Sulfate Radical-based Advanced Oxidation Processes Research Articles

Facile in situ synthesis of ZIF-67/cellulose hybrid membrane for activating peroxymonosulfate to degrade organic contaminants

In recent years, cobalt-based metal–organic frameworks (MOFs) have been used as catalytic materials to degrade organic contaminants in sulfate radical-based advanced oxidation processes (SR-AOPs). However, separating and recovering granular MOFs from the reaction system is difficult. Loading MOFs on the host material is currently the most effective way to promote their recyclability. Most reported aerogel materials are characterized by excessively long preparation and drying cycles. Considering this, herein, we report an in situ grown method to fabricate a ZIF-67/cellulose hybrid membrane, which was used as a catalyst for activating peroxymonosulfate to generate $${\text{SO}}_{4}^{ - }\cdot$$ and ·OH, resulting in the contaminants degradation. The catalytic results showed that the hybrid membrane/PMS system could degrade the methylene blue and rhodamine B within 1 min. In addition, the separation and recovery problems were solved. The ZIF-67/cellulose hybrid membrane with outstanding degradation of contaminants expands the application of MOFs/cellulose hybrid materials for wastewater purification via SR-AOPs.

Persulfate enhanced visible light photocatalytic degradation of iohexol by surface-loaded perylene diimide/acidified biochar

Persulfate (PS) is extensively employed as an oxidant to develop the sulfate radical-based advanced oxidation processes for removing organic pollutants and various PS activation methods have been explored. Iohexol (IOH), as a typical iodinated X-ray contrast media, poses a threat to human health and ecological environment, which is difficult to be removed by conventional treatment methods. In our work, a photocatalytic coupling persulfate system was constructed for efficient IOH degradation. A novel binary photocatalyst of biochar loaded with perylene diimide (PDI/BC, PB) was successfully prepared via a one-pot water bath heating method, which achieved BC acidification and PDI self-assembly simultaneously. Different mass ratios of BC and PDI lead to variance in average particle size, electronegativity, bandgap width and electron/hole separation efficiency. The optimized efficiency of 10 mg/L IOH on PB-9 (PDI:BC = 1:9, w/w) reached 100% in 2 h with 1.5 mM sodium persulfate under visible light irradiation. Based on the results of trapping experiments and electron paramagnetic resonance, holes and hydroxyl radicals were the dominant active species and the free radical chain reaction and mutual conversion reaction of active species occurred. The amide hydrolysis, amine and C-OH oxidation, hydrogen extraction, deiodination and OH addition were observed during the degradation process. Density functional theory calculation was conducted to confirm the free radical attack sites. The findings of this work demonstrate that metal-free supramolecular loaded photocatalyst has the potential for application in the removal of organic pollutants for water remediation.

Efficient Degradation of 2,4-Dichlorophenol on Activation of Peroxymonosulfate Mediated by MnO2.

Sulfate radical based-advanced oxidation process has received increasing interest in the remediation of wastewater and contaminated soil. In this study, degradation of 2, 4-dichlorophenol (2, 4-DCP) was investigated over peroxymonosulfate (PMS) activation by MnO2, which was prepared by liquid-phase oxidation method. The prepared MnO2 was characterized by transition electron microscopy, X-ray diffraction, N2 adsorption-desorption, and X-ray photoelectron spectroscopy. Characterization results showed that α-MnO2 exhibited the highest surface area and Mn (III) content. The PMS activation by MnO2 in 2, 4-DCP degradation followed the order of α-MnO2 > γ-MnO2 > β-MnO2, which is dependent on the properties of MnO2 including crystal structure, surface area and Mn (III) content. Influences of initial concentration of 2, 4-DCP, PMS and MnO2 dosage, pH and co-existing inorganic ions on the degradation were examined. Electron paramagnetic resonance (EPR) and quenching experiments with ethanol and tert-butanol suggested that sulfate radicals were the dominant radicals in the process. Findings in this study indicated that α-MnO2 was an attractive catalyst for activation of PMS to degrade 2, 4-DCP in aqueous solution.

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.

UV-A activation of peroxymonosulfate for the removal of micropollutants from secondary treated wastewater

The occurrence of micropollutants (MPs) in the aquatic environment poses a threat to the environment and to the human health. The application of sulfate radical-based advanced oxidation processes (SR-AOPs) to eliminate these contaminants has attracted attention in recent years. In this work, the simultaneous degradation of 20 multi-class MPs (classified into 5 main categories, namely antibiotics, beta-blockers, other pharmaceuticals, pesticides, and herbicides) was evaluated for the first time in secondary treated wastewater, by activating peroxymonosulfate (PMS) with UV-A radiation, without any pH adjustment or iron addition. The optimal PMS concentration to remove the spiked target MPs (100 μg L−1) from wastewater was 0.1 mM, leading to an average degradation of 80% after 60 min, with most of the elimination occurring during the first 5 min. Synergies between radiation and the oxidant were demonstrated and quantified, with an average extent of synergy of 69.1%. The optimized treatment was then tested using non-spiked wastewater, in which 12 out of the 20 target contaminants were detected. Among these, 7 were degraded at some extent, varying from 10.7% (acetamiprid) to 94.4% (ofloxacin), the lower removals being attributed to the quite inferior ratio of MPs to natural organic matter. Phytotoxicity tests carried out with the wastewater before and after photo-activated PMS oxidation revealed a decrease in the toxicity and that the plants were able to grow in the presence of the treated water. Therefore, despite the low degradation rates obtained for some MPs, the treatment effectively reduces the toxicity of the matrix, making the water safer for reuse.

Enhanced removal of methylparaben mediated by cobalt/carbon nanotubes (Co/CNTs) activated peroxymonosulfate in chloride-containing water: Reaction kinetics, mechanisms and pathways

Chloride ion (Cl−) widely presents in natural water and wastewater, which can significantly affect the performance of sulfate radical-based advanced oxidation processes (SR-AOPs). However, few studies are available now on the generation of chlorinated by-products in the peroxymonosulfate (PMS) based systems. Here a novel catalyst (cobalt/carbon nanotubes, Co/CNTs) was synthesized and used as a PMS activator to remove methylparaben (MeP) with and without Cl−. The morphology and chemical composition of the fresh and used Co/CNTs were characterized by TEM, SEM, XRD, BET, and XPS. Results revealed that Co/CNTs exhibited significant catalytic activity toward MeP removal, and the removal efficiency increased with the augment of reaction temperature and concentrations of Co/CNTs and PMS. In the absence of Cl−, 83.2% of 10 μM MeP was degraded within 60 min by using 2 mg/L Co/CNTs and 100 μM PMS at 25 °C with pH 7.0. However, complete removal of MeP was achieved within 20 min in the presence of 100 mM Cl−, which enhanced the apparent rate constant by a factor of 4.3. Consequently, TOC removal was enhanced from 8.1% to 19.2% within 60 min. Through the quenching experiments, both SO4− and OH were found responsible for MeP degradation without Cl−, while Cl2− was the main reactive oxygen species (ROS) with 100 mM Cl−. Based on the intermediates identified via TOF-LC-MS, four potential reaction pathways were proposed, including hydrogen abstraction coupling reaction, hydroxylation, OH attack, and Cl2− attack. The intermediates also exhibited decreased toxicity compared to the parent compound based on the ecotoxicity evaluation. In addition, Co/CNTs + PMS system achieved over 60% MeP removal from real wastewater with elevated PMS concentration, indicating the process applicability. These findings provide valuable information of SR-AOPs to facilitate organic contaminants removal in Cl−-containing water.

Synergistically enhanced heterogeneous activation of persulfate for aqueous carbamazepine degradation using Fe3O4@SBA-15

The exploration of low-cost, high-performance and stable catalytic materials for sulfate radical-based advanced oxidation processes (SR-AOPs) is of great importance. This study presents Fe3O4-wrapped SBA-15 mesoporous silica catalyst (Fe3O4@SBA-15) for persulfate (PS) activation. The Fe3O4@SBA-15 with an Fe3O4 to SBA-15 weight ratio of 3:1 exhibited an impressive carbamazepine (CBZ) removal efficiency of ~100% after 30 min of SR-AOP at an initial pH of 3.0, a temperature of 25 °C, an initial PS concentration of 300 mg L−1 and a catalyst concentration of 0.50 g L−1. The primary oxidizing species produced in the system were identified as SO4− and HO by electron paramagnetic resonance spectra and radical quenching experiments. Benefiting from the synergetic effects of improved Fe3O4 dispersion and enhanced adsorption of CBZ and PS by SBA-15, the as-obtained heterogeneous Fe3O4@SBA-15 catalysts offer large numbers of active sites for free radical generation and high surface concentrations of CBZ and PS for SR-AOPs, as verified by physicochemical characterization and Langmuir−Hinshelwood model analysis. In addition, the activity of Fe3O4@SBA-15 was maintained throughout six successive cycling tests. Various inorganic anions, including Cl−, NO3−, HCO3−, and CO32−, as well as organic material in natural water, exert a negative impact on the Fe3O4@SBA-15 catalyzed SR-AOPs and deserve special attention.

The cooperation of photothermal conversion, photocatalysis and sulfate radical-based advanced oxidation process on few-layered graphite modified graphitic carbon nitride

Sulfate radical-based advanced oxidation process is a promising technology to degrade organic pollutants for water remediation. Photo-activation of peroxymonosulfate (PMS) has received increasing attention. From the aspect of solar energy, the utilization of near-infrared (NIR) light which accounts for about 50% of the solar energy in PMS activation is still challenging. Herein, we designed and synthesized few-layered graphite modified graphitic carbon nitride (GrCN) for whole-spectrum photo-activation of PMS. During the reaction, NIR light was converted to heat on few-layered graphite through photothermal effect to accelerate the chemical reactions via raising the system temperature. In addition to the photothermal effect, few-layered graphite also acted as cocatalyst to alter the band structure and promote the charge separation. Therefore, GrCN exhibited excellent activity in the degradation of bisphenol A with the addition of PMS under illumination. In addition, GrCN presented high reusability in the presence of sulfate radicals under illumination.

Degradation of aniline by ferrous ions activated persulfate: Impacts, mechanisms, and by-products

Wastewater contains a large number of anions and organics which can scavenge reactive radicals and limit the application of sulfate radical-based advanced oxidation processes (SR-AOPs) in practical engineering. Here, we studied the removal rate and mechanism of aniline by SR-AOPs in different influencing factors, such as sodium persulfate dosage, ferrous ions dosage, solution pH, Cl-, HCO3-, NO3-, and other organic matter. By recognizing and analyzing free radicals, we concluded that SO4•- plays a major role in aniline degradation. The aniline removal rate increased with the initial concentrations of persulfate and ferrous ions, but aniline degradation was inhibited by excessive dosage. The aniline removal rate by ferrous-ions-catalyzed persulfate was higher under acidic conditions and could be improved under alkaline conditions if no ferrous ions were added. The addition of bicarbonate ions inhibited aniline removal, and the addition of nitrate ions barely caused the effect. While the addition of chloride ions promoted aniline degradation, which was confirmed that HClO generated from the reacting of Cl- and persulfate played a key role. However, TOC indicated that aniline was not completely mineralized in the process. Further analysis of the products from GC-MS demonstrated that chloride-ion additions produced some harmful halogenated by-products. Our results can act as a basis for developing processes for the aniline degradation in wastewater.

Optimal preparation of catalytic Metal-organic framework derivatives and their efficient application in advanced oxidation processes

Metal-organic frameworks (MOFs) have been widely concerned for their excellent user-configuration flexibility to be capable of different tasks. A popular trend of their diversified development is pyrolyzing them to produce derived materials with improved stability, conductivity, and well-inherited characteristics. Thanks to these properties, prepared MOF derivatives are gradually testified as alternative catalysts in advanced oxidation processes (AOPs), involving Fenton reaction, sulfate radical-based AOPs (SR-AOPs) as well as photocatalysis for efficient pollutants degradation. Unfortunately, the introduction of the synthetic method of MOF derivatives is relatively rough yet and a comprehensive understanding of the differences in their application to different AOPs systems has not emerged. This review creatively details synthetic strategies of MOF derivatives by analyzing their special conditions and procedures. And starting with suitable MOF precursors, the review focuses on their changes in structure and component during derivation and associates them with performance improvements in AOPs. Besides, the related mechanisms are also discussed respectively by distinguishing the functional sites in different systems. • The review details pyrolysis synthesis methods of MOF derivatives. • Different classes of MOF precursors available to be applied in AOPs are summarized. • The change of physical-chemical properties is associated with the improvement of performance. • Catalytic mechanism of MOF derivatives in individual advanced oxidation systems. • Future outlook and challenges for MOF derivatives based AOPs.

Synthesis strategies and emerging mechanisms of metal-organic frameworks for sulfate radical-based advanced oxidation process: A review

• State-of-the-art MOFs-based materials in SR-AOPs for environmental remediation are overviewed. • The synthetic strategies of multifarious MOFs-based materials are summarized. • The effects of structure on the catalytic activities and the circumstance of radical and non-radical pathways are discussed. • DFT for the exploration of possible mechanisms in MOFs-based SR-AOPs are exhibited. • Prospects are highlighted for future research in the field of MOFs-based SR-AOPs. Recently, metal–organic frameworks (MOFs) based materials as the emerging catalysts for sulfate radical-based advanced oxidation processes (SR-AOPs) applications have progressively become a burgeoning research field. Herein, an in-depth overview of state-of-the-art MOFs-based materials currently available in SR-AOPs applications for environmental remediation is presented. The synthetic strategies of different types of MOFs-based materials are summarized. Most importantly, particular emphasis is placed on the applications of MOFs-based materials in SR-AOPs for wastewater treatment. Identification of reactive oxygen species (ROS) generated from the radical and non-radical pathways is addressed. Moreover, the theoretical calculations based on density functional theory (DFT) to predict and explore the possible reaction mechanisms in MOFs-based SR-AOPs are summarized and discussed. Special attention has been focused on the effects of structure on the catalytic activities and the circumstance of radical and non-radical reaction mechanisms in MOFs-based SR-AOPs. Finally, the unresolved challenges of the existent MOFs-based SR-AOPs are pointed out and the outlooks of future research directions are proposed.

A Review Study on Sulfate-Radical-Based Advanced Oxidation Processes for Domestic/Industrial Wastewater Treatment: Degradation, Efficiency, and Mechanism.

High levels of toxic organic pollutants commonly detected during domestic/industrial wastewater treatment have been attracting research attention globally because they seriously threaten human health. Sulfate-radical-based advanced oxidation processes (SR-AOPs) have been successfully used in wastewater treatment, such as that containing antibiotics, pesticides, and persistent organic pollutants, for refractory contaminant degradation. This review summarizes activation methods, including physical, chemical, and other coupling approaches, for efficient generation of sulfate radicals and evaluates their applications and economic feasibility. The degradation behavior as well as the efficiency of the generated sulfate radicals of typical domestic and industrial wastewater treatment is investigated. The categories and characteristics of the intermediates are also evaluated. The role of sulfate radicals, their kinetic characteristics, and possible mechanisms for organic elimination are assessed. In the last section, current difficulties and future perspectives of SR-AOPs for wastewater treatment are summarized.

A heterogeneous photocatalytic sulfate radical-based oxidation process for efficient degradation of 4-chlorophenol using TiO2 anchored on Fe oxides@carbon

A photocatalytic sulfate radical-based advanced oxidation process was studied to degrade 4-chlorophenol (4-CP) using persulfate (PS) catalyzing UV light and heterogeneous catalyst. In this regards, ferroferric oxide nanoparticles anchored on activated carbon (FOC) was applied as a supporter of TiO2 nanoparticles for fabricating of a recoverable photocatalyst (FOCT). Some analysis techniques including PL, UV–vis DRS, XRD, FESEM-EDS, BET, TEM and VSM were utilized to determine the optical, structural, textural and physicochemical characteristics of FOCT. The reaction mechanisms of PS activation and the generation of free radicals were described in details. Moreover, degradation intermediate products were identified and reaction pathway were proposed. It was found that photocatalytic activity and oxidation performance of pure TiO2 were improved after decoration on FOC. An excellent elimination efficiency was achieved in coupling of FOCT and UV irradiation with PS. Over 99 % of 4-CP (60 mg/L) and 49 % of TOC were removed by FOCT/UV/PS at optimum operational conditions. Furthermore, high PCP decontamination rate (> 86 %) was obtained, even at high concentrations (100 mg/L). During consecutive five runs of catalyst use, the degradation rate was decreased slightly to 88 % with a negligible decline in Fe and Ti leaching, demonstrating the excellent reusability and durability of FOCT in oxidation process. SO4– and HO radicals were detected as main reactive species that involved in the degradation of 4-CP over FOCT/UV/PS system. Thanks to good performance and easy recovery of catalyst, FOCT/UV/PS hybrid system has a great potential for environmental remediation perspectives.

Photocatalytic Advanced Oxidation Processes for Water Treatment: Recent Advances and Perspective.

Nowadays, an ever-increasing variety of organic contaminants in water has caused hazards to the ecological environment and human health. Many of them are persistent and non-biodegradable. Various techniques have been studied for sewage treatment, including biological, physical and chemical methods. Photocatalytic advanced oxidation processes (AOPs) have received increasing attention due to their fast reaction rates and strong oxidation capability, low cost compared with the non-photolytic AOPs. This review is dedicated to summarizing up-to-date research progress in photocatalytic AOPs, such as Fenton or Fenton-like reaction, ozonation and sulfate radical-based advanced oxidation processes. Mechanisms and activation processes are discussed. Then, the paper summarizes photocatalytic materials and modification strategies, including defect chemistry, morphology control, heterostructure design, noble metal deposition. The future perspectives and challenges are also discussed.

A study on advanced oxidation mechanism of MnCo2O4/g-C3N4 degradation of nitrobenzene: Sacrificial oxidation and radical oxidation

In this study, the MnCo2O4/g-C3N4 (CMCN2) is used to activate peroxymonosulfate (PMS), for treating nitrobenzene (NB) and industrial wastewater containing nitrobenzene homologue. Different from traditional sulfate radical-based advanced oxidation processes (SR-AOPs), high-valent metal-oxo species (MIV(O)/MV(O)) is a major reactive component via dimethyl sulfoxide (DMSO) as a verify compound. The mechanism is speculated that the bond of nitrogen–metal = oxygen (N–M = O) activates PMS to form MIV(O)/MV(O) during sacrificial oxidation. The quenching experiments and electron spin resonance (ESR) confirm that CMCN2 activated PMS to form OH and SO4–. The Langmuir-Hinshelwood model conforms to the NB degradation curve, and the best removal efficiency is 96.7% in 240 min. The CMCN2/PMS system has excellent stability between pH 3–10. Also, the CMCN2/PMS system exhibited satisfactory removal of NB in the presence of inorganic anions and natural organic matters. The treatment effect of industrial wastewater containing phenyl homologues shows that CMCN2/PMS has a high mineralization capacity. This study details the electron transfer during the formation of active components and provides new ideas for selecting active ingredients that degrade phenyl pollutants in the field of advanced oxidation.

Egg shell biochar-based green catalysts for the removal of organic pollutants by activating persulfate

The sulfate radical based advanced oxidation processes (SR-AOPs) has shown great potential in environmental remediation. In recent years, metal-free catalysts have attracted great attention due to their properties of low environmental risk and high catalytic activity. Among them, biochar-based catalysts are widely studied for their low cost by using substance existing in nature as raw material. In this work, egg shell derived biochar (ES-biochar), which was prepared by a simple one-pot pyrolysis method, has been proven to be an effective and innovative catalyst to activate persulfate for aqueous organic pollutant degradation. In addition, ES-biochar showed superior performance in the degradation reaction with removal efficiency of more than 90% in 120 min for 2,4-dichlorophenol (2,4-DCP), which was selected as a representative organic pollutant. Further quenching tests and electron spin resonance spectroscopy demonstrated that both free-radicals and non-radicals pathways were involved in this process, and OH dominated in free-radicals process. More importantly, this work not only proposed a novel biochar material as an efficient persulfate activator, but also provided a value-added reuse approach for egg shell in line with the concept of resource recycling and environmental sustainability.

NOx attenuation in flue gas by •OH/SO4•--based advanced oxidation processes.

The combustion of fossil fuels has resulted in rapidly increasing emissions of nitrogen oxide (NOx), which has caused serious human health and environmental problems. NO capture has become a research focus in gas purification because NO accounts for more than 90% of NOx and is difficult to remove. Advanced oxidation processes (AOPs), features the little secondary pollution and the broad-spectrum strong oxidation of hydroxyl radicals (•OH), are effective and promising strategies for NO removal from coal-fired flue gas. This review provides the state of the art of NO removal by AOPs, highlighting several methods for producing •OH and SO4•-. According to the main radicals responsible for NO removal, these processes are classified into two categories: hydroxyl radical-based AOPs (HR-AOPs) and sulfate radical-based AOPs (SR-AOPs). This paper also reviews the mechanisms of NO capture by reactive oxygen species (ROS) and SO4•- in various AOPs. A HiGee (high-gravity) enhanced AOP process for improving NO removal, characterized by intensified gas-liquid mass transfer and efficient micro-mixing, is then proposed and discussed in brief. We believe that this review will be useful for workers in this field. Graphical abstract.

Stable and efficient metal-biochar supported catalyst: degradation of model pollutants through sulfate radical-based advanced oxidation processes

This study focuses on the synthesis of metal-based biochar catalysts and their catalytic activation of peroxymonosulfate (PMS, HSO5−) for the degradation of three different wastewater model pollutants employing advanced oxidation processes (AOP). Iron, copper, and two different cobalt-based catalysts were prepared and evaluated. The catalysts were supported on a biochar obtained from the pyrolysis of woody pruning wastes. They were characterized by C, H, and N elemental analysis, X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The metal content in each catalyst was determined by means of atomic absorption spectroscopy (AAS). The degradation reactions of benzoic acid (BA), catechol (C), and cinnamic acid (CA) were carried out in a lab scale batch glass reactor and were followed by UV–Visible spectroscopy (UV–Vis). A colorimetric technique was employed to verify the presence of oxidant during the reaction progress. The catalyst/oxidant optimal ratio was determined for the cobalt catalysts. The mineralization degree of the pollutants after the degradations was verified by means of total organic carbon (TOC) content in the residual liquids. After 4 h of reaction, the maximum mineralization was reached when C was treated with a cobalt-based catalyst (> 80%), and its stability was evaluated through successive cycles of use.

Mn3O4/p(DCPD)HIPE nanocomposites as an efficient catalyst for oxidative degradation of phenol

The increase in the amount of wastewater containing organic pollutants in various industrial processes creates serious problems for the environment. Sulfate radical-based advanced oxidation process (AOP) is an effective route to remove pollutants from wastewater. However, designing a new nano-based catalyst to generate sulfate radicals is an important factor for the AOP. For this vision, porous trimanganese tetraoxide-polydicyclopentadiene (Mn3O4/pDCPD) nanocomposite, having an open-cell structure, was successfully designed via high internal phase emulsion (HIPE) and ring-opening metathesis polymerization (ROMP) approaches. The effect of Mn3O4 nanoparticle concentration on the structure was investigated, and the resulting Mn3O4/p(DCPD)HIPE nanocomposites were fully characterized by FT-IR, XRD, FE-SEM, TEM, solid-state 13C CPMAS NMR, DSC, and TGA analysis. The selected nanocomposite containing 5 wt% of Mn3O4 was used as a model catalyst to mediate the heterogeneous oxidation of phenol in the presence of oxone. It is concluded that Mn3O4/p(DCPD)HIPE nanocomposite is a highly active catalyst to generate sulfate radicals for phenol degradation. Complete removal of 25 mg/L phenol was achieved in 30 min under the conditions of [catalyst] = 0.8 g/L, [oxone] = 2 g/L, and T = 25 °C. The phenol degradation followed the pseudo-first-order kinetic model, and the highest kinetic constant of 0.0611 min−1 was achieved. No significant loss in the activity of the catalyst was determined after four consecutive cycles.

Carbon nanofibers supported Co/Ag bimetallic nanoparticles for heterogeneous activation of peroxymonosulfate and efficient oxidation of amoxicillin

The carbon nanofibers supported Co/Ag bimetallic nanoparticles (Co@CNFs-Ag) were synthesized for heterogeneous activation of peroxymonosulfate and efficient oxidation of amoxicillin in this work. Co nanoparticles with a diameter of 20–30 nm were encapsulated in the carbon nanofibers to reduce the loss of Co during the preparation and catalysis processes. Ag nanoparticles (5–10 nm) were distributed on the surface of CNFs. Complete removal of amoxicillin could be achieved within 30 min by Co@CNFs-Ag activated peroxymonosulfate system. The high catalytic performance could be attributed to the large aspect ratio (> 10,000) of the carbon nanofibers and the mutual reaction of the Co/Ag bimetallic nanoparticles with peroxymonosulfate. The optimal mass ratio of oxidant and catalyst was 10 and the optimized pH was 7. Co@CNFs-Ag exhibited stable catalytic activity and minimal metal leakage over a period of 5 cycles. The activation energy of the system was 29.51 kJ/mol derived by the Arrhenius equation. Both hydroxyl and sulfate radicals contributed to amoxicillin degradation and the latter were key to the degradation. Finally, the reaction mechanism of bimetallic synergistic catalytic system and possible amoxicillin degradation pathways were elucidated. The results of this study provide novel insights for application of sulfate radical-based advanced oxidation processes in environmental remediation.