High-performance, stable CoNi LDH@Ni foam composite membrane with innovative peroxymonosulfate activation for 2,4-dichlorophenol destruction

In this study, the cobalt-nickel layered double hydroxides (CoNi LDH) were synthesized with a variety of Co/Ni mass ratio, as CoxNiy LDHs. In comparison, Co1Ni3 LDH presented the best peroxymonosulfate (PMS) activation efficiency for 2,4-dichlorophenol removal. Meanwhile, CoNi LDH@Nickel foam (CoNi LDH@NF) composite membrane was constructed for enhancing the stability of catalytic performance. Herein, CoNi LDH@NF-PMS system exerted high degradation efficiency of 99.22% within 90 min for 2,4-DCP when [PMS]0 = 0.4 g/L, Co1Ni3 LDH@NF = 2 cm × 2 cm (0.2 g/L), reaction temperature = 298 K. For the surface morphology and structure of the catalyst, it was demonstrated that the CoNi LDH@NF composite membrane possessed abundant cavity structure, good specific surface area and sufficient active sites. Importantly, ·OH, SO4·- and 1O2 played the primary role in the CoNi LDH@NF-PMS system for 2,4-DCP decomposition, which revealed the PMS activation mechanism in CoNi LDH@NF-PMS system. Hence, this study eliminated the stability and adaptability of CoNi LDH@NF composite membrane, proposing a new theoretical basis of PMS heterogeneous catalysts selection.

New insight into wastewater treatment by activation of sulfite with humic acid under visible light irradiation

Sulfite (S(IV)), as an alternative to persulfate, has demonstrated its cost-effectiveness and environmentally friendly nature, garnering increasing attention in Advanced Oxidation Processes (AOPs). Dissolved organic matter (DOM) commonly occurred in diverse environments and was often regarded as an interfering factor in sulfite-based AOPs. However, less attention has been paid to the promotion of the activation of sulfite by excited DOM, which could produce various reactive intermediates. The study focused on the activation of sulfite using visible light (VL) - excited humic acid (HA) to efficiently degrade many common organic pollutants, which was better than peroxydisulfate (PDS) and peroxymonosulfate (PMS) systems. Quenching experiments and electron paramagnetic resonance (EPR) analysis revealed that the triplet states of HA (3HA*) activated sulfite through energy transfer, resulting in the production of SO4·-, O2·-, and 1O2. The most significant active species found in the degradation of roxarsone (ROX) was 1O2, which was a non-radical pathway and exhibits high selectivity for pollutant degradation. This non-radical pathway was not commonly observed in traditional sulfite-based AOPs. Additionally, the coexistence of various inorganic anions, such as NO3-, Cl-, SO42-, CO32-, and PO43-, had little effect on the degradation of ROX. Furthermore, DOM from different natural water demonstrated efficient activation of S(IV) under light conditions, opening up new possibilities for applying sulfite-based advanced oxidation to the remediation of organic pollution in diverse sites and water bodies. In summary, this research offered promising insights into the potential application of sulfite-based AOPs, facilitated by photo-excited HA, as a new strategy for efficiently degrading organic pollutants in various environmental settings.

Degradation of norfloxacin by red mud-based prussian blue activating H2O2: A strategy for treating waste with waste

The massive accumulation of red mud (RM) and the abuse of antibiotics pose a threat to environment safety and human health. In this study, we synthesized RM-based Prussian blue (RM-PB) by acid solution-coprecipitation method to activate H2O2 to degrade norfloxacin, which reached about 90% degradation efficiency at pH 5 within 60 min and maintained excellent catalytic performance over a wide pH range (3-11). Due to better dispersion and unique pore properties, RM-PB exposed more active sites, thus the RM-PB/H2O2 system produced more reactive oxygen species. As a result, the removal rate of norfloxacin by RM-PB/H2O2 system was 8.58 times and 2.62 times of that by RM/H2O2 system and PB/H2O2 system, respectively. The reactive oxygen species (ROS) produced in the degradation process included ·OH, ·O2- and 1O2, with 1O2 playing a dominant role. The formation and transformation of these ROS was accompanied by the Fe(III)/Fe(II) cycle, which was conducive for the sustained production of ROS. The RM-PB/H2O2 system maintained a higher degradation efficiency after five cycles, and the material exhibited strong stability, with a low iron leaching concentration. Further research showed the degradation process was less affected by Cl-, SO42-, NO3-, and humic acids, but was inhibited by HCO3- and HPO42-. In addition, we also proposed the possible degradation pathway of norfloxacin. This work is expected to improve the resource utilization rate of RM and achieve treating waste with waste.

Insight into disparate nonradical mechanisms of peroxymonosulfate and peroxydisulfate activation by N-doped oxygen-rich biochar: Unraveling the role of active sites

In this study, we first comprehensively studied peroxymonosulfate (PMS) and peroxydisulfate (PDS) activation mechanisms using N, O codoped sludge biochar (NOSB) to degrade organics from water. Among the catalysts, NOSB with a higher content of graphitic N, optimal edge nitrogen (pyridinic N and pyrrolic N), CO groups, sp2-hybridized C, and rich defects were demonstrated to be a superior catalyst. Therefore, by activating PDS and PMS, NOSB exhibited the highest rate of BPA degradation, which was 22-fold and 13-fold that of pristine sludge biochar, respectively. However, owing to different oxidation potentials and molecular structures, PMS and PDS show different degradation performances due to various catalytic mechanisms occurring, even with the same biochar. Due to the asymmetrical structure of PMS, electrons passed from PMS to NOSB and further generated singlet oxygen (1O2), which governs the degradation of bisphenol A with an auxiliary contribution of single electron transfer. Meanwhile, PDS is reduced at the Lewis basic sites of NOSB, forming inner-surface-bound {PDS-NOSB}, which was oxidizing around neighboring carbon and decomposed targets through transferring single and double electrons. NOSB is promising for practical applications because of its adaptation to a wide pH range, anions, high total organic carbon removal, tunable active sites, and re-usability for degrading organics via PMS/PDS activation. This study unveils knowledge about N, O codoped sludge biochar catalysts for activating PMS/PDS and advocates a great approach for organics' degradation in the environment.

Singlet oxygen in the removal of organic pollutants: An updated review on the degradation pathways based on mass spectrometry and DFT calculations

The degradation of pollutants by a non-radical pathway involving singlet oxygen (1O2) is highly relevant in advanced oxidation processes. Photosensitizers, modified photocatalysts, and activated persulfates can generate highly selective 1O2 in the medium. The selective reaction of 1O2 with organic pollutants results in the evolution of different intermediate products. While these products can be identified using mass spectrometry (MS) techniques, predicting a proper degradation mechanism in a 1O2-based process is still challenging. Earlier studies utilized MS techniques in the identification of intermediate products and the mechanism was proposed with the support of theoretical calculations. Although some reviews have been reported on the generation of 1O2 and its environmental applications, a proper review of the degradation mechanism by 1O2 is not yet available. Hence, we reviewed the possible degradation pathways of organic contaminants in 1O2-mediated oxidation with the support of density functional theory (DFT). The Fukui function (FF, f-, f+, and f0), HOMO-LUMO energies, and Gibbs free energies obtained using DFT were used to identify the active site in the molecule and the degradation mechanism, respectively. Electrophilic addition, outer sphere type single electron transfer (SET), and addition to the hetero atoms are the key mechanisms involved in the degradation of organic contaminants by 1O2. Since environmental matrices contain several contaminants, it is difficult to experiment with all contaminants to identify their intermediate products. Therefore, the DFT studies are useful for predicting the intermediate compounds during the oxidative removal of the contaminants, especially for complex composition wastewater.

Pyridine-bridged cobalt tetra-aminophthalocyanine to active peroxymonosulphate for efficient degrading carbamazepine

In this study, each cobalt tetra-aminophthalocyanine (CoTAPc) molecule was immobilised with four isonicotinic acid (INA) molecules by amide bonding, a novel and highly efficient catalyst pyridine-bridged cobalt tetra-aminophthalocyanine (CoTAPc-TINA) was synthesised. The introduction of INA molecules promoted CoTAPc to expose more active sites, and increased the electron cloud density of cobalt ions promoting O-O bond homolysis of PMS to generate more active species, which significantly enhanced catalytic activity. With the pharmaceutical of carbamazepine (CBZ) as model pollutant, 0.1 g/L CoTAPc-TINA in dark in the presence of 0.4 mM PMS, 98.8% CBZ was removed within 10 min. However, under the same conditions the removed of CBZ was only 58.9% by CoTAPc/PMS system. Radical capture experiments combined electron paramagnetic resonance technology demonstrate that hydroxyl radicals, sulphate radicals, superoxide radicals and singlet oxygen are the main active species in the CoTAPc-TINA/PMS system. As the reaction proceeded, all aromatic intermediates were transformed to small molecular acids by these active species. This investigation provided a new insight for application of metal phthalocyanine in wastewater treatment.

Photocatalysis of carbamazepine via activating bisulfite by ultraviolet: Performance, transformation mechanism, and residual toxicity assessment of intermediates products

Carbamazepine (CBZ) as an extensively distributed emerging pollutant has menaced ecological security. The degradation performance of CBZ by UV driven bisulfite process was investigated in this work. The kinetics results indicated that CBZ was high-efficiently degraded by UV/bisulfite following a pseudo first-order kinetic model (K_obs = 0.0925 min^-1). SO₄^•- and •OH were verified as the reactive oxidants by EPR test and the radicals scavenging experiment using MeOH and TBA. SO₄^•- played a dominant role for CBZ degradation. The Density functional theory (DFT) and LC-qTOF-MS/MS clarified that hydroxylation, ketonation, ring opening reaction, and ring contraction were main transformation patterns of CBZ. As to influence factors, CBZ degradation was significantly hindered in presence of CO₃^2-, HPO₄^2- and NOM. Toxicological analysis derived from metabonomics suggested that the remarkable alteration of metabolic profile was triggered by exposure to intermediates mixture. CBZ intermediates interfered in several key metabolic pathways, including pentose phosphate, amino acids, lysine degradation, glycerophospholipid, glutathione, nucleotides and carbohydrate, which was alleviated after UV/bisulfite treatment. This work provided a meaningful support to potential risk of CBZ intermediates products, which shed light on the future application in eliminating drugs using UV /bisulfite.

Catalytic ozonation mechanisms of Norfloxacin using Cu-CuFe2O4

As an easily recoverable, environmentally friendly and cost-effective catalyst, CuFe₂O₄ is a promising candidate for the catalytic ozonation of antibiotics in wastewater. However, its catalytic activity is restricted due to its limited active sites and low electron transfer efficiency. In this study, cetyl trimethyl ammonium bromide (CTAB) and Cu⁰ were doped with CuFe₂O₄ to introduce more O_V, providing more active sites and improving electron transfer efficiency. Experimental results show that the optimum removal efficiency of the catalytic ozonation of Norfloxacin (NOR, a widely used antibiotic) using CTAB doped with Cu-CuFe₂O₄ as the catalyst is 81.58% with a first-order reaction kinetics constant of 0.03967 min^-1. The associated O₃ and catalyst dosages are 2.72 mg·L^-1 and 0.1 g·L^-1, respectively, which are 1.63 times and 2.22 times higher than those in an equivalent O₃ system. O_V can provide generation sites for surface hydroxyl groups and trigger ·O₂^- and ¹O₂ as the main active oxygen species. The synergistic redox cycles of Fe²⁺/Fe³⁺ and Cu⁰/Cu²⁺ accelerate electron transfer efficiency. The possible degradation pathways of NOR are identified as defluorination, naphthyridine ring-opening and piperazine ring-opening. In summary, this work proposes a new strategy for the modification of CuFe₂O₄ catalysts and provides new insights into the catalytic ozonation mechanisms for NOR removal.

Nano-CuOx for ciprofloxacin effective removal via wet peroxide oxidation catalysis and its practical application in wastewater

Using Cu(NO3)2·3H2O as active material and citric acid (CA) as complexing agent, heterogeneous catalyst nano-CuOx was prepared by sol-gel method. The catalytic wet peroxide oxidation (CWPO) reaction system was established accordingly. The system was used to treat ciprofloxacin (CIP) in simulated wastewater and real wastewater. The effects of the molar ratio of metal salt to CA, calcination temperature, H2O2 dosage, reaction temperature, and catalyst dosage on the physicochemical structure and the properties of CWPO were investigated. The results showed that when the molar ratio of CA to metal salt (Cu(NO3)2·3H2O) was 1.8, the calcination temperature was 500 °C, the concentration of H2O2 was 10 mmol · L–1, the reaction temperature was 95 °C, and the dosage of catalyst was 1 g · L–1, CWPO system has the best degradation effect on CIP. At thses optical conditions, the removal rate reached 86.8%, chemical oxygen demand (COD) removal rate reached 54.9%, and the recycling rate of the catalyst was very good. The refractory organics in actual pharmaceutical wastewater could be oxidized by this system as well, and the COD removal rate reaches 47%. The degradation mechanism of CIP showed that the main functions of the CWPO system were ·O2– and ·OH radicals. The possible degradation pathways were determined by ion chromatography to be intermediate products generated from piperazine ring cleavage, defluorination, decarboxylation, and quinoline hydroxylation of CIP. The catalyzing mechanism was investigated in detail; some useful information was obtained in this work.

The synergistic effect of calcite and Cu2+ on the degradation of sulfadiazine via PDS activation: A role of Cu(Ⅲ)

A system of Cu²⁺/calcite/PDS was constructed to degrade sulfadiazine (SDZ). Different from the traditional Cu-mediated activation, a low concentration of Cu²⁺ that met drinking water standards (≤ 1 mg/L) transformed into Cu(Ⅱ) solid in the presence of calcite, and then enhanced the degradation of SDZ via PDS activation over a pH range from 3 to 9. According to scavenger and chemical probe experiments, Cu(Ⅲ), rather than radicals (hydroxyl radicals and sulfate radicals) and singlet oxygen, was the predominant reactive species, which was responsible for the degradation of SDZ. Based on the results of XRD, ATR-FTIR, and CV curves et al., CuCO₃ was the main complex with high reactivity for PDS activation to form Cu(Ⅲ). Moreover, detailed degradation pathways of sulfadiazine were proposed according to the UPLC-ESI-MS/MS and their toxicity was predicted by ECOSAR. Besides, the real water matrix would not seriously affect the degradation of SDZ in the Cu²⁺/calcite/PDS system. In summary, this study reveals a new insight into the synergistic effect of Cu²⁺ and calcite on the SDZ degradation, and promotes an understanding of the environmental benefits of natural calcite.

Three-dimensional flower-like magnetic CoFe-LDHs/CoFe2O4 composites activating peroxymonosulfate for high efficient degradation of aniline

In this study, 3D flower-like magnetic CoFe-LDHs/CoFe₂O₄ was prepared by a facile urea hydrothermal method and utilized to activate peroxymonosulfate (PMS) for degrading aniline (AN). CoFe-LDHs/CoFe₂O₄ was systematically characterized to explore the relationship between its structure and catalytic performance. Compared with CoFe-LDHs synthesized by co-precipitation method, CoFe-LDHs/CoFe₂O₄ exhibited three dimensional structure and larger specific surface, which could increase the degradation efficiency of AN markedly. 96% of 10 mg L^-1 AN could be eliminated by 0.3 mM PMS and 50 mg L^-1 CoFe-LDHs/CoFe₂O₄ at initial pH 6 within 5 min and the total organic carbon (TOC) removal efficiency could be high to 52.8% in 30 min. CoFe-LDHs/CoFe₂O₄ can be separated by a magnet easily due to its magnetism, which makes it avoid secondary pollution and provide convenience. After recycling six times, the degradation efficiency still maintained at 92.6%. Besides, CoFe-LDHs/CoFe₂O₄/PMS can degrade AN in practical water samples effectively. In addition, the possible mechanism of CoFe-LDHs/CoFe₂O₄/PMS system for the degradation of AN was proposed. The radical scavenging experiments confirmed that SO₄·^-, HO· and O₂·^- were involved and SO₄·^- played a dominant role in the degradation of AN, and it was further proved by electron Paramagnetic Resonance (EPR) as well. Our findings can provide some new insights into the efficient and skillful design and application of heterogeneous catalyst for environmental remediation.

Transformation of sulfamethoxazole by sulfidated nanoscale zerovalent iron activated persulfate: Mechanism and risk assessment using environmental metabolomics

The threat caused by the misuse of antibiotics to ecology and human health has been aroused an extensive attention. Developing cost-effective techniques for removing antibiotics needs to put on the agenda. In current research, the degradation mechanism of sulfamethoxazole (SMX) by sulfidated nanoscale zerovalent iron (S-nZVI) driven persulfate, together with the potential risk of intermediates were studied. The degradation of SMX followed a pseudo-first order kinetics reaction with k_obs at 0.1176 min^-1. Both SO₄^•- and •OH were responsible for the degradation of SMX, and SO₄^•- was the predominant free radical. XPS analysis demonstrated that reduced sulfide species promoted the conversion of Fe (III) to Fe (II), resulting in the higher transformation rate of SMX. Six intermediates products were generated through hydroxylation, dehydration condensation, nucleophilic reaction, and hydrolysis. The risk of intermediates products is subsequently assessed using E. coli as a model microorganism. After E.coli exposure to intermediates for 24 h, the upmetabolism of carbohydrate, nucleotide, citrate acid cycle and downmetabolism of glutathione, sphingolipid, galactose by metabolomics analysis identified that SMX was effectively detoxified by oxidation treatment. These findings not only clarified the superiority of S-nZVI/persulfate, but also generated a novel insight into the security of advanced oxidation processes.

Fe Single-Atom Catalyst for Efficient and Rapid Fenton-Like Degradation of Organics and Disinfection against Bacteria

The Fenton-like reaction has great potential in water treatment. Herein, an efficient and reusable catalytic system is developed based on atomically dispersed Fe catalyst by anchoring Fe atoms on nitrogen-doped porous carbon (Fe SA/NPCs). The catalyst of Fe SA/NPCs exhibits enhanced performance in activating peroxymonosulfate (PMS) for organic pollutant degradation and bacterial inactivation. The Fe SA/NPCs + PMS system demonstrates a high turnover frequency of 39.31 min^-1 in Rhodamine B (RhB) degradation as well as a strong bactericidal activity that can completely sterilize an Escherichia coli culture within 5 min. Meanwhile, the degradation activity of RhB by Fe SA/NPCs is improved up to 28 to 371-fold in comparison with the controls. Complete degradation of RhB can be achieved in 30 s by the Fe SA/NPCs + PMS system, demonstrating an efficiency much higher than most traditional Fenton-like processes. Experiments with different radical scavengers and density functional theory calculations have revealed that singlet oxygen (¹ O₂ ) generated on the N-coordinated single Fe atom (Fe-N₄ ) sites is the key reactive species for the effective and rapid pollutant degradation and bacterial inactivation. This work innovatively affords a promising single-Fe-atom catalyst/PMS system for applying Fenton-like reactions in water treatment.

Activation of peroxymonosulfate by MgCoAl layered double hydroxide: Potential enhancement effects of catalyst morphology and coexisting anions

The morphology and specific surface area of layered double hydroxide (LDH) are of great significance for optimizing the application of LDH in sewage treatment. Herein, we present a study of the relation between the catalytic property and the morphology of LDH via activating peroxymonosulfate (PMS) for degradation of organic pollutants. The results demonstrated that LDH nanoscrolls possessed a superior performance for methylene blue (MB) degradation, which achieved almost 100% removal in 40 min and the calculated apparent rate constant was about 2.1, 4.5 and 11.5 times higher than that of LDH nanosheets, Co²⁺ and Co₃O₄, respectively. According to the results of X-ray photoelectrons spectroscopy (XPS) and electron paramagnetic resonance (EPR), ¹O₂ was confirmed to play a dominant role in the MB degradation, where the redox cycle of Co³⁺/Co²⁺ provided the impetus for the reaction. Moreover, the pH and ion tolerance abilities of LDH nanoscrolls in PMS activating process were determined as well. Remarkably, CO₃^2- and H₂PO₄^- could even promote the generation of •OH and ¹O₂ to facilitate the progress of reaction. Overall, these findings in the study may provide more opportunities in the preparation of high-efficiency catalysts and give insight into the accelerated degradation of refractory contaminants with surrounding anions.

Well-dispersed iron and nitrogen co-doped hollow carbon microsphere anchoring by g-C3N4 for efficient peroxymonosulfate activation

Developing single-atom Fenton-like catalysts with the maximum utilization of active sites present an attractive potential in environmental remediation. Herein, the single-atom Fe and N co-doped hollow carbon microsphere loaded g-C₃N₄ catalyst (HFeNC-g-C₃N₄) was prepared by an innovative cascade anchoring strategy using polystyrene as the hard template, iron phthalocyanine, polydopamine and urea as the Fe, N and C precursor, in which the in-situ generated g-C₃N₄ could not only effectively anchor Fe atom to create the well-dispersed Fe-N_x active sites, but also accelerate the electron transfer in peroxymonosulfate (PMS) activation. Taking advantages of such sequential protecting strategy, the as-synthesized HFeNC-g-C₃N₄ catalyst with single-atom Fe-N_x active sites, verified by XRD, XPS and HAADF-STEM, could work as an efficient Fenton-like catalyst for PMS activation, which achieved almost 100% removal of 4-chlorophenol (4-CP) in 5 min with the turnover frequency calculated to be 34.6 times higher than that of the homogeneous Fe²⁺ catalyst. The mechanism of O₂^•- dominated radical combined with nonradical ¹O₂ pathway was confirmed by quenching experiments and ESR analysis, which might be interrelated to the improvement of pH adaptability and interference immunity of HFeNC-g-C₃N₄/PMS system. Overall, the present findings provided an innovation strategy for the synthesis of excellent single-atom Fe based catalyst in wastewater purification.

Activation of peroxymonosulfate by bicarbonate and acceleration of the reaction by freezing

This study demonstrates the positive effects of dissolved bicarbonate and carbonate anions on peroxymonosulfate (PMS) induced oxidation and the remarkable acceleration of the reaction by freezing. More than 90% of the initial 4-chlorophenol (4-CP) decomposed in the frozen case, whereas only less than 20% of the 4-CP was removed in the aqueous case in the same time period. This accelerated reaction is attributed to the freeze-concentration of the dissolved substrates (i.e., PMS, bicarbonate, and pollutants) in the quasi-liquid layer at the ice grain boundaries between ice crystals. The reaction between bicarbonate and PMS was found to be unique because none of the effects were observed in the phosphate and hydroxide cooperated system with freezing, although the base activation of PMS could participate under basic conditions (pH > 9). Based on electron paramagnetic resonance spectroscopy measurements and comparison with the photo-excited Rose Bengal system as a reference system for singlet oxygen (¹O₂) generation, ¹O₂ was found to have a minor effect on the oxidation of 4-CP in the frozen bicarbonate-PMS system. While, direct electron transfer from the target organic substrate to the PMS was suggested as a major mechanism of 4-CP oxidation, because the selected target organic substrates were decomposed with different tendencies, and the consumption of PMS was accelerated by the presence of an electron donating compound. The results show the potential applicability of the freezing phenomenon, which occurs naturally in the mid-latitude and polar area, to help a decomposition of water dissolved organic pollutants by the imitation of the natural purification process.

Simultaneous oxidation and removal of arsenite by Fe(III)/CaO2 Fenton-like technology

Arsenite contaminated water is one of severe global environmental problems. It is challenging to treat As(III) pollution by a one-step technology. In this study, we developed a Fe(III)/CaO₂ Fenton-like technology for the treatment of As(III). The simultaneous oxidation of arsenite and removal of arsenic were achieved with efficiencies of nearly 100% and 95.8% respectively, which outperforms conventional technologies. It worked well in pH 3 to 9, and in the presence of cationic heavy metals, anions and humic acid. Moreover, the PO₄^3- inhibited the removal of As(III). •OH and ¹O₂ played the important roles in the oxidation of As(III). The Ca(II) derived from CaO₂ made a significant contribution to the oxidation and removal of As(III). The SEM and XPS studies confirmed that the formation of Ca-Fe nascent colloid caused the effective removal of arsenic. Our study demonstrates that the one-step Fe(III)/CaO₂ technology has a great potential for purification of the As(III)-contaminated water.

Efficient activation of peroxymonosulfate by Co-doped mesoporous CeO2 nanorods as a heterogeneous catalyst for phenol oxidation

Sulfate radical-based advanced oxidation processes have received considerable attentions in the remediation of organic pollutants due to their high oxidation ability. In this study, a novel Co3O4/CeO2 catalyst was fabricated and employed as a peroxymonosulfate (PMS) activator to generate SO4•- for phenol degradation. The Co3O4/CeO2 catalyst exhibited a good catalytic performance at a wide pH range of 3.4 to 10.8, and 100% phenol (20 mg/L) was removed within 50-min reaction under optimal conditions with 0.2 g/L catalyst and 2.0 g/L PMS at room temperature. The transformation products and total organic carbon during the degradation process were also determined. The quenching experiments and electron paramagnetic resonance spectra revealed that sulfate radical (SO4•-) rather than other species such as singlet oxygen (1O2) and hydroxyl radical (•OH) was primarily responsible for phenol degradation in the Co3O4/CeO2/PMS system, and a rational mechanism was proposed. Moreover, the recycling experiments as well as low cobalt leaching concentration manifested satisfactory reusability and stability. The effects of various inorganic anions and natural organic matter in real water matrix on phenol oxidation were further evaluated. We believe that the Co3O4/CeO2 composites have promising applications of PMS activation for the degradation of organic pollutants in wastewater treatment.

A novel route for catalytic activation of peroxymonosulfate by oxygen vacancies improved bismuth-doped titania for the removal of recalcitrant organic contaminant

In this work, bismuth-doped titania (Bi_xTiO₂) with improved oxygen vacancies was synthesized by sol-gel protocol as a novel peroxymonosulfate (PMS, HSO₅^-) activator. HSO₅^- and adsorbed oxygen molecules could efficiently be transformed into their respective radicals through defect ionization to attain charge balance after their trapping on oxygen vacancies of the catalyst. XRD study of Bi_xTiO₂ with 5 wt% Bi (5BiT) revealed anatase, crystalline nature, and successful doping of Bi into TiO₂ crystal lattice. The particle size obtained from BET data and SEM observations was in good agreement. PL spectra showed the formation rates of ^•OH by 3BiT, 7BiT, 5BiTC, and 5BiT as 0.720, 1.200, 1.489, and 2.153 μmol/h, respectively. 5BiT catalyst with high surface area (216.87 m² g^-1) and high porosity (29.81%) was observed the excellent HSO₅^- activator. The catalytic performance of 0BiT, 3BiT, 5BiT, and 7BiT when coupled with 2 mM HSO₅^- for recalcitrant flumequine (FLU) removal under dark was 10, 27, 55, and 37%, respectively. Only 5.4% decrease in catalytic efficiency was observed at the end of seventh cyclic run. Radical scavenging studies indicate that SO₄^•- is the dominant species that caused 62.0% degradation. Moreover, strong interaction between Bi and TiO₂ through Bi-O-Ti bonds prevents Bi leaching (0.081 mg L^-1) as shown by AAS. The kinetics, degradation pathways, ecotoxicity, and catalytic mechanism for recalcitrant FLU were also elucidated. Cost-efficient, environment-friendly, and high mineralization recommends this design strategy; Bi_xTiO₂/HSO₅^- system is a promising advanced oxidation process for the aquatic environment remediation.

Immobilized Co2+ and Cu2+ induced structural change of layered double hydroxide for efficient heterogeneous degradation of antibiotic

In this study, MgMn-layered double hydroxide (MgMnLDH) exhibited excellent remediation functionality for heavy metals-antibiotics combined pollution. On the one hand, Co²⁺ and Cu²⁺ was efficiently immobilized on MgMnLDH with maximum quantity of 4.30 and 10.65 mmol g^-1, respectively. A series of characterizations reflected the changes in structure and physicochemical properties of MgMnLDH after the immobilization. Density functional theory calculations (DFT) confirmed that the binding modes were lattice substitution for Co²⁺ and surface precipitation for Cu²⁺. On the other hand, the immobilized heavy metals enhanced the heterogeneous degradation for sulfamethoxazole (SMX) by peroxymonosulfate (PMS) activation. Complete degradation was achieved within 10 min in MgMnLDH-Co-4/PMS system and 60 min in MgMnLDH-Cu/PMS system, while only 20% in MgMnLDH/PMS system. The pH adaptability, reusability, stability and activation mechanism of two systems were systematically compared. The superior degradation performance of MgMnLDH-Co-4 benefited from the intense Co/Mn synergism and abundant oxygen vacancies, which could accelerate electron transfer during PMS activation process. The applicability of two catalysis system was confirmed in purifying other antibiotics and actual wastewater. The results highlight the importance of structural control in heterogeneous catalysis and provide new idea for environmental remediation.

Perovskite and Spinel Catalysts for Sulfate Radical-Based Advanced Oxidation of Organic Pollutants in Water and Wastewater Systems

Since environmental pollution by emerging organic contaminants is one of the most important problems, gaining ground year after year, the development of decontamination technologies of water systems is now imperative. Advanced oxidation processes (AOPs) with the formation of highly reactive radicals can provide attractive technologies for the degradation of organic pollutants in water systems. Among several AOPs that can be applied for the formation of active radicals, this review study focus on sulfate radical based-AOPs (SR-AOPs) through the heterogeneous catalytic activation of persulfate (PS) or peroxymonosulfate (PMS) using perovskite and spinel oxides as catalysts. Perovskites and spinels are currently receiving high attention and being used in substantial applications in the above research area. The widespread use of these materials is based mainly in the possibilities offered by their structure as it is possible to introduce into their structures different metal cations or to partially substitute them, without however destroying their structure. In this way a battery of catalysts with variable catalytic activities can be obtained. Due to the fact that Co ions have been reported to be one of the best activators of PMS, special emphasis has been placed on perovskite/spinel catalysts containing cobalt in their structure for the degradation of organic pollutants through heterogeneous catalysis. Among spinel materials, spinel ferrites (MFe2O4) are the most used catalysts for heterogeneous activation of PMS. Specifically, catalysts with cobalt ion in the A position were reported to be more efficient as PMS activators for the degradation of most organic pollutants compared with other transition metal catalysts. Substituted or immobilized catalysts show high rates of degradation, stability over a wider pH area and also address better the phenomena of secondary contamination by metal leaching, thus an effective method to upgrade catalytic performance.

Phototransformation of zinc oxide nanoparticles and coexisting pollutant: Role of reactive oxygen species

In this study, the photochemistry of ZnO NPs and their effect on phototransformation of coexisting pollutants (sulfamethazine, SMZ) were systematically investigated under UV illumination. SMZ (40 μM) degradation was accelerated by ZnO NPs, as the observed reaction rate constant (k_obs) increased from 0.0809 h^-1 to 0.7982 h^-1 at the concentration of 5-50 mg/L ZnO NPs. Free radical quenching and quantification experiments indicated the reactive oxygen species, especially the hydroxyl radicals (OH) and singlet oxygen (¹O₂), made great contributions to SMZ degradation. Moreover, SMZ was prone to be degraded at high pH with k_obs reaching upto 0.5734 h^-1 at pH 12.0. The presence of Cl^- (1000 mM) reduced the SMZ decomposition greatly by 2.4-fold while the effects of SO₄^2- (30 mM) were very limited. Natural organic matter including humic acid and tannic acid both inhibited the degradation of SMZ with k_obs decreasing by 35.4-fold and 132-fold, respectively. During the photoreaction process, ZnO NPs fragmented into relative small size pieces obviously along with the release of Zn²⁺. Finally, the possible cotransformation pathways of ZnO NPs and SMZ were proposed based on SMZ degradation intermediates and the above results. These findings of the present study suggested that the photoreactions of ZnO NPs greatly influenced the transformation of contaminants and ZnO NPs themselves in aquatic environment, which may have significant implications for the fate assessment of NPs and environmental pollutants.

Nitrogen-doped porous carbon encapsulating iron nanoparticles for enhanced sulfathiazole removal via peroxymonosulfate activation

Developing novel catalyst with both high efficiency and stability presents an enticing prospect for peroxymonosulfate (PMS) activation. In this paper, nitrogen-doped porous carbon encapsulating iron nanoparticles (CN-Fe) was fabricated by a facile carbothermal reduction process using polyaniline (PANI) and α-Fe₂O₃ as the precursors. The stubborn antibiotics, sulfathiazole (STZ), was employed as a target pollutant, demonstrating that CN-Fe coupled with PMS could achieve 96% removal efficiency and even 57% mineralization rate of STZ within 40 min. More importantly, the rate constant of CN-Fe was calculated to be 0.07665 min^-1, which was 6 times higher than that of the commercial α-Fe₂O₃ catalyst. Furthermore, CN-Fe also presented a favorable catalytic performance for removing other organic pollutants including phenolic compounds and organic dyes. Interestingly, the catalytic activity of the used CN-Fe catalyst could be regenerated after thermal treatment (600 °C) and the as-synthesized CN-Fe catalyst exhibited excellent long-term stability with almost no loss of activity after storage for three months. The catalytic mechanism in the CN-Fe/PMS system was elucidated by electron paramagnetic resonance (EPR), linear sweep voltammetry (LSV), radical and electron trapping tests, which confirmed that sulfate radicals (SO₄^-), hydroxyl radicals (OH), superoxide radicals (O₂^-) and singlet oxygen (¹O₂) were generated in the oxidation process with the assistance of electron transfer between PMS and catalyst. To our knowledge, this was the first attempt for the application of PANI-derived CN-Fe hybrid materials as PMS activators and the findings would provide a simple and promising strategy to fabricate highly efficient and environment-benign catalysts for wastewater remediation.

Phosphorus-doped carbon fibers as an efficient metal-free bifunctional catalyst for removing sulfamethoxazole and chromium (VI)

Developing an efficient and metal-free bifunctional catalyst for the simultaneous degradation of antibiotic and reduction of Cr (VI) has been regarded as increasingly attractive yet challenging objectives in the environmental catalysis field. Herein, phosphorus-doped carbon fibers (P-CFs) was innovatively prepared by doping and calcination methods, characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Sulfamethoxazole (SMX) as the target contaminant was selected to evaluate the catalytic activity of P-CFs in PMS activation, over 90% SMX removal and 82.75% mineralization were high-efficiently achieved in the P-CFs/peroxymonosulfate (PMS) system. Particularly, P-CFs/PMS system exhibited a superior catalytic oxidation performance over a wide pH range (3.5-9.5) and even in the complicated water matrix. Surprisingly, the presence of humic acid (HA) in the P-CFs/PMS system could achieve about 2 times enhancement on SMX removal, different from most reports about the inhibition of HA in PMS activation. More importantly, Brunauer-Emmett-Teller (BET) method and XPS analysis revealed that the highly toxic Cr (VI) could be reduced to Cr (III) by P-CFs. Furthermore, electron spin resonance (ESR) combined with various trapping agents demonstrated that SO₄•^-, •OH and ¹O₂. were generated and participated in the SMX degradation, while the free electron in P-CFs played a main role in Cr (VI) reduction. This finding not only provided a high-efficiency strategy in the treatment of wastewaters containing organic contaminants and heavy metals Cr (VI), but might open new insights into an innovative metal-free catalyst in environment remediation.

Multifunctional magnetic MgMn-oxide composite for efficient purification of Cd2+ and paracetamol pollution: Synergetic effect and stability

A multifunctional magnetic composite (0.3Ma-MgMnLDO-a) with the function of Cd²⁺ adsorption and paracetamol (PAM) degradation was successfully fabricated. Surface morphology showed that Fe₃O₄ agglomeration was overcome on composite. The composite had high specific surface area of 105.32 m² g^-1 and saturation magnetization of 40 emu∙g^-1. 0.3Ma-MgMnLDO-a could reach Cd²⁺ adsorption equilibrium within 5 min with 99 % removal rate. The maximum adsorption capacity was 3.76 mmol·g^-1 (422.62 mg g^-1), which apparently higher than that of Fe₃O₄-a and MgMnLDO-a, indicating that the Fe/Mn synergism results in excellent ability for Cd²⁺ adsorption. Moreover, the composite could efficiently activate peroxymonosulfate (PMS) to rapid degrade PAM with the highest first-order rate constants (k_obs = 0.116 min^-1) and total organic carbon (TOC) removal rate (67.7 %), which also due to the contribution of Fe/Mn synergism in PMS activation. The cycling of Mn^III/Mn^IV and Fe^II/Fe^III played an important role in activating PMS to generateO₂^-•, ¹O₂ and OH for degradation. The composite exhibited both stable adsorption and catalytic performance on wide pH (3-9) and five reuse cycles. Notably, there was mutual promotion between Cd²⁺ and PAM adsorption, while the coexistence of Cd²⁺ had slight inhibition on PAM degradation. Overall, the magnetic composite had promising application for purifying heavy metals and pharmaceuticals.

CuCo2O4 supported on activated carbon as a novel heterogeneous catalyst with enhanced peroxymonosulfate activity for efficient removal of organic pollutants

CuCo₂O₄ was synthesized via a relatively simple method, and innovatively supported onto the activated carbon (AC) by calcination to obtain a novel heterogeneous catalyst (AC-CuCo₂O₄). Brilliant red 3BF (3BF) was selected as the probe compound to investigate the catalytic activity of AC-CuCo₂O₄ in the presence of peroxymonosulfate (PMS). The results showed that 98% removal rate could be achieved and the reaction rate constant (0.476 min^-1) was 5.2 times greater than that of CuCo₂O₄ alone (0.091min^-1), suggesting that the introduction of AC could greatly enhance the catalytic activity of pure CuCo₂O₄. Typically, the 3BF removal was as high as 96% after five cycles, showing the good stability of catalyst reuse. Additionally, the effects of the initial pH, catalyst dosage, PMS concentration and reaction temperature on the 3BF removal were investigated, demonstrating that AC-CuCo₂O₄ effectively remove 3BF over a wide pH range (5.0-10.0) and possessed temperature-tolerant performance. To further explore the 3BF removal mechanism, electron paramagnetic resonance technology combining with trapping agents was employed to confirm the involvement of reactive oxygen species including SO₄^•-, ^•OH, O₂^•- and ¹O₂, which distinctly differed from the reported CuCo₂O₄ for PMS activation. These findings provided an addition promising strategy in environmental remediation.

Iron phthalocyanine-sensitized magnetic catalysts for BPA photodegradation

The catalytic behavior of iron phthalocyanine (FePc)-sensitized magnetic nanocatalysts was evaluated for their application in the oxidative treatment of Bisphenol A (BPA) under mild environmental conditions. Two types of FePc (Fe(II)Pc and Fe(III)Pc), which are highly photosensitive compounds, were immobilized on the surface of functionalized magnetite. The nanomaterials were characterized by high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analyses (TGA). The generation of singlet oxygen by nanomaterials was also investigated. In the presence of UVA light exposure (365 nm) and 15 mM H₂O₂, the M@Fe(III)Pc photocatalyst gave the best results; for a catalyst concentration of 2.0 g L ^− 1, around 60% BPA was removed after 120 min of reaction. These experimental conditions were further tested under natural solar light exposure, for which also M@Fe(III)Pc exhibited enhanced oxidative catalytic activity, being able to remove 83% of BPA in solution. The water samples were less cytotoxic after treatment, this being confirmed by the MCF-7 cell viability assay.

Innovatively employing magnetic CuO nanosheet to activate peroxymonosulfate for the treatment of high-salinity organic wastewater

Magnetic CuO nanosheet (Mag-CuO), as a cheap, stable, efficient and easily separated peroxymonosulfate (PMS) activator, was prepared by a simple one-step precipitation method for the removal of organic compounds from salt-containing wastewater. The experiments showed that the removal efficiencies of various organic pollutants including Acid Orange 7, Methylene Blue, Rhodamine B and atrazine in a high-salinity system (0.2 mol/L Na₂SO₄) with the Mag-CuO/PMS process were 95.81%, 74.57%, 100% and 100%, respectively. Meanwhile, Mag-CuO still maintained excellent catalytic activity in other salt systems including one or more salt components (NaCl, NaNO₃, Na₂HPO₄, NaHCO₃). A radical-quenching study and electron paramagnetic resonance analysis confirmed that singlet oxygen (¹O₂) was the dominant reactive oxygen species for the oxidation of organic pollutants in high-salinity systems, which is less susceptible to hindrance by background constituents in wastewater than radicals (^•OH or SO₄^•-). The surface hydroxylation of the catalyst and catalytic redox cycle including Cu and Fe are responsible for the generation of ¹O₂. The developed Mag-CuO catalyst shows good application prospects for the removal of organic pollutants from saline wastewater.

Metallic Active Sites on MoO2(110) Surface to Catalyze Advanced Oxidation Processes for Efficient Pollutant Removal

Advanced oxidation processes (AOPs) based on sulfate radicals (SO₄^⋅−) suffer from low conversion rate of Fe(III) to Fe(II) and produce a large amount of iron sludge as waste. Herein, we show that by using MoO₂ as a cocatalyst, the rate of Fe(III)/Fe(II) cycling in PMS system accelerated significantly, with a reaction rate constant 50 times that of PMS/Fe(II) system. Our results showed outstanding removal efficiency (96%) of L-RhB in 10 min with extremely low concentration of Fe(II) (0.036 mM), outperforming most reported SO₄^⋅−-based AOPs systems. Surface chemical analysis combined with density functional theory (DFT) calculation demonstrated that both Fe(III)/Fe(II) cycling and PMS activation occurred on the (110) crystal plane of MoO₂, whereas the exposed active sites of Mo(IV) on MoO₂ surface were responsible for accelerating PMS activation. Considering its performance, and non-toxicity, using MoO₂ as a cocatalyst is a promising technique for large-scale practical environmental remediation.

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The degradation rate of PMS/Fe(II)/MoO₂ system is 50 times higher than that without MoO₂

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Fe(III)/Fe(II) cycle on (110) surface of MoO₂ in PMS/Fe(II)/MoO₂ system was confirmed

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The metal active sites exposed to MoO₂ (110) surface are responsible for PMS activation

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Compared with MoS₂, MoO₂ co-catalytic system has less toxicity and no release of H₂S

Highly efficient removal of organic pollutants via a green catalytic oxidation system based on sodium metaborate and peroxymonosulfate

The development of highly efficient and green catalytic oxidation process based on peroxymonosulfate (PMS) activation has been identified to be a significant yet challenging objective in the environmental catalysis field. A simple, environmentally benign and highly effective catalytic oxidation system was innovatively constructed by coupling NaBO₂ and PMS for the removal of Acid Red 1. The catalytic mechanism in the NaBO₂/PMS system was elucidated by electron paramagnetic resonance (EPR) combined with several radical capture reagents (ascorbic acid, methanol, tert-butyl alcohol, ethanol and _l-histidine). The experimental results indicated that singlet oxygen (¹O₂) severed as the predominant reactive oxygen species (ROS) rather than the HO or during the catalytic oxidation process, at variance with the reported radical pathway in the Co²⁺/PMS system. Inspiringly, p-benzoquinone (p-BQ) as a trapping agent in most advanced oxidation process could be turned into the positive one in the NaBO₂/PMS system, achieving a nearly 3-times enhancement in terms of the rate constant for AR1 removal. More interestingly, sodium chloride (NaCl) presented the same enhancement effect as p-benzoquinone due to generation of hypochlorous acid (HOCl) and more ¹O₂, which was completely different from the reported. This study develops a highly efficient green oxidation process and opens up a new insight in the remediation of contaminated water.

Facile template synthesis of dumbbell-like Mn2O3 with oxygen vacancies for efficient degradation of organic pollutants by activating peroxymonosulfate

A novel dumbbell-like Mn₂O₃ microstructure prepared under mild conditions was used as a catalyst to PMS activation for RhB degradation. In the Mn₂O₃/PMS system, the reactive oxygen species were revealed in the degradation process by PMS activation.

Direct Electron-Transfer-Based Peroxymonosulfate Activation by Iron-Doped Manganese Oxide (δ-MnO2) and the Development of Galvanic Oxidation Processes (GOPs)

Manganese oxides have been recently investigated as excellent catalysts for peroxymonosulfate (PMS) activation, and the reported mechanisms are mostly forming reactive oxygen species (ROSs). This study investigated the use of iron-doped manganese oxide, synthesized via air oxidation under strong alkaline conditions. The oxidation of three substrates was affected by their adsorption at the catalyst surface, solution pH, and co-solutes. Common ROS scavengers inhibited the oxidation of bisphenol A (BPA), suggesting the possible involvement of ROSs; however, the PMS decomposition tests with and without BPA and the comparison with a ¹O₂-generation system ruled out the formation of ROSs and pointed to direct electron transfer between the adsorbed BPA and complexed PMS as the mechanism. To prove this mechanism, the catalyst was coated to graphite sheets and a galvanic oxidation process (GOP) was developed to separate BPA and PMS into two half cells. Upon PMS addition into one cell, BPA was quickly oxidized in the other cell, confirming the occurrence of electron transfer. The GOP system successfully degraded BPA in both surface water and hypersaline shale gas-produced water. Overall, this study developed a new catalyst for PMS activation and unveiled the advantages and potential applications of electron shuttling catalysts.

Environmental application of MgMn-layered double oxide for simultaneous efficient removal of tetracycline and Cd pollution: Performance and mechanism

The MgMn-layered double oxide (MgMn-LDO), which was fabricated by calcining MgMn-layered double hydroxide (MgMn-LDH), was used to remove tetracycline (TC) and cadmium (Cd) pollution. In MgMn-LDO activated peroxymonosulfate (PMS) system, 97.1% of TC was degraded within 20 min. The high oxidizing sites exposed on MgMn-LDO surface played a main role on activating PMS to generate OH, SO₄^-, O₂^- and ¹O₂ (the key species) for TC degradation. MgMn-LDO could keep excellent degradation performance in a wide range of pH (from 4 to 10). The degradation degree of TC in distilled water is basically the same as that in Pearl River water, and even above 80% of TC could be degraded in human urine. The good reusability and high structure stability of MgMn-LDO were further verified. Meanwhile, Cd immobilization on MgMn-LDO reached equilibrium within 10 min, and its maximum fixed quantity was 8.234 mmol g^-1 (922.208 mg g^-1). The outstanding Cd fixed ability resulted from the formation of CdCO₃ and Cd (OH)₂. In combined system, the existence of TC promoted the immobilization of Cd on MgMn-LDO. Low concentration of Cd (0.0125 mM) had synergism effect on TC degradation, while high concentration of Cd (0.025 and 0.05 mM) had inhibiting action. Finally, a column filled with MgMn-LDO was designed for repairing TC and Cd pollution hierarchically. This study provided an effective strategy to clean up the organic-heavy metal combined pollution.

Fe@C carbonized resin for peroxymonosulfate activation and bisphenol S degradation

Aiming at realizing heavy metal recycling and resource utilization, a carbon-based iron catalyst (Fe@C) was synthesized through a resin carbonization method, and adopted for peroxymonosulfate (PMS) activation to remove bisphenol S (BPS), an emerging aquatic contaminant. This study demonstrated that Fe@C exhibited excellent catalytic potential for BPS degradation with a relatively low activation energy (E_a = 29.90 kJ/mol). Kinetic factors affecting the activation performance were thoroughly investigated. The obtained results indicated that Fe@C composite exhibited the superior uniformity with carbon as the framework and granular iron oxide as the coverage. pH increase could cause the inhibitive effect on BPS degradation, while the increasing catalyst loading (0.05-0.5 g/L) was conducive for the catalytic performance of Fe@C, with an optimal PMS concentration at 1.0 mM. A negative influence on BPS degradation was obtained in the presence of SO₄^2-, HCO₃^- and lower concentration of Cl^- (0-20 mM), compared to the promotion at higher concentration of Cl^- (>50 mM). Based on the electron spin resonance (ESR) monitoring and radical scavenging results, it is demonstrated that singlet oxygen, a non-radical species, emerged together with ·SO₄^- and ·OH for BPS degradation. A three-channel catalytic mechanism was verified through typical characterizations. Furthermore, the degradation pathway of BPS was proposed based on the identified intermediates. This novel carbon-based activator for PMS showed notable potential for the waste resin recycling and water decontamination. A novel Fe-based activator carbonized from a saturated resin exhibits excellent performance for Bisphenol S degradation with activated peroxymonosulfate.

Activation of peroxymonosulfate by magnetic carbon supported Prussian blue nanocomposite for the degradation of organic contaminants with singlet oxygen and superoxide radicals

In order to develop efficient and green catalyst for organic pollutants removal, magnetic carbon supported Prussian blue nanocomposite Fe₃O₄@C/PB was prepared for the first time. The performance of Fe₃O₄@C/PB in activating peroxymonosulfate (PMS) for the degradation of 2,4-dichlorophenol (2,4-DCP) was investigated. 2,4-DCP could be effectively degraded under the "Fe₃O₄@C/PB + PMS" system within a broad pH range of 2-9. Without pH adjustment (pH 3), 2,4-DCP (20 mg/L) was completely degraded in 50 min along with a 70% removal of TOC; while the required time for complete degradation of 2,4-DCP was shortened to 40 min under initial solution pH at 7. Fe₃O₄@C/PB could also activate PMS for the degradation of phenol, Acid Orange II, Reactive brilliant red X-3B, Rhodamine B and Methylene blue. The degradation rates higher than 95% could be achieved for all these contaminants within the time scale of 15-60 min. The studies of radical-quenching and electron paramagnetic resonance demonstrated that singlet oxygen (¹O₂) and superoxide radicals (O₂^-), rather than sulfate (SO₄^-) and hydroxyl (OH) radicals, were the dominant species responsible for the oxidation of organic pollutants. The plausible mechanism of the catalytic degradation was proposed and the enhanced activity of Fe₃O₄@C/PB was assumed to be related to the increased electron transfer owing to the synergic effect between the magnetic carbon and the mixed-valence units in PB. Fe₃O₄@C/PB is promising in wastewater treatment owing to its high efficiency, excellent stability and reusability, environmental friendliness and magnetic separability.

Application of nickel foam-supported Co3O4-Bi2O3 as a heterogeneous catalyst for BPA removal by peroxymonosulfate activation

Nickel foam (NF)-functionalized Co₃O₄-Bi₂O₃ nanoparticles (CBO@NF) synthesized using a facile one-step microwave-assistant method were employed as catalysts to activate peroxymonosulfate (PMS) with bisphenol A (BPA) as the target pollutant. The crystallinity, morphology, and chemical valence state of the synthesized CBO@NF were analyzed using XRD, SEM, and XPS, respectively. Moreover, effects of the preparation parameters, including the calcination temperature and calcination time as well as the loading dosage, were evaluated in detail. A degradation efficiency of 95.6% was achieved within 30 min with the optimal degradation system. The CBO@NF/PMS system shows great catalytic activity in a pH range from 3.0 to 11.0. The stability and reusability of the CBO@NF supported catalyst was evaluated through a recycling experiment. In addition, the possible degradation mechanism was also explored using a quenching experiment and electron paramagnetic resonance (EPR) detection. The result shows that both the surface-bound SO₄^- and OH play significant roles during the degradation process, where the electron transfer of Co²⁺/Co³⁺, Bi³⁺/Bi⁵⁺, and Ni²⁺/Ni³⁺ realizes the sustained regeneration of the active radicals. This work provides new insight for the practical applications of sulfate radical-based advanced oxidation processes (SR-AOPs) in wastewater treatment.

Carbon fiber-assisted iron carbide nanoparticles as an efficient catalyst via peroxymonosulfate activation for organic contaminant removal

The introduction of carbon fibers enhances the ability of iron carbide nanoparticles to activate PMS to remove contaminants.

Magnetic Co-based carbon materials derived from core–shell metal–organic frameworks for organic contaminant elimination with peroxymonosulfates

The exploitation of highly efficient and reusable catalysts based on peroxymonosulfate (PMS) activation has attracted considerable attention in the environmental catalysis field.