Peroxymonosulfate Dosage Research Articles

Insights into the performance and kinetics of face mask-derived nitrogen-doped porous carbon as peroxymonosulfate activator for gatifloxacin removal

The outbreak of COVID-19 has led to the increase in face mask waste globally. In this study, face mask-derived carbocatalysts doped with nitrogen (N-Mask) were fabricated through one-step pyrolysis of 1:5 w/w mixture of face mask and urea at different temperatures to activate peroxymonosulfate (PMS) for gatifloxacin (GAT) degradation. The N-Mask prepared at 800 °C (N-Mask800) exhibited the highest GAT degradation rate with kapp = 0.093 min−1 which could be attributed to its high N doping level (17.1 wt%) and highest specific surface area (237.13 m2 g−1). The relationship between kapp, catalyst loading and PMS dosage at various pHs on GAT degradation were successfully established. It was also found that the GAT degradation rate was inhibited in the sequential operating mode compared to the simultaneous operating mode. It was construed that adsorption and catalysis share the same active sites. Deterioration in catalytic performance was observed over successive cycles due to the surface chemistry change during catalysis, and difficulty in catalyst recovery after treatment. Radical scavenger study revealed that both radical and nonradical pathways were involved during GAT degradation, with nonradical pathway playing a dominant role. XPS analysis revealed that pyrrolic N and graphitic N can facilitate PMS activation via radical and nonradical pathways. Based on the LC-MS/MS analysis, the GAT degradation intermediates were identified, and the possible degradation pathways were tentatively proposed. Overall, this study demonstrated that carbocatalyst derived from face mask could be transformed into cost-effective and environmentally friendly PMS activator for environmental wastewater treatment applications.

Synergistic activation of peroxymonosulfate by nickel-cobalt hexacyanoferrate derived hybrid metal oxides for efficient sulfamethoxazole degradation

The development of a heterogeneous catalyst for efficient activation of peroxymonosulfate (PMS) is still highly desired in metal-based advanced oxidation processes. In this study, nickel-cobalt-iron hybrid oxides (NiCoFe-HO) catalyst was fabricated via direct thermal decomposition of nickel-cobalt hexacyanoferrate to activate PMS for sulfamethoxazole (SMX) degradation. NiCoFe-HO presented a much greater catalytic performance in SMX degradation with PMS under neutral pH (k = 0.079 min−1). The degradation rate of SMX with NiCoFe-HO was 2.3 and 3.0 times higher than that with nickel-iron hybrid oxides and cobalt-iron hybrid oxides, respectively. The synergistic effect among Ni, Co and Fe was experimentally verified to elucidate the superior catalytic activity. Sulfate radical and singlet oxygen were identified as the predominant reactive species in the current oxidation process. SMX degradation efficiency was gradually enhanced with the increase of catalyst dosage, PMS dosage and temperature but decreased with the increase of pH. In addition, NiCoFe-HO showed good stability and reusability. This study extends the design of hybrid metal oxides as efficient heterogeneous catalysts for PMS activation.

Microwave-assisted synthesis of amorphous cobalt nanoparticle decorated N-doped biochar for highly efficient degradation of sulfamethazine via peroxymonosulfate activation

In the present work, a microwave-assisted and secondary roasting preparation process was used to synthesize nanocomposite materials. These materials were modified with amorphous cobalt nanoparticles (Co NPs) on the surface of biochar doped with different nitrogen sources (melamine (Me), 1,10-phenanthroline (Ph), and urea (Ur)). The nanocomposite (Co-N-C(Ur)) with urea as the nitrogen source promoted the generation of mesopores on the surface of carbon materials due to its evaporation during the preparation process thus enhancing the attachment sites of cobalt nanoparticles. The Co-N-C(Ur) had a more significant degradation effect on the primary carcinogen sulfamethazine (SMT) by activating peroxymonosulfate (PMS). The degradation rate of SMT pollutants was 96.6 % within 30 min. The optimal reaction conditions were as follows: catalyst dosage of 0.4 g L−1, PMS dosage of 0.812 mM, SMT concentration of 10 mg L−1, and pH of 5.67. Additionally, the Co-N-C(Ur) catalysts possess excellent specific surface area due to the evaporation effect of the calcination process of urea itself compared to other nitrogen source doping. Electrochemical tests revealed that the composites prepared with urea as the nitrogen source had higher PMS-induced current density and lowered material impedance values, which effectively promoted the catalytic performance of SMT degradation. Concurrently, the Co-N-C (Ur) + PMS reaction system exhibited excellent catalytic performance against other antibiotic organic pollutants. Subsequently, through the capture experiments and electron paramagnetic resonance technical analyses, it was determined that the singlet 1O2 played a leading role in the reaction system. Finally, a thorough liquid chromatography-mass spectrometry analysis suggested the possible SMT degradation pathways, thereby providing a new strategy for the subsequent heterogeneous catalysts to degrade persistent organic pollutants.

Removal of antibiotic resistant bacteria, genes and inhibition of plasmid-mediated horizontal transfer by peroxymonosulfate: Efficiency and mechanisms

As the emerging contaminants, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have caught considerable research attention, horizontal gene transfer is one of the most primary contributors to antibiotic resistance dissemination. The application of the oxidant peroxymonosulfate (PMS) as a disinfection alternative has been systemically explored. Also, the effects of various process parameters on ARB inactivation and plasmid-mediated horizontal transfer inhibition, initial bacterial concentration, pH value and temperature, were systemically investigated. The changes in cell substances (cell membrane integrity and intracellular reactive oxygen species) were determined by flow cytometry. The results suggested that the inactivation efficiency of Escherichia coli DH5α (donor) and Pseudomonas sp. HLS-6 (recipient) by 0.8 mM PMS treatment reached 4.45 log and 4.15 log in 30 min, respectively. The conjugative transfer didn’t arise after treatment for only 1 min when the dosage of PMS exceeded 0.4 mM. PMS could work in a wide pH and ambient temperature range. It also showed significant removal efficiency on intracellular ARGs and extracellular ARGs. To identify the underlying mechanisms of restraining conjugative transfer, the mRNA expression of conjugative genes, oxidative stress genes, save our souls (SOS) response-related gene, cell outer membrane proteins genes and global regulatory genes were evaluated. The results demonstrated that the expressions of these genes were altered by 0.8 mM PMS treatment. PMS has the advantages of low cost, easy operation and technical applicability. This study illustrated that PMS treatment showed great potential for controlling the antibiotic resistance for wastewater treatment.

Synergistic removal of aqueous ciprofloxacin hydrochloride by water surface plasma coupled with peroxymonosulfate activation

A novel method of water surface plasma (WSP) combined with peroxymonosulfate (PMS) was developed for synergistic degradation of aqueous ciprofloxacin hydrochloride (CIP). The synergistic effect between WSP and PMS was demonstrated with the synergistic factor of 3.224. The CIP removal efficiency of the synergistic system was up to 96.6 % after 30 min of treatment, corresponding to the kinetic constant of 0.113 min−1. The degradation performance experiments revealed that the PMS dosage of 6.4 mM, air flow rate of 0 L/min, peak voltage of 23 kV, initial pH and initial CIP concentration of acidic and 20 mg/L, respectively, were favorable for CIP removal. The combined system could maintain high removal efficiency (93.9 %) for the treatment of wastewater with high initial conductivity (950 μS/cm). OH, SO4−, O3, O2− and high-energy electrons were the active species responsible for CIP degradation, among which OH was the main active factor. UV–vis spectra and three-dimensional fluorescence spectra demonstrated the efficient removal of CIP. Possible degradation pathways and synergistic degradation mechanism were summarized. PMS was probably activated by O3, ultraviolet light and high-energy electrons generated in WSP. The presence of Cl−, SO42− and HCO3− had a certain negative effect on CIP degradation in the WSP + PMS system, while HA had little effect on the final removal of CIP. The WSP + PMS degradation method has the advantages of high efficiency, high rate and low energy consumption compared with the previous literatures.

Accelerated Removal of Acid Orange 7 by Natural Iron Ore Activated Peroxymonosulfate System with Hydroxylamine for Promoting Fe(III)/Fe(II) Cycle

In this study, peroxymonosulfate (PMS) was activated by cheap and readily available natural iron ore to remove Acid Orange 7 (AO7) in water with the assistance of hydroxylamine (HA). Results show that the presence of HA could accelerate the Fe(II)/Fe(III) cycle on the ore surface, promoting the activation of PMS to generate reactive oxidative species. The effects of ore dosage, PMS dosage, HA dosage and initial pH on the degradation of AO7 were investigated in the HA/Ore/PMS system. Under the optimal conditions, the removal of AO7 could reach 93.1% during 30 min, which was 41.4% higher than the ore/PMS system. The AO7 removal increased with the increase of HA, PMS and ore dosage, but was unaffected by the initial solution pH. Based on radical scavenging experiments and EPR tests, the dominant reactive species in the HA/Ore/PMS system were revealed to be the sulfate radical (SO4•−), singlet oxygen (1O2), superoxide radical (O2•−) and hydroxyl radical (•OH), which were responsible for the AO7 degradation. Furthermore, the possible reaction mechanism of PMS activation was proposed. This study provides an efficient technique for the removal of azo dye organic contaminant in water, which has great practical significance.

Magnetic spent coffee biochar (Fe-BC) activated peroxymonosulfate system for humic acid removal from water and membrane fouling mitigation

Applying membrane technology to water purification has been done for several decades now and is widespread. However, membrane fouling is a serious problem and continues to limit the success of membrane processes. In this study, magnetic biochar (Fe-BC) was prepared using easily available spent coffee grounds to activate peroxymonosulfate (PMS) as a UF membrane pretreatment strategy. Results showed that the average removal rates of humic acid (HA, 10 mg/L) were 55.23 % and 73.55 %, at the Fe-BC dosage of 300 mg/L and PMS dosage of 300 mg/L and 900 mg/L, respectively. The Fe-BC/PMS pretreatment significantly reduced the total (44 %) and reversible (61 %) UF membrane fouling after five filtration cycles at a relatively high flux of 200 L/m2·h, and the Fe-BC and PMS dosage of 100 mg/L. Modeling fit results indicated that pretreatment shifted complete blocking to standard blocking. Therefore, stopping HA-induced membrane fouling could be possible if the load is reduced and complete blocking alleviated.

Degradation of 4-chlorophenol using MnOOH and γ-MnOOH nanomaterials as porous catalyst: Performance, synergistic mechanism, and effect of co-existing anions

Transition metal catalysts have been proven to be a highly-potent catalyst for peroxymonosulfate (PMS) activation. The present work aimed to synthesizes the γ-MnOOH and MnOOH based on the one-pot hydrothermal method as PMS activators for efficient degradation of 4-chlorophenol (4-CP). The effect of operational parameters including solution pH, γ-MnOOH and MnOOH dose, PMS dose, 4-CP concentration, and also mixture media composition was elaborated. The results showed that the combination of MnOOH and γ-MnOOH with PMS noticeably creates a synergistic effect (SF) in 4-CP degradation by both PMS/MnOOH and PMS/γ-MnOOH process, with a SF value of 48.14 and 97.42, respectively. In both systems, the removal of 4-CP decreased in severely alkaline and acidic conditions, while no significant changes were observed in pH 5 to 9. Also, coexisting PO43ˉ significantly reduced the removal efficiency of both systems. In addition, the effect of humic acid (HA) as a classical scavenger was investigated and showed that presence of 4 mg/L HA reduced the removal efficiency of 4-CP in the PMS/MnOOH process from 97.44% to 79.3%. The three consecutive use of both catalysts turned out that MnOOH has better stability than γ-MnOOH with lower Mn ions leaching. More importantly, quenching experiment showed that both non-radical (1O2 and O2−) and radical (SO4− and OH) pathways are involved in 4-CP degradation and non-radical pathway was the dominant one in both systems.

Unravelling the formation mechanism and performance of nitrogen, sulfur codoped biochar as peroxymonosulfate activator for gatifloxacin removal

Multi-heteroatom doping is a promising approach to increase the affinity of biochar for catalysis. Herein, a series of N, S-codoped biochar (BSN) were synthesized at different temperatures using a one-pot calcination protocol. Investigation on the physiochemical characteristics of these BSNs revealed that g-C3N4 was first formed from the precursors at lower temperature, engulfing the biochar. At higher synthesis temperature, the g-C3N4 decomposed and coalesce with the biochar to form BSN. The performance of BSN as peroxymonosulfate (PMS) activator for gatifloxacin (GAT) removal was evaluated. The results indicated that BSN prepared at 800 °C (BSN-800) exhibited the greatest performance due to its relatively high specific surface area and synergism between heteroatoms. A kinetic model based on the second-order PMS consumption and first-order GAT removal was developed to describe GAT removal and PMS consumption simultaneously at various operating conditions including BSN-800 loading, PMS dosage and pH. The proposed kinetic model has better fit compared to the conventional pseudo first-order kinetics. The major PMS activation mechanism was identified using chemical scavenger and electrochemical studies indicating that the nonradical pathway involving 1O2 generation and electron mediator mechanisms are dominant with graphitic N and thiophenic S acting as the active sites. Despite its restricted reusability, BSN-800 can be used effectively to remove GAT in various water matrixes including river water, secondary water and tap water. The GAT degradation intermediates were identified, and the degradation pathway was also proposed. Overall, this study provides a better understanding on the development of multi-heteroatom-doped biochar as promising catalyst for antibiotics removal.

Efficient degradation of antibiotics over Co(II)-doped Bi2MoO6 nanohybrid via the synergy of peroxymonosulfate activation and photocatalytic reaction under visible irradiation.

Developing efficient photocatalysts based on the peroxymonosulfate (PMS) activation for effective degradation of threatening antibiotic contamination under visible light is still a challenging subject. Herein, a Co-doped Bi2MoO6 (CBMO) spherical crystals were synthesized via a facile hydrothermal method and used to degrade artificial antibiotic wastewater via PMS activation under visible light. The obtained 3wt% Co-doped B2MoO6 (3CBMO) can effectively remove 98.95% of norfloxacin (NOF) within 40min, 100% of tetracycline (TC) and metronidazole (MNZ) within 30min. Compared with the contrasting catalysts, the superior catalytic activity of 3CBMO was attributed to the synergistic effect of photocatalytic and Co(II) activated PMS degradations. Quenching tests in combination with EPR measurements revealed that the hole (h+), sulfate (SO4-•) and hydroxyl (•OH) were the primary radicals all contributed to NOF degradation. The influences of initial concentration, catalyst dosage, PMS dosage and various interfering ions (NO3-, Cl-, SO42-, and HCO3-) on the degradation efficiency of NOF were systematically examined. Furthermore, possible degradation pathways of NOF were proposed by LC-MS. This novel 3CBMO catalyst might be a promising candidate for degradation of the main sources of antibiotic contamination in pharmaceutical wastewater.

A novel partially carbonized Fe3O4@PANI-p catalyst for tetracycline degradation via peroxymonosulfate activation

A novel polyaniline (PANI) partially carbonized core–shell material (Fe3O4@PANI-p) was prepared and used to activate peroxymonosulfate (PMS) for tetracycline (TC) degradation. Partial carbonization of the polyaniline layer introduced carbon catalytic sites into the catalyst. The polyaniline/carbon bilayer structure of the catalyst confined the metal oxides in the shell layer, which improved the catalytic performance of the material and reduced the leaching of metal ions. The effect of various influencing factors, such as PMS dosage, pollutant concentration, and initial pH on TC degradation was further investigated. The TC degradation efficiency was positively correlated with PMS dosage and negatively correlated with TC concentration. In the pH range of 3.0–9.0, the degradation efficiency of TC (C0 = 20 mg/L) reached more than 87.0 % within 90 min, and the highest efficiency was 89.8 %. HCO3– promoted the degradation of TC to a higher efficiency (95.9 %), whereas H2PO4− slightly inhibited it (88.1 %). The effect of humic acid (HA) in water on TC degradation was not significant. After three cycles, the degradation efficiency still reached 77.5 % and the degradation efficiency was restored to 83.7 % after pyrolysis regeneration. According to quenching experiments and electron paramagnetic resonance (EPR) characterization, the main reactive oxygen species (ROS) in the degradation process were singlet oxygen (1O2), followed by superoxide radicals (O2·−), sulfate radicals (SO4·−), and hydroxyl radicals (·OH). The above findings provide a reference for the application of new multilayer core–shell composites for antibiotic wastewater treatment.

Enhanced degradation of DDT using a novel iron-assisted hydrochar catalyst combined with peroxymonosulfate: Experiment and mechanism analysis

Poplar wood (PW) hydrochar modified by iron (Fe@HC) was prepared greenly by one-step hydrothermal method. The adsorption and degradation performance of DDT was investigated in a heterogeneous advanced oxidation system (Fe@HC/PMS) formed by Fe@HC collaborated with peroxymonosulfate (PMS). The effects of Fe@HC dosage, PMS dosage and DDT initial concentration were quantitatively analyzed. The results showed that DDT removal efficiency can reach to 88.62% in 240 min under optimal conditions (4 g/L Fe@HC, 10 mM PMS, 0.5 mg/L DDT, 5.5 pH0) in Fe@HC/PMS system. Furthermore, Fe@HC/PMS system exhibited high degradation rate and TOC removal efficiency for the removal of various organic contaminants. The influence mechanisms of Fe@HC/PMS system on DDT adsorption and degradation were proposed based on electron paramagnetic resonance (EPR) testing analysis and radical quenching experiments. Based on the mechanism analysis, the influence of Fe@HC/PMS on DDT removal efficiency can be concluded in the order: Active substance indirect degradation (60.95%) > Fe@HC direct degradation (10.13%) > Fe@HC adsorption (17.54%). Among active substance indirect degradation, SO4•−, •OH, O2•− and 1O2 occupied 27.56%, 15.74%, 5.33% and 12.32%, respectively. Moreover, DDT degradation intermediates were detected by a gas chromatography-mass spectrometer (GC-MS) to predict DDT degradation pathways. This study provided a green progress for the reuse of biomass resources and a new way for the enhanced degradation of DDT.

Highly efficient activation of peroxymonosulfate by Co, S co-doped bamboo biochar for sulfamethoxazole degradation: Insights into the role of S

Recently, highly efficient activation of peroxymonosulfate (PMS) by S-doped cobalt-based catalysts are receiving increased attention. The effect of S is worth exploring since it has a great influence on PMS activation performance. In this work, dimethyl sulfoxide was adopted as an S source and loaded on bamboo biochar (BB) with Co to form CoS/BBC, which served as an efficient catalyst for PMS activation to degrade sulfamethoxazole (SMX). The experiment results showed that CoS/BBC exhibits an excellent catalytic activity and the SMX (20 mg/L) can be completely degraded under the attack of species of ·OH, SO4-·, 1O2 and electron transfer. The SMX degradation conformed to pseudo first-order kinetics with rate constant reaching 0.442 min−1 in 10 min under the optimal conditions (a catalyst dose of 0.02 g/L, a PMS dose of 0.3 g/L and an initial pH = 7.0). The electrochemical experiments and density functional theory (DFT) calculation revealed that the introduction of S can accelerate electron transfer and promote the decomposition of PMS while facilitating Co(III)/Co(II) redox cycling. Furthermore, liquid chromatograph-mass spectrometer (LC-MS) and ecological structure activity relationships (ECOSAR) proved that the degradation process of SMX in CoS/BBC/PMS system has low ecotoxicity and is harmless to the environment. This work provides a new strategy for enhancing electron transfer by S-doped metal materials and the synthesis of efficient catalysts for SMX removal.

A copper-loaded N-doped carbon catalyst with mesoporous hollow sphere structure for bisphenol A removing via peroxymonosulfate activation

In this study a copper-loaded N-doped carbon catalyst with mesoporous hollow sphere structure characteristic (Cu–NCHS) was prepared by in-situ synthesis followed with calcination and hydrothermal etching. Its catalytic performance for peroxymonosulfate (PMS) activation was evaluated using bisphenol A (BPA) as target pollutant. Owing to the coordination of more active sites provided by copper-loading and the mesoporous hollow structure characterized with high specific surface area (SSA) of 282.2 m2 g−1 and large pore volume of 0.831 cm3 g−1, Cu–NCHS showed significantly better catalytic performance in BPA degradation (96.8% within 120 min) than those of NCHS (16.4%) and Cu-NC (19.6%) under the same initial conditions of BPA (20 mg L−1), PMS (100 mg L−1) and catalyst dosage (50 mg L−1). The possible mechanism of PMS activation by Cu–NCHS was also explored by ESR analysis and quenching experiments, and both radical and non-radical pathways were confirmed to be involved in BPA degradation process in Cu–NCHS/PMS system. Singlet oxygen (1O2), hydroxyl radical (•OH) and sulfate radical (SO4•−) were identified to be the reactive oxygen species (ROS), of which 1O2 was the dominant ROS. Besides, the Cu–NCHS/PMS system showed excellent adaptability to pH change (from 3 to 11), common inorganic anions (Cl−, HCO3−, HPO42−, SO42−) and natural organic matter (humic acid) in water. Meanwhile, the Cu–NCHS catalyst also showed good stability (with low Cu leaching of 0.14 mg L−1) and well reusability in recycling tests (the removal rate of BPA dropped by 14.0% after four successive runs). Combined with the experimental results in actual water (river water and wastewater), we demonstrated this study might provide a new insight for developing copper-loaded catalyst with high effect toward water treatment.

Peroxymonosulfate activation by bimetallic modified syderolite pellets catalyst for degradation of brominobenzonitrile

In this study, syderolite (Sd) pellets loaded with bimetallic oxides (Sd-Ni-Co) catalyst was prepared for the first time, which was used to activate peroxymonosulfate (PMS) for the degradation of Brominobenzonitrile (BMN). The effects of the Sd-Ni-Co dose, PMS dose, pH value, BMN concentration, and different anions on the degradation experiment were explored. The optimal reaction conditions for the degradation of 50 mg/L BMN were 100 g/L Sd-Ni-Co and 0.2 g/L of PMS, and the degradation was complete at room temperature within 40 min. The ten continuous cycle test shows the perfect structural stability of Sd-Ni-Co. Sd-Ni-Co/PMS system not only shows a good degradation performance on BMN but also on other organics, indicating that the method has a good universality. The radical quenching experiments (ethanol and tert-butanol) show that both •OH and SO4-·play an important role in this reaction system, and further confirmed the result by electron paramagnetic resonance (EPR) spectra. The Sd-Ni-Co was characterized by SEM, XRD, XPS, and BET. The degradation process was analyzed by triple quadrupole liquid chromatography-mass spectrometry (LC-MS), and the possible degradation pathway and mechanism were proposed.

The simple preparation of robust mesoporous N/C co-doped Cu7.2S4 for effectively removal of oxytetracycline based on activating peroxymonosulfate

In this work, the robust mesoporous N/C co-doped Cu7.2S4 (N/C-Cu7.2S4) and CuS were synthesized by simple one-step hydrothermal method for degradation of oxytetracycline (OTC). Based on the XRD, SEM, TEM, EDX as well as BET analysis, robust phase structure and dispersed active sites favorable to degradation process was proved. Systematically exploring the effect of experiment index (i.e., the dosage of peroxymonosulfate and catalyst, temperature, pH, etc.) on the degradation performance to obtain the optimal operating conditions. Degradation efficiency of 99.9 % could be achieved within 30 min, under suitable conditions. Moreover, HCO3- played a promoting role in the early stage of degradation mainly due to the CO3•- which was beneficial to the selective removal of OTC. The degradation efficiency of the material could still reach 94.8 % after three cycles. The •OH radical and 1O2 played a major role in degradation process, which was proved by radical quenching experiments and electron paramagnetic resonance (EPR). The possible degradation pathways of OTC were investigated on the basis of liquid chromatography-mass spectrometry (LC-MS). Different actual water sample tests confirmed its applicability in various filed, in which the degradation efficiency of OTC still could reach up 74.6 % in hospital wastewater. The experimental results showed that the N/C-Cu7.2S4 has outstanding performance, good stability and cyclability for the effective degradation of OTC.

MOFs-derived hollow FeCo@C as peroxymonosulfate activator for degradation of organic pollutants: Insight into the catalytic sites by experimental and theoretical study

A hollow sphere (FeCo@C) is developed and serves as a highly efficient catalyst of peroxymonosulfate (PMS) for degradation of orange G (OG) with a pseudo first-order constant of 0.119 min−1 that was 5.15 and 1.43 times of Fe@C and Co@C, respectively. X-ray photoelectron spectroscopy and Density Functional Theory (DFT) calculations demonstrated that the (110) crystal plane of FeCo alloy was the most active site for activation of PMS to generate SO4− and OH. The quenching experiments and EPR test indicated that SO4−, OH, and 1O2 were generated in FeCo@C/PMS system and acted as the predominant reactive species. The synergistic effects between Fe and Co species were responsible for the high catalytic performance of FeCo@C. The carbon in FeCo@C act as a carrier to improve the stability with good reusability over five cycles at pH 7.0 and 9.0, as well as an electron mediator and activator to enhance the catalytic performance. Effects of PMS dosage, catalyst concentration, solution pH, and humic acids on OG removal were also investigated. Furthermore, the reduced toxicity of intermediate products was verified by quantitative structure–activity relationship (QSAR). This work demonstrates a feasible strategy for designing of high-performance and stable catalysts for the organic pollutant degradation based on PMS oxidation processes.

Enhanced degradation of carbamazepine in water over SC-modified NiFe2S4 nanocomposites by peroxymonosulfate activation

In this study, novel Semi-coke-modified NiFe2S4 nanocomposites with different mass ratios are successfully prepared by hydrothermal method to activate peroxymonosulfate (PMS) for the degradation of carbamazepine (CBZ) in water. The factors affecting the degradation of CBZ, such as initial solution pH, PMS and catalyst dosage, inorganic anions, and humic acid (HA) are investigated. The possible PMS activation mechanism and CBZ possible degradation pathways are also explored. The results show that the performance of SCNF-0.5/PMS (mass ratio of SC:NiFe2S4 = 1:2) is better than that of monomeric NiFe2S4 and semi-coke (SC). X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) spectrometer, and free radical quenching experiments show that both non-radical (1O2 and Ov) and free radical pathways (SO4− and OH) may be responsible for the degradation of CBZ, but 1O2 is dominant active species. S2− promotes the Ni2+/Ni3+, Fe2+/Fe3+ cycle to ensure the stable performance of the catalyst, and the oxygen vacancies (Ov) in the SC act synergistically with the catalyst to promote the degradation of CBZ. This study may provide new insights into the degradation of antibiotics in water by modifying stable bimetallic sulfide to activate PMS.

Highly efficient removing refractory organics continuously using a Fenton-like Filter: The role of in-situ galvanic effect enhanced peroxymonosulfate activation

Peroxymonosulfate (PMS) activation by heterogeneous catalysts is a promising method for removing organic contaminants in wastewater. However, recovery and stability of the catalyst limit its practical applications. Here we demonstrate that Co incorporated chitosan and immobilized on carbon-fiber (CF) sheets (Co-N/CF) by annealing can catalytically activate PMS for efficiently degrading refractory organic pollutants, and show excellent stability and recovery within a Fenton-like filtration device. Batch tests reveal the excellent activity of the Co-N/CF and the optimized synthesis condition. Radical-quenching experiments and EPR measurements confirm that the generated singlet oxygen (1O2) is the main reactive species. Excellent continuously treating performance is obtained under various conditions, including different initial organic concentration, various organic pollutants, PMS dosage, pH, co-existing anions, and natural organic matter. For example, under the conditions of 20 mg L−1 RhB, 25 ppm PMS and a flux rate of 15 mL min−1, the reactor can maintain 100% RhB removal rate for more than 32 h while the Co leaching is much lower than the standard value. Interestingly, in the presence of electrolytes, the removal rate can keep 100% under a much higher flux rate over 450 mL min−1, which is about 16 times higher than the wastewater without electrolyte. Based on the differential concentration in the filter and the conductivity of carbon based Co-N/CF and electrolyte, an in-situ galvanic effect between the upper and lower Co-N/CF plates can be formed, which can boost the generation of reactive species, thereby significantly improving the degradation performance. Present study provided a rational strategy for PMS activation in equipment level, and also presented a new insight into the mechanism of PMS heterogeneous activation.

Promotional effect of Ca doping on Bi2Fe4O9 as peroxymonosulfate activator for gatifloxacin removal

A series of Ca-doped bismuth ferrite was prepared at various %w/w of Ca via a facile hydrothermal method to obtain Bi2XCa2(1-X)Fe4O9 (denoted as BFOCa-X, where X = 1, 0.95, 0.90, 0.80, 0.50). The BFOCa-X catalysts were characterized, and the results showed that they consist of pure phase BFO with nanosheet-like morphology. The as-prepared BFOCa-X catalysts were used as peroxymonosulfate (PMS) activator for gatifloxacin (GAT) removal. It was found that the catalytic activity decreased in the following order: BFOCa-0.8 (90.2% GAT removal efficiency in 45 min, kapp = 0.084 min−1)>BFOCa-0.95 > BFOCa-0.9 > BFOCa-0.5 > BFO indicating that BFOCa-0.8 has the optimized active sites for catalysis. The Ca dopant contributed to the increased oxygen vacancies and surface hydroxyl groups, promoting the catalytic PMS activation process. The kapp value increased gradually with increasing catalyst loading and PMS dosage while pH 9 presented the highest GAT removal rate. The GAT degradation rate was inhibited by PO43ˉ, humic acid and NH4+ but promoted in the presence of Clˉ, NO3ˉ and HCO3ˉ. It was also found that the GAT can undergo several degradation pathways in the catalytic PMS system, which eventually mineralized into innocuous compounds. The dominant reactive oxygen species (ROS) were identified using chemical scavengers, revealing that SO4•ˉ, 1O2 and •OH contributed significantly to GAT degradation. Based on the XPS study, PMS was activated by the Fe2+/Fe3+ redox cycling and oxygen vacancies to produce SO4•ˉ/•OH and 1O2, respectively. Overall, the BFOCa-0.8 also showed excellent reusability up to at least 4 cycles with low Bi and Fe leaching (<7 and 62 μg L−1, respectively), indicating that it has promising potential for application as PMS activator for antibiotics removal.