Peroxymonosulfate Activation Performance Research Articles

Catalytic degradation of oxytetracycline via FeVO4 nanorods activating PMS and the insights into the performance and mechanism

In this work, FeVO4 nanorods were successfully synthesized and employed as peroxymonosulfate (PMS) activators for oxytetracycline (OTC) degradation. The obtained FeVO4 nanorods exhibited excellent catalytic performance for PMS activation because of the synchronous transformations of Fe3+/Fe2+, V5+/V4+ and Fe3+/V4+, and abundant adsorbed oxygen (Oads). Almost 100% of OTC can be decomposed via FeVO4 activating PMS in 40 min and the reaction rate constant (k) was 0.1073 min−1, being 5.65 times of commercial Co3O4 (0.0219 min−1). Meanwhile, FeVO4 exhibited a good stability and reusability. In addition, the impacts of experimental parameters (catalysts and PMS dosage, temperature, pH, and co-existing anions) on OTC degradation were detected in detail. It was proved that •O2−, •OH and 1O2 were generated and the contribution role in OTC degradation followed the sequence” •OH >1O2 ≈ •O2−. The possible mechanism of PMS activation by FeVO4 was deeply explored and the OTC degradation pathway was deduced according to the detected degradation intermediates. This study develops one new environmental-friendly, low cost, high efficiency and stable PMS activator for the efficient removal of antibiotics.

Enhanced degradation of bisphenol A by mixed ZIF derived CoZn oxide encapsulated N-doped carbon via peroxymonosulfate activation: The importance of N doping amount

In this study, mixed metal cobalt zinc oxide embedded nitrogen enriched porous carbon composites (CoZnO-PC) were prepared via pyrolyzing polyvinylpyrrolidone (PVP) encapsulated Co, Zn-bimetal centered zeolitic imidazolate frameworks (ZIF). The prepared composites were then used to activate peroxymonosulfate (PMS) for bisphenol A (BPA) removal in water. When mole ratio of Co/Zn was 2/1, the resulted Co2Zn1O-PC possessed spinel structure with prominent degradation capability, in which the introduction of Zn accelerated the PMS activation performance of Co through establishing bimetal synergistic interactions. Both radical and non-radical activation pathways were existed in the Co2Zn1O-PC/PMS system, in which Co2Zn1O dominated the radical pathway whereas PC dominated the non-radical way. Since PVP contained abundant nitrogen atoms and could form strong coordination interactions with the ZIF precursor, the introduction of PVP in the ZIF precursor prevented pore collapsing during pyrolysis process, as well as enhancing the nitrogen content in the pyrolzed composites, which significantly promoted the generation of singlet oxygen. With combined pathways, the Co2Zn1O-PC/PMS system showed a wide pH application range with promising mineralization rate. Meanwhile, the spinel-structured Co2Zn1O-PC was magnetically separable with desirable recyclability. This study presents a novel composite with remarkable performance for the removal of refractory organic pollutants in municipal wastewater.

Photocatalytic activation of peroxymonosulfate by carbon quantum dots functionalized carbon nitride for efficient degradation of bisphenol A under visible-light irradiation

Advanced oxidation process (AOP) through the photocatalytic activation of peroxymonosulfate (PMS) has attracted much attention in wastewater treatment. Herein, a metal-free carbon quantum dots (CQDs) functioned polymer carbon nitride (PCN) was synthesized and used as an efficient photocatalyst for PMS activation toward bisphenol A (BPA) degradation under visible-light irradiation. The incorporation of CQDs in PCN endowed it with enlarged surface area, enhanced light absorption and improved charge separation, which were advantageous to photocatalytic activation of PMS. As a result, the CQDs functionalized carbon nitride exhibited an enhanced performance in photocatalytic activation of PMS toward BPA removal. The influencing factors such as catalyst dosage, PMS concentration, pH value, and anion additive on the photocatalytic performance were well examined. The catalyst exhibited a good cyclic stability. Furthermore, the reactive species and intermediates involved in BPA degradation were also investigated to elucidate the possible mineralization pathway of BPA. This work provides a facile synthetic strategy to prepare metal-free catalyst for photocatalytic activation of PMS in wastewater treatment.

ZIF‐67 Loaded on Fe3O4‐MnO2 as Efficient Peroxymonosulfate Activator for Rapid Degradation of Carbamazepine

AbstractPoor sorption capacity and low biodegradability of carbamazepine (CBZ) lead to the difficulties in CBZ removal from water. Sulfate radical‐based advanced oxidation process shows great potential for organic pollutant removal. Metal organic frameworks (MOFs) demonstrate great potential in catalytic field due to their excellent properties. Hence, cobalt‐based metal organic framework (ZIF‐67) nanoparticles are loaded on Fe3O4‐MnO2 composite, and then this composite is applied as peroxymonosulfate (PMS) activator for CBZ degradation. The prepared catalyst exhibits excellent catalytic performance because of the central metal cobalt of ZIF‐67 and the synergistic effect between MnO2 and ZIF‐67. 81% of CBZ with a high initial concentration of 20 mg L−1 is rapidly removed from water within 2.5 min. The prepared catalyst can be convenient to recycle under magnetic field while maintaining its high catalytic stability. Degradation mechanism analysis indicates that both •OH and SO4•− contribute to CBZ degradation, but SO4•− is the main radical species. XPS spectra reveal that Co(II)/Co(III), Mn(II)/Mn(III)/Mn(IV), and Fe(II)/Fe(III) are involved in PMS activation. The degradation pathway is put forward based on the detection of intermediates. This study provides a new inspiration for the fabrication of magnetic metal oxide‐MOFs catalysts with outstanding recycling performance for PMS activation.

Fe-N/C single-atom catalysts with high density of Fe-Nx sites toward peroxymonosulfate activation for high-efficient oxidation of bisphenol A: Electron-transfer mechanism

A high-efficient iron-based heterogeneous catalyst is desired to active peroxymonosulfate (PMS). Due to a large catalytic contribution of atomically dispersed Fe-Nx sites, single-atom iron–nitrogen-carbon catalysts exhibit superior performance in the catalytic activation of PMS. Herein, a sequence of Fe-N-C SACs with atomically dispersed Fe-Nx sites, FeSA-N-C and FeSA-N/C, were prepared from Fe-doped ZIF-8 and FePc@ZIF-8, respectively. Single-atom Fe-Nx sites were confirmed to be the main active sites for PMS activation. FeSA-N/C-20 with a higher density of Fe-Nx sites exhibited superior catalytic performance to N/C, FeSA-N-C, FeSA-N/C-15, and FeSA-N/C-25 for BPA degradation. Integrated with chemical quenching experiments, electron spin resonance (ESR), in-situ Raman spectra, and electrochemical analysis, a nonradical pathway was demonstrated to dominate the degradation of BPA in the PMS + FeSA-N/C-20 system. More importantly, the nature of this nonradical pathway was found to be an electron-transfer regime instead of a high-valent iron or singlet oxygenation process. The BPA was adsorbed onto the Fe-Nx site by a “donor–acceptor complex” mechanism to form a nonradical PMS* intermediate during the process. Benefiting from this mechanism, the PMS + FeSA-N/C-20 system showed wide pH adaptation and high resistance to inorganic anions.

Enhanced peroxymonosulfate decomposition into [rad]OH and 1O2 for sulfamethoxazole degradation over Se doped g-C3N4 due to induced exfoliation and N vacancies formation

The development of low-cost and facile synthesized metal-free peroxymonosulfate (PMS) activation catalysts is paramount important for the practical remediation of organic pollution caused by antibiotics. Graphitic carbon nitride (g-C3N4) as a promising alternative, to improve its PMS activation performance, we proposed an efficient method to prepare exfoliated Se doped g-C3N4 (Se-g-C3N4) with 0.095 wt% Se and more exposed reactive N vacancies through the thermal polycondensation of melamine and Se powder at 550 ℃. The results proved that 93.0% of sulfamethoxazole (SMX) can be degraded over Se-g-C3N4 with PMS in 180 min, and the corresponding degradation rate constant of 0.0149 min−1 was even 4-fold higher than that of bulk g-C3N4 (0.0039 min−1). It was found that more 1O2 was generated and OH was further identified because of the enhanced PMS self-decomposition process, especially PMS reduction via electron transfer from Se-g-C3N4. The introduction of Se atom in g-C3N4 structure not only induced the formation of nitrogen vacancies to modulate the electron distribution of g-C3N4, but also favored the exfoliation of inter-facial stacking to increase the exposure of active sites due to the large atomic radius of Se. Hence, this work offered a new strategy for improving the PMS activation performance of g-C3N4 by regulating its electron deficiency and exposing more reactive N vacancies simultaneously.

Electron transfer enhancing Fe(II)/Fe(III) cycle by sulfur and biochar in magnetic FeS@biochar to active peroxymonosulfate for 2,4-dichlorophenoxyacetic acid degradation

The synergistic mechanisms of 2,4-D degradation in the PMS activation by MFB-500. • A novel combination of biochar and FeS was used to complete pesticide degradation. • The coupled kinetic model of interface adsorption and catalysis was established. • The combination of SO 4 •- , •OH and 1 O 2 in MFB-500/PMS dominated 2,4-D degradation. • Fe(II)/Fe(III) cycle was enhanced by electron transfer from sulfur and biochar. • The optimized reaction parameters of MFB-500/PMS were determined. A highly active mediator (magnetic FeS@biochar, MFB) for peroxymonosulfate (PMS) activation was prepared by employing FeSO 4 ·7H 2 O and poplar sawdust as the precursor, for pesticides remediation in soil and groundwater. The magnetic FeS@biochar prepared at 500 °C (MFB-500) did not only showed good performance in activating PMS to degrade 2,4-dichlorophenoxyacetic acid (2,4-D), but also longer lifetime. Due to the introduction of FeS, the defect degree of MFB-500 was higher according to Raman spectra result and favored in PMS activation. The X-ray photoelectron spectroscopy (XPS) and Mössbauer spectra confirmed that sulfur species promoted the regeneration of Fe(II). Moreover, EPFRs also showed an electron shuttle to enhance the recycle of Fe(II)/Fe(III) and increased the PMS activation performance. Electron paramagnetic resonance (EPR) spectroscopy identified SO 4 •- , •OH and 1 O 2 as the reactive oxygen species (ROS) in 2,4-D degradation. The optimized reaction parameters of MFB-500/PMS were determined as [MFB-500] = 700 mg/L, [PMS] = 2.6 mM, [2,4-D] = 0.045 mM. Meanwhile, the interfacial adsorption and catalytic reaction of 2,4-D degradation by MFB-500/PMS is accurately described by a newly mixed order kinetics model with adsorption and decay dominant rate constants k α and k γ , respectively. The effect of pH 0 and coexisting anions was also studied, and it was found that acidic conditions are conducive to the degradation of 2,4-D, while alkaline conditions inhibited. Cl - , NO 3 – and SO 4 2- play a slight inhibitory effect, and HCO 3 – and H 2 PO 4 - will play a significant inhibitory effect. This work provides a promising approach to the rational design of high-performance active mediators for environmental remediation.

Oily sludge derived carbons as peroxymonosulfate activators for removing aqueous organic pollutants: Performances and the key role of carbonyl groups in electron-transfer mechanism

In this work, low-cost carbon-based materials were developed via a facile one-pot pyrolysis of oily sludge (OS) and used as catalysts to activate peroxymonosulfate (PMS) for removing aqueous recalcitrant pollutants. By adjusting the pyrolysis temperature, the optimized OS-derived carbocatalyst manifested good performance for PMS activation to abate diverse organic pollutants in water treatment. Particularly, an average removal rate of 0.87mol phenol per mol PMS per hour at a catalyst dosage of 0.2gL-1 is attained by the OS-derived carbocatalyst, higher than many other documented catalysts. A series of experimental evidences consolidated that organic pollutants were oxidized mainly via electron-transfer mechanism albeit the detection of singlet oxygen (1O2) from PMS activation driven by the OS-derived carbocatalyst. Specifically, the proportion of carbonyl groups (C˭O) in the carbocatalyst adopted with selective modification treatments to tailor the surface chemistry was found to be linearly correlated with the catalytic activity and theoretical calculations demonstrated that the reactions between C˭O and PMS to form surface reactive complexes were more energetically favorable compared to 1O2 generation. Herein, this study not only offers a new strategy for reusing OS as value-added persulfate activators but also deepens the fundamental understanding on the nonradical regime.

Copper in LaMnO3 to promote peroxymonosulfate activation by regulating the reactive oxygen species in sulfamethoxazole degradation

Perovskites with flexible texture structures and excellent catalytic properties have attracted considerable attention in peroxymonosulfate (PMS) activation for addressing organic contaminants in water. In this study, the role of copper to promote PMS activation performance of LaMnO3 was investigated. 100% sulfamethoxazole (SMX) degradation and 34% mineralization were achieved over copper doped LaMnO3 while only 60% SMX was removed without TOC removal by LaMnO3. Especially, compared with LaMnO3, the pseudo-first-order reaction rate constant was increased by 8.30 times when the atomic ratio of Cu/Mn was 1:3. It proved that only 1O2 was generated in LaMnO3 while 1O2, especially •OH and SO4•- were all detected in Cu-LaMnO3/PMS system. The characterization results showed that Cu induced the formation of LaMnO3 and La2CuO4 heterostructure with enhanced content of relatively low-valence Mn and Cu and abundant oxygen vacancies (OVs). Hence, the efficient PMS activation by Cu-LaMnO3 was due to regulating the produced reactive oxygen species (ROS). A radical dominant instead of 1O2 involved PMS activation mechanism over LaMnO3-La2CuO4 was proposed for efficient degradation of SMX. Finally, the possible degradation pathways of SMX were discussed based on HPLC-MS analysis. This study provided a new insight of improving the catalytic activity of perovskites in PMS activation in water treatment.

MOFs-derived magnetic C@Cu–Ni bimetal particles: An efficient peroxymonosulfate activator for 2,4,6-trichlorophenol degradation

In this study, magnetic Cu and Ni bimetallic particles embedded carbon sheets, namely as C@Cu–Ni, was derived via calcining a mixture of Cu-MOFs and Ni-MOFs (mass ratio = 4:6) under N2 protection and served as a catalyst for the degradation of 2,4,6-trichlorophenol (2,4,6-TCP) by peroxymonosulfate (PMS). The results showed that more than 98.5% of 2,4,6-TCP (10 mg L−1) was rapidly decomposed at initial pH = 5, PMS = 1 mM and catalyst dosage = 0.1 g L−1 within 30 min, accompanied by 42.47% removal of total organic carbon (TOC). This fully confirmed that C@Cu–Ni possessed excellent catalytic performance for PMS activation. The radical quenching experiments and electron paramagnetic resonance (EPR) investigation testified that the reactive oxygen species (ROS) included SO4•−, •OH, O2•− radicals and singlet oxygen (1O2), which were responsible for the rapid degradation of 2,4,6-TCP. Among them, O2•−and 1O2 played a decisive role. Cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) revealed that C@Cu–Ni material possessed superior electrical conductivity and electron transfer, improving its catalytic activity. What is more, C@Cu–Ni displayed excellent stability and could be consecutively used for five times without any decline of catalytic performance. The main intermediates of the 2,4,6-TCP degradation were analyzed by high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) and possible pathways of 2,4,6-TCP degradation were further proposed. The extraordinary stability and superior catalytic activity of C@Cu–Ni coupled with its easy separation from wastewater due to magnetism suggest that the newly synthesized material may offer a promising alternative approach to efficiently degrade organic pollutants by PMS.

Efficient degradation of sulfamethoxazole by CoCu LDH composite membrane activating peroxymonosulfate with decreased metal ion leaching

• Two types of membranes decorated with CoCu-LDH nanoparticles was fabricated. • LDH-based membranes exhibited excellent activity in PMS activation process. • The practical applicability of LDH@PVDF membrane was investigated. • The reactive mechanism of LDH@PVDF/PMS system was proposed. In this study, we prepared two types of composite membranes decorated with CoCu layered double hydroxide (LDH) nanoparticles, i.e. LDH@Calotropis gigantean fiber (LDH@CGF) and LDH@polyvinylidene fluoride (LDH@PVDF) for the first time. Besides, the application potential of different types of composite functional membranes based on LDH in PMS activation system was compared. Both of the LDH-based composite membranes exhibited excellent activity in peroxymonosulfate (PMS) activation process. More importantly, the composite membrane could be separated from the treated water to meet the need of practical application. The superior composite membrane was identified as LDH@PVDF, which was with excellent PMS activation capability and pretty lower metal ions leaching concentration (cobalt 0.044 mg L −1 , copper 0.026 mg L −1 ). And then, LDH@PVDF was employed to investigate the PMS activation performance in various pharmaceutical pollutants removal processes. Besides, the activity of LDH@PVDF for SMX degradation in real aquatic environment (tap water and wastewater) was detected, proving the wide practical applicability of LDH@PVDF membrane. Finally, the possible SMX degradation pathway and PMS activation mechanism occurring in LDH-based composite membrane/PMS system were proposed. Hence, this study for LDH-based membranes construction may provide new insights into the environmentally-friendly catalytic membranes preparation and practical application in wastewater treatment.

Galvanic corrosion of zero-valent iron to intensify Fe2+ generation for peroxymonosulfate activation

Zero-valent iron (ZVI) usually activates peroxymonosulfate (PMS) through the generation of Fe2+ from the self-corrosion of ZVI in a Fenton-like reaction. However, the generation rate of Fe2+ forms the reaction rate-limiting step. Against this, a microscopic Fe-graphitic carbon galvanic cell array (GCA) was created to intensify the PMS activation process. The synergistic effect between a ZVI anode and a graphitic carbon cathode accelerated the generation of Fe2+ via ZVI galvanic corrosion to significantly increase the PMS activation performance. Distinctive short-circuiting of the anode and cathode in GCA effectively enhanced the galvanic corrosion. The electrochemical behavior of GCA was characterized in detail to elucidate the PMS activation mechanism. The microscopic Fe-graphitic carbon galvanic cell array provided a promising pathway for pollutant remediation.

The enhanced P-nitrophenol degradation with Fe/Co3O4 mesoporous nanosheets via peroxymonosulfate activation and its mechanism insight

In current work, iron doping Co3O4 (Fe/Co3O4) mesoporous nanosheets with different iron ratios were successfully prepared to degrade P-nitrophenol (PNP) via peroxymonosulfate (PMS) activation. The obtained optimal 0.15Fe/Co3O4 exhibited the best PMS activation performance, almost 100% of PNP can be removed at pH = 5.5 in 60 min with negligible Co leaching. The excellent PMS activation performance of 0.15Fe/Co3O4 was mainly attributed to the enhanced electron transfer efficiency of Co2+/Co3+ and Fe2+/Fe3+ cycles and abundant oxygen vacancies, which benefiting in promoting more hydroxyl radical (•OH), sulfate radical (SO4•−), and singlet oxygen (1O2) generation. And the intimate relationship between PNP degradation efficiency and the contents of Co2+, Fe2+, Ovac in xFe/Co3O4 was obseved. Meanwhile, the mechanism for improved PMS activation efficiency was proposed based on ROSs quenching, XPS, and ESR results. In addition, the degradation pathway of PNP was explored based on the intermediates determined via the gas chromatography-mass spectrometer (GC-MS). This study can provide an effective strategy to obtain Co based catalysts with excellent PMS activation for recalcitrant pollutants degradation.

Thermal removal of partial nitrogen atoms in N-doped graphene for enhanced catalytic oxidation

Carbon materials are effective catalysts to activate peroxymonosulfate (PMS) for organic pollutant degradation. Both nitrogen doping and structural defects could enhance their catalytic performance for PMS activation. In this study, nitrogen-doped graphene (NG) is first synthesized by the calcination of graphene oxide (GO) with ammonium nitrate (NH4NO3). The obtained NG is then annealed further at a higher temperature under a N2 atmosphere to remove partially doped N atoms and create new structural defects. The obtained defective nitrogen-doped graphene (D-NG) can activate PMS for bisphenol A (BPA) degradation more effectively. Different annealing temperatures from 850 to 1150 °C are investigated, and D-NG synthesized at 1050 °C exhibits the highest activity. The enhanced catalytic performance is proposed to originate from the synergistic effect between doped N atoms and created structural defects. According to radical quenching, electron paramagnetic resonance (EPR), and electrochemical results, both radical and nonradical pathways are present during PMS activation, and the nonradical pathway plays the dominant role. This study provides a facile method for metal-free catalyst synthesis, which also enriches the synergistic mechanism between doped N and structural defects and thus should have great potential in wastewater remediation.

A novel peroxymonosulfate activation process by periclase for efficient singlet oxygen-mediated degradation of organic pollutants

In this study, a novel peroxymonosulfate (PMS) activator, periclase (MgO) was applied to the activation of PMS for the degradation of organic contaminants in aqueous solution. It was found that MgO exerts an excellent and stable catalytic performance for PMS activation to degrade a wide range of pollutants including bisphenol A (BPA), phenol, chlorophenol, and dye, with degradation efficiencies of 100%, 100%, 41%, and 59%, respectively. Results from a combination of electron spin resonance (ESR), free radical quenching, chemical probe and isotope labeling investigations confirm that singlet oxygen (1O2) was the dominant reactive species generated in the PMS/MgO system and accounted for BPA degradation. The steady-state concentration of 1O2 was 13.2 × 10−13 M. Further evidence from X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR) spectroscopy, and density functional theory (DFT) suggested that 1O2 was generated by the self-decomposition of PMS induced by surface hydroxyl groups on MgO. In addition, the degradation of BPA was hardly affected by anions and humic acid (HA) that commonly existed in the environmental matrices. The naturally occurring periclase also has high catalytic ability for PMS activation and BPA degradation. Compared with other transition metals-based radical pathways and carbonaceous materials-based non-radical pathways of PMS activation, MgO exerts a comparable catalytic performance but less potential risk and cheaper. This study developed a novel environmentally friendly catalyst with low cost and high efficiency for the selective degradation of organic pollutants in wastewater treatment.

Sludge-derived biochar as efficient persulfate activators: Sulfurization-induced electronic structure modulation and disparate nonradical mechanisms

Sulfurized biochar derived from sewage sludge (SSB) was facilely synthesized and manifested upgraded performance in activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS) for bisphenol A (BPA) elimination. The incorporated zigzag-edge sulfur effectively activated the sp2-hybridized graphene lattice, leading to the creation of more Lewis acid and basic sites in SSB. Singlet oxygen (1O2) generated from PMS oxidation at the Lewis acid sites was confirmed to be the dominated reactive species for BPA removal in the SSB/PMS system, whereas electron-transfer reactions comprising surface-confined complexes originated from the intimate contact between PDS and Lewis basic sites played the decisive role in the SSB/PDS system. Nineteen intermediates were identified in the two systems and degradation pathways of BPA were deduced accurately as well. This work not only provides a novel modification strategy for the cost-effective and environment friendly biochar-based catalysts but also deepen the insight into mechanisms of persulfate activation with carbonaceous materials.

Sulfamethoxazole degradation by visible light assisted peroxymonosulfate process based on nanohybrid manganese dioxide incorporating ferric oxide

In this study, the application potential of a nanohybrid MnO2 incorporating Fe2O3 (MF) as a peroxymonosulfate (PMS) activator was demonstrated under visible light irradiation. Due to the optical band structure of MF, electron dense regions could be formed by introducing Fe2O3 nanoparticles via photogenerated carriers migration. The PMS activation performance coupled with visible light photocatalysis was evaluated to remove various organic pollutants in water, specifically sulfamethoxazole, sulfacetamide, carbamazepine, malachite green, tartrazine, rhodamine B, and 4-chlorophenol, accordingly, 90.0 %, 91.5 %, 87.6 %, 93.1 %, 97.1 %, 100 %, and 94.8 % of degradation efficiencies were achieved. Besides, the initial pH and co-existing inorganic ions at diverse concentrations did not significantly affect the degradation efficiency. More important, the sulfamethoxazole degradation pathway and reaction mechanism of the MF/PMS/Vis system were proposed. Therefore, this work might provide new insights into the visible-light-assisted PMS activation mechanisms and is useful to construct environmentally-friendly catalytic processes for the efficient degradation of organic pollutants.

Synthetic NiO catalyst-assisted peroxymonosulfate for degradation of benzoic acid from aqueous solution.

A heterogeneous NiO catalyst was prepared by a precipitation process using nickel nitrate with oxalic acid and tested for heterogeneous oxidation of benzoic acid (BA) in the presence of peroxymonosulfate (PMS). It was found that the synthetic NiO is highly effective in heterogeneous activation of PMS to produce sulfate radicals ( ) and hydroxyl radicals (· OH), and also presents stable performance in the heterogeneous activation of PMS for BA degradation. Physicochemical properties of the NiO catalyst were characterized by several techniques, such as thermogravimetric analysis, Brunauer-Emmett-Teller, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. It was found that NiO and NiOOH were formed on the synthetic NiO catalyst and were stably distributed on the catalyst surface. Nearly 95% decomposition could be achieved in 30min at the conditions of 500ml 20μM BA solution, 0.25g catalyst, and [PMS]:[BA]=30:1. The heterogeneous reactions, the effects of PMS concentration, and catalyst dosage on the BA degradation were investigated. The heterogeneous BA degradation reactions followed first-order kinetics. Additionally, quenching experiments proved that the dominant radical in the solution was · OH. The experiments results also showed that this approach is effective for the degradation of many other pollutants (such as tetracycline hydrochloride, 2, 4-dichlorophenol, Acid orange 7, rhodamine B, and methyl red). PRACTITIONER POINTS: A novel NiO material was fabricated for degradation of benzoic acid. The synthetic NiO catalyst comprised active NiO and NiOOH. The main radical for benzoic acid removal rate was · OH. A plausible mechanism for catalyzed degradation of the benzoic acid was proposed.

Degradation of tartrazine by peroxymonosulfate through magnetic Fe2O3/Mn2O3 composites activation

In this study, Fe2O3/Mn2O3 composite was synthesized by a facile two-step technique, and several methods were carried out to characterize it. Then, the decomposition experiments of tartrazine (TTZ), a kind of refractory organic pollutant, were conducted under various environmental condition to detect the catalyst performance, such as reaction system, the dosage of catalyst, peroxymonosulfate (PMS) concentration, initial pH, different natural water substances. The results exhibited that Fe2O3/Mn2O3 composite with the mole rate 2:3 had the best PMS activation performance and the removal efficiency was 97.3% within 30 min. Besides, the optimum degradation conditions of TTZ were also discussed, that is catalyst dosage (0.6 g/L), PMS concentration (0.8 g/L) and the initial pH 11. In addition, proved by the natural water substances adding experiments, HPO42−, HCO3‒, NO3‒ and NOM (nature organic matter) could slow down the experiments progressing, but Cl‒ could boost it. Then inhibitor experiments indicated both the HO and SO4‒ played a vital role in the experiments. Reusability and ions leaching experiments as well as the used catalyst physical characterization images exhibited the excellent stability and cyclicity of the Fe2O3/Mn2O3 composite. Finally, based on the XPS (X-ray photoelectron spectroscopy) and the experiments results, the possible mechanism of TTZ degradation was proposed. This system might provide a novel thought for the decomposition of refractory organic pollutant and had potential in promotion of actual sewage treatment technology.

Enhanced peroxymonosulfate activation by supported microporous carbon for degradation of tetracycline via non-radical mechanism

Carbon-based peroxymonosulfate (PMS) activator as a promising candidate for substituting metal-based heterogeneous catalysts has drawn increasing concerns. In this study, we reported two supported microporous carbon based PMS activators after treatment by KOH and ZnCl2 (denoted as SMC-K and SMC-Z). Their catalytic activity was evaluated and compared by the degradation efficiency of a typical antibiotics of tetracycline (TC). The results indicated that SMC-K exhibited a higher PMS activation performance than SMC-Z. TC degradation data followed the pseudo-first-order kinetics with reaction rate constants of 0.0818 and 0.0392 min−1, respectively. Based on the characterization results, SMC-K had an extensive microporous structure with abundant vacancy defects and catalytic active sites, accompanied by more basic site distribution. The PMS activation mechanism was further explored via quenching tests, electron paramagnetic resonance (EPR) and electrochemical impedance spectroscopy (EIS). TC degradation occurred via a non-radical oxidation mechanism: (1) direct oxidation by activated PMS where SMC-K acted as the electron transfer shuttle, (2) oxidized by 1O2 instead of SO4− or OH generated from PMS self-decomposition. Furthermore, a reasonable degradation pathway of TC based on the non-radical oxidation has been proposed. This work benefits to develop new treatment technologies for organic pollutants removal in practical application.