Activated Peroxymonosulfate System Research Articles

Enhancement on the degradation of naproxen in Cu0 activated peroxymonosulfate system by complexing reagents

In recent years, there has been growing interest in the mechanism (radical or nonradical) of persulfate activation processes. In this study, the enhancement of naproxen (NPX) degradation in a Cu0/peroxymonosulfate (PMS) system by complexing reagents was investigated. Surprisingly, neocuproine (NCP) alters the nature of reactive species in the Cu0/PMS system. A high-valent copper species, Cu(III)-NCP, was found to dominate NPX degradation rather than radicals under acid conditions for the first time. Moreover, systematically designed experiments revealed that the Cu(III)-NCP complex was a strong selective oxidant that reacted with organics through a single electron transfer pathway. Meanwhile, the degradation efficiency of NPX was highly dependent on the solution pH and dosage of Cu0 and NCP, but was irrelevant to the concentration of NPX. Additionally, the enhancement of NCP on other copper based PMS activation systems (i.e., Cu2+/HA/PMS and Cu0/HA/PMS systems) was investigated. Considering that the released copper can be removed by a simple precipitation method to meet the effluent standards, the new complex-enhanced Cu0/PMS system provided a new method to enhance the degradation efficiencies of pollutants by a copper-catalyzed Fenton-like system.

Effect of phosphates on oxidative species generation and sulfamethoxazole degradation in a pig manure derived biochar activated peroxymonosulfate system

The peroxymonosulfate (PMS) oxidation processes have received considerable attention for water treatment. The influence of monohydrogen phosphate and dihydrogen phosphate on PMS system is still controversial. A biochar activated PMS system was constructed to investigate the HPO42−/H2PO4− effects on sulfamethoxazole degradation. Results showed that the presence of H2PO4− inhibited PMS activation, while the co-existing HPO42− played a positive role. Therefore, it might be inaccurate to assess the activation capacity of a catalyst for PMS activation when using phosphate as a buffer solution. Importantly, H2PO4− inhibited the function of CO, pyridine N and defects for PMS activation. However, HPO42− promoted CO and graphitic N sites for sulfamethoxazole (SMX) degradation. The contributions of OH and SO4− to SMX degradation decreased with the increase of H2PO4− concentration. The production of SO4− was accelerated with the increase of HPO42− concentration, promoting pollutants degradation. The contribution of 1O2 first increased and then decreased with the rise of HPO42−/H2PO4− concentration. This study elucidated the roles of H2PO4− and HPO42− in PMS system and revealed the corresponding specific influence mechanisms, promoting the application of PMS systems for antibiotic wastewater purification.

Electrochemical activation of peroxymonosulfate at Ti/La2O3-PbO2 anode to enhance the degradation of typical antibiotic wastewater

In this study, a novel electrochemically anodic activated peroxymonosulfate (PMS) system ((Ti/La2O3-PbO2)EA-PMS) was constructed by combining the Ti/La2O3-PbO2 anode with PMS. The prepared (Ti/La2O3-PbO2)EA-PMS system removed 98.07% of cefadroxil (CFR), which was 17.85% higher than that of the single electrochemical (EC) system and 78.10 % higher than that of the PMS system. In addition, the (Ti/La2O3-PbO2)EA-PMS system showed the satisfactory applicability to the single and mixed wastewater of CFR, tetracycline (TC), and levofloxacin (LFX) with the degradation rate greater than ~95%, the stability and degradation performance was much better than the conventional PMS activation systems. The excellent degradation performance was partially attributed to the excellent physico-chemical and electrochemical performances of Ti/La2O3-PbO2 anode, such as the rougher and compact surface, faster mass and electron transfer performance, the higher proportion of the adsorbed hydroxyl oxygen (Oads) for the production of reactive oxygen species (ROS) and a higher oxygen evolution overpotential to inhibit the occurrence of the electrolysis of water. In addition, the collaboration of Ti/La2O3-PbO2 anode and PMS activation produced a synergistic effect on the degradation of antibiotics, which mainly reflected at the direct-electron-transfer controlled non-free radical oxidation occurred on the surface of Ti/La2O3-PbO2 anode and the free radical oxidation dominated by adsorbed OH (PbO2(OH)), free hydroxyl radical (OH) and sulfate radical (SO4−). Moreover, the effects of operating parameters (PMS concentration, current density and initial pH value) and water background components on the removal of CFR by (Ti/La2O3-PbO2)EA-PMS system were investigated. The possible degradation pathways of CFR were also speculated. The electrochemically anodic activated PMS system based on Ti/La2O3-PbO2 anode was expected to provide an efficient technology for the treatment of actual pharmaceutical wastewater and this work also provided a significant reference for the design of novel advanced oxidation process combined with PMS (AOP-PMS) systems.

Kinetics and mechanisms of diniconazole degradation by α-MnO2 activated peroxymonosulfate

As one of the high-efficiency triazole fungicides, diniconazole (DIN) has been used on a large scale in agricultural production. Due to its high stability and toxicity, DIN is usually persisted in soil and water and has been demonstrated to be a potential threat to environment and humans. In this study, the degradation kinetics, mechanisms, and degradation products of DIN by peroxymonosulfate (PMS) activated with α-MnO2 were systematically studied. The results showed that DIN was rapidly degraded in α-MnO2 activated PMS system, and the degradation kinetics of DIN in this reaction system could be described by the pseudo-first-order kinetic model. The degradation of DIN was affected by environmental conditions. Acidic condition was beneficial to the degradation of DIN, whereas co-existing anions (HPO42-, Cl- and HCO3–) and humic acid inhibited the degradation of DIN in MnO2 activated PMS system. SO4- and HO generating from PMS activated by α-MnO2 were confirmed as the major active species in degradation of DIN. The potential sites attacked in the DIN structure might be 11Cl, 10Cl, 14C and 17C based on the DFT calculation. Moreover, the degradation pathways of DIN were proposed, including hydroxylation, hydroxyl addition, cleavage of 14C-15N and intramolecular cyclization.

Degradation of 1,4-dioxane by biochar activating peroxymonosulfate under continuous flow conditions

1,4-Dioxane degradation under both batch-scale and column experiments has been investigated within the biochar activated peroxymonosulfate (PMS) system for in-situ remediation of 1,4-dioxane contaminated groundwater. In case of the batch experiments, the 1,4-dioxane degradation efficiencies were significantly increased with the increased biochar pyrolysis temperatures. The optimized 1,4-dioxane degradation efficiency at 89.2% was achieved with 1.0 g L−1 of biochar (E800) and 8.0 mM PMS. In the absence of PMS, the breakthrough rates of 1,4-dioxane in biochar packed column experiments under the dynamic flow conditions were relatively slow compared with those in sand packed columns. Simultaneously, based on the integrated areas (IA) from the 1,4-dioxane breakthrough curves, the degradation efficiency at 70.2% was estimated in biochar packed column (WE800:WSand = 1:9) under continuous injections of 16.0 mM PMS. Electron paramagnetic resonance (EPR) indicated that hydroxyl, sulfate and superoxide radicals were generated within the biochar/PMS systems and alcohol quenching experiments suggested that the dominated hydroxyl and sulfate radicals were responsible for 1,4-dioxane degradation. The findings of this study suggested that the biochar activated PMS system is a promising and cost-effective strategy for the remediation of 1,4-dioxane contaminated groundwater.

Gravity-driven layered double hydroxide nanosheet membrane activated peroxymonosulfate system for micropollutant degradation

For the first time in this study, CoAl-layered double hydroxide nanosheet membrane (LDHm) with abundant active sites was fabricated for peroxymonosulfate (PMS) activation with the mindset to catalytically degrade micropollutants. Depending on the catalyst loading, the developed LDHm can be driven under gravity at a permeate flux of approximately 80 L/m2 h and 210 L/m2 h at LDH loading of 0.80 mg/cm2 and 0.08 mg/cm2, respectively. Notably, the LDHm (0.63 mg) exhibited excellent PMS activation efficiency as indicated by 87.8% removal of the probe chemical (ranitidine) at 0.2 mM PMS, which was higher than that (37–44%) achieved by conventional LDH (5–20 mg)/PMS (0.2 mM) system. In addition to efficient degradation of several micropollutants, LDHm/PMS performance was not inhibited by variation in solution pH (4−8) as well as during long-term (29 h) continuous-flow operation. SO4•− and 1O2 were identified as the primary reactive species in the LDHm/PMS system, while both Co and Al participated in PMS activation. This study offers a simple strategy for efficient removal of several micropollutants with significantly reduced catalyst leaching, which could be applied sustainably in water treatment.

Insights into the multiple roles of Ca2+ ion in peroxymonosulfate activation over Mn2O3 for organic pollutants degradation

The development of efficient and eco-friendly catalysts for peroxymonosulfate (PMS) activation is highly desired for pollutants removal in wastewater. Recently calcium ion (Ca2+) has been recognized to promote the catalytic performance of Mn oxides by enhancing the oxidizing power of PMS. However, the impact of pollutants types and influence of solution pH on the catalyst-oxidant interaction towards Ca2+ promotion have not been considered until now. This study investigated the effect of Ca2+ for pollutant degradation by Mn2O3 activated PMS system, with various factors considered in detail such as the dose of Ca2+, pKa of organic pollutants, and solution pH. To deepen the understanding of the formation of Mn2O3/PMS complex in the presence of Ca2+, XPS, ATR-FTIR, radical scavenging, EPR, as well as PMS decomposition experiments, were analyzed. The binding of Ca2+ on the surface of Mn2O3 efficiently promoted PMS decomposition and accelerated the redox cycles of Mn(III)/Mn(IV) with a faster rate for the production of HO• and 1O2. Ca2+ also enriched the pollutants with negative charges around the catalyst to speed up the degradation process. This work points out a novel thought on the improvement of the PMS activation system with nonreducible metal ions.

Efficient activation of peroxymonosulfate on CuS@MIL-101(Fe) spheres featured with abundant sulfur vacancies for coumarin degradation: Performance and mechanisms

For improving the catalytic activity and recyclability of CuS in Fenton-like reaction processes, novel sulfur vacancies-enriched CuS@MIL-101(Fe) was constructed, characterized, and examined as heterogeneous catalysts for activating peroxymonosulfate (PMS) to degrade coumarin (COU). Thanks to the redox pairs of Fe3+/Fe2+, Cu+/Cu2+, S2−/S22−/S0/sulfate species, copper-iron synergistic effect and sulfur vacancies, the CuS@MIL-101(Fe) realized a complete removal of COU (30 μM) in 10 min with reaction rate constant of 0.577 min−1, which was 11.1 and 17.0 times of CuS and MIL-101(Fe), respectively. The effect of various experimental conditions (i.e., initial pH, CuS@MIL-101(Fe) dosage, PMS concentration, and background anions) on COU degradation was discussed, and the stability and versatility of CuS@MIL-101(Fe) was studied as well. Radical scavenging experiments and electron paramagnetic resonance (EPR) spectroscopy identified •OH and 1O2 as the main reactive oxygen species (ROS). Finally, the possible mechanism of higher COU degradation efficiency in the CuS@MIL-101(Fe) activated PMS system and the degradation pathways were also deeply explored. Consequently, this work provided a novel insight into construction of sulfur vacancies-enriched heterogeneous catalysts for efficiently activating PMS for refractory organic pollutants elimination.

Fe@C activated peroxymonosulfate system for effectively degrading emerging contaminants: Analysis of the formation and activation mechanism of Fe coordinately unsaturated metal sites

Carbon-encapsulated Fe nanocomposites (Fe@C), obtained by pyrolysis of metal-organic frameworks (MOFs), can activate peroxymonosulfate (PMS) to remove emerging contaminants (ECs). Unfortunately, the current MOFs-derived catalysts always inevitably produce more iron-oxide compounds that unfavorable for PMS activation. In this work, according to the thermogravimetric curve of Fe(II)-MOF-74, to discuss the role of pyrolysis temperature on the structural characteristics of Fe@C. The results demonstrated that Fe@C-4 could obtain abundant coordinately unsaturated metal sites and exhibited the best activation performance. Radical-quenching experiments and EPR measurements confirm that the generated sulfate radical (SO4−˙) and singlet oxygen (1O2) only degraded approximately 35% of TBBPA. Meanwhile, negatively charged complex intermediates formed by the weak interaction between Fe@C-4 and PMS was proposed as the dominant reactive species, and approximately 65% of TBBPA was degraded. This work optimizes the synthesis strategy and mechanism of Fe@C and provides a methodological reference for the design of Fe-based catalysts.

Study on the Transformation of I− in Fe2+ Activated PMS System

In order to solve the problem of more and more iodinated by-products in water, the advanced oxidation system of peroxymonosulfate (PMS) activated by ferrous (Fe2+) was used to study the transformation process and principle of iodine ion (I−) as the initial target under different influencing factors in this system. The results showed that when the pH value was 3, the molar concentration ratio of Fe2+ and PMS was 0.8:1, the conversion effect was the best. When the concentration of I− was 20 μmol/L, the conversion rate of I− was 94 %. Under the action of sulfate radical (SO4 −), the final conversion product of I− is only iodate (IO3 −). With the increase of pH value, the conversion effect will also decrease. The concentration of I− itself also affects the reaction.

Degradation of acetaminophen by activated peroxymonosulfate using Co(OH)2 hollow microsphere supported titanate nanotubes: Insights into sulfate radical production pathway through CoOH+ activation

Pharmaceuticals and personal care products (PPCPs) are of great concern due to their increasing health effects, so advanced treatment technologies for PPCPs removal are urgently needed. In this study, titanate nanotubes decorated Co(OH)2 hollow microsphere (CoM/TNTs) composites were synthesized by a two-step solvothermal method, and used to activate peroxymonosulfate (PMS) through heterogenous catalysis for acetaminophen (ACE) degradation in water. The optimum material (CoM/TNTs0.5) activated PMS system exhibited high ACE removal efficiency and quick kinetic, as 93.0% ACE was degraded even within 10 min. The two components in CoM/TNTs showed a synergetic effect on PMS activation for radicals production: Co(OH)+ from CoM was the primary active species to active PMS, while TNTs could offer abundant –OH groups for Co(OH)+ formation. Density functional theory (DFT) calculation further interpreted the mechanism of Co(OH)+ for PMS activation by means of reaction potential energy surface (PES) analysis. Both the scavenger quenching tests and electron paramagnetic resonance analysis revealed that the sulfate radical (SO4-·) played a dominant role in ACE degradation. Moreover, DFT calculation also suggested that the ACE atoms with high Fukui index (f-) represented the active sites for electrophilic attack by SO4-·. The toxicity analysis based on quantitative structure-activity relationship (QSAR) verified the reduced toxicity of transformation products. Furthermore, CoM/TNTs also had good reusability and stability over five cycles. This work provides deep insights into the reaction mechanisms of radical production and organics attack in cobalt-based PMS activation system.

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

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

Reactive oxygen species generation in FeOCl nanosheets activated peroxymonosulfate system: Radicals and non-radical pathways

Iron oxychloride (FeOCl) is utilized as a activator of peroxymonosulfate (PMS) for the degradation of paracetamol (APAP) and phenacetin (PNCT) in response to the water pollution by persistent pharmaceuticals. The degradation process was well fitted with a pseudo-first order kinetic pattern, and the excellent catalytic performance towards APAP (100 % removal) and PNCT (86.5 % removal) was obtained in the presence of 0.2 g/L FeOCl and 2.0 mM PMS at pH 7.0 in 30 min. In-situ electron spin resonance (ESR) and scavenging tests revealed the generation of a series of ROS (·OH, SO4−, O2−, 1O2), which was highly dependent on pH. Besides, the non-radical pathways process involved 1O2 was dominant in APAP oxidation, while both ·OH and 1O2 are significant in PNCT removal. Furthermore, the formation of disinfection by-products (DBPs) during post-chlorination showed neglectable increment at neutral and alkaline condition with FeOCl/PMS pre-oxidation, and the calculated cytotoxicity would experience a continuous deterioration with pH increase. These results displayed high efficiency of FeOCl/PMS system in micropollutants degradation and a relatively comprehensive activation process of PMS, which may promote practical application in environmental remediation.

Kinetic mechanism of ozone activated peroxymonosulfate system for enhanced removal of anti-inflammatory drugs

Peroxymonosulfate (PMS) was employed as an activator of ozone (O3) to degrade non-steroidal anti-inflammatory drugs (NSAIDs) (aspirin (ASA) and phenacetin (PNT)) in study. The combination of PMS in O3 system promoted the O3 decomposition and NSAIDs removal significantly. O3 molecule, hydroxyl radical (OH) and sulfate radical (SO4−) were responsible for the removal of target pollutants in O3/PMS system. The second-rate constants between O3, OH and SO4− with ASA were determined to be 7.32, 4.18 × 109 and 3.46 × 108 M−1·s−1, and 37.3, 4.99 × 109 and 5.64 × 108 M−1·s−1 for PNT, respectively. The pattern of pollutant removal and contributions of oxidative species were fitted by experiments and two models. Nevertheless, the wide variety of two models suggested that a comprehensive model for O3/PMS based on a first-principles approach was not yet possible, due to the number of radicals and subsequent chain reaction, such as SO5− or O3−. In addition, the formation of five typical CX3R -type disinfection by products was evaluated from post‑chlorine tests and theoretically calculation by frontier electron density calculation. The calculated toxicity of typical CX3R -type DBPs was found to decrease with the increase of pH. The results of this study provide a basis for exploring the mechanism of pollutant degradation in O3 system.

Photoelectrocatalytic degradation of endocrine-disruptor bisphenol – A with significantly activated peroxymonosulfate by Co-BiVO4 photoanode

Bisphenol A (BPA) is known as an endocrine-disrupting chemical, generally present in the environment. It has a harmful effect on aquatic lives and human health, therefore it is needful to exploit highly efficient innovative treatment methods for its removal. Herein, we report a Co-BiVO4 photoanode to activate peroxymonosulfate (PMS) for the complete removal of BPA via a photoelectrochemical (PEC) process. The Co-BiVO4 could degrade 99.16% of BPA in the presence of 2 mM PMS within 60 min, whereas the degradation rate constant is 0.08034 min−1, which was 20.86 times higher than the electrocatalytic (EC) and 5.35 times higher than the photocatalytic (PC) process. Notably, Co-BiVO4 showed significant activity toward PMS activation and BPA degradation as compared to other synthesized photocatalysts. Their photoelectrocatalytic performance followed the sequence Co-BiVO4 > Fe-BiVO4 > Ni-BiVO4 > pure-BiVO4 > without catalysts. Several influencing factors on the decomposition process, such as the effect of PMS concentration, applied potential, illumination time, initial pH, BPA concentration, Co loading, and co-existing anions were studied in detail. Radical scavenging experiment and transient absorption result showed that sulfate radicals (SO4•─) were the dominant reactive species. Moreover, a significant synergistic effect was noticed in Co-BiVO4/PEC/PMS system for BPA degradation. Degradation mechanism and reaction intermediates were studied by in-situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) and liquid chromatography-mass spectroscopy (LC-MS) presenting the enhanced bond cleavage in PEC activated PMS system. The BPA showed 92.47% and 87.27% removal in tap and river water samples after 60 min of reaction using Co-BiVO4/PMS PEC system. Our finding proposed an efficient method for wastewater treatment in an eco-friendly way.

Catalytic degradation of organic pollutants in Fe(III)/peroxymonosulfate (PMS) system: performance, influencing factors, and pathway.

This study demonstrated, for the first time, Fe(III)/peroximonosulphate (PMS) could be an efficient advanced oxidation process (AOP) for wastewater treatment. Bisphenol A (BPA) was chosen as a model pollutant in the present study. Fe(III)-activated PMS system proved very effective to eliminate 92.18% of BPA (20 mg/L) for 30-min reaction time at 0.50 mM PMS, 1.5 g/L Fe(III), pH 7.0. The maximum degradation of BPA occurred at neutral pH, while it was suppressed at both strongly acidic and alkaline conditions. Organic and inorganic ions can interfere with system efficiency either positively or negatively, so their interaction was thoroughly investigated. Furthermore, the presence of organic acids also affected BPA degradation rate, especially the addition of 10 mM citric acid decreased the degradation rate from 92.18 to 66.08%. Radical scavenging experiments showed that SO4•- was the dominant reactive species in Fe(III)/PMS system. A total of 5 BPA intermediates were found by using LC/MS. A possible degradation pathway was proposed which underwent through bridge cleavage and hydroxylation processes. Acute toxicity of the BPA degradation products was assessed using Escherichia coli growth inhibition test. These findings proved to be promising and economical to deal with wastewater using iron mineral for the elimination of organic pollutants. Graphical abstract.

Hydroxylamine enhanced degradation of naproxen in Cu2+ activated peroxymonosulfate system at acidic condition: Efficiency, mechanisms and pathway

Peroxymonosulfate (PMS) activated by Cu+ has been regarded as an effective activation method to generate sulfate radical and hydroxyl radical, however, this process is limited for the poor reduction of Cu2+ to Cu+ by PMS. In this study, hydroxylamine (HAm) was introduced to improve the oxidation capacity of Cu2+/PMS process, meanwhile the degradation efficiency of naproxen (NPX) in Cu2+/HAm/PMS system was investigated for the first time. It was found that HAm could accelerate the redox cycle of Cu2+/Cu+, leading to an enhancement on NPX degradation. The NPX degradation efficiency in Cu2+/HAm/PMS system was 10 times and 2 times of that in Cu2+/PMS and HAm/PMS in 5 min at pH 4.0. The analysis of steady-state concentration of Cu species showed that HAm could enhance the transformation of Cu2+ to Cu+, leading to an improvement on NPX degradation in Cu2+/HAm/PMS system. Both sulfate radical and hydroxyl radical were identified as the dominant reactive species by indirect and direct methods, and PMS activation was attributed to the formation of Cu+ proved by neocuproine experiments. Eight degradation products of NPX were identified by LC-MS/MS, and four oxidation pathways were proposed. This study gives a preliminary interpretation on the enhancement of NPX degradation in Cu2+/HAm/PMS system under the acidic condition, and broadens the scope of HAm enhanced Cu-catalyzed PMS system for the treatment of organic contaminants.

Iron-doped ordered mesoporous Co3O4 activation of peroxymonosulfate for ciprofloxacin degradation: Performance, mechanism and degradation pathway

Ordered mesoporous Co3O4 (OM-Co3O4) displayed superior performance for peroxymonosulfate (PMS) activation. While, the separation and recovery of the catalyst after catalytic oxidation needed tedious operation. In this study, the as-synthesized iron-doped OM-Co3O4 not only inherited the merits of ordered mesoporous materials such as high surface area and abundant mesoporous structure, but endowed them with ferromagnetism, facilitating their separation from the solution. Compared with spinel Co3O4, iron-doped OM-Co3O4 showed superior catalytic activity, wide application scope, excellent reusability and long-term stability, fully validated that iron-doped OM-Co3O4 can be a promising heterogeneous PMS activator for environmental application. High catalyst loading and PMS concentration were both beneficial to CIP degradation. The best CIP degradation occurred under base conditions. Chlorine and bicarbonate presented completely opposite two-side effects. The mechanism of CIP degradation was primarily attributed to SO4− and OH to a lesser extent. The rapid redox cycles of M2+/M3+ (M = Co, Fe) and O2−/O2 ensured the continuous generation of reactive oxygen species and the efficient degradation of CIP. The cleavage of piperazine ring, hydroxylation and defluorination were identified as the main oxidation pathways for CIP degradation in iron-doped OM-Co3O4 activated PMS system.

Degradation of carbamazepine by radiation-induced activation of peroxymonosulfate

In this study, the radiation-induced activation of peroxymonosulfate (PMS) was investigated for the degradation of carbamazepine (CBZ), and compared with single PMS system, single radiation system and Fe(II)-activated PMS system. The results showed that gamma radiation can effectively activate PMS, and the presence of PMS could decrease the absorbed dose required to completely degrade CBZ. Moreover, the removal efficiency of TOC was 38.3% in the gamma radiation-induced activation of PMS system, which was higher than that in the single PMS system, single radiation system and the Fe(II)-activated PMS system. Hydroxyl radicals played major role in the degradation of CBZ. However, the contribution of hydroxyl radicals for the CBZ degradation decreased as the absorbed dose increased from 100 Gy to 800 Gy. In addition, the sulfate radical and persulfate formed during the radiation/PMS process also contributed to CBZ degradation. The maximum decomposition efficiency was found with the molar ratio of PMS to CBZ of 20:1 at adsorbed dose of 300 Gy. Furthermore, the intermediate products were identified, and the degradation pathway of CBZ was tentatively proposed. In summary, the gamma radiation-induced activation of PMS system could be a promising technology for the removal of recalcitrant organic pollutants.

Degradation of Orange II in ferrous activated peroxymonosulfate system: Efficiency, situ EPR spin trapping and degradation pathway study

Abstract The degradation of Orange II (Org II) by ferrous activated peroxymonosulfate (PMS) was inspected. The maximum degradation efficiency of 62.3% in 90 min occurred at 0.286 mM [PMS]0, corresponding to 1:1 molar ratio of Fe2+: PMS. Results show that poor recovery of Fe2+ accounts for poor degradation in the slow stage. The species of reactive radicals were determined through indirect way by quenching agents, as well as directly by in situ EPR spin trapping tests. Results indicated that hydroxyl radicals instead of sulfate radicals were responsible for Org II degradation. The removal of Org II degradation would increase to 93.3% in 90 min as reaction temperature increased to 60 °C. The activation energy for PMS and Fe2+/PMS alone was calculated to be 77.2 kJ/mol and 34.7 kJ/mol, respectively. The removal efficiency of total organic carbon (TOC) was 11.0% and 43.8% when [Fe2+]0:[PMS]0:[Org II]0 was 5:5:1 and 34:34:1, respectively. The main degradation products of Org II in system were supposed to be heterocyclic compounds containing a five-atom ring. Results demonstrated that Fe2+/PMS technology is promising technology for water pollution.