Identification of hydroxyl and sulfate free radicals involved in the reaction of 1,4-dioxane with peroxone activated persulfate oxidant

l-Cysteine-Tuned the Hierarchical Structure Based on Benzimidazole: Synthesis, Characterization, and Application in Ratiometric Electrochemiluminescence Immunoassay

Efficient and robust electrochemiluminescence (ECL) emitters are crucial for enhancing the ECL immunosensor sensitivity. This study introduces a novel ECL emitter, CoBIM/Cys, featuring a hierarchical core-shell structure. The core of the structure is created through the swift coordination between the sulfhydryl and carboxyl groups of l-cysteine (l-Cys) and cobalt ions (Co2+), while the shell is constructed by sequentially coordinating benzimidazole (BIM) with Co2+. This design yields a greater specific surface area and a more intricate porous structure compared to CoBIM, markedly enhancing mass transfer and luminophore accessibility. Moreover, the l-Cys and Co2+ core introduces Co-S and Co-O catalytic sites, which improve the catalytic decomposition of H2O2, leading to an increased production of hydroperoxyl radicals (OOH•). This mechanism substantially amplifies the ECL performance. Leveraging the competitive interaction between isoluminol and BIM for OOH• during ECL emission, we developed a ratiometric immunosensor for cardiac troponin I (cTnI) detection. This immunosensor demonstrates a remarkably broad detection range (1 pg mL-1 to 10 ng mL-1), a low detection limit (0.4 pg mL-1), and exceptional reproducibility and specificity.

Fe-ZSM-5 zeolite catalyst for heterogeneous Fenton oxidation of 1,4-dioxane: effect of Si/Al ratios and contributions of reactive oxygen species

Heterogeneous Fenton oxidation using traditional catalysts with H2O2 for the degradation of 1,4-dioxane (1,4-DX) still presents challenge. In this study, we explored the potential of Fe-ZSM-5 zeolites (Fe-zeolite) with three Si/Al ratios (25, 100, 300) as heterogeneous Fenton catalysts for the removal of 1,4-DX from aqueous solution. Fe2O3 or ZSM-5 alone provided ineffective in degrading 1,4-DX when combined with H2O2. However, the efficient removal of 1,4-DX using H2O2 was observed when Fe2O3 was loaded on ZSM-5. Notably, the Brønsted acid sites of Fe-zeolite played a crucial role during the degradation of 1,4-DX. Fe-zeolites, in combination with H2O2, effectively removed 1,4-DX via a combination of adsorption and oxidation. Initially, Fe-zeolites demonstrated excellent affinity for 1,4-DX, achieving adsorption equilibrium rapidly in about 10 min, followed by effective catalytic oxidative degradation. Among the Fe-ZSM-5 catalysts, Fe-ZSM-5 (25) exhibited the highest catalytic activity and degraded 1,4-DX the fastest. We identified hydroxyl radicals (·OH) and singlet oxygen (1O2) as the primary reactive oxygen species (ROS) responsible for 1,4-DX degradation, with superoxide anions (HO2·/O2·-) mainly converting into 1O2 and ·OH. The degradation primarily occurred at the Fe-zeolite interface, with the degradation rate constants proportional to the amount of Brønsted acid sites on the Fe-zeolite. Fe-zeolites were effective over a wide working pH range, with alkaline pH conditions favoring 1,4-DX degradation. Overall, our study provides valuable insights into the selection of suitable catalysts for effective removal of 1,4-DX using a heterogeneous Fenton technology.

Deep mineralization of VOCs in an embedded hybrid structure CoFe2O4/MoS2/PMS wet scrubber system

Peroxymonosulfate (PMS)-based advanced oxidation processes in liquid phase systems can actively degrade toluene. In this work, the catechol structural surfactant was introduced to synthesize the dispersed and homogeneous CoFe2O4 nanospheres and embedded into MoS2 nanoflowers to form magnetically separable heterojunction catalysts. The innovative approach effectively mitigated the traditionally low reduction efficiency of transition metal ions during the heterogeneous activation process. In CoFe2O4/MoS2/PMS system, the toluene removal efficiency remained 95% within 2 h. The contribution of SO4⋅-, ·O2-, ·OH, and 1O2 was revealed by radical quenching experiment and electron paramagnetic resonance spectroscopy. The results illustrated that MoS2 offers ample reduction sites for facilitating PMS activation via Fe3+/Fe2+ redox interactions. Furthermore, an investigation into the toluene degradation pathway within the CoFe2O4/MoS2/PMS system revealed its capability to suppress the formation of toxic byproducts. This ambient-temperature liquid-phase method presented promising route for the removal of industrial volatile organic pollutants.

Investigation of BiVO4-based advanced oxidation system for decomposition of organic compounds and production of reactive sulfate species

Growth of population and expansion of industries lead to increasing contamination of environment with various organic pollutants. If not properly cleaned, wastewater contaminates freshwater resources, aquatic environment and has huge negative impact on ecosystems, quality of drinking water and human health, therefore new and effective purification systems are in demand. In this work bismuth vanadate-based advanced oxidation system (AOS) for the decomposition of organic compounds and production of reactive sulfate species (RSS) was investigated. Pure and Mo-doped BiVO₄ coatings were synthesized using sol-gel process. Composition and morphology of coatings were characterized using X-ray diffraction and scanning electron microscopy techniques. Optical properties were analyzed using UV-vis spectrometry. Photoelectrochemical performance was studied using linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy. It was shown that increase in Mo content affects the morphology of BiVO₄ films, reduces charge transfer resistance and enhances the photocurrent in the solutions of sodium borate buffer (with and without glucose) and Na₂SO₄. Mo-doping of 5-10 at.% leads to 2- to 3-fold increase in photocurrents. Faradaic efficiencies of RSS formation ranged between 70 and 90 % for all samples irrespective of Mo content. All studied coatings demonstrated high stability in long-lasting photoelectrolysis. In addition, effective light-assisted bactericidal performance of the films in deactivation of Gram positive Bacillus sp. bacteria was demonstrated. Advanced oxidation system designed in this work can be applied in sustainable and environmentally friendly water purification systems.

Rapid activation of peroxymonosulfate with iron(Ⅲ) complex for organic pollutants degradation via a non-radical pathway

Developing high-performance catalytic systems for eliminating contaminants effectively in water has received a lot of attention. However, the complexity of practical wastewater poses a challenge for degrading organic pollutants. Non-radical active species with strong resistance to interference have shown great advantages in degrading organic pollutants under complex aqueous conditions. Herein, a novel system was constructed by Fe(dpa)Cl₂ (FeL, dpa = N, N'-(4-nitro-1,2-phenylene) dipicolinamide) activating peroxymonosulfate (PMS). The mechanism study verified that the FeL/PMS system had high efficiency in producing high-valent iron-oxo and singlet oxygen (¹O₂) to degrade various organic pollutants. In addition, the chemical bonding between PMS and FeL was elucidated by the density functional theory (DFT) calculations. The FeL/PMS system could remove 96% Reactive Red 195 (RR195) in 2 min, which was much higher than other systems involved in this study. More attractively, the FeL/PMS system demonstrated general resistance to interference from common anions (Cl^-, HCO₃^-, NO₃^- and SO₄^2-), humic acid (HA) and pH changes and were thus compatible with various natural waters. This work provides a new approach for producing non-radical active species, which is a promising catalytic system for water treatment.

Total Oxidizable Precursor (TOP) Assay-Best Practices, Capabilities and Limitations for PFAS Site Investigation and Remediation

The comprehensive characterization of per- and polyfluoroalkyl substances (PFASs) is necessary for the effective assessment and management of risk at contaminated sites. While current analytical methods are capable of quantitatively measuring a number of specific PFASs, they do not provide a complete picture of the thousands of PFASs that are utilized in commercial products and potentially released into the environment. These unmeasured PFASs include many PFAS precursors, which may be converted into related PFAS chemicals through oxidation. The total oxidizable precursor (TOP) assay offers a means of bridging this gap by oxidizing unknown PFAS precursors and intermediates and converting them into stable PFASs with established analytical standards. The application of the TOP assay to samples from PFAS-contaminated sites has generated several new insights, but it has also presented various technical challenges for laboratories. Despite the increased number of literature studies that include the TOP assay, there is a critical and growing gap in the application of this method beyond researchers in academia. This article outlines the benefits and challenges of using the TOP assay with aqueous samples for site assessments and suggests ways to address some of its limitations.

Low-temperature persulfate activation by powdered activated carbon for simultaneous destruction of perfluorinated carboxylic acids and 1,4-dioxane

Carbonaceous materials have emerged as a method of persulfate activation for remediation. In this study, persulfate activation using powdered activated carbon (PAC) was demonstrated at temperatures relevant to groundwater (5-25 °C). At room temperature, increasing doses of PAC (1-20 g L^-1) led to increased persulfate activation (3.06 × 10^-6s^-1 to 2.10 × 10^-4 with 1 and 20 g L^-1 PAC). Activation slowed at lower temperatures (5 and 11 °C); however, substantial (>70 %) persulfate activation was achieved. PAC characterization showed that persulfate is activated at the surface of the PAC, as indicated by an increase in the PAC C:O ratio. Similarly, electron paramagnetic resonance (EPR) spectroscopy studies with a spin trapping agents (5,5-dimethyl-1-pyrroline N-oxide (DMPO)) and 2,2,6,6-tetramethylpiperidine (TEMP) revealed that singlet oxygen was not the main oxidizing species in the reaction. DMPO was oxidized to form 5,5-dimethylpyrrolidone-2(2)-oxyl-(1) (DMPOX), which forms in the presence of strong oxidizers, such as sulfate radicals. The persulfate/PAC system is demonstrated to simultaneously degrade both perfluorooctanoic acid (PFOA) and 1,4-dioxane at room temperature and 11 °C. With a 20 g L^-1 PAC and 75 mM persulfate, 80 % and 70 % of the PFOA and 1,4-dioxane, respectively, degraded within 6 h at room temperature. At 11 °C, the same PAC and persulfate doses led to 57% dioxane degradation and 54 % PFOA degradation within 6 h. Coupling PAC with persulfate offers an effective, low-cost treatment for simultaneous destruction of 1,4-dioxane and PFOA.

Low-Temperature Reduction Synthesis of γ-Fe2O3-x@biochar Catalysts and Their Combining with Peroxymonosulfate for Quinclorac Degradation

Biochar loading mixed-phase iron oxide shows great advantages as a promising catalyst owing to its eco-friendliness and low cost. Here, γ-Fe₂O_3-x@biochar (E/Fe-N-BC) composite was successfully prepared by the sol-gel method combined with low-temperature (280 °C) reduction. The Scanning Electron Microscope (SEM) result indicated that γ-Fe₂O_3-x particles with the size of approximately 200 nm were well-dispersed on the surface of biochar. The CO derived from biomass pyrolysis is the main reducing component for the generation of Fe (II). The high content of Fe (II) contributed to the excellent catalytic performance of E/Fe-N-BC for quinclorac (QNC) degradation in the presence of peroxymonosulfate (PMS). The removal efficiency of 10 mg/L of QNC was 100% within 30 min using 0.3 g/L γ-Fe₂O_3-x@biochar catalyst and 0.8 mM PMS. The radical quenching experiments and electron paramagnetic resonance analysis confirmed that •OH and SO₄•^- were the main radicals during the degradation of QNC. The facile and easily mass-production of γ-Fe₂O_3-x@biochar with high catalytic activity make it a promising catalyst to activate PMS for the removal of organic pollutants.

Identification and characterization of Fe3O4/peroxodisulfate advanced oxidation products from sulfameter

Sulfonamides (SAs) are one of the most widely used antibiotics and their residuals in the environment could cause some negative environmental issues. Advanced oxidation such as Fenton-like reaction has been widely applied in the treatment of SAs polluted water. Degradation rates of 95%-99.7% were achieved in this work for the tested 8 SAs, including sulfisomidine, sulfameter (SME), phthalylsulfathiazole, sulfamethoxypyridazine, sulfamonomethoxine, sulfisoxazole, sulfachloropyridazine, and sulfadimethoxine, in the Fe₃O₄/peroxodisulfate (PDS) oxidation system after the optimization of PDS concentration and pH. Meanwhile, it was found that a lot of unknown oxidation products were formed, which brought up the uncertainty of health risks to the environment, and the identification of these unknown products was critical. Therefore, SME was selected as the model compound, from which the oxidation products were never elucidated, to identify these intermediates/products. With liquid chromatography-high resolution tandem mass spectrometry (LC-HRMS/MS), 10 new products were identified, in which 2-amino-5-methoxypyrimidine (AMP) was confirmed by its standard. The investigation of the oxidation process of SME indicated that most of the products were not stable and the degradation pathways were very complicated as multiple reactions, such as oxidation of the amino group, SO₂ extrusion, and potential cross-reaction occurred simultaneously. Though most of the products were not verified due to the lack of standards, our results could be helpful in the evaluation of the treatment performance of SAs containing wastewater.

Fast peroxydisulfate oxidation of the antibiotic norfloxacin catalyzed by cyanobacterial biochar

Peroxydisulfate (PDS) is a common oxidant for organic contaminant remediation. PDS is typically activated by metal catalysts to generate reactive radicals. Unfortunately, as radicals are non-selective and metal catalysts may cause secondary contamination, alternative selective non-radical pathways and non-metal catalysts need attention. Here we investigated PDS oxidation of commonly detected antibiotic Norfloxacin (NOR) using cyanobacterial nitrogen rich biochars (CBs) as catalysts. NOR was fully degraded by CB pyrolysed at 950 °C (CB950) within 120 min. CB950 caused threefold faster degradation than low pyrolysis temperature (PT) CBs and achieved a maximum surface area normalized rate constant of 4.38 × 10^-2 min^-1 m^-2 L compared to widely used metal catalysts. CB950 maintained full reactivity after four repeated uses. High defluorination (82%) and mineralization (>82%) were observed for CB950/PDS. CBs were active over a broad pH range (3-10), but with twice as high rates under alkaline compared with neutral conditions. NOR is degraded by organic, ^•OH and SO₄^•- radicals in low PT CBs/PDS systems, where the presence of Mn^II promotes radical generation. Electron transfer reactions with radicals supplemented dominate high PT CBs/PDS systems. This study demonstrates high PT biochars from algal bloom biomass may find use as catalysts for organic contaminant oxidation.

Sucralose as an oxidative-attenuation tracer for characterizing the application of in situ chemical oxidation for the treatment of 1,4-dioxane

In situ chemical oxidation (ISCO) has become a widely used soil and groundwater remediation method. Oxidative-attenuation tracers can be used to provide real-time, explicit delineation of contaminant mass-transfer and transformation behavior during an ISCO remediation project. The objective of this study was to evaluate the potential of employing sucralose, a widely used artificial sweetener, as an oxidative-attenuation tracer to characterize the remediation efficiency of 1,4-dioxane (dioxane) by persulfate-based ISCO. Batch and miscible-displacement experiments were conducted to examine the degradation rate and transport behavior of sucralose compared to that of dioxane. Comparable magnitudes and rates of degradation were observed for sucralose and dioxane in batch-reactor experiments with soil and persulfate. The breakthrough curves of sucralose and dioxane transport in a soil-packed column were coincident. The retardation factors were 1.1 for both compounds, indicating limited sorption for both sucralose and dioxane by the soil. Limited degradation was observed in the miscible-displacement experiments, consistent with the short residence time compared to the half-lives of sucralose and dioxane. Persulfate transport and decomposition behavior in the soil-packed columns was similar in the presence of sucralose or dioxane. A simulated tracer test was conducted to illustrate the application of sucralose as an oxidative-attenuation tracer at the pilot scale. These results demonstrate the potential of sucralose as an oxidative-attenuation tracer to support the robust design of ISCO applications for dioxane. The oxidative-attenuation tracer test method is anticipated to be an effective approach for characterizing mass-removal behavior of other emerging contaminants with appropriate selection of tracer.

Activation of ozone by peroxymonosulfate for selective degradation of 1,4-dioxane: Limited water matrices effects

The presence of 1,4-dioxane in various water streams poses a threat to the health of human beings. In this study, the oxidative combination of ozone with peroxymonosulfate (PMS) was for the first time used to remove 1,4-dioxane from water. Near complete abatement of 1,4-dioxane was achieved by ozone-PMS after reaction of only 15 min and the degradation kinetics was found to be positively correlated with doses of PMS and ozone. Ozone-PMS oxidation had the optimum performance at slight base pH values. Both sulfate radicals and hydroxyl radicals were generated in ozone-PMS oxidation and these radicals resulted in the degradation of 1,4-dioxane. The effects of common water constituents and real water matrices were investigated. It was found that bicarbonate ions with a concentration up to 10 mM had a slight promoting effect, while either chloride ions or natural organic matter inhibited only slightly the degradation. Meanwhile, no obvious difference in the degradation of 1,4-dioxane was found among the real water matrices and deionized water, which demonstrates that ozone-PMS oxidation has high tolerance and stability. The results from this study demonstrate that ozone-PMS may be a promising technology for the removal of 1,4-dioxane from various water matrices.

Comparative study of PMS oxidation with Fenton oxidation as an advanced oxidation process for Co-EDTA decomplexation

In nuclear industry, Co-EDTA complex is generated due to the decontamination activities of nuclear power plants (NPPs). This complex is extremely refractory to the convention methods and can escalate the mobility of Co radionuclide in the environment. Due to its hazardous impact on human and environment, the effective treatments of Co-EDTA complexes are highly recommended. In this study, for the first time, we applied both hydroxyl (OH) and sulfate radical (SO₄^-) based advanced oxidation processes (AOPs) namely Fenton and peroxymonosulfate (PMS) reactions for the Co-EDTA decomplexation. Both reactions exhibited higher Co-EDTA decomplexation at pH = 3, however, the PMS based reaction was found to be superior, which showed highest decomplexation efficiency (without pH adjustment) over Fenton reaction (pH = 1-13). Moreover, PMS based system was found to be more suitable than Fenton reaction, because PMS showed best Co-EDTA decomplexation efficiency without any additional catalyst dosages at the shorter reaction time. XRD data confirmed the presence of both CoO and Co(OH)₂ in the precipitates after treatment. The electron spin resonance spectroscopy (ESR) analysis identified OH and SO₄^- in Fenton and PMS system, respectively. From this study, we believe that PMS based reaction is a superior alternative of Fenton reaction for the Co-EDTA decomplexation.

Efficient catalyst prepared from water treatment residuals and industrial glucose using hydrothermal treatment: Preparation, characterization and its catalytic performance for activating peroxymonosulfate to degrade imidacloprid

Water treatment residuals (WTRs), as by-products of drinking water treatment plant, were used as catalyst for persulfate activation to degrade organic pollutants. In this study, G-HWTRs were successfully prepared by hydrothermal treatment, which combined WTRs and a hydrothermal reducing agent (industrial glucose) in different ratios. These materials manifested upgraded performance compared with raw WTRs and HWTRs (prepared only with WTRs under hydrothermal condition) in imidacloprid (IMD) degradation. The elemental composition, structure, morphological and magnetic properties of the G-HWTRs were investigated. And the influences of peroxymonosulfate (PMS) concentration, G-HWTRs dosage, initial pH, water matrix on IMD degradation were determined. The results demonstrated that G-HWTRs-3 had the best catalytic performance, 10 μM IMD was almost completely degraded in the system of G-HWTRs (0.2 g L^-1) and PMS (0.1 mM) within 2 h without pH adjustment. Based on the results of the electron spin-resonance spectroscopy (ESR) tests and radicals scavenging experiments, all of SO₄^-, OH, ¹O₂ and O₂- were the reactive oxygen species driving the IMD degradation, and OH was regarded as the main role of IMD degradation. The possible degradation pathways of IMD were further proposed based on the degradation intermediates that identified by LC-MS. Besides, further experiments indicated G-HWTRs has degradation potential for various pollutants, the degradation rate of atrazine (ATZ), acetochlor (ACE) and simazine (SMX) within 2 h achieved 92.54%, 83.88% and 90.25%, respectively. These results confirmed G-HWTRs has good catalytic performance and activation potential on PMS, providing an effective method for remediating organic polluted wastewater.

Shifts of surface-bound •OH to homogeneous •OH in BDD electrochemical system via UV irradiation for enhanced degradation of hydrophilic aromatic compounds

Indirect electrochemical oxidation by hydroxyl radicals is the predominant degradation mechanism in electrolysis with a boron-doped diamond (BDD) anode. However, this electrochemical method exhibits low reactivity in removal of hydrophilic aromatic pollutants owing to mass transfer limitation. In this study, the combination of ultraviolet light and BDD electrolysis could increase the degradation rate of hydrophilic aromatic pollutants by approximately 8-10 times relative to electrolysis alone. According to the results of the scavenging experiments and identification of benzoic acid oxidation products, surface-bound hydroxyl radical (•OH_(surface)) was the primary reactive species degrading aromatic pollutants in the BDD electrolysis process, whereas freely-diffusing homogeneous hydroxyl radical (•OH_(free)) was the major reactive species in the UV-assisted BDD electrolysis process. Cyclic voltammetry revealed that UV light decomposed H₂O₂ formed on the BDD anode surface, thus retarding O₂ evolution and facilitating •OH_(free) generation. This work also explored the potential application of UV-assisted BDD electrolysis in removing COD from bio-pretreated landfill leachate containing high concentrations of hydrophilic aromatic pollutants. This study shed light on the importance of the existing state of •OH on removal of pollutants during BDD electrolysis, and provided a facile and efficient UV-assisted strategy for promoting degradation of hydrophilic aromatic pollutants.

Peroxone activated persulfate oxidation of 1,4-Dioxane under column scale conditions

The research presented herein investigates a peroxone activated persulfate (PAP) oxidant, commercialized under the trade name OxyZone®, and its effects on 1,4-Dioxane (dioxane) contaminated water under column scale conditions in the presence of porous material. There is a limited understanding of the underlying processes that govern PAP oxidation, including the oxidation rates in the presence of aquifer material, and how these reactions proceed once the oxidant is injected into a contaminant plume. Initial batch experiments with porous material (e.g. sand) provided data on the reaction rates of dioxane oxidation as a function of the oxidant: contaminant ratio. The observed degradation rates were approximately 4 times lower than those reported for aqueous solutions containing no porous media. Subsequent column experiments simulated two PAP injections schemes along the flowpath of a dioxane plume to study if the injection of one oxidant slug may yield different results than injecting the same oxidant volume at two separate locations. The injection of one oxidant slug was found more effective, resulting in near complete destruction of dioxane over a prolonged time at a rate more than an order of magnitude greater than in the two-slug injection scenario. Tracer test results suggest that the prolonged oxidant reactivity was in part caused by the high density of the injected oxidant solution. Overall, the results underline the importance of accounting for the properties of both the oxidant solution and the porous material when considering the injection of PAP oxidant into an impacted aquifer.

New insights into FeS/persulfate system for tetracycline elimination: Iron valence, homogeneous-heterogeneous reactions and degradation pathways

In this study, complete tetracycline (TTC) and above 50% of total organic carbon (TOC) were removed by FeS/PS after 30 min under optimized conditions. Although free radicals and high-valent iron ions were identified to generate in the process, the apparent similarity between intermediate products of FeS/PS, Fe/PS, and UV/PS systems demonstrated that the degradation of TTC was due to sulfate radicals (SO₄^⋅-) and hydroxyl radicals (⋅OH). Based on the reaction between free radicals and organic matter, we speculated that TTC in the FeS/PS system was decomposed and mineralized by dehydration, dehydrogenation, hydroxyl addition, demethylation, substitution, E-transfer, and ring-opening. Furthermore, a new understanding of FeS-mediated PS activation based on stoichiometry and kinetic analysis showed that there were both homogeneous and heterogeneous reactions that occurred in the entire progress. However, due to the effect of pH on the dissolution of iron ions, the homogeneous reaction became the principal process with iron ions concentration exceeding 1.35 mg/L. This work provides a theoretical basis for the study of the degradation of TTC-containing wastewater by the iron-based advanced oxidation process.

Single-Atom Cobalt Incorporated in a 2D Graphene Oxide Membrane for Catalytic Pollutant Degradation

We introduce a new graphene oxide (GO)-based membrane architecture that hosts cobalt catalysts within its nanoscale pore walls. Such an architecture would not be possible with catalysts in nanoscale, the current benchmark, since they would block the pores or alter the pore structure. Therefore, we developed a new synthesis procedure to load cobalt in an atomically dispersed fashion, the theoretical limit in material downsizing. The use of vitamin C as a mild reducing agent was critical to load Co as dispersed atoms (Co₁), preserving the well-stacked 2D structure of GO layers. With the addition of peroxymonosulfate (PMS), the Co₁-GO membrane efficiently degraded 1,4-dioxane, a small, neutral pollutant that passes through nanopores in single-pass treatment. The observed 1,4-dioxane degradation kinetics were much faster (>640 times) than the kinetics in suspension and the highest among reported persulfate-based 1,4-dioxane destruction. The capability of the membrane to reject large organic molecules alleviated their effects on radical scavenging. Furthermore, the advanced oxidation also mitigated membrane fouling. The findings of this study present a critical advance toward developing catalytic membranes with which two distinctive and complementary processes, membrane filtration and advanced oxidation, can be combined into a single-step treatment.

Efficient degradation of minocycline by natural bornite-activated hydrogen peroxide and persulfate: kinetics and mechanisms

Natural bornite (NBo), a sulfide mineral of copper and iron, is one of the main mineral raw materials for copper extraction. In this study, NBo-activated hydrogen peroxide (H₂O₂) and persulfate processes (PS) for the degradation of minocycline (MNC) in aqueous solution were systemically investigated and compared. The MNC removal rates with the NBo/PS and NBo/H₂O₂ processes were 86.40% and 87.50%, respectively. The mineralization rate of NBo/PS (33.96%) was higher than that of NBo/H₂O₂ (29.94%) after reaction for 180 min. The effects of oxidant and activator dosage, pH, common inorganic anions (i.e., Cl^-, NO₃^-, and HCO₃^-), and water composition on MNC degradation were systematically evaluated. In addition, the degradation of MNC in natural water matrix and toxicity evaluation was also studied to better evaluate the feasibility of practical application of those two processes. The results of free radical quenching experiments and electron paramagnetic resonance spectroscopy (EPR) showed that HO· was the main activated species in the NBo/H₂O₂ system, while SO₄^·- and HO· were the main activated species in the NBo/PS system. The degradation of MNC in the NBo/PS system was achieved through electron transfer, while the degradation of MNC in the NBo/H₂O₂ system was mainly achieved through free radical addition. The degradation pathway mainly included deamidation reactions, C-C bond breakage and hydroxylation. Reusability of NBo showed that NBo was considerably stable in activating PS and H₂O₂ for degradation of MNC, which was cost-effective activator. This work provides a new perspective on the degradation mechanism of pollutants by Fe-Cu bimetallic sulfide activation of PS and H₂O₂.

The graceful art, significant function and wide application behavior of ultrasound research and understanding in carbamazepine (CBZ) enhanced removal and degradation by Fe0/PDS/US

Carbamazepine (CBZ) antibiotic organic contamination wastewater poses a huge threat to environmental safety. An advanced oxidation technology (Fe⁰/PDS/US) of using ultrasound (US) enhanced zero-valent iron/potassium persulfate (Fe⁰/PDS) can remove CBZ effectively. The optimal reaction conditions were determined by exploring the effect of single-factor experimental conditions such as ultrasonic power, ultrasonic frequency, CBZ concentration, solution pH, PDS dosage, and Fe⁰ dosage on the removal of CBZ. In addition, we also investigated into the effect of background ions (PO₄^3-, HCO₃^-, Cl^- and HA) on Fe⁰/PDS/US and analyzed the related results. The mechanism of CBZ removal in Fe⁰/PDS/US were explored by analyzing CBZ removal efficiency and reaction rates, the ion concentration of S₂O₈^2-, SO₄^2-, Fe²⁺ and Fe³⁺, pH and the active radicals. The result indicates that US can improve the efficiency of activated PDS and expand the pH range of Fe⁰/PDS. It has prominent performance in catalytically degrading CBZ when the pH is 10.0. SO₄^•-, ^•OH and O₂^•- all coexist in the Fe⁰/PDS/US and make contribution to CBZ removal, whereas the SO₄^•- plays a key role. US can greatly promotes the degradation of target pollutant CBZ by speeding up the dissolution of the outer portion of iron powder, producing sufficient amount of Fe²⁺ with a continuous and stable way, and better activating S₂O₈^2- to generate sufficient SO₄^•- radicals. The degradation of CBZ may embrace three reaction processes, in which organic intermediate products with low molecular weight and biological toxicity is produced, boosting further mineralization and biodegradation of products. The Fe⁰/PDS/US is of great potential application value in removal of organic pollution and environmental purification.

A microwave irradiation-persulfate-formate system for achieving the detoxification and alkali-activated composite geopolymerization of the chromate-contaminated soil

A microwave (MA) irradiation-persulfate-formate system was constructed to detoxify Cr contamination and solidify the geopolymerization of the alkali-activated composite material. Three series of experiments were correspondingly conducted to evaluate the treatment for the chromate-contaminated soil. The changes in the molar ratios of formate to persulfate and the mass rates of fortifier to soil led to a significantly greater reduction of Cr^VI in the detoxification experiments. The increase of blast furnace slag from 50% to 80% in the composite cementitious materials (CCM) intensified the immobilization efficiencies of chromate and the compressive strengths of geopolymer blocks. MA irradiation potentially enhanced the binding of Ca cations to the aluminosilicate compounds. The degree of reaction in the phenomenological kinetics model mathematically verified the geopolymerization process. Ettringite was formed within the structure of the geopolymer in the coupling system. Sulfate radicals released from persulfate not only contributed to the detoxification process but also strengthened the immobilization process.

Characterization of dissolved organic matter during the O3-based advanced oxidation of mature landfill leachate with and without biological pre-treatment and operating cost analysis

In this study, the organic matter in an O₃-based advanced oxidation process (AOP) for treating raw leachate (RL) and bio-treated leachate (BTL) was characterized. The optimal conditions for COD removal in RL and BTL treatment were as follows: initial pH of 6.0 and H₂O₂ dosage of 9 mL 30% H₂O₂ L^-1 leachate, and initial pH of 12 without H₂O₂ addition, respectively. H₂O₂ addition had little influence on COD removal in the BTL treatment as sufficient hydroxyl radicals may not be produced at extremely high pH levels. The differences in the alkalinity between RL and BTL caused differences in the optimum pH of the AOPs. Overall, the initial pH more affected COD removal than the H₂O₂ dosage. O₃-based AOP converted organics with high molecular weight fractions into low ones. Meanwhile, it preferentially degraded hydrophobic substances over hydrophilic substances. The organic matter in the BTL contained more refractory and hydrophobic fractions; therefore, higher COD removal was achieved in the treatment of RL. The organics in the treatment of RL and BTL were identified by excitation-emission matrix spectroscopy combined with parallel factor analysis, and their degradation decreased in the following order: terrestrial humic-like > microbial humic-like > combination of tryptophan and humic-like components. O₃-based AOP significantly enhanced biodegradability. According to the economic analysis results, as an intermediate treatment, O₃-based AOP is a cost-effective strategy of ensuring that leachate effluent meets the discharge standards, with the lowest operating cost of $4.62 m^-3. This study provides a reference for the application of O₃-based AOP in full-scale landfill leachate treatment.

Identification of Dose-Dependent DNA Damage and Repair Responses From Subchronic Exposure to 1,4-Dioxane in Mice Using a Systems Analysis Approach

1,4-Dioxane (1,4-DX) is an environmental contaminant found in drinking water throughout the United States. Although it is a suspected liver carcinogen, there is no federal or state maximum contaminant level for 1,4-DX in drinking water. Very little is known about the mechanisms by which this chemical elicits liver carcinogenicity. In the present study, female BDF-1 mice were exposed to 1,4-DX (0, 50, 500, and 5,000mg/L) in their drinking water for 1 or 4 weeks, to explore the toxic effects. Histopathological studies and a multi-omics approach (transcriptomics and metabolomics) were performed to investigate potential mechanisms of toxicity. Immunohistochemical analysis of the liver revealed increased H2AXγ-positive hepatocytes (a marker of DNA double-strand breaks), and an expansion of precholangiocytes (reflecting both DNA damage and repair mechanisms) after exposure. Liver transcriptomics revealed 1,4-DX-induced perturbations in signaling pathways predicted to impact the oxidative stress response, detoxification, and DNA damage. Liver, kidney, feces, and urine metabolomic profiling revealed no effect of 1,4-DX exposure, and bile acid quantification in liver and feces similarly showed no effect of exposure. We speculate that the results may be reflective of DNA damage being counterbalanced by the repair response, with the net result being a null overall effect on the systemic biochemistry of the exposed mice. Our results show a novel approach for the investigation of environmental chemicals that do not elicit cell death but have activated the repair systems in response to 1,4-DX exposure.

In-depth investigation of Sodium percarbonate as oxidant of PAHs from soil contaminated with diesel oil

Sodium percarbonate (SPC, 2Na₂CO₃∙3H₂O₂), is a compound that can be used under multiple environmental applications. In this work, SPC was employed as oxidant in the treatment of soil contaminated with diesel oil. The soil samples were collected during the earthmoving stage of RNEST Oil Refinery (Petrobras), Brazil. Then, the samples were air-dried, mixed and characterized. Subsequently, raw soil was contaminated with diesel and treated by photo-Fenton reaction (H₂O₂/Fe²⁺/UV). SPC played a significant role in the generation of hydroxyl radicals under the catalytic effect of ferrous ions (Fe²⁺), hydrogen peroxide (H₂O₂) and radiation. These radicals provoked the photodegradation of polycyclic aromatic hydrocarbons (PAHs), in the soil remediation. A factorial design 3³ was carried out to assess the variables which most influenced the decrease in total organic carbon (TOC). The study was performed with the following variables: initial concentration of [H₂O₂] and [Fe²⁺], between 190.0 and 950.0 mmol L^-1 and 0.0-14.4 mmol L^-1, respectively. UV radiation was supplied from sunlight, blacklight lamps, and system without radiation. All experiments were performed with 5.0 g of contaminated soil in 50.0 mL of solution. The initial concentration of Fe²⁺ showed the statistically most significant effect. The oxidation efficiency evaluated in the best condition showed a decrease from 34,765 mg kg^-1 to 15,801 mg kg^-1 in TOC and from 85.750 mg kg^-1 to 20.770 mg kg^-1 in PAHs content. Moreover, the sums of low and high molecular weight polycyclic aromatic hydrocarbons (LMW-PAHs and HMW-PAHs) were 19.537 mg kg^-1 and 1.233 mg kg^-1, respectively. Both values are within the limits recommended by the United Sates Environmental Protection Agency (USEPA) and evidenced the satisfactory removal of PAHs from contaminated soil, being an alternative to classic oxidation protocols.

Sulfate radical-induced destruction of emerging contaminants using traces of cobalt ions as catalysts

Cobalt is part of vitamin B12, which is essential to maintain human health, and trace levels of cobalt ions are ubiquitous in water and soil environments. In this study, the destruction of 1,4-dioxane (1,4-D) by peroxymonosulfate (PMS) under the catalysis of trace levels of Co²⁺ was investigated under buffered conditions. The results showed that near 100% removal of 1,4-D was achieved after reaction for 6 and 10 min with 50 and 25 μg/L Co²⁺, respectively, in the presence of 5 mM phosphate ions. Mechanism studies revealed that radicals mediated the destruction of 1,4-D and sulfate radicals were the primary reactive species. The traces of Co²⁺ had the greatest reactivity for the catalysis of PMS in neutral environments (pH 7.0). However, pH 5.5 was observed to be the best condition for 1,4-D destruction, which was probably caused by the involvement of phosphate radicals. Common water components including chloride ions and bicarbonate ions were observed to have promoting and inhibiting effects, respectively, on the removal of 1,4-D. To further demonstrate the potential of Co²⁺-PMS in practical applications, we explored the simultaneous degradation of 20 antibiotics using trace levels of Co²⁺. The results showed that all the investigated antibiotics, except for lomefloxacin, could be efficiently degraded by Co²⁺-PMS with removal rates of greater than 97%. The findings from this study demonstrate the promise of using trace levels of cobalt for environmental remediation applications, even when high concentrations of phosphate ions are co-present.

Enhanced Activation of Persulfate by Co-Doped Bismuth Ferrite Nanocomposites for Degradation of Levofloxacin Under Visible Light Irradiation

In this study, magnetic visible light driven photocatalysts (bismuth ferrite, Bi₂Fe₄O₉, BFO and Co-doped bismuth ferrite, Co-BFO) were successfully prepared by the facile hydrothermal method. The catalyst was used in the application of heterogeneous persulfate (PS) system under visible LED light irradiation for the degradation of levofloxacin (LFX), proving to be an excellent photocatalyst when evaluated by various characterization methods. The effect of Co-doping in the BFO structure was investigated that the decrease of band gap width and the generated photoelectrons and holes would effectively reduce the recombination of photogenerated electron-hole pairs, leading to the enhancement photocatalytic activity. The results demonstrated that Co-BFO catalyst had a high photodegradation efficiency over a wide pH range of 3.0-9.0 and the Co-BFO-2 composite displayed the optimal catalytic performance. It was found that the degradation rate of LFX by Co-BFO-2 catalyst was 3.52 times higher than that of pure BFO catalyst under visible light condition. The free radical trapping experiments and EPR tests demonstrated that superoxide, photogenerated holes and sulfate radicals were the main active species in the photocatalytic degradation of LFX. And a possible photocatalytic degradation mechanism of LFX was proposed in the Vis/Co-BFO/PS process. These findings provided new insight of the mechanism of heterogeneous activation of persulfate by Co-BFO under visible light irradiation.