MoS2/CoMoO4 composite heterogeneous catalyst towards enhanced activation of peroxymonosulfate for the efficient degradation of tetracycline hydrochloride

In this research, a composite catalyst of MoS2-modified CoMoO4 (MoS2/CoMoO4) was effectively synthesized and utilized to activate peroxymonosulfate (PMS) for the removal of tetracycline hydrochloride (TCH) in water. It was found that the MoS2/CoMoO4/PMS system possessed a greater ability to eliminate TCH compared with CoMoO4/PMS system. The experimental results demonstrated that the 0.6-MoS2/CoMoO4/PMS system eliminated 92.1% TCH (15 mg/L) and removed 50.3% TOC within 30 min under the conditions of 40 mg/L 0.6-MoS2/CoMoO4 and 0.5 mM PMS. The main active substances produced by MoS2/CoMoO4 activated PMS were sulfate radicals (SO4•-), hydroxyl radicals (•OH), singlet oxygen (1O2), and superoxide radicals (O2•-), as determined by scavenging experiments and EPR analyses. Probable catalytic mechanism of 0.6-MoS2/CoMoO4 for activating PMS was proposed from two aspects: one is the synergy of Co3+/Co2+ and Mo6+/Mo4+ cycles in 0.6-MoS2/CoMoO4/PMS system; on the other hand, the low valence molybdenum and sulfur promoted the Co3+/Co2+ redox recycle during PMS activation. After four reuses, the removal performance of TCH still reached 85.1%, and the crystal structure and the element compositions of the catalyst did not alter, implying that 0.6-MoS2/CoMoO4 composite had good reusability. Thus,0.6-MoS2/CoMoO4 composite has broad application prospects in removing organic contaminants.

Urban wastewater disinfection by FeCl3-activated biochar/peroxymonosulfate system: Escherichia coli inactivation and microplastics interference

Biochar coupled with peroxymonosulfate (PMS) to produce sulfate radicals and its application to urban wastewater disinfection has been rarely investigated and no information is available about microplastics (MPs) interference on the disinfection process. In this study, FeCl3-activated biochar (Fe-BC) was coupled to PMS to evaluate the inactivation of Escherichia coli (E. coli) in real secondary treated urban wastewater. Surface morphology of Fe-BC sample, characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), showed a rough texture with uniform distribution of iron particles over the entire surface area. E. coli inactivation improved (∼3.8 log units, detection limit = 1 CFU/100 mL) as Fe-BC concentration was decreased (from 1.0 g/L to 0.5 g/L), at a constant PMS dose (300 mg/L). Besides, removal efficiency of E. coli was negatively affected by the presence of small (30-50 μm) polyethylene MPs (PE MPs) (200 mg/L), which could be attributed to the adsorption of MPs on Fe-BC surface, according to SEM images of post-treated Fe-BC. The low disinfection efficiency of Fe-BC/PMS system in presence MPs could be due to blocking of Fe-BC sites for PMS activation and/or radicals scavenging during treatment. These results allowed to unveil the mechanisms of MPs interference on E. coli inactivation by Fe-BC/PMS, as well as the potential of this process to make the effluent in compliance with the stringent limit for agricultural reuse.

FeCo@hydrochar nanocomposites as efficient peroxymonosulfate activator for organic pollutant degradation

Sulfate radical-based advanced oxidation processes (SR-AOPs) are renowned for their exceptional capacity to degrade refractory organic pollutants due to their wide applicability, cost-effectiveness, and swift mineralization and oxidation rates. The primary sources of radicals in AOPs are persulfate (PS) and peroxymonosulfate (PMS) ions, sparking significant interest in their mechanistic and catalytic aspects. To develop a novel nanocatalyst for SR-AOPs, particularly for PMS activation, we synthesized carbon-coated FeCo nanoparticles (NPs) using solvothermal methods based on the polyol approach. Various synthesis conditions were investigated, and the NPs were thoroughly characterized regarding their structure, morphology, magnetic properties, and catalytic efficiency. The FeCo phase was primarily obtained at [OH-] / [Metal] = 26 and [Fe] / [Co] = 2 ratios. Moreover, as the [Fe]/[Co] ratio increased, the degree of xylose carbonization to form a carbon coating (hydrochar) on the NPs also increased. The NPs exhibited a spherical morphology with agglomerates of varying sizes. Vibrating-sample magnetometer analysis (VSM) indicated that a higher proportion of iron resulted in NPs with higher saturation magnetization (up to 167.8 emu g-1), attributed to a larger proportion of FeCo bcc phase in the nanocomposite. The best catalytic conditions for degrading 100 ppm Rhodamine B (RhB) included 0.05 g L-1 of NPs, 2 mM PMS, pH 7.0, and a 20-min reaction at 25 °C. Notably, singlet oxygen was the predominant specie formed in the experiments in the SR-AOP, followed by sulfate and hydroxyl radicals. The catalyst could be reused for up to five cycles, retaining over 98% RhB degradation, albeit with increased metal leaching. Even in the first use, dissolved Fe and Co concentrations were 0.8 ± 0.3 and 4.0 ± 0.5 mg L-1, respectively. The FeCo catalyst proved to be effective in dye degradation and offers the potential for further refinement to minimize Co2+ leaching.

One-pot solvothermal synthesis of Cu-Fe-MOF for efficiently activating peroxymonosulfate to degrade organic pollutants in water:Effect of electron shuttle

Persulfate-based advanced oxidation processes (PS-AOPs) show a bright prospect in sewage purification. The development of efficient catalysts with simple preparation process and eco-friendliness is the key for their applying in practical water treatment. Herein, a bimetallic Cu-Fe metal organic framework (MOF) was simply synthesized by using one-pot solvothermal methods and employed for activating peroxymonosulfate (PMS) to degrade organic pollutants in water. The Cu-Fe-MOF/PMS exhibited excellent degradation efficiencies (over 95% in 30 min) for a variety of pollutants, including phenol, bisphenol A, 2,4-dichlorophenol, methyl blue, rhodamine B, tetracycline and sulfamethoxazole. The degradation efficiency was impacted by dosages of Cu-Fe-MOF, PMS concentrations, reaction temperature, solution pH and anionic species. Phenol could be efficiently decomposed in a wide pH range of 5-9, with the highest degradation and mineralization efficiency of nearly 100% and 70%, respectively. Free radicals and non-free radicals participated in degrading of phenol at the same time, with dominantly free radical process, because sulfate radicals (SO4·-) and hydroxyl radicals (·OH) were the primary active substances by contribution calculation. Cu-Fe-MOF was acted as electron shuttle between molecules of phenol and PMS, and the cooperation effect of Fe and Cu on the Cu-Fe-MOF promoted the electron transfer, achieving the high degradation efficiency of phenol. Thus, Cu-Fe-MOF is an ideal catalyst for activating PMS, which is conducive to promote the applying of catalyst-activated PMS processes for practical wastewater treatments.

Degradation of Ampicillin with antibiotic activity removal using persulfate and submersible UVC LED: Kinetics, mechanism, electrical energy and cost analysis

Effective water treatment to remove antibiotics and its activity from contaminated water is urgently needed to prevent antibiotic-resistant bacteria (ARB) emergence. In this study, we investigated degradation of Ampicillin (AMP), an extensively used β-lactam antibiotic, using submersible Ultraviolet C Light Emitting Diode (λmax = 276 nm) irradiation source, and Persulfate (UVC LED/PS system). Pseudo first order rate constant (kobs) for degradation of AMP (1 ppm) by UVC LED/PS system was determined to be 0.5133 min-1 (PS = 0.2 mM). kobs value at pH 2.5 (0.7259 min-1) was found to be higher than pH 6.5 (0.5133 min-1) and pH 12 (0.1745 min-1). kobs value for degradation of AMP in deionized water spiked with inorganic anions (Cl-=0.5369 min-1,SO42-=0.4545 min-1, NO3-=0.1526 min-1, HCO3-=0.0226 min-1), in real tap water (0.1182 min-1) and simulated ground water (0.0372 min-1) were presented. Radical scavenging experiment reveal involvement of sulfate radical anion and hydroxyl radical in UVC LED/PS system. EPR analysis confirms the generation of sulfate radical anion and hydroxyl radical. Importantly, 74% reduction of total organic carbon (TOC) occurred within 60 min of AMP treatment by UVC LED/PS system. Seven degradation by-products were identified by high resolution mass spectrometry, and degradation pathways were proposed. Antibacterial activity of AMP towards Bacillus subtilis and Staphylococcus aureus was completely removed after UVC LED/PS treatment. ECOSAR model predicted no very toxic degradation by-products generation by UVC LED/PS system. Electrical Energy per order (EEo) and cost of UVC LED/PS system were determined to be 0.9351 kW/m3/order and ₹ 7.91/m3 ($ 0.095/m3 or € 0.087/m3), respectively. Overall, this study highlights, UVC LED/PS system as energy efficient, low-cost, and its potential to emerge as sulfate radical anion based advanced oxidation process (AOP) to treat water with antibiotics.

Sea Urchin-like NiCo2O4 Catalyst Activated Peroxymonosulfate for Degradation of Phenol: Performance and Mechanism

How to efficiently activate peroxymonosulfate (PMS) in a complex water matrix to degrade organic pollutants still needs greater efforts, and cobalt-based bimetallic nanomaterials are desirable catalysts. In this paper, sea urchin-like NiCo2O4 nanomaterials were successfully prepared and comprehensively characterized for their structural, morphological and chemical properties via techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), among others. The sea urchin-like NiCo2O4 nanomaterials exhibited remarkable catalytic performance in activating PMS to degrade phenol. Within the NiCo2O4/PMS system, the removal rate of phenol (50 mg L-1, 250 mL) reached 100% after 45 min, with a reaction rate constant k of 0.091 min-1, which was 1.4-times higher than that of the monometallic compound Co3O4/PMS system. The outstanding catalytic activity of sea urchin-like NiCo2O4 primarily arises from the synergistic effect between Ni and Co ions. Additionally, a comprehensive analysis of key parameters influencing the catalytic activity of the sea urchin-like NiCo2O4/PMS system, including reaction temperature, initial pH of solution, initial concentration, catalyst and PMS dosages and coexisting anions (HCO3-, Cl-, NO3- and humic acid), was conducted. Cycling experiments show that the material has good chemical stability. Electron paramagnetic resonance (EPR) and quenching experiments verified that both radical activation (SO4•-, •OH, O2•-) and nonradical activation (1O2) are present in the NiCo2O4/PMS system. Finally, the possible degradation pathways in the NiCo2O4/PMS system were proposed based on gas chromatography-mass spectrometry (GC-MS). Favorably, sea urchin-like NiCo2O4-activated PMS is a promising technology for environmental treatment and the remediation of phenol-induced water pollution problems.

A confined expansion pore-making strategy to transform Zn-MOF to porous carbon nanofiber for water treatment: Insight into formation and degradation mechanism

Electrospinning MOFs nanoparticles derived porous carbon nanofibers with rational structure and design are recently as environmentally friendly and highly efficient catalytic materials for wastewater treatment. However, most of the pore-making strategies are based on precursors structural shrinkage during pyrolysis, which is a challenge to create abundant large pores and open channels. Here, a confined expansion pore-making strategy with active MOF is introduced, where energetic Zn-MOF (Zn2+/triazole) and ZIF-67 (Co2+/dimethylimidazole) are utilized as pore forming additive and precursor of active sites, respectively. The high nitrogen content gives triazole the ability to puff up and realizes N-doped during pyrolysis. Moreover, degradation mechanisms and pathways of pollutants were measured by 3D EEM, LC-MS, quenching experiments, and Fukui function. This pore-making strategy via energetic MOF local contraction and expansion provides a novel method to prepare diversiform function porous carbon materials for environmental remediation.

Peroxymonosulfate activation by magnetic CoNi-MOF catalyst for degradation of organic dye

In this work, Fe₃O₄/CoNi-MOF was synthesized by a simple solvothermal method. The catalytic performance of 0.2-Fe₃O₄/CoNi-MOF toward PMS activation was studied by degradation of 20 mg/L methylene blue (MB). The results indicated that 0.2-Fe₃O₄/CoNi-MOF had good catalytic ability, the removal rate of MB was 99.4% within 60 min with 125 mg/L PMS and 150 mg/L catalyst. Quenching experiment and electron paramagnetic resonance (EPR) analysis revealed that the singlet oxygen (¹O₂), superoxide radical (•O₂^-) and sulfate radical (SO₄^•-) played a crucial role in the catalytic degradation process. Meantime, mechanism of PMS activation by 0.2-Fe₃O₄/CoNi-MOF was proposed, the electrons donated by Fe²⁺ can also enhance the Co-Ni cycles. In conclusion, Fe₃O₄/CoNi-MOF composite catalyst has the advantages of simple preparation, excellent catalytic activity and reusability, which is an effective catalyst for water pollution control.

Yolk-shell Co3 O4 @Fe3 O4 /C Nanocomposites as a Heterogeneous Fenton-like Catalyst for Organic Dye Removal

The yolk-shell Co₃ O₄ @Fe₃ O₄ /C nanocomposites with Co₃ O₄ as the core, Fe₃ O₄ /C as the shell, and a cavity structure were synthesized by the hard template method. The physical and chemical properties of the composites were characterized by SEM, TEM, XRD, TGA, XPS, BET, and VSM. The specific surface area of yolk-shell Co₃ O₄ @Fe₃ O₄ /C nanocomposites is 175.9 m²  g^-1 , showing superparamagnetic properties. The yolk-shell Co₃ O₄ @Fe₃ O₄ /C nanocomposites were used as heterogeneous Fenton catalysts to activate peroxymonosulfate (PMS) to degrade MB, which showed high catalytic degradation performance. The degradation rate of MB reached 100 % within 30 min under the circumstances of the yolk-shell Co₃ O₄ @Fe₃ O₄ /C nanocomposites dosage of 0.1 g L^-1 , the PMS dosage of 1.0 g L^-1 , the initial MB concentration of 100 mg L^-1 , an initial pH of 5.5, and a temperature of 30±2 °C. The enhanced catalytic performance of the yolk-shell Co₃ O₄ @Fe₃ O₄ /C nanocomposites can be attributed to the synergistic effect of the two catalytically active materials and the middle cavity. The effects of different operating parameters and co-existing anion species on MB degradation were also investigated. Electron paramagnetic resonance (EPR) analysis and quenching experiments confirmed that the formation of SO₄ ⋅^- in the yolk-shell Co₃ O₄ @Fe₃ O₄ /C/PMS system contributes to MB degradation. In addition, yolk-shell Co₃ O₄ @Fe₃ O₄ /C nanocomposites can be easily separated from the pollutant solution under the action of an external magnetic field, and the degradation rate of MB can still reach 98 % after five cycles, indicating that it has good stability and reusability and has broad application prospects in the field of water purification.

Coupling the effect of Co and Mo on peroxymonosulfate activation for the removal of organic pollutants

Although heterogeneous cobalt-based catalysts have been widely studied and used in SO₄^•- based advanced oxidation processes, the efficiencies were still not high enough due to the limiting step of Co(III)/Co(II) cycle in the system. In this study, a bimetallic oxide composed of Co and Mo was designed and used for enhancing the performance of peroxymonosulfate activation on organic pollutants removal. The CoMoO₄ nanorods exhibited superior catalytic activity for methylene blue (MB) degradation than Co₃O₄, MoO₃, and their mechanical mixture, which was attributed to the synergetic effect between Co and Mo. CoMoO₄ nanorods were able to efficiently degrade MB under a wide pH range of 3-11 and could maintain high efficiency in 5 cycles with less leakage of metal ions. Moreover, CoMoO₄ nanorods displayed broad spectrum applicability to the different water matrix and a variety of pollutants such as phenol and Congo red. The Co(II) was proved to be the main active site of the catalyst, while Mo played an important role in promoting the Co(III)/Co(II) cycle. Surface free radicals are the main active species in the degradation process. This work provides new insights into the design of cobalt-based bimetallic catalyst and the improvement on PMS activation.

Orange G degradation by heterogeneous peroxymonosulfate activation based on magnetic MnFe2O4/α-MnO2 hybrid

Wastewater containing an azo dye Orange G (OG) causes massive environmental pollution, thus it is critical to develop a highly effective, environmental-friendly, and reusable catalyst in peroxymonosulfate (PMS) activation for OG degradation. In this work, we successfully applied a magnetic MnFe₂O₄/α-MnO₂ hybrid fabricated by a simple hydrothermal method for OG removal in water. The characteristics of the hybrid were investigated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller method, vibrating sample magnetometry, electron paramagnetic resonance, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The effects of operational parameters (i.e., catalytic system, catalytic dose, solution pH, and temperature) were investigated. The results exhibited that 96.8% of OG degradation was obtained with MnFe₂O₄/α-MnO₂(1:9)/PMS system in 30 min regardless of solution pH changes. Furthermore, the possible reaction mechanism of the coupling system was proposed, and the degradation intermediates of OG were identified by mass spectroscopy. The radical quenching experiments and EPR tests demonstrated that SO₄^•̶, O₂^•̶, and ¹O₂ were the primary reactive oxygen species responsible for the OG degradation. The hybrid also displayed unusual stability with less than 30% loss in the OG removal after four sequential cycles. Overall, magnetic MnFe₂O₄/α-MnO₂ hybrid could be used as a high potential activator of PMS to remove orange G and maybe other dyes from wastewater.

Non-radical-dominated catalytic degradation of methylene blue by magnetic CoMoO4/CoFe2O4 composite peroxymonosulfate activators

In this study, magnetic CoMoO₄/CoFe₂O₄ (CMO/CFO) nanospheres with a core-shell structure were synthesized via two-step hydrothermal methods. The obtained particles were employed as catalysts to activate peroxymonosulfate (PMS) and degrade methylene blue (MB). The physico-chemical characterizations of the synthesized CMO/CFO showed that the CMO shell contributed to the enhancement of redox conversion and the increase in the concentration of oxygen vacancies (OVs). By examining reactive oxygen species (ROS) in the CMO/CFO/PMS system, the MB degradation was dominated by a non-radical pathway, and ¹O₂ was identified as the most abundant ROS. Besides, the CMO/CFO exhibited faster reaction kinetics than the pristine CFO. Moreover, the magnetic properties guaranteed the recycling and reuse of CMO/CFO, and the removal rate of MB was maintained at ∼94% after continuous use five times. Both the tolerance to SO₄^2-and the wide pH range where the material is applicable make it a promising catalyst for dyeing wastewater treatment.

Efficient Degradation of Congo Red in Water by UV-Vis Driven CoMoO4/PDS Photo-Fenton System

In order to improve the catalytic activity of cobalt molybdate (CoMoO₄), a PDS-activated and UV-vis assisted system was constructed. CoMoO₄ was prepared by coprecipitation and calcination, and characterized by XRD, FTIR, Raman, SEM, TEM, XPS, TGA Zeta potential, BET, and UV-Vis DRS. The results showed that the morphology of the CoMoO₄ nanolumps consisted of stacked nanosheets. XRD indicated the monoclinic structures with C2/m (C³_2h, #12) space group, which belong to α-CoMoO₄, and both Co²⁺ and Mo⁶⁺ ions occupy distorted octahedral sites. The pH of the isoelectric point (pHIEP) of CMO-8 at pH = 4.88 and the band gap of CoMoO₄ was 1.92 eV. The catalytic activity of CoMoO₄ was evaluated by photo-Fenton degradation of Congo red (CR). The catalytic performance was affected by calcination temperature, catalyst dosage, PDS dosage, and pH. Under the best conditions (0.8 g/L CMO-8, PDS 1 mL), the degradation efficiency of CR was 96.972%. The excellent catalytic activity of CoMoO₄ was attributed to the synergistic effect of photo catalysis and CoMoO₄-activated PDS degradation. The capture experiments and the ESR showed that superoxide radical (·O₂^-), singlet oxygen (¹O₂), hole (h⁺), sulfate (SO₄^-·), and hydroxyl (·OH^-) were the main free radicals leading to the degradation of CR. The results can provide valuable information and support for the design and application of high-efficiency transition metal oxide catalysts.

Amorphous NiSn and FeOOH as bifunctional co-catalysts for oxygen reduction and phenol (water) oxidation over BiVO4 under visible light

Monoclinic BiVO₄ (BiV) has been widely used as a photoanode for water oxidation, but rarely as a photocatalyst for organic oxidation due to slow reaction of O₂. In this work, BiV has been modified with poorly crystallized sFe and sNi, where sFe is FeOOH, and sNi is a mixture of Ni(OH)₂ and polysulfide. Under light, sFe/BiV and sNi/BiV in aqueous solution were more active than BiV, respectively, not only for phenol oxidation but also for O₂ reduction. Importantly, the rate of phenol oxidation obtained for sFe/sNi/BiV was larger than the sum of the rates measured for sFe/BiV and sNi/BiV, by a factor of approximately 1.5. Moreover, on a film electrode, O₂ reduction had a current of sFe/sNi/BiV > sNi/BiV > sFe/BiV > BiV, while water (photo)oxidation had a current of sFe/sNi/BiV > sNi/BiV > sFe/BiV > BiV. A possible mechanism is proposed, involving formation of a reduced sulfur species for O₂ reduction and an oxidized iron species for phenol oxidation. In sFe/sNi/BiV, there is a mutual promotion between the sNi-mediated electron transfer and the sFe-mediated hole transfer. This results in a further improved efficiency of charge separation for O₂ reduction and phenol oxidation.

Iron molydate catalyzed activation of peroxymonosulfate for bisphenol AF degradation via synergetic non-radical and radical pathways

Though molybdate oxides have been demonstrated as desirable catalysts for environmental remediation, the mechanism of catalytic activation of peroxymonosulfate (PMS) by iron (II) molybdate (FeMoO₄) remains unclear. In this study, FeMoO₄ was synthesized and applied for the activation of PMS to degrade bisphenol-AF (BPAF). FeMoO₄ showed excellent catalytic activity, high stability, and superior mineralization. The influence of operation parameters (i.e., FeMoO₄ dosage, PMS concentration, initial pH, co-existing anions, and temperature) on the removal of BPAF were also investigated in detail. Furthermore, the possible oxidation mechanism was proposed via the chemical quenching tests and electron spin resonance (ESR) analysis, which certified that both free radical (SO₄^-• and ^•OH) and non-radical (¹O₂) were the main reactive oxygen species for degrading BPAF. X-ray photoelectron spectroscopy (XPS) analysis indicated that the radicals were mainly generated via the continuous circulation of Fe³⁺/Fe²⁺ and Mo⁶⁺/Mo⁴⁺ redox cycles to enhance PMS activation. Finally, the degradation pathways of BPAF was proposed based on LC/MS results. This work showed the notable potential of the FeMoO₄/PMS system for degrading organic contaminants in the environment remediation and would promote the understanding of the mechanism of Fe-based molybdate in advanced oxidation.

Efficient degradation of Rhodamine B by magnetically recoverable Fe3O4-modified ternary CoFeCu-layered double hydroxides via activating peroxymonosulfate

Environment-friendly nano-catalysts capable of activating peroxymonosulfate (PMS) have received increasing attention recently. Nevertheless, traditional nano-catalysts are generally well dispersed and difficult to be separated from reaction system, so it is particularly important to develop nano-catalysts with both good catalytic activity and excellent recycling efficiency. In this work, magnetically recoverable Fe₃O₄-modified ternary CoFeCu-layered double hydroxides (Fe₃O₄/CoFeCu-LDHs) was prepared by a simple co-precipitation method and initially applied to activate PMS for the degradation of Rhodamine B (RhB). X-ray diffraction (XRD), fourier transform infrared spectrometer (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller method (BET), and vibrating sample magnetometer (VSM) were applied to characterize morphology, structure, specific surface area and magnetism. In addition, the effects of several key parameters were evaluated. The Fe₃O₄/CoFeCu-LDHs exhibited high catalytic activity, and RhB degradation efficiency could reach 100% within 20 min by adding 0.2 g/L of catalyst and 1 mmol/L of PMS into 50 mg/L of RhB solution under a wide pH condition (3.0-7.0). Notably, the Fe₃O₄/CoFeCu-LDHs showed good super-paramagnetism and excellent stability, which could be effectively and quickly recovered under magnetic condition, and the degradation efficiency after ten cycles could still maintain 98.95%. Both radicals quenching tests and electron spin resonance (ESR) identified both HO• and SO₄^•- were involved and SO₄^•- played a dominant role on the RhB degradation. Finally, the chemical states of the sample's surface elements were measured by X-ray photoelectron spectroscopy (XPS), and the possible activation mechanism in Fe₃O₄/CoFeCu-LDHs/PMS system was proposed according to comprehensive analysis.

Novel zero-valent Co-Fe encapsulated in nitrogen-doped porous carbon nanocomposites derived from CoFe2O4@ZIF-67 for boosting 4-chlorophenol removal via coupling peroxymonosulfate

Environment-friendly treatment process relies on the robustness, durability, and performance of catalysts to drive the development of cutting-edge sustainable technologies for the elimination of refractory contaminants. Herein, nanocomposites prepared from zero-valent Co-Fe encapsulated in nitrogen-containing carbon (NC) nanoparticles (CFNC-30 NPs) derived from CoFe₂O₄@zeolitic imidazolate frameworks-67 were successfully prepared through pyrolysis integrated with self-reduction, and further utilized as the novel catalysts to degrade 4-chlorophenol (4-CP) by coupling with peroxymonosulfate (PMS). Three optimized parameters (CFNC-30 NPs dosage of 0.089 g L^-1, PMS concentration of 1.1 g L^-1, and initial pH of 6.6) were obtained via response surface methodology by using the Box-Behnken design model. Benefiting from the larger specific surface area, pore-volume, and existence of abundant hydroxyl groups, CFNC-30 NPs with more available active sites exhibited an excellent efficiency of 99.1% toward catalytic degradation of 4-CP within 30 min under the optimal conditions. Moreover, CFNC-30 NPs demonstrated durability and long-term stability even during the five consecutive cycle tests without a significant drop in its catalytic performance. The scavenging experiments and electron paramagnetic resonance technologies revealed that non-radical singlet oxygen (¹O₂), sulfate radicals (SO₄^-), and hydroxyl radicals (HO) were involved as active species in the CFNC-30/PMS system, contributing 46.8, 35.6, and 17.6% efficiency toward 4-CP degradation, respectively. Besides, the reaction mechanism on the CFNC-30 NPs and degradation pathways toward 4-CP were speculated under PMS activation. The results indicated that the synergistic effects between zero-valent Co-Fe and NC structures not only significantly boosted the removal efficiency and long-term stability of CFNC-30 NPs, but also facilitated the redox cycles of Co³⁺/Co²⁺ and Fe³⁺/Fe²⁺. This proof-of-concept approach to develop such high-efficient zero-valent Co-Fe encapsulated in NC structures opens up novel avenues for wastewater decontamination via PMS activation.

Synergistic coupling Co3Fe7 alloy and CoFe2O4 spinel for highly efficient removal of 2,4-dichlorophenol by activating peroxymonosulfate

Efficient wastewater restoration depends on the robustness and capability of the catalyst to promote sophisticated decontamination technologies. In this study, Co₃Fe₇-CoFe₂O₄ nanoparticles (NPs) prepared by facile pyrolysis were completely characterized and used to decompose 2,4-dichlorophenol (2,4-DCP). Furthermore, the catalytic performance and relevant mechanisms involved in the activation of peroxymonosulfate (PMS) were also investigated. The optimal conditions were achieved at the catalyst loading of 0.05 g L^-1, PMS dosage of 1.26 g L^-1, and pH of 7.7 through the response surface methodology by using the Box-Behnken design model. Under optimal conditions, 97.1% efficiency of 2,4-DCP removal was obtained within 30 min. Moreover, the quenching experiments and electron paramagnetic resonance result indicated that sulfate (SO₄^•-) and hydroxyl (HO^•) radicals were considered as the dominant reactive oxygen species, which resulted in the effective removal of 2,4-DCP in the Co₃Fe₇-CoFe₂O₄/PMS system. Moreover, Co₃Fe₇-CoFe₂O₄ showed efficient catalytic performance in continuous five runs and exhibited less metal leaching of 0.052 and 0.036 mg L^-1 for Co and Fe species, respectively. Furthermore, no considerable change was observed in the structural characteristics of the fresh and used Co₃Fe₇-CoFe₂O₄ catalytic system. The above-mentioned results indicated that the synergistic effects between Co₃Fe₇ alloy and CoFe₂O₄ spinel not only significantly improved the activity and long-term durability of the catalyst, but also accelerated the Co³⁺/Co²⁺ and Fe³⁺/Fe²⁺ redox cycles. Overall, the Co₃Fe₇-CoFe₂O₄/PMS system provides a novel advanced oxidation approach to further develop multifunctional transition metal-based nanomaterials responsible for producing surface-bound radicals and enhancing the remediation of refractory pollutants in the environmental application.

Catalytic activation of peroxymonosulfate with manganese cobaltite nanoparticles for the degradation of organic dyes

In this work, we report the facile hydrothermal synthesis of manganese cobaltite nanoparticles (MnCo₂O_4.5 NPs) which can efficiently activate peroxymonosulfate (PMS) for the generation of sulfate free radicals (SO₄˙⁻) and degradation of organic dyes. The synthesized MnCo₂O_4.5 NPs have a polyhedral morphology with cubic spinel structure, homogeneously distributed Mn, Co, and O elements, and an average size less than 50 nm. As demonstrated, MnCo₂O_4.5 NPs showed the highest catalytic activity among all tested catalysts (MnO₂, CoO) and outperformed other spinel-based catalysts for Methylene Blue (MB) degradation. The MB degradation efficiency reached 100% after 25 min of reaction under initial conditions of 500 mg L⁻¹ Oxone, 20 mg L⁻¹ MnCo₂O_4.5, 20 mg L⁻¹ MB, unadjusted pH, and T = 25 °C. MnCo₂O_4.5 NPs showed a great catalytic activity in a wide pH range (3.5–11), catalyst dose (10–60 mg L⁻¹), Oxone concentration (300–1500 mg L⁻¹), MB concentration (5–40 mg L⁻¹), and temperature (25–55 °C). HCO₃⁻, CO₃²⁻ and particularly Cl⁻ coexisting anions were found to inhibit the catalytic activity of MnCo₂O_4.5 NPs. Radical quenching experiments revealed that sulfate radicals are primarily responsible for MB degradation. A reaction sequence for the catalytic activation of PMS was proposed. The as-prepared MnCo₂O_4.5 NPs could be reused for at least three consecutive cycles with small deterioration in their performance due to low metal leaching. This study suggests a facile route for synthesizing MnCo₂O_4.5 NPs with high catalytic activity for PMS activation and efficient degradation of organic dyes.

Catalytic degradation of organic dyes via manganese cobaltite nanoparticles-activated peroxymonosulfate.

Cobalt-impregnated biochar (Co-SCG) for heterogeneous activation of peroxymonosulfate for removal of tetracycline in water

Cobalt-impregnated spent coffee ground biochar (Co-SCG) was synthesized and applied for tetracycline (TC) removal from water. The results showed that Co-SCG biochar exhibited marked adsorption capacity and catalyst activity. The maximum adsorption capacity of Co-SCG biochar toward TC was 370.37 mg g^-1. TC was almost completely degraded in 25 min with a rate constant of 17.78 × 10^-2 min^-1 under the following optimal condition: TC concentration of 0.2 mM, PMS concentration of 0.6 mM, Co-SCG dosage of 100 mg L^-1, and pH of 7.0. Co-SCG was characterized for surface properties by SEM, TEM, HRTEM, and BET. The concentration of 16 PAHs in Co-SCG biochar was studied also. Results demonstrated that Co-SCG was an effective eco-friendly material for the removal of tetracycline from water.

Polyaniline: A New Metal-Free Catalyst for Peroxymonosulfate Activation with Highly Efficient and Durable Removal of Organic Pollutants

Metal-free heterogeneous catalysts are receiving more and more attention for wastewater remediation by activating peroxymonosulfate (PMS) due to their environmental benign. However, carbon-based materials as the most typical metal-free heterogeneous always suffer from poor durability. Inspired by the fact that a conjugated system may facilitate the electron transfer during PMS activation, we innovatively select polyaniline (PANI) as a new PMS activator and investigate its catalytic performance in detail. It is found that PANI can display better catalytic performance than traditional metal-based catalysts and popular N-doped carbocatalysts in methyl orange (MO) degradation. More importantly, PANI is not only universal for various pollutants degradation but also maintains its catalytic performance in repeated degradation experiments. The stable N sites in the conjugated chains and the oxidation-resistance benzene rings as the building units are considered to be responsible for such an excellent durability. In addition, the influences of some routine factors and actual water backgrounds are comprehensively checked and analyzed. The quenching experiments and electron paramagnetic resonance confirm that MO degradation is achieved through both radical and nonradical pathways, where SO₄^•- and ¹O₂ are primary reactive species. The reaction mechanism is also proposed with the assistance of X-ray photoelectron spectroscopy.

Complete mineralization of a humic acid by SO4 ·- generated on CoMoO4/gC3N4 under visible-light irradiation

The sulfate radical ([Formula: see text]), almost a most active species, is believed to be the best oxidant in the elimination of aquatic organics in advanced oxidation processes. However, acquiring their steady-state generation with high concentration is still challenging work. In this report, we focused on designing a novel composite, in which uniform and rod-like CoMoO₄ was fabricated on gC₃N₄ through Co-N coordination. In this way, the composite acquired an immobilization of Co (II) in its refraining from leaking, and synchronically, a dense heterojunction between CoMoO₄ and gC₃N₄. Over the heterojunctions, photogenerated electrons gained a prolonged lifetime through their efficient separation from holes. The life-prolonged electrons, together with Co (II) in CoMoO₄, effectively activated the persulfate, and a concentration of steady-state [Formula: see text] as high as 1.8 × 10^-14 mol · l^-1 was obtained. With [Formula: see text] fast and complete mineralization of a humic acid was achieved.

High Catalytic Efficiency of Nanostructured β-CoMoO₄ in the Reduction of the Ortho-, Meta- and Para-Nitrophenol Isomers

Nanostructured β-CoMoO₄ catalysts have been prepared via the thermal decomposition of an oxalate precursor. The catalyst was characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller method (BET), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The efficiency of these nanoparticles in the reduction of ortho- and meta-nitrophenol isomers (2-NP, 3-NP, and 4-NP) to their corresponding aminophenols was tested using UV-visible spectroscopy measurements. It was found that, with a β-CoMoO₄ catalyst, NaBH₄ reduces 3-NP instantaneously, whilst the reduction of 2-NP and 4-NP is slower at 8 min. This difference is thought to arise from the lower acidity of 3-NP, where the negative charge of the phenolate could not be delocalized onto the oxygen atoms of the meta-nitro group.

Facile synthesis of yolk shell Mn2O3@Mn5O8 as an effective catalyst for peroxymonosulfate activation

The Mn₂O₃@Mn₅O₈ catalyst exhibits unique structural properties for catalytic activities and shows efficient performance for the degradation of 4-CP in a PMS system.

A magnetic CoFe2O4–CNS nanocomposite as an efficient, recyclable catalyst for peroxymonosulfate activation and pollutant degradation

An efficient, stable, easily recoverable hybrid nanomaterial for heterogeneous activation of PMS and sulfonamide degradation.