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A treatment process utilizing visible-light-activated (Vis) persulfates (PS) in the presence of an organic promoter (glucose) was developed for the simultaneous decolorization of a rhodamine B (RhB) and methylene blue (MB) mixture. Various doses of glucose, PS concentrations, pH values, initial dye concentrations and process time were tested to find out the most appropriate parameters for degrading the RhB/MB mixture in the PS/Vis/Glucose process. Under optimal conditions (C0[RhB/MB] = 5 ppm; pH = 4; glucose dosage = 230 mM; PS concentration = 30 mM; time = 120 min), the degradation of MB and RhB in the mixture was set to 87.8% and 54.7%. The degradation process followed the pseudo-first-order kinetic model with the correlation coefficient R2 = 97%-99%. The PS/Vis/Glucose process is more economical than other existing studies and technologies. The energy efficiency at the optimal conditions were 1.2 and 2.1 kWh m-3 for RhB and MB, respectively. The domination of MB degradation over RhB was confirmed and found to appear as a result of the different physicochemical properties of the dyes and their state of charge, which enables the direct transfer of electrons from the dyes to the PS and leads to the decolorization of the dyes. This work provides an important source of information on the parameters influencing the simultaneous degradation of mixtures of dyes (rhodamine B, methylene blue). The experimental results showed that the PS/Vis/Glucose process may have a positive role in treating color solution mixtures with various dye concentrations (1-20 ppm). [ABSTRACT FROM AUTHOR]

[Display omitted] Due to the immiscibility of inorganic persulfate and non-aqueous phase liquids (NAPLs), conventional persulfate-based in situ chemical oxidation (ISCO) of NAPLs is limited by NAPLs/water interphase mass transfer. To overcome this challenge, quaternary ammonium persulfates (QAPs) have been developed as organic-soluble oxidants to offer organic-phase ISCO of NAPLs. This study first evaluated the stability of QAPs in various organic solvents (ethanol, propanol and butanol), to identify the most suitable solvent. Tert-butanol (TBA) was selected due to its low negative impact on QAPs stability. Subsequently, the kinetics, thermodynamics, and mechanisms of the thermolysis of QAPs in TBA were investigated through thermolysis experiments and density-functional theory calculations, as well as 5,5-dimethyl-1-pyrroline N-oxide trapping experiments. Finally, oxidation of trichloroethene liquids (TCE, one of the most commonly encountered NAPLs at contaminated sites) with thermally activated QAPs in TBA were conducted to tentatively evaluate the feasibility of organic-phase ISCO. The results indicate that thermally activated QAPs efficiently produce sulfate radical species to oxidize TCE in TBA, with significantly enhanced oxidation efficacy and oxidant utilization efficiency over conventional thermally activated inorganic persulfate. Overall, this study demonstrates the potential of organic-phase ISCO for NAPLs remediation. [ABSTRACT FROM AUTHOR]

The electrochemical activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS) for pollutant degradation has gained increasing attention. In this work, reticulated vitreous carbon (RVC) electrodes were prepared at a low cost and investigated for the cathodic activation of PMS/PDS for Acid Orange 7 degradation. The RVC was characterized by SEM, TGA, XRD, Raman spectroscopy, XPS, EIS, and compression test. The superior activity outperformed previous reports in terms of low current density operation (1–10 mA/cm2), high degradation rates (0.13–0.49 min−1), low energy consumption (0.03–0.23 kWh/m3/order) without involvement of catalysts. The process was optimized for current density, PMS dosage, pollutant concentration, pH, water matrix, and supporting electrolyte. Under the optimal current density (3 mA/cm2), the addition of 0.5 mM of PMS boosted the degradation rate by 9.6 times to 0.4470 min−1 and reduced the electrical energy consumption by 90.1 % to 0.0243 kWh/m3/order in 50 mM of Na 2 SO 4. Moreover, up to 117 mg/L of H 2 O 2 was produced in 1 hour by the reduction of oxygen, with current efficiencies between 78–24 %. The process showed little deterioration in 10 cycles, worked for a variety of pollutants, and was not affected by the water matrix. The H-cell experiments confirmed that 90 % degradation took place on the cathode. Scavenging experiments and electrochemical tests suggested that the transitional state of PMS* and O 2 •− mediated the direct electron transfer mechanism for AO7 degradation. Eighteen degradation products were identified by HPLC-MS and categorized into 4 degradation pathways. Finally, their toxicity was assessed by the ECOSAR programme. [Display omitted] • Low-cost electrochemical activation of persulfates was achieved with RVC cathode. • The transition state PMS* and O 2 •− mediated a direct electron transfer mechanism for AO7 degradation. • A small dosage of PMS (0.5 mM) enhanced the degradation by 9.6 times with 10 % energy consumption. • PMS addition altered the formation of degradation products and lowered the toxicity. • The process showed high durability and wide applicability for diverse pollutants. [ABSTRACT FROM AUTHOR]

• Oxidation of ILs in PCD, PCD/persulfate and UV/persulfate combinations was studied. • Long alkyl chain had a negative effect on the efficiency of ionic liquid oxidation. • Bromide anions substantially reduce the oxidation efficiency of imidazolium cation. • PCD and UV/PDS combination proved the most energy efficient for ILs degradation. Ionic liquids (ILs) are salts with exceptional properties important for future development, although potentially hazardous for humans and aquatic life due to their high aqueous solubility and toxicity. Biodegradation of ILs depends on the anion nature and cation structure: many ILs are not readily degraded during conventional wastewater treatment, thus requiring alternative cost-effective and energy-efficient solutions. In this research, the degradation of aqueous imidazolium-based ILs by pulsed corona discharge (PCD) and UV photolysis combined with persulfates was studied, using peroxymonosulfate (PMS) and peroxydisulfate (PDS) as extrinsic oxidants. 1-Ethyl-3-methylimidazolium chloride ([Emim][Cl]), 1-methyl-3-octylimidazolium chloride ([Omim][Cl]), and 1-ethyl-3-methylimidazolium bromide ([Emim][Br]) were chosen as imidazolium-based ILs with different alkyl chain lengths and anions in oxidation experiments under variable operation factors - pH, concentrations of persulfates, pulse repetition frequency in PCD. Pulsed corona discharge has previously shown high energy efficiency in the degradation of micropollutants but has not yet been applied to ionic liquids. The experimental results showed the ability of PCD, PCD/oxidant and UV/oxidant combinations to completely degrade the ILs with the degradation rates in descending order [Emim][Cl] > [Omim][Cl] > [Emim][Br], indicating an impact of both the alkyl chain length and the type of anion on the oxidation rate. The strong activation of persulfates was observed in UV/oxidant combinations, whereas PCD demonstrated the effect of persulfates addition between slight acceleration and moderate deceleration of oxidation dependent on the concentration of extrinsic oxidants. The addition of the sulfate radicals' scavenger, however, showed the presence of those in all combinations indicating a certain replacement of PCD-generated reactive oxygen species with secondary reactants formed from persulfates. The unassisted PCD and UV/PDS combination demonstrated similar energy efficiencies of about 54 and 26 mmol kWh−1 for [Emim][Cl] and [Emim][Br] degradation, respectively, while for [Omim][Cl] the UV/PDS combination showed energy efficiency 1.42 times higher than unassisted PCD. [ABSTRACT FROM AUTHOR]

Degradation and mineralization of antidiabetic metformin (MTF) and opioid tramadol (TMD) in water were studied in UV photolytic oxidation and pulsed corona discharge (PCD) combined with extrinsic persulfate (PS) as UV/PS and PCD/PS systems. The effect of PS dose variation on the oxidation rate and efficiency was assessed. The UV/PS combination showed considerable effect in MTF and TMD removal, enhancing the removal of TOC up to 60–65% at maximum applied PS dose, thus providing the highest cost efficiency. As for the PCD/PS oxidation, the synergy was noticed for MTF, moderately increasing the oxidation rate and mineralization at somewhat increased expense. The PS addition to PCD treatment, however, demonstrated no effect on TMD oxidation. The highest energy efficiency in MTF and TMD degradation was thus showed by non-assisted PCD treatment with an energy yield at 90% conversion of the target compound of 5.6 and 13 g kW-1 h-1, respectively, confirming its practical applicability. The effective mineralization of the target compounds in persulfate photolysis makes it promising for use in advanced water purification. To assess the environmental safety of the studied oxidation processes, the acute toxicity of the treated MTF and TMD solutions to luminous bacteria (Vibrio fischeri) was examined. [Display omitted] [ABSTRACT FROM AUTHOR]

• Virus was inactivated by low-dose iron oxide and oxidant in UVA at near-neutral pH. • Virus inactivation was enhanced with PMS in the presence of bacteria. • Humic acid-incorporated iron oxides promoted virus inactivation with PMS. • ·OH was the main radical in H 2 O 2 and PDS systems. • 1O 2 was the predominant reactive species in PMS system. The photo-Fenton process is effective for pathogen removal, and its low-cost versions can be applied in resource-poor contexts. Herein, a photo-Fenton-like system was proposed using low concentrations of iron oxides (hematite and magnetite) and persulfates (peroxymonosulfate – PMS, and peroxydisulfate - PDS), which exhibited excellent inactivation performance towards MS2 bacteriophages. In the presence of bacteria, MS2 inactivation was inhibited in H 2 O 2 and PDS systems but promoted in PMS-involved systems. The inactivation efficacy of all the proposed systems for mixed bacteria and viruses was greater than that of the sole bacteria, showing potential practical applications. The inactivation performance of humic acid-incorporated iron oxides mediating photo-Fenton-like processes was also studied; except for the PMS-involved system, the inactivation efficacy of the H 2 O 2 - and PDS-involved systems was inhibited, but the PDS-involved system was still acceptable (< 2 h). Reactive species exploration experiments indicated that ·OH was the main radical in the H 2 O 2 and PDS systems, whereas 1O 2 played a key role in the PMS-involved system. In summary, hematite- and magnetite-mediated persulfate-assisted photo-Fenton-like systems at low concentrations can be used as alternatives to the photo-Fenton process for virus inactivation in sunny areas, providing more possibilities for point-of-use drinking water treatment in developing countries. [Display omitted] [ABSTRACT FROM AUTHOR]

Among the most typical artificial sweeteners, acesulfame (ACE) is now ubiquitously detected in aquatic environments. The degradation of ACE by ultraviolet (UV)-activated peroxymonosulfate (PMS) process was systematically investigated. ACE degradation via UV/PMS fits the pseudo-first-order kinetics. 97.63% degradation of ACE (4.78 µM) was achieved after 24 min of treatment with 25 µM PMS. Compared with the neutral pH condition (pH = 7.17), an acidic pH (pH = 2.75 or 5.03) weakly promoted the degradation of ACE, whereas an alkaline condition (pH = 10.90) significantly promoted it. Inorganic anions had varied effects on ACE degradation, with promoting effect of NO3 - and inhibitory effects of HCO3 - and Cl-. ACE degradation was also reduced by the presence of humic acid and fulvic acid. Inhibitory effect on ACE degradation was also observed when the experiment was carried out in natural water. Four degradation by-products of ACE were identified and the degradation mechanisms were proposed. Hydroxyl radicals were identified as the primary contributor to ACE degradation based on quenching experiments. UV/PMS was more favorable than UV/H2O2 considering the degradation and mineralization efficiencies of ACE, although it was inferior to that of UV-activated peroxydisulfate. [ABSTRACT FROM AUTHOR]

In the treatment of water and wastewater, more emphasis is paid to the advanced oxidation process (AOP) based on (S2O82-) radicals. In this work, the degradation of a toxic dye (Orange G) using the heat-activated persulfate was examined Plackett and Burman designs experiments were used to investigate the effects of several parameters on the oxidation of the OG by K2S2O8, including persulfate concentration K2S2O8, the initial dye concentration, the reaction time, the initial solution pH, and temperature. The screening results identify three more influential factors that are subsequently studied by the response surface methodology employing Box--Behnken design to determine optimal conditions for maximal degradation effectiveness. The estimated values agreed with the experimental data, with a coefficient of the determination R² = 0.9429. The forecasted data revealed that with a concentration of Orange G 2 mg/L, a concentration of persulfates of 27.018 mM and a temperature of 45.5°C, a maximum orange degradation of 100% could be attained. The efficacy and the benefits of the advanced oxidation method using heat-activated persulfate for technological and industrial applications for the degradation of the organic pollutants have been well-proven in this work. [ABSTRACT FROM AUTHOR]

[Display omitted] • State-of-the-art strategies for probing defects and fabricating intended defective catalysts are discussed in detail. • Roles of defects in the catalytic kinetics of persulfate are elaborately highlighted. • The essence of defects in switching the radical to non-radical pathway cross-over is revisited. Defect engineering have demonstrated promise in heterogeneous persulfate activation for water remediation, yet the underling mechanisms of defects remain ambiguous. This review describes the cutting-edge progress of defects in persulfate activation regimes. The primary emphasis lies in deciphering how defects impact the catalytic kinetics of persulfate by serving as adsorption sites, regulating electronic structure and thus affecting adsorption energies, inducing surface reconstitution, and providing bonding sites for creating new active centers. Moreover, methodologies for identifying defects (e.g., advanced characterization techniques, defect screening, and theoretical calculations) are outlined alongside strategies for manufacturing tailored defects through in-situ synthesis and post-processing methods. Strikingly, the role of defects in switching persulfate activation pathways is highlighted, illuminating the design of tailored defective catalysts for diverse environmental scenarios. Concluding with a forward-looking perspective envisaging critical challenges and insights for defect design, mechanistic exploration, and practical implementation. [ABSTRACT FROM AUTHOR]

The triclosan (TC) is classified as antibacterial compound as an emerging pollutant, which is extensively used in pharmaceuticals and personal care products. The present study evaluated the degradation efficiency of TC by combination of persulfate radical and electrocoagulation (PS-EC) process from synthetic industrial wastewater. To obtain optimum condition, the effect of influencing parameter on PS-EC process including solution pH, reaction time, current density, PS dose, concentration of electrolyte, initial concentration of TC, and electrode arrangement were systematically investigated. The increase of the current densities from 0.67 to 2.71 mA/cm² resulted in an increase of TC degradation efficiency from 58.7% to 65.9% after 35 min of reaction time. Up to 99.5% of TC was degraded by PS-EC process after 35 min reaction time at optimum condition including PS dose: 250 mg/L, current density: 2.71 mA/cm², electrolyte concentration: 2.5 g/L, and solution pH: 7. The operating cost including electrode and energy was calculated as 164,782 Rial/m³. The Brunauer-Emmett-Teller analysis of produced sludge during PS-EC process indicated that the specific surface area, total pore volume, and mean pore diameter were 97.8 m²/g, 0.19 cm³/g, and 7.8 nm, respectively. [ABSTRACT FROM AUTHOR]

• Efficiency of thermal induced activation of persulfate in removing micropollutants in WW. • Up to 95% abatement with 200 µM of persulfate and 65 °C on a solar pilot equipment. • Smart heat management system to tackle solar energy intermittency. Thermal activation of new oxidant chemicals like Persulfate (PS) has recently gained attention in driving advanced oxidation processes (AOP) for a number of applications. On the other hand, addressing energy demand with carbon free and sustainable energy solutions represents an asset for new technologies in the modern society. This paper then investigates on the removal of pharmaceuticals residues in wastewater (WW), conducted with PS advanced oxidation reactions on a solar thermal pilot equipment. Indoor preliminary investigations on small scale laboratory experimentations show how increasing temperature has a direct positive impact on pollutants degradations rate (k app value ranging from 0.4·10−3s−1 at ambient to 10.4·10−3 s−1 at 75 °C). However, after an experimental screening methodology, 65 °C and 200 µM appear as the appropriate target temperature and PS oxidant dosage to cope with both activation of PS oxidant and degradation of ten target micropollutants typically found in WW stream. Outdoor experimentations on the solar pilot equipment were conducted according to a batch running mode at a treatment capacity scale of a cubic meter. 95% pollutant removal rate is achieved within 2 h once the temperature has raised up to the target value (65 °C) in the bulk treated WW effluent. Series of treatment cycles under the natural day/night period demonstrate the reproducibility of the performance. As an early step result of the process optimization approach, heat recovery demonstration on the pilot equipment improves significantly the energetic balance over the now innovative thermal solar water treatment. [ABSTRACT FROM AUTHOR]

• PFOA degradation by In 2 O 3 nanoparticles was negatively affected by pH, SO 4 2−, Cl−, and H 2 O 2. • Close to 100% PFOA degradation took place when the solution pH was 2. • With the increase of pH, decomposition of PFOA decreased. • In 2 O 3 nanoparticles work best for degrading PFOA in anion-free and low pH solutions. Nanophotocatalysts have shown great potential for degrading poly- and perfluorinated substances (PFAS). In light of the fact that most of these catalysts were studied in pure water, this study was designed to elucidate effects from common environmental factors on decomposing and defluorinating perfluorooctanoic acid (PFOA) by In 2 O 3 nanoparticles. Results from this work demonstrated that among the seven parameters, pH, sulfate, chloride, H 2 O 2 , In 2 O 3 dose, NOM and O 2 , the first four had statistically significant negative effects on PFOA degradation. Since PFOA is a strong acid, the best condition leading to the highest PFOA removal was identified for two pH ranges. When pH was between 4 and 8, the optimal condition was: pH = 4.2; sulfate = 5.00 mg/L; chloride = 20.43 mg/L; H 2 O 2 = 0 mmol/L. Under this condition, PFOA decomposition and defluorination were 55.22 and 23.56%, respectively. When pH was between 2 and 6, the optimal condition was: pH = 2; sulfate = 5.00 mg/L; chloride = 27.31 mg/L; H 2 O 2 = 0 mmol/L. With this condition, the modeled PFOA decomposition was 97.59% with a defluorination of approximately 100%. These predicted results were all confirmed by experimental data. Thus, In 2 O 3 nanoparticles can be used for degrading PFOA in aqueous solutions. This approach works best when the target contaminated water contains low concentrations of NOM, sulfate and chloride and at a low pH. Image, graphical abstract [ABSTRACT FROM AUTHOR]

[Display omitted] • This review summarizes in detail the latest advances in in-situ heterogeneous activation of persulfates. • The different activation mechanisms of persulfate are comprehensively analyzed. • The reasons for the evolution of the various activation mechanisms are summarized. • In-depth studies on the problems and challenges exposed by the persulfate activation system are presented. • Subsequent applications of PS-AOPs and development trends are assessed in detail. This review provides a focused and comprehensive overview of the cutting-edge advancements in advanced oxidation processes employing heterogeneous persulfate activation technologies (PS-AOPs), which can serve as effective tools for tackling emerging organic pollutants. This review focuses on the evolution of PS activation mechanisms and the possible challenges in system application. The review delineates traditional radical mechanisms and elucidates non-radical pathways, such as singlet oxygen, high-valent metal-oxo species, electron transfer, and direct oxidation transfer process. By extensively using empirical data, this review also summarizes the reasons behind the emergence of different oxidation mechanisms and offers potential methods to modulate reaction pathways. It also explores the ecological impacts of the system and suggests prospective strategies for improving by-product management to optimize pollutant removal and ecological sustainability. This review can reveal the untapped potential and future directions of heterogeneous PS-AOPs, making an essential contribution to environmental remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two biochars were prepared from APS/KPS-pretreated bamboo. • Cation types in persulfate impact physicochemical properties of biochar. • The KPS-pretreated bamboo-derived biochar has a higher adsorptive capacity for MB. • The discrepancy in adsorption capacity of two biochar for MB was analyzed. • Electrostatic action is the main adsorption mechanism for MB onto biochars. The adsorption behaviors of biochar are largely impacted by biomass feedstock. In this study, two biochars were prepared from torrefaction of ammonium persulfate- and potassium persulfate-pretreated bamboo and then activated by cold alkali, which are named as ASBC and KSBC, respectively. The two biochars were characterized by different instruments, and their adsorption properties over cationic methylene blue (MB) were compared. The type of persulfates little affected the specific surface areas, but significantly impacted O (29.54 % vs. 35.113 %) and N (12.13 % vs. 3.74 %) contents, functional groups, and zeta potentials of biochars. MB adsorption onto ASBC/KSBC is a single-layer chemical endothermic process and ASBC/KSBC exhibit high adsorption capacity over MB (475/881 mg·g−1) at 303 K. Obviously, the sorption capacity of MB onto KSBC much surpasses that of MB onto ASBC. These results indicate biomass pre-treatment is a cheap and convenient method to prepare biochars with unique physicochemical and adsorptive properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • The fundamentals and synthesis strategies of MXenes are summarized. • The research progress of MXenes in photocatalytic and PS-based AOPs is reviewed. • Various strategies to enhance efficiency of MXene-based catalysts are discussed. • Photocatalytic and persulfates activation mechanisms of MXene-based catalysts are appraised. • The application of MXene-based catalysts for real matrices is discussed. There is a growing concern about wastewater treatment due to the presence of various stubborn pollutants that require advanced catalysts and techniques for effective treatment. As two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, MXene is considered a promising candidate for environmental applications owing to outstanding characteristics, including high surface area, hydrophilic surface, structural flexibility, and surface tunable chemistry. This review consolidates the recent advancements in the utilization of MXenes in photocatalysis and persulfate-based advanced oxidation processes (PS-AOPs) for the abatement of various pollutants from water and wastewater. The fundamentals and synthesis techniques for the MXene and MXene-based catalysts are summarized. Furthermore, strategies to boost the photocatalytic efficiency of MXene-based catalysts, catalytic degradation performance, and reaction mechanisms for organic pollutants removal by inducing binary/multicomponent heterojunctions, S-scheme/Z-scheme, metal/non-metal doping, and defects/vacancies engineering are emphasized in detail. It also offers new perspectives on the single-use of MXene, the MXene reducibility, MXene as support and co-catalyst for persulfate activation, and photocatalytic activated persulfate by MXene-based catalysts and the corresponding mechanisms are elucidated. Applications of MXene-based processes for real matrices, toxicity assessment, and MXene stability for pollutants removal are highlighted. Finally, the review focuses on the conclusions, challenges, and opportunities of MXene-based catalysts in environmental applications to attain high catalytic efficiency. This review provides enlightening knowledge into the utilization of MXene-based catalysts in the field of photocatalysis and PS-AOPs. [ABSTRACT FROM AUTHOR]

• Fe(IV) is the dominant reactive intermediate in the Fe(II)/PMS system at acid pH. • Fe(IV) is also formed at circumneutral pH in the Fe(II)/PMS system. • 18O labeled studies further verified the formation of Fe(IV)-oxo species. • Evolution of Fe(IV) in Fe(II)/persulfates systems was predicted by a kinetic model. • Evolution of Fe(IV) was monitored by a stopped-flow spectrophotometer. Very recently, we have interestingly found that the Fe(II)-activated peroxydisulfate (PDS) process can oxidize methyl phenyl sulfoxide (PMSO) to its oxygen transfer product methyl phenyl sulfone (PMSO 2), suggesting the possible occurrence of a ferryl intermediate (Fe(IV)) rather than long recognized sulfate radical (SO 4 −) in this process. In this work, the formation of PMSO 2 was also observed when PMSO was treated by the Fe(II)/peroxymonosulfate (PMS) system over the pH range of 3–7, and the yield of PMSO 2 (i.e., the molar ratio of PMSO 2 formed to PMSO lost) was quantified to be approximately 100% under acidic conditions, similar to the Fe(II)/PDS system. Moreover, 18O from isotope-labeled water (H 2 18O) was successfully incorporated into PMSO 2 product when PMSO was oxidized by the Fe(II)/PDS and Fe(II)/PMS systems in H 2 18O, likely due to the competitive oxygen exchange of Fe(IV)-oxo species with H 2 18O. Further, Fe(IV) evolution profiles in both systems were predicted by a Fe(IV)-mediated kinetic model, and these results are in good agreement with the experimental data obtained with a stopped-flow spectrophotometer. [ABSTRACT FROM AUTHOR]

Persulfate activation has been applied as one of the efficient advanced oxidation processes (AOPs) to remediate polluted environments. In this study, a novel α-FeOOH anchored by graphene oxide (GO)-carbon nanotubes (CNTs) aerogel (α-FeOOH@GCA) nanocomposite activated persulfate system (α-FeOOH@GCA + K 2 S 2 O 8) was applied for decolorization of Orange II (OII). The decolorization of OII was remarkably enhanced to a level of ~ 99% in this system compared with that of pristine α-FeOOH (~ 44%) or GO-CNTs (~ 18%). The enhanced catalytic activity of α-FeOOH@GCA was due to the formation of a heterojunction by α-FeOOH and GO-CNTs as confirmed by the presence of Fe–O–C chemical bonds. The degradation intermediates of OII were comprehensively identified. The proposed degradation pathway of OII begins with the destruction of the conjugated structures of OII by the dominant reactive oxygen species, surface-bound SO 4 •−. The decolorization efficiency of OII by the α-FeOOH@GCA activated persulfate system decreased from the first to third cycle of recycling. Ultraviolet (UV) irradiation or introduction of a small amount of Fe2+ could restore the activation of this system. The results show that the α-FeOOH@GCA persulfate activation system promises to be a highly efficient environmental remediation method for organic pollutants. Unlabelled Image [ABSTRACT FROM AUTHOR]

• Antioxidants/persulfates were successfully and covalently grafted on Co-Cr substrate. • The persulfated-engineered substrates present rapid re-endothelialization. • Gallic acid persulfate and rutin persulfate exhibit low protein adsorption. • Rutin and rutin persulfate demonstrate reduced platelet adhesion and activation. • These modification processes does not cause any inflammatory responses. Drug-eluting stents (DESs) have been used for the treatment of cardiovascular diseases including stenosis. However, in-stent restenosis, thrombosis, and delayed re-endothelialization represent challenges for their clinical applications. Here, we demonstrate a novel work to overcome these limitations through surface modification technology. The cobalt-chromium (Co-Cr) surface was modified with antioxidants such as gallic acid (GA) and rutin (Ru) and the corresponding persulfates derivatives (i.e., GAS, and RuS) through a simple conjugation procedure. Various analyses tools such as ATR-FTIR, XPS, water contact angle, SEM, and AFM characterized the functionalized surface. The surface characterization confirmed that the antioxidant and the additional persulfates were successfully bonded to the Co-Cr surface. The results of in vitro endothelial cells proved that the persulfates derivatives showed the highest tendency to get rapid re-endothelialization especially RuS. In addition, it showed inhibition to smooth muscle cells (SMCs) as compared to control Co-Cr substrate. The persulfates modified substrates reduced the amount of adsorbed fibrinogen and albumin with higher stability to fetal bovine serum. Moreover, platelet study also demonstrated that Ru and RuS presented lower platelet adhesion with round shape morphology, whereas the control Co-Cr adhere and activate many platelets with pseudopodium morphology. Moreover, these modification processes did not cause any inflammatory responses. In conclusion, it is believed that the persulfates flavonoids have a great potential in the field of drug-eluting stents and blood contacting medical implants to improve blood compatibility, suppress SMCs, and get rapid re-endothelialization. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Magnetic nickel ferrite/carbon sphere was synthesized for persulfate activation. • The influence factors of levofloxacin elimination were optimized and evaluated. • Magnetic nickel ferrite/carbon sphere showed good stability and reusability. • The catalytic mechanism of nickel ferrite/carbon sphere/persulfate system was proposed. Abstract In this study, magnetic nickel ferrite/carbon sphere (NiFe 2 O 4 /CS) composite was synthesized through hydrothermal strategy. Afterwards, several measurements were conducted to illuminate physicochemical properties of composite. Meanwhile, NiFe 2 O 4 /CS was also applied to activate persulfate (PS) for elimination of levofloxacin. The result showed that NiFe 2 O 4 /CS composite owned stronger capacity for PS activation than pure NiFe 2 O 4 and CS. Furthermore, the influence factors, such as the dosage of catalyst, the concentration of PS and the initial pH, were optimized and analyzed. Also, when the levofloxacin degradation carried out under the optimized condition, with 0.6 g/L NiFe 2 O 4 /CS composite and 1.8 g/L persulfate being added and the initial pH being adjusting to 5, 67% levofloxacin was degraded within 1 h. In addition, the possible mechanism of NiFe 2 O 4 /CS nanocomposite activating PS was proposed through the radical scavengers and the result of XPS. More importantly, the repeated experiment was conducted for several times, which proved that the NiFe 2 O 4 /CS composite owned retrievability and reusability, providing a potentially useful catalyst for contaminants removal in water/wastewater treatment. [ABSTRACT FROM AUTHOR]

Phthalic acid esters (PAEs) are often detected in groundwater. Degradation of PAEs in groundwaters is more difficult than in surface waters because of their lower temperatures. Degradation of three PAEs (di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), and dimethyl phthalate (DMP)) were investigated in ZVI-persulfate system at 15°C, 20°C, 25°C, and 30°C. Degradation rates of these PAEs were much faster when persulfate was activated by ZVI in comparison with the persulfate activated by heat only. PAEs degradation slowed down as temperature decreased. Degradation of DEHP, DBP, and DMP at 15°C in 180 min was 32%, 47%, and 5%, respectively. PAEs with longer carbon chains degraded more than PAEs with shorter carbon chains at 25°C-30°C. Conversion of persulfate into sulfate, release of iron ions, and variation in pH values in the solutions were also investigated. Persulfate ions consumption and dissolution of iron ions increased as temperature increased. About 47-57 mg/L of sulfate ions formed from 60 mg/L of persulfate. pH values remained in the 3.5-4. range. Our work provides basic and guidance knowledge for in situ PAEs remediation from groundwaters. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • BC/Fe(III)/PS system showed excellent performance for SMX degradation. • Electron transfer process occurred between the BC surface and Fe(III). • The carbon-centered persistent free radicals were proved as electron donors. • Tert-butanol resulted in an overestimation of HO · proportion. • The C–S bond severing was a reasonable degradation pathway of SMX by SO 4 · - attack. Abstract In this study, the biochar (BC)-induced Fe(III) reduction for persulfate (PS) activation system was used for the first time in sulfamethoxazole (SMX) degradation. The apparent rate constant of the BC/Fe(III)/PS system was 31.3 and 8.2 times that of BC/PS system and Fe(III)/PS system, respectively. The carbon-centered persistent free radicals contained in BC acted as electron donors. Electron transfer occurred between the BC surface and Fe(III) successfully. Fe(II) was thus generated and played a key role for the subsequent PS activation. Scavenger quenching experiments and electron spin resonance spectrometry confirmed the presence of sulfate (SO 4 · - ) and hydroxyl radicals ( HO ·), which brought about the efficient SMX degradation in the BC/Fe(III)/PS system. Furthermore, the frontier molecular orbital (FMO) theory and dual descriptor (DD) method were employed in predicting radical attacking sites of SMX. According to the results of theoretical computations and the experimental detection, degradation pathways of SMX in the BC/Fe(III)/PS system were deduced accurately. This study gives new insight into the possible mediatory roles of biochar in PS activation by transition metal ions. The BC/Fe(III)/PS system is a promising process for groundwater and soil remediation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel 3D galvanic cell/Fe2+/persulfate system could remove AR E. coli efficiently. • GAC offered more sites for redox reactions to enhance the disinfection effect. • Sulfate radicals and hydroxyl radicals were responsible for disinfection. • 83.2% antibiotic resistance gene ampC were eliminated within 60 min by this system. • Cycled GAC performed very good repeatability on disinfection test even for 6 times. Abstract A novel and efficient three-dimensional electrode galvanic cell enhanced Fe2+/persulfate (3D-GFP) system was used to inactivate antibiotic resistant E. coli (AR E. coli) for the first time. The 3D-GFP system was compared with two-dimensional electrode GFP. The 3D-GDP system obviously had a better disinfection effect than the 2D electrode GDP and achieved a 4.6 log disinfection of bacteria within 10 min. Several disinfection experiments were conducted to evaluate the impact of operational conditions (i.e. granular active carbon (GAC) dosage, initial bacteria concentration, additional Cl¯ content and repetitive use of recycled GAC) on the 3D-GFP process. The stability of GAC in this system was confirmed by the excellent disinfection performance demonstrated in the sixth repetitive test. Sulfate radicals and hydroxyl radicals were identified as the factors responsible for disinfection. Biologically, lipid peroxidation, membrane permeability and potential, Ca2+ leakage, ATP level, ATPase activity, removal of DNA and antibiotic resistance genes ampC were analysed to demonstrate the toxicological effect of 3D-GFP on AR E. coli. These results highlighted 3D-GFP as a promising disinfection method. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Persulfate activation by activated carbon is a non-radical process. • Pathways of p -chloroaniline degradation in non-radical oxidation system have been proposed. • Activated carbon shows good catalytic activity and structural stability during oxidation. Abstract Persistent organic pollutants (POPs) are widely distributed and have significant negative environmental impacts. Advanced oxidation processes (AOPs) based on sulfate radicals produced from persulfate (PS) have attracted considerable attention for the degradation of POPs, however, there are several disadvantages with these radical activation systems. This study examined the degradation of p -chloroaniline (PCA) by persulfate (PS) activated with activated carbon (AC). The effects of initial pH and dosage of AC were also investigated. Results showed that AC exhibits good catalytic activity toward PS. Increasing AC dosage significantly improved the PCA degradation rate but PCA removal was not obviously influenced by initial pH ranging from 3 to 9. PS activation in the PS/AC system was a non-radical process as demonstrated by (i) ethanol and tert -butyl alcohol having little effect on PCA removal and (ii) Electron Paramagnetic Resonance results showing no radicals signals in the PS/AC system. Results also demonstrated that TOC could be removed in PS oxidation and PCA dechlorination was rapid (in the initial 30 min). The three major intermediates identified during the PCA degradation in the non-radical oxidation process were N-(4-chloro-phenyl)-benzene-1,4-diamine, 4-chloro-phenyl-diazene and hydroquinone and two pathways of PCA degradation was proposed. This study proposes a new insights into the mechanism of PS activation by AC and an efficient method for POPs removal. [ABSTRACT FROM AUTHOR]

Abstract Sulfate radical (SO 4 -) -based advanced oxidation processes (SR-AOPs) have proven effective for simultaneously removing refractory dissolved organic matter (DOM) and ammonia in municipal landfill leachates. However, the knowledge on the competition of leachate DOM and ammonia for SO 4 -, the utilization efficiency of persulfate, as well as the reaction pathways and final products of ammonia oxidation during the SR-AOP treatment remains little known, thereby leading to a lack of a comprehensive evaluation of the emerging leachate treatment technology. The objective of this study was to further investigate the performance of a thermally activated persulfate system for treatment of a mature landfill leachate and re-evaluate the benefits and restrictions of SR-AOPs for leachate treatment. The laboratory experimental results showed that removal patterns of chemical oxygen demand (COD) and ammonia relied heavily upon the dose of persulfate that could be thermally activated to produce reactive sulfate radicals, reflecting the competition of leachate DOM, ammonia, and non-target leachate constituents for SO 4 -. The utilization efficiency of the added persulfate could be more efficiently utilized for removing the two target leachate pollutants at a lower persulfate dose, whereas more persulfate was wasted due to the reactions with non-target leachate constituents (e.g. Cl− and CO 3 2−) and/or self-decomposition with the increasing persulfate dose. During the treatment, ammonia was oxidized, via the direct attack of SO 4 - and/or by molecular chlorine produced from the reactions of chloride and sulfate radicals, into nitrate and nitrogen gas, while nitrite was not detected. Of importance, this study highlighted three potentially negative impacts of SR-AOPs on the quality of treated leachate, including accumulation of total dissolved solids, the production of undesirable nitrate, and the pH decrease due to the continuous formation of hydrochloric acid. Therefore, the three issues should be carefully evaluated when a SR-AOP is selected for leachate treatment. Because these impacts become less pronounced with a decreasing persulfate dose, SR-AOPs as a pre-treatment, which is achieved at a relatively low persulfate dose, may be an appropriate option for the SR-AOP application to leachate treatment. Graphical abstract Image 1 Highlights • Sulfate radicals are competed among organics, NH 3 , and other leachate constituents. • Utilization efficiency of sulfate radicals is decreased with an increasing persulfate dose. • Oxidation products of NH 3 after SR-AOP treatment include nitrate and nitrogen gas. • Cl− inhibits COD removal but improves the abatement of NH 3 -N during SR-AOP treatments. • TDS increase, nitrate formation, and pH decrease may restrict SR-AOPs for leachate treatment. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Magnetic MnO 2 /MnFe 2 O 4 nanocomposite was fabricated as the PMS activator. • Controlling factors of Rh B degradation were evaluated. • Magnetic MnO 2 /MnFe 2 O 4 nanocomposite exhibited high activity and stability. • The mechanism of PMS activation by MnO 2 /MnFe 2 O 4 was elucidated. Abstract Novel magnetic MnO 2 /MnFe 2 O 4 nanocomposite was successfully fabricated by hydrothermal method. Subsequently, this nanocomposite was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microcopy (TEM), X-ray photoelectron spectra (XPS), vibrating sample magnetometer (VSM) and Brunauer-Emmett-Teller (BET) measurements. Then the material was applied to activate PMS for Rhodamine B (Rh B) degradation. The results displayed that the decomposition efficiency of the MnO 2 /MnFe 2 O 4 nanocomposite with a mole ratio of 7:1 was 90% for Rh B within 5 min in the presence of PMS, higher than other MnO 2 /MnFe 2 O 4 ratio, homogeneous catalysts (Fe3+ and Mn2+), pure MnO 2 and pure MnFe 2 O 4. In addition, influences of pivotal factors (PMS concentration, catalyst dosage and initial pH value), performance of different processes and reusability of MnO 2 /MnFe 2 O 4 nanocomposite were also evaluated. Radical scavenging experiments were conducted and SO 4 − was indicated as the primary radical. What's more, the MnO 2 /MnFe 2 O 4 nanocomposite could be convenient to recycle in practical application benefited from its magnetism. Finally, according to the results and previous studies, the believable mechanism of activating PMS by MnO 2 /MnFe 2 O 4 nanocomposite was put forward, which could occupy an important position as a fast treatment option in sewage disposal. [ABSTRACT FROM AUTHOR]

Highlights • A novel magnetic carbon coated Fe-C/N composite is successfully prepared. • Fe-C/N significantly promotes the degradation rate of Acid Red 73 (AR 73) by persulfate. • Cyclic degradation tests show the catalyst is highly active, stable and recoverable. • Singlet oxygen is dominantly attributed to the AR 73 degradation. Abstract A magnetic carbon-coated Fe-C/N composite was synthesized by a simple impregnation method and its performance in activating persulfate (PS) to degrade Acid Red 73 (AR 73) was investigated. The as-prepared carbon-coated Fe-C/N hybrid material was characterized via transmission electron microscopy, Raman spectra, X-ray diffraction and X-ray photoelectron spectrum. Degradation experiments showed that 98.11% of AR 73 could be degraded in 10 min, but its COD was partly removed. The effects of initial reaction pH and temperature were also evaluated. An increase of temperature was beneficial for the removal of AR 73, while the increase of pH had an opposite result. The activation energy of the AR 73 degradation was determined to be 46.12 KJ/mol, smaller than those in relative literatures. The recycling test showed that the carbon-coated Fe-C/N composite had good stability. The mechanism study indicated that the catalytic performance of Fe-C/N was due to the synergistic effect between Fe 3 C and Fe 3 N, and the N doped carbon shell suppressed the rate of Fe leaching, thus enhancing its stability. [ABSTRACT FROM AUTHOR]

Abstract The objective of this research was to evaluate slow-release permanganate and unactivated persulfate for in situ treatment of dioxane and associated chlorinated solvents. Laboratory batch studies with unactivated persulfate in deionized water or in soil and groundwater demonstrated dioxane removal with pseudo second-order rate constants ranging from 10−5 to 10−3 M−1 s−1. Flow-through column studies demonstrated over 99% dioxane removal with slow-release unactivated persulfate but not with slow-release permanganate. The slow-release permanganate cylinders became coated with a rind that limited oxidant mass transfer and dioxane oxidation. A field study was conducted with slow-release persulfate cylinders transverse to groundwater flow. Over 99% removal of dioxane and chlorinated solvents was observed 2.5 m downgradient of the cylinders. Density-driven flow associated with the released persulfate was observed and was attributed to a low horizontal hydraulic gradient. Thus, most of the contaminant and persulfate flux was thought to be isolated to a deep aquifer zone that was bound by an underlying silt aquitard. Contaminant reductions were also observed in shallow groundwater samples, albeit at a lesser extent. The longevity of the persulfate oxidant cylinders was estimated to be 6–12 months. Results of this study demonstrate that dioxane and co-mingled chlorinated solvents can be effectively treated using slow-release persulfate cylinders. Careful consideration to cylinder placement during the design phase is essential to prevent the contaminant plume from bypassing and not coming into contact with the released oxidant. Highlights • Persulfate without added activators and permanganate promoted dioxane and chlorinated solvent destruction. • A rind formed around slow-release permanganate cylinders limited permanganate release, resulting in poor dioxane destruction. • 99% removal of dioxane and chlorinated solvents was observed in a field study using slow-release persulfate cylinders. • Density-driven flow was observed and was attributed to a low horizontal gradient at the site. [ABSTRACT FROM AUTHOR]

Abstract This research describes the function of oxygen vacancy on CoFe 2 O 4-x for persulfate (PS) activation. Novel CoFe 2 O 4-x with different vacancy degrees that were successfully developed via hydrogen calcination were characterized using X-ray diffraction analyzer (XRD), Fourier transform infrared (FTIR) spectra, Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), H 2 temperature-programmed reduction (H 2 -TPR), cyclic voltammetry (CV), electrochemical impedance spectra (EIS), nitrogen adsorption-desorption isotherms and dynamic light scattering. The activation of catalysts was analyzed using Bisphenol A (BPA) as pollutant, and the main active species generated during the reaction were identified by using N 2 bubbling and scavenger experiments. Possible oxidation degradation pathways of BPA were speculated using gas chromatography–mass spectrophotometry (GC-MS) and total organic carbon (TOC) analysis. Findings indicated that the oxygen vacancies promoted electronic transfer and participated in the redox cycle from Co3+/Fe3+ to Co2+/Fe2+ to generate 1O 2 and O 2 -. O 2 -, OH and SO 4 - generated from oxygen vacancy; moreover, PS activation could further degrade BPA to small molecules, such as benzenes and quinones. Finally, the toxicity of the reaction mixtures was evaluated and found that the acute toxicity to Daphnia magna decreased after 120 min treatment. Graphical abstract Novel CoFe 2 O 4−x with abundant oxygen vacancies that were successfully developed via hydrogen calcination were used for persulfate (PS) activation. Oxygen vacancies not only promote the redox cycle of Co3+/Co2+ and Fe3+/Fe2+ to produce SO 4 − and OH but also provide O 2 − and 1O 2 for the degradation of BPA. Image 1 Highlights • A novel oxygen vacancy-rich CoFe 2 O 4-x was developed. • 200-HCFO/PS system can accommodate a wide pH range. • The function of oxygen vacancies and transition metals for the PS activation was firstly discussed. [ABSTRACT FROM AUTHOR]

Abstract Chemical conditioning before mechanical dewatering is an indispensable step to enhance the waste activated sludge (WAS) dewaterability and solid-liquid separation. Feasibility of utilizing Fe(II)/S 2 O 8 2− oxidation integrated with microwave irradiation (MW) in improving gel-like floc destruction, water seepage and WAS dewaterability was investigated. Comprehensive characterization of the treated WAS was conducted to explore the effects of MW on the catalyzing kinetics of Fe(II)/S 2 O 8 2− oxidation and reveal the underlying dewatering principle. The results demonstrated that MW-Fe(II)/S 2 O 8 2–process was more cost-efficient, reagent-saving than single Fe(II)/S 2 O 8 2− oxidation or MW irradiation in stimulating WAS dewaterability and the optimal conditions were 0.4/0.5 mmol-Fe(II)/S 2 O 8 2− g−1-TS (total solids) and 500 W with 94.6% capillary suction time (CST) reduction within 120 s of conditioning. Thermal effect of MW reduced the activation energy of S 2 O 8 2− decomposition and stimulated the generation of more SO 4 −· while athermal effect could create additional gel-network destruction and cell lysis, which reduced the water-binding energy and induced the seepage of more extracellular polymeric substances (EPS)-bound and cell water. Further analysis via fluorescence excitation-emission matrix combined with parallel factor analysis demonstrated that protein-like, humic- and fulvic-like substances in slime EPS (S-EPS) and loosely bound EPS (LB-EPS) together affected sludge dewaterability. Additionally, the hybrid process could further remove the released COD and ammonia, facilitating the subsequent advanced treatment. Graphical abstract Image 1 Highlights • Microwave accelerated Fe(II)/S 2 O 8 2− process for enhancing sludge dewaterability. • 94.6% capillary suction time reduction was obtained within 120 s of conditioning. • Rupture of extracellular polymeric substances and cells induced bound liberation. • Hybrid process further mineralized the released pollutants (COD and ammonia). [ABSTRACT FROM AUTHOR]

Abstract In this study, the degradation kinetics of iopamidol (IPM) by three different UV-based oxidation processes including UV/hydrogen peroxide (H 2 O 2), UV/persulfate (PDS) and UV/chlorine (NaClO) were examined and the potential formation of iodinated disinfection byproducts (I-DBPs) in these processes followed by sequential chlorination was comparatively investigated. Increasing pH led to the decrease of IPM degradation rate in UV/NaClO, while it showed negligible impact in UV/PDS and UV/H 2 O 2. Common background constituents such as chloride ions (Cl−), carbonate (HCO 3 −) and natural organic matter (NOM) inhibited IPM degradation in UV/H 2 O 2 and UV/PDS, while IPM degradation in UV/NaClO was only suppressed by NOM but not Cl− and HCO 3 −. The differences in transformation products of IPM treated by hydroxyl radical (HO*), sulfate radical (SO 4 *-), as well as Cl 2 *- and ClO* generated in these processes, respectively, were also analyzed. The results suggested that hydroxyl radical (HO*) preferred to form hydroxylated derivatives. Sulfate radical (SO4*-) preferred to oxidize amino group of IPM to nitro group, while Cl 2 *- and ClO* favored the generation of chlorine-containing products. Moreover, specific I-DBPs (i.e., iodoform (IF) and monoiodacetic acid (MIAA)) were detected in the three processes followed by chlorination. The addition of NOM had little effect on IF formation of three processes, while MIAA formation decreased in all processes except UV/H 2 O 2. Given that the formation of I-DBPs in UV/NaClO was less than those formed in the other two processes, UV/NaClO seems to be a more promising strategy for effectively removing IPM with alleviation of I-DBPs in treated water effluents. Graphical abstract Image 1 Highlights • Degradation of IPM by H 2 O 2 , PDS and NaClO under UV irradiation was examined. • Kinetics modeling was performed based on reaction rates of radicals with IPM. • Oxidation products of IPM by different reactive radicals were identified. • Formation potential of I-DBPs in three UV-based oxidation processes was compared. [ABSTRACT FROM AUTHOR]

Highlights • Sulfate activated persulfate oxidation effectively degrade DTZ. • Operation condition parameters for DTZ degradation were optimized. • DFT was employed to examine DTZ degradation paths. Abstract As a type of iodinated contrast medium (ICM), the diatrizoate (DTZ) found in aquatic systems has posed a serious threat to the ecosystem and to human health. In this study, Fe(II)-activated persulfate (Fe2+/PS) oxidation was employed to degrade DTZ, and the optimal operating conditions were determined. Electron paramagnetic resonance (EPR) spectra and density functional theory (DFT) calculations were adopted to determine the dominant radicals and analyze the degradation paths, respectively. It was found that a PS concentration of 10 mmol/L, an n(Fe2+)/n(PS) ratio of 1:10, an initial pH of 3.0, and a high temperature increased the degradation efficiency of DTZ. After suppression of the oxidation process by tertiary butyl alcohol (TBA) and methanol (MtOH), the EPR spectra demonstrated that DTZ degradation was attributed to the combined effects of SO 4 − and OH and that OH played a more important role. Based on the theoretical calculation and comparison of the reduction energies of possible degradation products, the path from DTZ to TP630 and then to TP628 and finally to TP602 was recognized as the main DTZ degradation pathway during the Fe2+/PS oxidation process. These findings validated and demonstrated that DTZ could be effectively degraded by Fe2+/PS oxidation, which is a promising approach to remove DTZ from water. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The EC/CFO/PS system was developed for the degradation of atrazine in water. • The optimal operating conditions were obtained through parameter optimization. • Sulfate radical was the main radical responsible for atrazine degradation. • The atrazine degradation pathway in EC/CFO/PS system was put forward. • The synergistic mechanism of the EC/CFO/PS process was proposed. Abstract In this study, CuFe 2 O 4 (CFO) magnetic nanoparticles are used as both particle electrode and catalyst for persulfate (PS), applying in the three-dimensional (3D) electrochemical process for atrazine (ATZ) degradation. We studied the effects of operating parameters (i.e., CFO dosage, PS concentration, initial pH, and current density) on ATZ degradation. The optimum ATZ degradation efficiency (>99%) and TOC removal (22.1%) were achieved after 35 min treatment with CFO dosage of 3.0 g/L, PS concentration of 4.0 mM, current density of 4 mA/cm2, and initial pH of 6.3. Several comparative studies of control experiments were carried out, confirming the superior performance of EC/CFO/PS system for ATZ degradation. CFO magnetic nanoparticle electrodes (MNPEs) exhibited a favorable stability during the five runs under optimal conditions. Quenching experiments and electron paramagnetic resonance (EPR) study proved that ATZ was destroyed by free radicals. Meanwhile, the monitored sulfate radical and hydroxyl radical concentration in EC/CFO/PS system revealed that sulfate radical was the dominant reactive radical in ATZ degradation process. Based on the detected intermediates by LC-MS, the pathways of ATZ degradation in the EC/CFO/PS system were proposed. Finally, the study proposed the reaction mechanism of EC/CFO/PS three-dimensional electrochemical process. In brief, EC/CFO/PS 3D electrochemical process was found to be a reliable technology for the remediation of surface water and groundwater contaminated by atrazine. [ABSTRACT FROM AUTHOR]

Highlights • Both Fenton and Fe2+/PS processes are efficient for TPhP degradation from water. • Natural water matrix significantly affected TPhP degradation. • HO and SO4 − are predominant radicals in Fenton and Fe2+/PS process, respectively. • Similar intermediates of TPhP in both processes were identified using LC-MS. Abstract The efficacies of ferrous ion-activated hydrogen peroxide (Fe2+/H 2 O 2 , Fenton) and persulfate (Fe2+/S 2 O 8 2−, Fe2+/PS) processes for degrading triphenyl phosphate (TPhP) in aqueous solutions were systemically investigated and compared. Both Fenton and Fe2+/PS processes can effectively degrade TPhP in water. A fast TPhP degradation was achieved in 5 min by Fenton oxidation, while TPhP was gradually degraded with prolonging reaction time via Fe2+/PS oxidation. The effects of operating parameters, including oxidant and Fe2+ dosage, pH, and water constitutes, on TPhP degradation were systemically evaluated. TPhP removal was increased as the oxidant and Fe2+ dosage increase, while TPhP degradation was not greatly changed under the examined pH (4.0–9.0). Water constitutes, humic acid, and anions (Cl− and NO 3 −) did not obviously influence TPhP degradation for both processes. However, HCO 3 − significantly inhibited TPhP oxidation, and the inhibition was inversely related to HCO 3 − concentrations. Radical quenching experiments and electron paramagnetic resonance spectrometry revealed that HO was the dominant radical in Fenton process whereas SO4 − played a dominant role in Fe2+/PS process for TPhP degradation. Moreover, TPhP removal in various natural water matrices was examined to better understand the feasibility of AOPs on the elimination of TPhP from natural waters. The lower removal of TPhP indicates that both of high oxidant dosage and/or long reaction time were required to achieve high removal efficiency and high mineralization. Furthermore, TPhP degradation products were identified through LC-MS/MS technology. Similar products were observed in both oxidation processes, and the degradation pathways mainly involved hydroxylation and phenoxy bond cleavage. The results of this study indicates that it is technically feasible for applying HO and SO 4 − based AOPs to treat TPhP contamination in water/wastewater. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • UV/pre-Fe0/PS enhanced degradation 2.2 times and reduced 86% costs compared with UV/Fe0/PS. • Synergetic factor (6.1–12.3) in UV/pre-Fe0/PS were much larger than in UV/Fe0/PS (2.3–5.4). • Both more OH and SO 4 − radical were produced in UV/pre-Fe0/PS system. • UV/pre-Fe0/PS system could achieve good performance in different SWEs. • UV/pre-Fe0/PS was more cost-effective to remove ECs compared with other AOPs. Abstract Emerging contaminants (ECs) have been frequently detected in the aquatic environment and have adverse effect on the environment. In our present study, four ECs (800 μgL−1 oxytetracycline (OTC) and tetracycline (TC); 400 μgL−1 sulfadiazine (SD) and sulfamethazine (SMT)) spiked into the secondary wastewater effluent (SWE) were treated by novel UV/pre-magnetized Fe0/PS process (UV/pre-Fe0/PS). TC, OTC and SMT could be completely removed within 30 min and 98.4% SD could be removed within 60 min, while less than 10%, 20% and 60% ECs could be removed by Fe0/PS, pre-Fe0/PS and UV process within 60 min. Synergetic factor values (6.1–12.3) in UV/pre-Fe0/PS were much larger than in UV/Fe0/PS (2.3–5.4) to remove various ECs, achieving 0.7–2.2 times enhancement in degradation rate constants and 45%–86% reduction in treatment costs. EPR spectra and scavenging tests by tert-butyl alcohol and methanol confirmed that not only faster and more SO 4 − and OH radicals were produced but also their contributions to SMT removal were enhanced. Optimization of dosage of Fe0 (0–0.4 mM) and dosage of PS (0–0.4 mM) indicated that 0.2 mM Fe0 and 0.2 mM PS was the optimal dosage. Meanwhile, this process not only could enhance 0.7–15.8 times degradation rate constant but also could reduce about 14.3–97.9% costs to remove various ECs compared with US/Fe0/PS, ozonation, VUV/UV/Fe3+ and UV/H 2 O 2 process. Moreover, it could enhance 1.4 times of degradation rate constant and reduce about 62% cost to remove SMT in another SWE, indicating the applicability in different wastewaters. Therefore, UV/pre-Fe0/PS process is promising and cost-effective to remove ECs in SWEs. [ABSTRACT FROM AUTHOR]

Highlights • Activation of persulfate by gamma radiation was effective to improve ERY degradation. • k obs increased 1.4–6.5 times in three kinds of waters by Gamma/PS system. • TOC reduction increased to 3.4–52% compared to 0.9–25% by gamma radiation alone. • No antimicrobial activity was observed at 10 kGy to S. aureus in Gamma/PS system. • A higher yield of formic and acetic acids by Gamma/PS treatment was observed. Abstract The degradation of macrolide antibiotic erythromycin (ERY) and the reduction of antimicrobial activity was performed using persulfate activated by gamma radiation in different water matrices. The results showed that the rate constant k obs of ERY degradation in γ ray-activated S 2 O 8 2− (Gamma/PS) system increased by 6.5 times in deionized water, 5.0 times in groundwater and 1.4 times in treated wastewater, respectively. A significant improvement in mineralization rate was observed in Gamma/PS system, with 3.4–52% TOC reduction, compared to 0.9–25% in γ ray system. The results of antimicrobial activity of ERY against E. coli and S. aureus in the three kinds of waters showed that no antimicrobial activity to E. coli was observed at 1 kGy in Gamma/PS system, which required 6 kGy by γ ray alone. The inhibition to S. aureus was still observed at 10 kGy using gamma radiation in groundwater and treated wastewater, which disappeared in Gamma/PS system. The presence of organic substances inhibited ERY degradation more significantly than inorganic anions. In such cases, the ERY degradation rate was promoted by around 2 times and 12 times, respectively in the presence of peptone and glucose in Gamma/PS system. The 14-membered ring of ERY was destroyed by gamma radiation. Formic acid and acetic acid were detected and their yield was higher in Gamma/PS system. The γ ray-activated persulfate process is promising to treat ERY-containing water and wastewater. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • PS activation with nZVI/OMt can efficiently degrade sulfamethazine (SMZ). • Both SO 4 − and OH were identified in nZVI/OMt-activated PS process. • Degradation pathway was proposed based on intermediates identified by LC-QTOF. Abstract Sulfamethazine (SMZ) is one of the most widely used sulfonamides and is frequently detected in water resources, posing threats to human and ecological health. To address this concern, SMZ degradation was investigated using nanoscale zero-valent iron (nZVI) supported on an organo-montmorillonite (OMt) composite (nZVI/OMt), which was synthesized by reduction of Fe2+ with NaBH 4 , to activate persulfate (PS). Up to 97% degradation of 20 mg/L SMZ was achieved within 10 min using 1.5 mM nZVI/OMt (mass/mass, 3/1) and 4 mM persulfate at pH 6.8 and 25 °C. Experimental results indicated that SMZ degradation obeyed pseudo-first-order reaction kinetics, and the observed pseudo-first-order rate constant (k obs) in the nZVI/OMt-activated PS process was 1.5 times that for the nZVI-activated PS process. SMZ transformation was improved by increasing the PS concentration and temperature. Natural water constituents, such as Cl−, NO 3 −, and humic acid, slightly inhibited SMZ degradation, whereas SMZ transformation was significantly reduced by HCO 3 −. Electron paramagnetic resonance and radical scavenger experiments demonstrated that both OH and SO 4 − participated in SMZ degradation; however, SO 4 − was the dominant reaction mechanism. Degradation products were analyzed by UPLC-QTOF-MS and confirmed three reaction pathways: cleavage of the S–N bond; smiles-type rearrangement; and, oxidation of the aniline moiety. Overall, the experimental results suggest that nZVI/OMt-activated PS oxidation is an easy, low-cost, and efficient method for rapid remediation of SMZ-contaminated water. [ABSTRACT FROM AUTHOR]

Abstract Removal of polycyclic aromatic hydrocarbons (PAHs) from different soil fractions of contaminated soil was investigated by using activated persulfate oxidation remediation in our research. The results showed that the light fraction, which accounted for only 10% of the soil, contained 30% of the PAHs at a concentration of 4352 mg/kg. The heavy fraction contained more high-molecular-weight PAHs, and the total PAH concentration was 625 mg/kg. After being oxidized, the removal rate of PAHs was 39% in the light fraction and nearly 90% in the heavy fraction. Among the different fractions of the heavy fraction, humic acid contained the highest concentration of PAHs, and consequently, the highest removal efficiency of PAHs was also in humic acid. Compared with the light fraction, the heavy fraction has more aromatic compounds and those compounds were broken down during the oxidation process, which may be the removal mechanism involved in the oxidation of high-ring PAHs. Similarly, the enhancement of C = C bonds after oxidation can also explain the poor removal of high-ring PAHs in the light fraction. These results imply that different fractions of soil vary in composition and structure, leading to differences in the distribution and oxidation efficiencies of PAHs. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Highlights • The pre-Fe0/PS process can efficiently degrade nitrobenzene (NB) • HCO 3 −, SO 4 2− and NO 3 − hindered the efficiency of pre-Fe0/PS and Fe0/PS processes. • Cl− imposed contrary impact on the pre-Fe0/PS and Fe0/PS processes. • Humic acid hindered NB degradation in both pre-Fe0/PS and Fe0/PS processes. • A pre-Fe0 column was effective for the NB removal in the pre-Fe0/PS process. Abstract Nitrobenzene (NB) is toxic and resistant to biodegradation and widespread in surface water and groundwater. The persulfate (PS) system has been employed for the NB degradation and proved to be effective. Zero-valent iron (Fe0) has been used for the activation of PS (Fe0/PS) recently. However, the process exhibits a significant drawback of slow release of Fe2+ from Fe0, resulting in low efficiency of the approach as Fe2+ is the primary species for the PS activation. In this study, a weak magnetic field was utilized to pre-treat Fe0 for PS activation (pre-Fe0/PS) based on the magnetic memory of iron. The efficiency of the pre-Fe0/PS process was tested on the degradation of NB in simulated groundwater under anoxic conditions. The NB removal in the pre-Fe0/PS process was significantly enhanced compared with that in the Fe0/PS process. The effect of Fe0, PS, and NB concentration on the NB degradation was investigated. The influence of single inorganic ions, anion couples and humic acids as ubiquitous species in groundwater on the NB removal in the pre-Fe0/PS and Fe0/PS processes were studied and discussed. A column filled with pre-Fe0 was designed to test the NB removal in the pre-Fe0/PS process in a continuous-flow mode. The experimental results indicated that pre-Fe0/PS is a promising approach for the remediation of groundwater with high NB concentration. [ABSTRACT FROM AUTHOR]

Abstract This study aim to explore an effective approach of persulfate (PS) activation based on multi-walled carbon nanotubes (CNTs) for the phenol degradation. The nitric acid/annealing modified CNTs were obtained by oxidation with concentrated nitric acid followed by annealing at various high temperatures (400–1000 °C). The modified CNTs catalysts were characterized and their catalytic degradation performances of phenol with PS were investigated. The results reveal that the modified CNTs can obviously enhance the phenol removal. The catalytic activity is improved by nitric acid modification and obviously influenced by the annealing temperature. PS concentration and solution pH could also affect the catalytic degradation of phenol. The mechanism of enhanced PS activation by the nitric acid/annealing modified CNTs was proposed that the nitric acid modification resulted in more defective edges and oxygen-containing groups, and subsequent annealing at high temperate facilitated the conversion of sp3 to sp2 carbon, then the catalytic activity for PS activation was enhanced by the active sites of C O group and sp2-hybridized carbon at the defective edges. In addition, a non-radical process of phenol degradation was demonstrated in terms of the radical quenching tests and electron paramagnetic resonance (EPR) spectra analyses. It is suggested that 1O 2 is likely the main reactive specie generated in PS activation by the modified CNTs for the phenol removal. Highlights • The catalytic activity of CNTs is enhanced by nitic acid/annealing modification. • Nitric acid modification caused more defective edges and oxygen-containing groups. • Annealing at high temperate facilitated the conversion of sp3 to sp2 carbon. • C=O group and sp2-hybridized carbon are the origins of the catalytic activity. • 1O 2 is likely the main reactive specie generated in PS activation by modified CNTs. [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]

Graphical abstract Highlights • CNFe heterojunction exhibited superior activity over pure g-C 3 N 4 and Fe 2 O 3. • The presence of PDS accelerated the charge transfer in CNFe nanocomposite. • PDS-mediated photocatalytic oxidation of BPA on CNFe was enhanced by electricity. • Efficient mineralization of BPA was achieved in the Vis-MFC/CNFe/PDS system. • SO 4 − was considered as the dominant active species responsible for BPA oxidation. Abstract Photocatalysis and sulfate radical based advanced oxidation processes have gained considerable popularity in the field of contaminant degradation. However, there are few reports focusing on the combination of these two promising technologies, especially the coupling of a visible light responsive catalyst with an electro-assisted persulfate activation system. Herein, a traditional g-C 3 N 4 /Fe 2 O 3 (CNFe) heterojunction was prepared by a facile one-pot calcination and it could efficiently activate peroxydisulfate (PDS) for bisphenol A (BPA) decomposition with visible light and low-voltage bioelectricity supplied by a microbial fuel cell (MFC). The CNFe catalyst demonstrated good stability and could be reused at least five runs with negligible iron leaching. Sulfate and hydroxyl radicals and singlet oxygen were responsible for the BPA degradation. A mechanism for BPA destruction in the studied system is proposed based on the results of electron paramagnetic resonance (EPR), trapping experiments, X-ray photoelectron spectroscopy (XPS) and the band edge potential of g-C 3 N 4 and Fe 2 O 3. The effects of reaction conditions on the BPA oxidation were explored and 92.2% of BPA was removed after 60 min reaction using 10 mM of PDS, 0.5 g L−1 of CNFe, 100 mA m−2 of current density and natural pH. The total organic carbon (TOC) removal was only 70.0%, but when the time was extended to 2 h, it rose to 91.0%, indicating high mineralization of the proposed system. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Sulfide-modified NZVI showed better properties in activating persulfate than NZVI. • The Fe/S molar ratio significantly influenced the TCE degradation by NZVI-S/PS. • The typical groundwater components exerted slight influence on the TCE degradation. • The contributions of OH and SO 4 − were evaluated under different pH conditions. • The possible pathways of TCE degradation were illustrated. Abstract Sulfide-modified nanoscale zero-valent iron (NZVI-S) has been considered as a promising material for in-situ chemical reduction processes (ISCRPs) for groundwater remediation. However, studies utilizing NZVI-S for in-situ chemical oxidation processes (ISCOPs) were relative rare. In this study, NZVI-S was synthesized and utilized to activate persulfate (PS) for the degradation of TCE. The effects of Fe/S molar ratio, initial pH on TCE removal and dechlorination by NZVI-S activated PS were studied. The results showed that, compared with bare NZVI, NZVI-S showed better properties in activating PS which included better pH adaptiveness, higher TCE removal and mineralization efficiency, and faster removal rate. The Fe/S molar ratio significantly influenced the TCE degradation, and the highest TCE degradation was observed at Fe/S molar ratio of 25–30. The underlying mechanisms of NZVI-S exceling NZVI in activating PS were elucidated through spectroscopic analyses that accounted for the higher iron dissolution rates and iron sulfides (e.g., FeS and FeS x) generated on its surface, which elevated the quantity and accelerated the transfer rate of electrons for activating PS. Besides, hydroxyl radical was observed as a dominant reactive radical in degrading TCE at various pH conditions, but sulfate radical also played an important part especially under acidic condition. Finally, the degradation products of TCE were analyzed and the possible pathways of TCE degradation were illustrated. And the slight influence of natural substances in groundwater on the degradation process suggests NZVI-S activated PS would be a promising approach for groundwater remediation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Heat-activated PS degraded DBP and DEP efficiently and DBP was degraded faster. • Both SO 4 - · and OH were involved in oxidation process. • The effects of reaction parameters on PAEs degradation were studied. • Bromate and brominated disinfection byproducts were formed in the presence of Br−. • The proposed DEP and DBP degradation paths were analyzed by the DFT. Abstract The degradation kinetics of two phthalate esters (PAEs) (i.e., diethyl phthalate (DEP) and dibutyl phthalate (DBP)) in heat-activated persulfate (PS) system were studied and followed pseudo-first-order kinetics. Results demonstrated that both sulfate radical (SO 4 - ·) and hydroxyl radical (HO) were responsible for degrading DEP and DBP. The pseudo-first-order rate constant (k obs) enhanced remarkably as reaction temperature and PS dosages increased, while it decreased as the initial PAEs concentrations increased. Lower pH values promoted the degradation over the pH range chosen here (5.0–8.0). Natural organic matter (NOM) and HCO 3 - showed inhibitory effects on PAEs degradation by quenching SO 4 - · and HO. At any pH value studied here, Cl− enhanced PAEs degradation at lower concentrations while it suppressed degradation as Cl− concentration further increased. The coexisting Br− hindered the degradation of PAEs mainly by suppressing SO 4 - ·. Significant formation of dibromoacetonitrile (DBAN) and bromoform (TBM) was verified with Br− and NOM in the degradation system, while only TBM was detected without NOM. Bromate was also detected in the Br− containing degradation system. Generally, NOM facilitated the formation of brominated disinfection byproducts (Br-DBPs), while it suppressed the generation of bromate. Additionally, it is noteworthy that the degradation efficiency of DBP was higher than that of DEP probably owing to the longer alkyl side chain of DBP. The DBP degradation system was observed to form slightly more Br-DBPs than DEP, while bromate had an opposite trend. Besides, the potential initial degradation pathways of DEP and DBP were discussed by the computational analysis. [ABSTRACT FROM AUTHOR]

Graphical abstract This study delineates the remarkable synergistic effect of the chemisorption and radical pathway due to the BC surface -OFeO species forming and transforming. Highlights • The active species type and its transformation on the nZVI/BC 5 surface were developed. • The formation and transformation of the BC surface -OFeO species were the dominant processes in the radical pathways. • Persistent free radicals (PFRs) generated through the reactions or transformed from active species. • Chemisorption and radical pathways showed synergistic effect for aromatic pollutants degradation in alkaline wastewater. Abstract In this study, a nanocomposite material synthesized by loading nanoscale zerovalent iron (nZVI) onto biochar (BC, gasification plant byproduct) was successfully prepared, and the nZVI/BC 5 (mass ratio 1:5) exhibited oxidative resistance, reutilization and stability via COD removal experiments. The nZVI/BC 5 nanocomposites was used in persulfate (PS) activation for the synergistic degradation of aromatic pollutants in alkaline wastewater. The nZVI/BC 5 selectively adsorbed aromatic pollutants through π-π, π-π-metal (BC surface -OFeO) bonding interactions in textile dyeing wastewater (TDWW), and make the free radicals easier to react to aromatic pollutants. FTIR, XPS and EPR analyses showed that some PFRs generated through the reaction between nZVI and the surface functional groups of BC, the other PFRs were transformed from the BC surface -OFeO species. The chemisorption provided electrons for the BC surface -O-Fe(III)O- to produce the BC surface - O ̇ ·· Fe (II) - O - (persistent free radicals, PFRs). The formation and transformation of the BC surface -OFeO species were the dominant processes in the radical pathways, they could quickly and sustainably produce SO 4 · - and ·OH through heterogeneous catalytic oxidation of water (mediator) and S 2 O 8 2 - (from 0.81 to 0.02 g/L). Finally, a favorable synergistic combined process was initiated via chemisorption and degradation of aromatic pollutants. The BC surface -OFeO species offer a new understanding of synergistic heterogeneous degradation in alkaline solutions. The byproduct BC could be reused and applied in wastewater pretreatment by this new feasible strategy. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Nitrobenzene reduction by ZVI was greatly accelerated with the presence of pyrite. • Pyrite could suppress the pH increase during the reaction of ZVI with nitrobenzene. • Much surface bound Fe2+ of high reactivity was produced in ZVI/pyrite system. • Pyrite could activate the ZVI surface through in-situ sulfidation. Abstract Zero-valent iron (ZVI) is a popular reductant that has been successfully applied for remediation of groundwater contaminated with various pollutants, but it still suffers from surface passivation and pH increase in the reaction media. In this study, pyrite, a ubiquitous sulfide mineral in anaerobic environment, was adopted to enhance the reactivity of ZVI for removal of nitrobenzene. The synergetic effect between pyrite and ZVI was observed for nitrobenzene reduction, and the rate constant k obs at the initial pH (pH 0) 6.0 was enhanced by 8.55–23.1 folds due to the presence of pyrite with pyrite/ZVI mass ratio ranging from 1.0 to 6.0. Moreover, nitrobenzene could be removed effectively at pH 0 ranging from 5.0 to 10.0 in the presence of pyrite, while negligible removal of nitrobenzene by ZVI (0.5 g/L) alone was observed at pH 0 ≥7.0. ZVI sample recovered from the reacted ZVI/pyrite mixture was also more effective for nitrobenzene degradation than pristine ZVI. The mechanism study revealed that pyrite could suppress the pH increase in reaction media, boost the production of reactive Fe2+, and activate the ZVI surface through replacing partially the passive oxide film with iron sulfide (FeS). In particular, the formation of highly reactive FeS@Fe in the reaction system of ZVI/pyrite mixture was proved by XRD, Mössbauer, XANES, XPS and SEM-EDS analyses, which provides a facile way for in-situ sulfidation of ZVI and for enhancing the removal of contaminants with ZVI technology. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Leachate treatment by coupled microwave-persulfate (MW-PS) system was investigated. • COD removal of 67% and ammonia removal of 93% were observed in MW-PS system. • The COD removal rate constant increased with increase in PS dosage in MW-PS system. • Maximum COD removal was achieved at 20 g/L PS dosage and 500 W MW power. • Cost and toxicity analysis were used to check suitability of MW coupled systems. Abstract The possibility of landfill leachate treatment in a coupled microwave-persulfate (MW-PS) system with and without pretreatment, i.e. coagulation-flocculation (C-F) was investigated. The C-F pretreatment with alum and FeCl 3 has reduced the turbidity from 90 NTU to 43 NTU and 10 NTU, respectively, at the optimized coagulant dosage. Moreover, 73% COD and 86% color removal was observed in C-F pretreatment with FeCl 3. The application of MW-PS system (at 10 g/L of PS dosage) for pretreated leachate (FeCl 3 dosage 1 g/L and pH 5.5) has produced a final COD removal of 89%. Similarly, alum pretreatment (dosage 1.6 g/L, pH 8.2) coupled with MW-PS system has achieved a total COD removal of 62%. In MW-PS system, the ratio of initial PS dosage to initial COD ratio has shown significant effect on leachate treatment. However, slightly lesser ammonia removal was observed in MW-PS (93%) compared to MW alone (97%) owing to reduction in pH of the system. The comparison of bio-toxicity (i.e. inhibition to aliivibrio fischeri) of treated samples from MW-PS and MW alone after pretreatment, i.e. 12.1 mg/L and 6.8 mg/L of equivalent ZnSO 4 toxicity, indicated that MW-PS treated sample were found to be more toxic than MW alone treatment and raw leachate (7.6 mg/L and 7.2 mg/L of equivalent ZnSO 4 toxicity, respectively) due to sulfate ion. This indicates that C-F followed by MW alone would be an ideal option for leachate treatment. The cost and energy estimation of MW and MW coupled systems well supported the above findings. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Fenitrothion could be efficiently degraded by Fe0 activated persulfate. • SO 4 − contributed mainly to Fe0/PS induced FNT degradation at pH 3.0. • Twelve transformation products of FNT were determined by LC-TOF-MS. • S O substitution, demethylation and P O bond cleavage were observed. Abstract Fenitrothion (FNT), a common organophosphorus pesticide, has been regarded as a contaminant because it is adverse to the environment. In this study, we chose the highly effective technique, persulfate (PS) activation by zero-valent iron powder (Fe0), to degrade FNT. The effects of several experimental parameters including PS and Fe0 dosages, pH, temperature, and common natural water constituents were systematically investigated via kinetics studies. We found that the addition of Fe0 significantly enhanced the FNT degradation by PS under any of the studied conditions. Under the optimal conditions of [FNT]:[PS] = 1:500 (molar ratio), Fe0:PS = 1:1.5 (molar ratio), pH = 3.0, and 35 °C, 10 mg L−1 of FNT could be completely degraded in 45 min and 20 μg L−1 FNT was removed 96 ± 0% in 12 h. Sulfate (SO 4 −) radicals led the degradation of FNT in the Fe0/PS system. Twelve transformation products of FNT were determined by LC-MS/MS analysis, and the vulnerable sites in FNT were predicted by a density-functional-theory-based descriptor, 2∑(C ri HOMO)2, to illustrate the generation of initial reaction products. The overall acute and chronic toxicity of FNT and its products, as predicted by the ecological structure–activity relationship model (ECOSAR), decreased in the Fe0/PS process. The present work proves that FNT could be efficiently degraded by Fe0-activated PS, which may also contribute to future research on the removal of other organophosphorus pesticides. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • ERY degradation in mycelial dreg by heat-activated PS oxidation was investigated. • 99.0% ERY was degraded by 25 g PS/kg EMD under 80 °C within 120 min. • Six intermediate products of ERY through the oxidation process were clarified. • Ere(B), erm(A), and erm(B) were reduced by heat-activated PS oxidation. Abstract Erythromycin mycelial dreg (EMD) is a bio-fermentation residue of the pharmaceutical industry that may be used as a nutrient resource. However, the contaminants present in EMD need to be considered and controlled at an acceptable level prior to utilization. In this study, heat-activated persulfate (PS) oxidation of EMD was developed to degrade the residual erythromycin (ERY) and inactivate the ERY-resistant genes. The effects of temperature, initial PS concentration, and pH on the removal of ERY in EMD were studied. The results revealed that 99.0% ERY was degraded by 25 g PS/kg EMD under 80 °C within 120 min. The apparent rate constant (k app) in the acidic condition was higher than that in the alkaline condition. The contribution of sulfate radical (SO 4 · - ) and hydroxyl radical (HO) on ERY removal in EMD was found to be 36.8% and 29.4%, respectively. Six intermediate products (IPs) of ERY were clarified, and total organic carbon (TOC) was efficiently reduced by 99.4%. Finally, the detected ERY-resistant genes ere(B), erm(A), and erm(B) obviously presented a reduction during the heat-activated PS oxidation process. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • UV/PDS is proposed to be unsuitable for treatment of bromophenols compared to UV/H 2 O 2. • Brominated polymeric products can be formed in UV-based oxidation process. • BrO 3 − evolution in the degradation of 2,4-DBP by UV/PDS exhibited biphasic kinetics. Abstract The sustained massive use of bromophenols in industrial products leads to their especially pernicious in aquatic environments. This study explored the oxidation kinetics of 2,4-bromophenol (2,4-DBP) and formation potential of bromate (BrO 3 −) and brominated polymeric products of concern during water treatment by UV/persulfate (PDS) and UV/hydrogen peroxide (H 2 O 2). 2,4-DBP exhibited appreciable reactivity toward sulfate radical (SO 4 −) and hydroxyl radical (HO). The second-order rate constants of SO 4 − and/or HO with 2,4-DBP at pH 9 were higher than those at pH 5 and 7. It is mainly due to the deprotonation of the hydroxyl group in 2,4-DBP when pH > pKa (pKa = 7.79). The chloride ions (Cl−) significantly inhibited 2,4-DBP degradation in UV/PDS process, which showed little inhibition in the UV/H 2 O 2 process. Carbonate/bicarbonate (CO 3 2−/HCO 3 −) and natural organic matters (NOM) significantly retarded 2,4-DBP degradation in both processes. BrO 3 − formation in UV/PDS process in the presence of 2,4-DBP (as organic carbon model compound) exhibited biphasic kinetics, i.e., BrO 3 − was undetectable in the lag phase and rapid generated in the secondary rapid phase. However, BrO 3 − was not detected throughout UV/H 2 O 2 process. According to the analysis by electrospray ionization-triple quadruple mass spectrometry, tentative oxidation pathway was proposed. The results showed that brominated polymeric products in the reaction of 2,4-DBP with SO 4 − and/or HO were readily produced by electrophilic addition and coupling reactions. Given the enhanced toxicological effects of these BrO 3 − and brominated polymeric products compared with the bromophenols precursors, it is important to better understand their reactivities and fates when UV/PDS or UV/H 2 O 2 is applied for the oxidative treatment of bromophenols-containing waters. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • High removal efficiency for p-Chloroaniline is achieved with Co@NC/persulfate. • Co@NC/persulfate shows high catalytic activities in a wide pH range of 5–9. • The catalyst remains high activity after five successive cycles. • A radical and non-radical mechanism is proposed for the p-Chloroaniline removal by Co@NC/persulfate. Abstract Cobalt-based nanostructures have shown a great potential for radical production by activating persulfate (PS). Here, we report a facile strategy to synthesize nitrogen-doped porous Co@C nanoboxes (Co@NC) by pyrolysis of zeolitic imidazolate frameworks (ZIF-67), followed by partially etching away the metallic cobalt. With a nitrogen-enriched hollow porous carbon nanobox and embedded Co nanoparticles, the Co@NC shows high efficiency in PS activation for p-Chloroaniline (PCA) removal. The degradation study shows that a complete removal of high concentration PCA is done within two minutes, which is superior to most of the reported PCA removals with PS-based advanced oxidation processes (AOPs). More importantly, the Co@NC exhibits high catalytic activities in a wide range of pH from 5 to 9. The Co@NC also shows very limited Co2+ release with a dissolution proportion of 0.28%, much lower than previously reported Co-based catalysts, and remains high efficiency after five successive reaction cycles. A heterogeneous activation mechanism though surface reaction is proposed, in which PCA firstly absorbs on the carbon nanobox surface, then being oxidized by generated radicals and non-radical species. The unique structure and outstanding performance of Co@NC catalysts present new insights in catalyst design for PS-based advanced oxidation for organic pollutants removal in waste water. [ABSTRACT FROM AUTHOR]