Mechanism Of Peroxymonosulfate Activation Research Articles

Visible-light-assisted peroxymonosulfate activation by metal-free g-C3N4 isotype heterojunction for water purification: Surface-activated complex and 1O2 dominated non-radical mechanisms

Visible-light-assisted peroxymonosulfate (PMS) activation is flourishing in wastewater decontamination, but exploiting safe and efficient activators remains challenging due to a deficient cognition of the activated mechanisms. Hereby, a metal-free g-C3N4 isotype heterojunction (HCN) was successfully synthesized and activated PMS under visible light. The Z-scheme isotype heterojunction significantly meliorated light absorption and carrier migration, thereby enhancing PMS activation. The optimal HCN + PMS system almost completely removed ranitidine (RAN) in 30 min with 7.46–8.48 times higher activity than the monomers. Through systematic experiments and characterizations, we proposed a non-radical mechanism of PMS activation, which generated predominated surface-activated complex and singlet oxygen (1O2) for pollutant removal. The surface-activated complex degraded RAN by drawing its electrons. This non-radical pathway exhibited tolerance towards background substances and pH fluctuations. Additionally, the broad-spectrum decontamination and recyclability of the system further enhanced its practical applicability. Notably, intermediate analyses confirmed the RAN degradation pathways predicted by theoretical calculations, with the resulting intermediates found to be non-toxic. This study significantly contributes to our understanding of the non-radical mechanisms of PMS activation on g-C3N4-based activators for micropollutant degradation.

Non-radical activation of peroxymonosulfate by modified activated carbon for efficient degradation of oxytetracycline: Mechanisms and applications

The application of heterogeneous metal-free catalysis for non-radical peroxymonosulfate (PMS) oxidation is of great significance because of its low environmental effects and mild oxidant dosage. The purpose of this study was to investigate the activation mechanism of PMS using acid-modified activated carbon and oxytetracycline (OTC) as a representative pollutant. Modified activated carbon (MAC)/PMS system was capable of achieving 100 % degradation efficiency of OTC within 60 min, with an observed rate constant (kobs) of 0.0414 min−1. The degradation of OTC is dominated by non-radical oxidation pathways involved in mediated singlet oxygen (1O2) and electron-transfer process through electron paramagnetic resonance (EPR) and radicals quenching studies. The activation of PMS is attributed to the structural defects of MAC, persistent free radicals, and oxygen functional groups such as C-OOH. Moreover, the MAC/PMS system consistently demonstrates high and reliable contaminant removal in various water matrices. A continuous-flow device utilizing MAC shows excellent performance in purifying micro-polluted water. Additionally, the degradation pathways of pollutants and changes in toxicity during the degradation process were identified through density functional theory (DFT) calculations, liquid chromatography-mass spectrometry (LC-MS), and toxicological analysis. Finally, the cultivation of green beans, peas, and wheat was found to significantly decrease the toxicity of contaminated water through degradation. This study proposes a low-cost method to enhance the activation pathway of non-radical PMS by utilizing modified activated carbon materials for pollutant remediation.

Salt assistant bimetallic sludge-derived porous carbon for efficient peroxymonosulfate activation

The development of cost-effective, environmentally benign, and high-performance peroxymonosulfate (PMS) activation towards wastewater treatment is still considered a challenge. In this work, the sludge-derived porous carbon loaded with bimetal oxides (DSC-FeMn) was fabricated by molten salt assistant strategy using the combination of zinc chloride, metal ions and Fe containing sludge. The obtained DSC-FeMn exhibited high catalytic activity for nearly 100 % 4-chlorophenol (4-CP) removal within 30 min with the k of 0.304 min−1, which was 1.07 and 11.94 times that of the single Fe and Mn-sludge-derived carbon (DSC-Fe, DSC-Mn), respectively. Quenching experiments, electron paramagnetic resonance tests (EPR), X-ray photoelectron spectroscopy (XPS), H2-temperature programmed reduction (H2-TPR) and electrochemical experiments proved that the radical pathway, dominated by OH and SO4−, led to the excellent degradation performance of DSC-FeMn, which was attributed to the redox cycling between Fe and Mn. This study provides a new idea for sludge resource utilization, and it deepens the understanding of the mechanism of PMS activation by the synergistic interaction between bimetal.

Anchored Cobalt Nanoparticles on Layered Perovskites for Rapid Peroxymonosulfate Activation in Antibiotic Degradation.

In the Fenton-like reaction, revealing the dynamic evolution of the active sites is crucial to achieve the activity improvement and stability of the catalyst. This study reports a perovskite oxide in which atomic (Co0) in situ embedded exsolution occurs during the high-temperature phase transition. This unique anchoring strategy significantly improves the Co3+/Co2+ cycling efficiency at the interface and inhibits metal leaching during peroxymonosulfate (PMS) activation. The Co@L-PBMC catalyst exhibits superior PMS activation ability and could achieve 99% degradation of tetracycline within 5min. The combination of experimental characterization and density functional theory (DFT) calculations elucidates that the electron-deficient oxygen vacancy accepts an electron from the Co 3d-orbital, resulting in a significant electron delocalization of the Co site, thereby facilitating the adsorption of the *HSO5/*OH intermediate onto the "metal-VO bridge" structure. This work provides insights into the PMS activation mechanism at the atomic level, which will guide the rational design of next-generation catalysts for environmental remediation.

Sulfur and chloride co-doped g-C3N4 in photocatalytic peroxymonosulfate activation for enhanced acetaminophen removal: Combination of experiments and DFT calculations

As a green photocatalyst with simple synthesis method, excellent electronic structure, and metal-free properties, the deficiencies of pristine graphitic carbon nitride, such as high electron transfer resistance and narrow energy band gap, inhibit its photocatalytic activity to some extent. In this paper, we synthesized a sulfur and chlorine co-doped g-C3N4 (SCl-CN) capable of efficient photocatalytic activation of peroxymonosulfate (PMS) by calcining a mixture of ammonium chloride and thiourea. By means of DFT calculation, the contribution of sulfur and chlorine to photogenic electron hole separation was discussed. The electrostatic potential of SCl-CN and the adsorption model between SCl-CN and PMS were deduced, and the activation mechanism of PMS was further analyzed. According to the calculated results, the incorporation of sulfur and chlorine tuned the electronic configuration of the material and intensified the interactions between SCl-CN and PMS. It is shown that free and non-free radicals act simultaneously in the SCl-CN/PMS/Vis system. This study provides a new idea for the study of photocatalytic activation of PMS by non-metallic co-doped carbon nitride.

LaCoO3/SBA-15 as a high surface area catalyst to activate peroxymonosulfate for degrading atrazine in water

An efficient perovskite-based heterogeneous catalyst is highly desired to activate peroxymonosulfate (PMS) for removing organic pollutants in water. A high surface area PMS-activator was fabricated by loading LaCoO3 on SBA-15 to degrade atrazine (ATR) in water. The LaCoO3/SBA-15 depicted better textural properties and higher catalytic activity than LaCoO3. In 6.0 min, atrazine (ATZ) degradation in the selected LaCoO3/SBA-15/PMS system, LaCoO3, adsorption by LaCoO3/SBA-15, sole PMS processes reached approximately 100%, 55.15%, 12.80%, and 16.65 % respectively. Furthermore, 0.04 mg L−1 Co was leached from LaCoO3/SBA-15 during PMS activation by LaCoO3/SBA-15. The LaCoO3/SBA-15 showed stable catalytic activity after reuse. The use of radical scavengers and electron paramagnetic resonance spectroscopy (EPR) demonstrated that ROS such as 1O2, O2•−, •OH, and SO4•− were generated by PMS activated by LaCoO3/SBA-15 owing to redox reactions [Co2+/Co3+, and O2−/O2]. EPR, XPS, ATR-FTIR, EIS, LSV, and chronoamperometric measurements were used to explain the catalytic mechanism for PMS activation. Excellent atrazine degradation was due to high surface area, porous nature, diffusion-friendly structure, and ROS. Our investigation proposes that perovskites with different A and B metals and modified perovskites can be loaded on high surface area materials to activate PMS into ROS.

Fe doping strategy induces peroxymonosulfate activation by ZIF-67 through a non-radical reaction pathway with dominant 1O2 generation

Zeolitic Imidazole Framework-67 (ZIF-67), which can be large-scale synthesized under mild conditions, has been widely reported as a promising and efficient catalyst in peroxymonosulfate (PMS)-based advanced oxidation process. However, ZIF-67 typically activates PMS through a monotonous free radical reaction pathway, which limits its reusability, resistance to environmental interference, and degradation selectivity. In this study, controlled doping of Fe atoms into the lattice structure of ZIF-67 (FexCo1-x-ZIF) was employed, resulting in the nearly complete conversion of PMS to 1O2 through a unique non-radical pathway. Series of experiments, characterizations, and theoretical calculations were employed to elucidate the micro-level mechanism of PMS activation. The results indicate that the tetrahedral coordinated Co-N4 sites in ZIF-67 are transformed into unsaturated Co-N2 sites due to the competitive coordination effect upon the introduction of Fe. PMS adsorption is enhanced as both oxygen atoms bind simultaneously to the Co-N2 site, inducing the removal of a hydrogen atom from PMS and electron transfer from PMS to the Co-N2 site, thus facilitating the generation of 1O2. The 1O2-dominated non-radical degradation reaction enhances the excellent degradation performance, reusability, and environmental tolerance of the FexCo1-x-ZIF/PMS system under diverse natural water conditions, presenting significant prospects for practical applications.

Magnetic CuFe2O4 nanoparticles immobilized on mesoporous alumina as highly efficient peroxymonosulfate activator for enhanced degradation of tetracycline hydrochloride

Nanoscaled magnetic copper ferrite (CuFe2O4) is widely used as a peroxymonosulfate (PMS) activator but suffers from agglomeration owing to its inherent magnetic properties and high surface energy. In this work, spinel structured CuFe2O4 anchored on mesoporous alumina (denoted as CFO@AO) were synthesized, characterized, and applied as a PMS activator for the removal of tetracycline hydrochloride (TC·HCl). Approximately 97.5 % of TC·HCl was decomposed within 10 min in 30 %–CFO@AO (0.2 g/L)/PMS (0.3 g/L) system, and the corresponding kinetic rate constant of 30 %–CFO@AO/PMS (0.417 min−1) was around 1.57 times higher than that of CuFe2O4/PMS (0.266 min−1), which indicating that the existence of synergistic catalysis between CuFe2O4 and Al2O3 enhanced the degradation of TC·HCl. Moreover, nano-sized CuFe2O4 were successfully anchored on the surface of Al2O3 because of FeOAl bond, which could account for the enhanced catalytic activity, superior pH flexibility, and high chemical stability and reusability of 30 %–CFO@AO. Quenching experimentals, electron paramagnetic resonance, and methyl phenyl sulfoxide (PMSO) chemical probe assays confirmed that both radical oxidation (OH) and non-radical oxidation (1O2 and Fe(IV)O) were proposed in the developed CFO@AO/PMS system, and OH played a key role in the process. Meanwhile, the PMS activation mechanism by CFO@AO composite was also analyzed based on the results of adsorption energy, which was calculated via DFT. Based on UPLC–MS technique, a possible degradation pathway for TC·HCl destruction in 30 %–CFO@AO/PMS system was proposed. The toxicity assessment showed that the catalytic degradation of TC·HCl in 30 %–CFO@AO/PMS system reduced the toxicity of most of degradation intermediates. Present work proved that CuFe2O4@Al2O3 composite is an efficient, environment-friendly, and recyclable heterogeneous catalyst for practical wastewater treatment via PMS activation.

Heat enhanced bisphenol AF degradation in CoFe2O4@BC activated peroxymonosulfate process: Mechanism and the role of inorganic anions

Carbon-based materials and heat activated peroxymonosulfate (PMS) have emerged as promising technologies for the remediation of contaminated water. This study investigated the feasibility of Bisphenol AF (BPAF) degradation by coupling CoFe2O4@BC catalyst with heat activated PMS technology. Heat significantly enhanced the catalytic performance of CoFe2O4@BC for PMS activation, resulting in 87.0 % removal of BPAF. Meanwhile, the effects of PMS concentration, CoFe2O4@BC catalyst dosage, initial pH, and the inorganic anions on BPAF degradation were investigated. The presence of HCO3− and HPO42− were found to enhance BPAF degradation by promoting PMS decomposition, while humic acid (HA) significantly inhibited BPAF removal. Electron paramagnetic resonance (EPR) and quenching experiments suggested that sulfate radicals (SO4•−) were the dominant reactive oxygen species (ROS) in the system, with hydroxyl radicals (•OH) and singlet oxygen (1O2) also contributing to BPAF degradation. Based on the Density Functional Theory (DFT) and intermediates analysis, two degradation pathways of BPAF were proposed, including hydroxylation and β-scission reactions. This work reveals the underlying mechanism of PMS activation under the coupling of heat with the CoFe2O4@BC system and presents a potential method for contaminants decomposition.

One-step synthesis of CoxS/Ni3S2@NF on 3D nickel foam with different sulfur sources as a novel heterogeneous catalyst efficient activation of peroxymonosulfate in lomefloxacin degradation

In this study, we have successfully synthesized Co9S8/CoS/Ni3S2 and Co3S4/Ni3S2 materials in situ on three-dimensional (3D) nickel foam (NF) substrates using a one-step hydrothermal process with different sulfur sources. Under the experimental conditions of catalyst dosage of 0.50 cm × 0.50 cm and peroxymonosulfate (PMS) dosage of 0.30 g/L, the Co3S4/Ni3S2@NF catalyst exhibited superior catalytic performance in activating PMS and degrading 91.0 % of lomefloxacin (LOM) as compared to 76 % of Co9S8/CoS/Ni3S2@NF. Both Co9S8/CoS/Ni3S2@NF and Co3S4/Ni3S2@NF showed excellent stability and performed effectively over a wide pH range. The Co9S8/CoS/Ni3S2@NF and Co3S4/Ni3S2@NF demonstrated significant differences in morphology, crystal plane properties, surface functional groups, chemical composition, elemental valence states, and coordination environment as revealed by XRD, TEM, SEM, FTIR, and XPS analyses, contributing to their distinct mechanisms and performance in LOM degradation. Additionally, the NF acted as a support carrier, exposing multiple active sites to enhance electron transport and providing a nickel source for the catalytic reaction. The degradation of LOM in the CoxS/Ni3S2@NF&PMS system was thoroughly investigated, revealing the involvement of SO4−, OH, 1O2, and electron transfer in the process. Additionally, the mechanism of PMS activation and the pathway of LOM decomposition in the reaction system were elucidated by theoretical analysis. Furthermore, the ecotoxicity of the by-products generated during LOM degradation was assessed using the ECOSAR software. In summary, the CoxS/Ni3S2@NF catalysts proved to be efficient, stable, easily prepared, environmentally friendly, and recyclable heterogeneous nanocomposites. It is a promising candidate for heterogeneous PMS process.

Facet-dependent peroxymonosulfate activity and mechanism of CuO for degradation of organic pollutants

CuO is currently used as an effective activator for peroxymonosulfate (PMS), which exhibits complex radical, nonradical, or both activation pathways. However, there exists a knowledge gap concerning the relationship between CuO exposed facets and the PMS activation pathway, which should require further investigation. This study employed a simple and facile hydrothermal method to controllably prepare CuO samples with exposed {010} and {001} facets (referred to as CuO-010 and CuO-001, respectively). The main aim was to further study the facet-dependent PMS activation mechanism. The experimental results showed that the CuO-001 exhibited significantly higher activation efficiency than the CuO-010 due to the different surface atomic arrangement. Furthermore, scavenging experiments and EPR analyses revealed that CuO-010 exhibited both radical (SO4•− and •OH) and non-radical (1O2) pathways, synergistically degraded tetracycline (TC) and 4-nitrophenol (4-NP). Conversely, the CuO-001 displayed non-radical (1O2) and Cu(Ⅲ) intermediates, collaborating to oxidize the degradation of TC and 4-NP. More importantly, the generated 1O2 species and Cu(Ⅲ) intermediates exhibited a preference for reacting with amino or phenolic compounds containing electron-rich functional groups. Moreover, the CuO-001 also showed excellent resistance to anion interference, stability, and compatibility of a wide pH range. The outcomes of this study provide new insights into the comprehensiveness facet-dependent activation of PMS and the design of efficient metal oxide catalysts using the facet strategy for effective degradation of amino/phenolic pollutants in wastewater.

Electronic interaction between biochar and montmorillonite toward enhanced peroxymonosulfate activation

Biochar works as the catalyst for activating peroxymonosulfate (PMS) to produce highly oxidizing radicals to remove organic contaminants from wastewater, but its activity requires further improvement. Recent research demonstrates that the PMS activation performance of biochar is closely related to the oxygen-containing functional groups (OFGs). Therefore, biochar/montmorillonite (BC/Mt) composites are designed for activating PMS toward degrading tetracycline. The negative charge of Mt. induced the electron transfer form Mt. to BC, which increases the nucleophilicity of CO groups that promote the activation of PMS to •OH and SO4•− radicals. Meanwhile, the pyrolysis path of rice straw is tuned by Mt., and the amount of COO groups is increased from 8.99% to 9.79% that promotes the generation of 1O2. Moreover, electron paramagnetic resonance and quenching experiments reveal that the activation mechanism of PMS by the BC/Mt. is comprised of both the radical and the non-radical pathway. Consequently, the tetracycline degradation kinetics using the optimized BC/Mt. (0.117 min−1) is higher than either bare BC (0.0866 min−1) or bare Mt. (0.0258 min−1), highlighting the significance of the rational design of electrocatalysts toward the enhanced catalytic chemistry. This work provides a facile route to improve the catalytic performance of biochar by hybridizing with clay minerals and is of great significance to promote the practical application of PMS-based advanced oxidation processes.

Unravelling the activation mechanism of oxidants using copper ferrite nanopowder and its application in the treatment of real waters contaminated by phenolic compounds

Copper ferrites (CuFe2O4) nanopowder was prepared via hydrothermal method followed by annealing at 500 °C, and XRD, SEM, XPS and UPS were employed for its characterization. CuFe2O4 was tested for the catalytic degradation of bisphenol A (BPA) in the dark and under UVA light, both in the presence of peroxymonosulfate (PMS) or peroxydisulfate (PDS) as radical precursor under natural pH of 6.2. While the individual photo-induced processes i.e., photocatalysis (using CuFe2O4 alone) and photolysis of either PMS or PDS, exhibited limited efficiencies in BPA degradation, a significant increase of performance was observed by combining CuFe2O4 and UVA light with either PMS or PDS with a synergy effect of 3.8 and 34.1, respectively. Under the optimal conditions, employing 0.5 g/L of nanopowder, the degradation constant of 25 µM BPA was 0.211 min−1 with 2 mM of PMS and 0.018 min−1 with 2 mM of PDS, and resulted in the complete degradation of BPA within less than 20 min. The activation mechanism of PMS and PDS using CuFe2O4 was elucidated, revealing sulfate radicals as the primary reactive species in PMS-containing systems, whereas a predominantly non-radical pathway was observed in the presence of PDS. Indeed, advanced spectroscopic techniques indicated that surface copper played an important role in the non-radical pathway. Furthermore, the CuFe2O4/PMS/UVA system exhibited high performance in the degradation of different phenolic compounds including BPA, phenol and p-nitrophenol in real water matrices. These achievements were observed across different real water matrices with a particular emphasis on sewage treatment plant water.

Application of 3D hierarchical porous NiCo-spinel nanosheet array for enhancement of synergistic activation of peroxymonosulfate: Degradation, Intermediates, mechanism and degradation pathway of tetracycline

The rational design of the morphology and structure of bimetallic-based heterogeneous Fenton-like catalyst derived from metal-organic-frameworks (MOFs) for peroxymonosulfate (PMS) activation via a non-radical pathway is attractive but challenging. Herein, a spinel-type 3D hierarchical porous NiCo2O4 nanosheet array for the activation of PMS is rationally designed by surfactant-assisted interfacial engineering. The experimental results showed that the NiCo2O4/PMS system demonstrated remarkable oxidative degradation of tetracycline (TC) through 1O2 attack and electron transfer process. In literature, it was thought that the PMS activation process in above system is dominated by radical pathway. In this work, we employ surfactant modified-nanostructure engineering to design hierarchical mesoporous nanosheet array structures and combined them with intrinsic bimetallic synergy to enhance catalytic activity, and interestingly the strategy transformed the PMS activation pathway into a nonradical (1O2 and electron transfer)-dominated process. This is benefit from the favorable morphological and electronic structure of the designed catalysts to facilitate mass transfer and electron transfer processes. The system also possessed a broad spectrum for degrading other typical contaminants, and was effective in tolerating actual water matrix and pH changes, as well as resisting interference from anions and organic matter. Furthermore, the robust stability of the structure and catalytic activity make it promising for practical water treatment. It can be expected that this proposal will provide insights for the delicate structural design and the understanding of its PMS activation mechanism of bimetallic-based Fenton-like catalysts, as well as for the efficient degradation of emerging organic pollutants.

Novel MIL-68(Fe)/MoS2 composites promote peroxymonosulfate activation for efficiently removing Rhodamine B

The development of efficient catalysts to activate peroxymonosulfate (PMS) for pollutant degradation has captured tremendous attentions. Herein, a series of high-performance MIL-68(Fe)/MoS2 (68M) composite catalysts with Fe-Mo bimetallic active sites were synthesized. Several characterization results confirmed the successful preparation of these composite materials. The PMS activation by MIL-68(Fe)/MoS2 was systematically evaluated by degrading Rhodamine B (RhB). It was shown that the RhB removal rate could reach up to 99% within 15 min with catalyst and PMS dosage of 0.2 g/L and 0.4 mM, respectively. It could be attributed to the synergistic effects of Fe-site, Mo-site and S-vacancy. The RhB removal rate could achieve 91%− 99% under a broad PH range (2−10) in 68M-10/PMS system. The RhB removal efficiency still maintained higher-level (92.2%) after being used for five cycles, suggesting the outstanding reusability of 68M-10. The PMS activation mechanism was explored by XPS, EPR and the RhB degradation pathway was also proposed based on HR-MS results. Above results highlighted the bright application prospect of the synthesized catalysts in solving the increasing dye crisis.

Sliver-doped α-MnO2 to enhance peroxymonosulfate activation for efficient degradation of sulfamethoxazole: Cooperation between radical and non-radical mechanisms

The application of metal doping has emerged as a prominent approach for modifying transition-metal-based heterogeneous catalysts in activating peroxymonosulfate (PMS). Herein, silver-doped α-MnO2 (Ag-α-MnO2) was synthesized via a one-step hydrothermal approach and utilized for activating PMS to degrade sulfamethoxazole (SMX). The catalyst was systematically characterized and examined to determine that the efficientdispersionof Ag increased thespecific surface area and pore volume of α-MnO2. The degradation experiments demonstrated that SMX could be efficiently degraded by a combination of PMS and Ag-α-MnO2 within 60 min. The apparent kinetic rate constant was 0.039 min−1, which was approximately ten times higher than that of α-MnO2. The impacts of external water conditions on catalytic performance and the stability of Ag-α-MnO2 were subsequently investigated. Density functional theory calculations revealed that Ag as a crucial active center reduced the PMS adsorption energy, promoted electron transfer, and orchestrated electron distribution. EPR spectra, quenching experiments, electrochemical tests, and XPS analysis were performed to validate the radical and non-radical mechanisms, including SO4−, OH, O2− and 1O2. The two redox cycles of Ag+/Ag0 and Mn4+/Mn3+ on the surface of Ag-α-MnO2 contributed to the activation of PMS. Additionally, probable degradation pathways for SMX were presented. This study provides an initially valuable insight into the cooperative mechanism of PMS activation for SMX degradation employing Mn-based catalysts doped with precious metal silver.

Design of active dual atom Ni-Co-2H-MoS2 catalyst: Synergistic effect of Ni-adsorption and co-catalysis for activating peroxymonosulfate

Peroxymonosulfate (PMS)-based advanced oxidation processes synergistically activated by dual atom catalysts (DACs) have become a cutting-edge technology for environmental remediation. Herein, a Ni-Co-2H-MoS2 (NCMS) DAC was successfully prepared by introducing bimetals (Ni and Co) into the framework of the 2H-MoS2 co-catalyst through a host–guest strategy. The NCMS/PMS catalysis system exhibits significant decontamination performance for tetracycline, and its removal efficiency of 99.6% is 3.7 times and 4.0 times higher than that of the Ni-2H-MoS2/PMS and Co-2H-MoS2/PMS single atom catalysts, respectively. Besides, density functional theory (DFT) was employed to disclosure the role of the active sites of NCMS DAC, investigate the influence of heteronuclear diatomic doping on electron aggregation and delocalization, and analyze the mechanism of PMS activation and TC degradation. Experimental results and theoretical simulations demonstrate that Ni and Co atoms of NCMS exert a reasonable regulation effect on the coordination environment and electronic structure, thereby promoting PMS activation with a unique synergy mode. The introduction of Ni lowers the adsorption energy barrier of PMS on the DAC, facilitating subsequent PMS activation. Meanwhile, the interaction between Co and Mo accelerates valence restoration and evolution of Co2+/Co3+ and Mo4+/ Mo5+/ Mo6+, further improving catalytic activity. This work provides a novel strategy for the on-demand design of Fenton-like reactions by regulating microenvironment of the catalyst.

The activation mechanism of peroxymonosulfate and peroxydisulfate by modified hydrochar: Based on the multiple active sites formed by N and Fe

Modified hydrochar (NHC@Fe), with multiple functional groups and transition metal oxide-containing surface, was successfully synthesized by one-step hydrothermal method. The differences in its catalytic activity for peroxymonosulfate (PMS) and peroxydisulfate (PDS) activation were studied in detail. Experimental and DFT studies showed that abundant active sites, namely, transition metals and functional groups on NHC@Fe provided multiple effective pathways for the activation of persulfate (PS). The NHC@Fe/PMS and NHC@Fe/PDS systems could degrade about 80% of tetracycline hydrochloride (TC) in 120 min and were found to be better than those modified by iron or nitrogen alone. This emphasized the advantage of N–Fe co-modification in persulfate activation. Although the Fe2+/Fe3+ cycle accelerated the activation, the activation of PMS mainly relied on Fe3+, whereas that of PDS mainly relied on Fe2+. Moreover, Fe–N, pyrrolic N, pyridine N, C–O, and O–CO groups also played a key role in the activation process, but the dominant action sites were not the same. Multiple free radicals, such as SO4•—, •OH, O2•—, and 1O2 were generated in PMS and PDS activation systems. 1O2 induced non-free radical pathway was mainly involved in the degradation of TC in both activation systems, but the generation pathway of 1O2 was more direct and rapid in the PDS system. This study provides detailed DFT models of the active sites activated by PMS and PDS and discusses the activation pathways of PMS and PDS along with the similarities and differences in ROS reaction mechanisms.

The utilization of microwaves in revitalizing peroxymonosulfate for tetracycline decomposition: optimization via response surface methodology

Abstract Antibiotic contamination in water has received significant attention in recent years for the reason that the residuals of antibiotics can promote the progression of antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs). It is difficult to treat antibiotics using conventional biological treatment methods. In order to investigate an efficient new method of treating antibiotics in water, in this study, microwave (MW) was employed in revitalizing peroxymonosulfate (PMS) to treat typical antibiotic tetracycline (TC). The Box–Behnken design (BBD) was applied to organize the experimental schemes. The response surface methodology (RSM) optimization was run to derive the best experimental conditions and validated using actual data. Moreover, the main mechanisms of PMS activation via MW were resolved. The results demonstrated that the relationship between TC removal rate and influencing factors was consistent with a quadratic model, where the P-value was less than 0.05, and the model was considered significant. The optimal condition resulting from the model optimization were power = 800 W, [PMS] = 0.4 mM, and pH = 6.0. Under such conditions, the actual removal of TC was 99.3%, very close to the predicted value of 99%. The quenching experiment confirmed that SO4•− and •OH were jointly responsible for TC removal.

Shape stability control of a 3D-printed clay/biochar-based monolith to support Fe catalyst for continuous levofloxacin degradation with low metal leaching

Disposing of wet solid waste sludge has become a prominent issue because it has high environmental risks. Herein, a clay/biochar-based monolith (CBM) is prepared using a three-dimensional (3D) printing design method. The CBM is loaded with iron (Fe) and used as a catalyst (Fe/CBM) to activate peroxymonosulfate (PMS) for degrading levofloxacin (LVF) in an aqueous solution. The monolith preparation process is inexpensive, and the monolith has designable flow paths that facilitate improved mass transport and material recycling. ZnCl2, as a chemical activator, is added to the 3D-printed slurry to improve the catalytic performance of Fe/CBM. Oscillatory stress sweep and frequency sweep tests prove that incorporating ZnCl2-containing sludge in the slurry effectively increases the elastic modulus and critical stress, improving structural stability and constructability. The slurry containing 10% sludge (S10%-Zn with 1 M ZnCl2), exhibits 30% higher static yield stress than the slurry containing only clay and water (S0%). Fe/CBM is prepared by loading Fe active sites onto the surface of CBM via an impregnation method, and it leaches very low amounts of Fe (<0.2 mg/L) and other heavy metals (e.g., Cd, and Pd, etc). Fe/CBM-S10%-Zn/PMS with 10% mass fraction of sludge exhibits much higher (∼80% at 20 min) degradation efficiency than Fe/CBM-S0%/PMS (∼15% at 20 min) and Fe/CBM-S10%/PMS (∼43% at 20 min). Combining with XPS results, when ZnCl2 is added to the slurry, the content of Fe2+ in the catalytic material increases, improving the catalytic performance. The PMS activation mechanism of Fe/CBM-S10%-Zn for LVF degradation is also discussed, which is ascribed to the radical and nonradical pathways. This provides new insights on how to recycle solid waste and make high-performance clay/biochar-based monolith catalysts for the continuous wastewater treatment.