditions. Results showed that TCE and 1,4-dioxane could be effectively degraded during oxygenation of rNAu-2 in both single and commingled systems. Compared with the single compound system, the degradation rates and efficiencies of TCE and 1,4-dioxane decreased in the commingled system. The negative effect was more significant for TCE than 1,4-dioxane. The commingled TCE and 1,4-dioxane impacted the degradation pattern of each other, due to their difference in •OH scavenging efficiency, surface affinity to rNAu-2 and solubility. Moreover, solution pH, buffer type, rNAu-2 dosage, and dissolved organic matter all affected •OH production and contaminant degradation efficiency. Our findings provide new insights for investigating the natural attenuation of commingled chlorinated solvents and 1,4-dioxane by RIC in redox-fluctuating environments and offer guidance for developing possible in-situ remediation strategies. [Display omitted] • Hydroxyl radicals produced from Fe(II)-bearing clay minerals can effectively degrade co-mingled TCE and 1,4-dioxane. • Comingled TCE and 1,4-dioxane negatively impacted the degradation pattern of each other to different extents. • TCE and 1,4-dioxane exhibited different sensitivity to environmental conditions. [ABSTRACT FROM AUTHOR]

Abstract: The removal of antibiotic tetracycline (TC) from water by electrochemical advanced oxidation process (EAOP) was performed using a carbon-felt cathode and a DSA (Ti/RuO2–IrO2) anode. The influence of applied current, initial pH and initial TC concentration on TC removal efficiency was investigated. Response surface methodology (RSM) based on Box-Behnken statistical experiment design (BBD) was applied to analyze the experimental variables. The positive and negative effects of variables and the interaction between variables on TC removal efficiency were determined. The applied current showed positive effect, while the initial pH value and initial tetracycline concentration gave negative effect on TC removal. The interaction between applied current and initial pH value was significant, while the interactions of initial TC concentration with applied current or initial pH were not pronounced. The results of adequacy check confirmed that the proposed models were accurate and reliable to analyze the variables of EAOP. The reaction intermediates were identified by high-performance liquid chromatography–mass spectrometry (LC–MS) technique and a plausible degradation pathway for tetracycline degradation was proposed. The acute toxicity experiments illustrated that the Daphnia magna immobilization rate reached the maximum after 240min of electrolysis and then decreased with the progress of the reaction. [Copyright &y& Elsevier]

Abstract: The use of organic matter from compost to promote the catalytic photodegradation of micropollutants by solar light appears to be environmentally promising. However, quantitative evaluation of the photodegradation potential of the compost is needed. Our goal was to measure the formation rate of hydroxyl radicals and singlet oxygen, two strongly oxidant species, from irradiated compost organic matter. These two reactive species were photogenerated in all of our extracts regardless of the origin of the compost or the extraction procedure; however, their formation rates increased with composting time. Two herbicides and a fungicide were successfully photodegraded when irradiated with simulated or natural solar light in the presence of the compost organic matter or compost suspensions. For reasons of simplification and ease, the use of the latter is recommended in practice. [Copyright &y& Elsevier]

Abstract: A novel horseradish peroxidase (HRP)-catalyzed H2O2 process in the presence of reduced nicotinamide adenine dinucleotide (NADH) was applied to remove aqueous pentachlorophenol (PCP). Parameters (pH, H2O2 concentration, HRP activity and NADH dosage) on PCP removal were investigated. It was found that initial 0.05mM PCP was removed by 98% in HRP–NADH–H2O2 system at pH 5.0 and 30°C for 1h. Addition of O2 in HRP–NADH–H2O2 system enhanced the removal rate of PCP due to promoting hydroxyl radicals ( OH) and superoxide anion radical () generation, which were confirmed by electron paramagnetic resonance (EPR)-spin trapping method. PCP removal efficiency decreased when and H2O2 were scavenged by superoxide dismutase and catalase in HRP–NADH–O2 system, indicating that OH/ played a great role in the degradation of PCP. Gas chromatography–mass spectrometry (GC–MS) analysis revealed that octachlorinated dibenzodioxin (OCDD) in residual solution was reduced after treated by the HRP–NADH–O2 process, resulting in lower toxicity of treated solution than conventional enzymatic process. Two enzymatic-catalysis pathways were proposed for PCP removal in HRP–NADH–H2O2/O2 system: (i) OH/ free radical oxidation (ii) conventional phenoxy polymerization. [Copyright &y& Elsevier]