Methyl Phenyl Sulfoxide Research Articles

Revealing the Generation of High-Valent Cobalt Species and Chlorine Dioxide in the Co3O4-Activated Chlorite Process: Insight into the Proton Enhancement Effect.

A Co3O4-activated chlorite (Co3O4/chlorite) process was developed to enable the simultaneous generation of high-valent cobalt species [Co(IV)] and ClO2 for efficient oxidation of organic contaminants. The formation of Co(IV) in the Co3O4/chlorite process was demonstrated through phenylmethyl sulfoxide (PMSO) probe and 18O-isotope-labeling tests. Both experiments and theoretical calculations revealed that chlorite activation involved oxygen atom transfer (OAT) during Co(IV) formation and proton-coupled electron transfer (PCET) in the Co(IV)-mediated ClO2 generation. Protons not only promoted the generation of Co(IV) and ClO2 by lowering the energy barrier but also strengthened the resistance of the Co3O4/chlorite process to coexisting anions, which we termed a proton enhancement effect. Although both Co(IV) and ClO2 exhibited direct oxidation of contaminants, their contributions varied with pH changes. When pH increased from 3 to 5, the deprotonation of contaminants facilitated the electrophilic attack of ClO2, while as pH increased from 5 to 8, Co(IV) gradually became the main contributor to contaminant degradation owing to its higher stability than ClO2. Moreover, ClO2- was transformed into nontoxic Cl- rather than ClO3- after the reaction, thus greatly reducing possible environmental risks. This work described a Co(IV)-involved chlorite activation process for efficient removal of organic contaminants, and a proton enhancement mechanism was revealed.

Cooperative photocatalysis of dye-Ti-MCM-41 with trimethylamine for selective aerobic oxidation of sulfides illuminated by blue light.

Ti-incorporated mesoporous materials have widespread applications in photocatalysis. Their adjustable pores could accommodate dyes like alizarin red S (ARS) to circumvent the lack of visible light response. Herein, Ti-MCM-41 was obtained to anchor visible light-capturing ARS, forming ARS-Ti-MCM-41. The ARS-Ti-MCM-41 was screened for the selective photocatalytic oxidation of organic sulfides. To improve the stability of the anchored ARS, electron transfer was orchestrated by a mediator trimethylamine (TMA, 2mol%) illuminated by blue LEDs. Phenyl methyl sulfide could be almost entirely converted into phenyl methyl sulfoxide with 99% of selectivity within 18min. In addition, Ti-MCM-41 was beneficial for the anchored ARS, which in turn guaranteed good recycling performance of ARS-Ti-MCM-41. The solvent trifluoroethanol enabled the stability of TMA and facilitated the highly selective formation of the target sulfoxides. This work sheds light on the vast possibility for visible light photocatalysis of dye-mesoporous materials.

Roles of MnO2 Colloids and Mn(III) during the Oxidation of Organic Contaminants by Permanganate.

Although intermediate manganese species can be generated during the reactions of permanganate (Mn(VII)) with organic pollutants in water, the role of the in situ generated MnO2 colloids in the Mn(VII) oxidation process remained controversial and the contribution of Mn(III) was largely neglected. This study showed that the apparent second-order rate constants (kapp) of Mn(VII) oxidation of methyl phenyl sulfoxide and carbamazepine remained constant with time. However, the degradation of four selected phenolic contaminants by Mn(VII) exhibited an autoaccelerating trend and a linear trend at pH 3.0-6.0 and pH 7.0-9.0, respectively. Multiple lines of evidence revealed that the occurrence of the autoaccelerating trend in the Mn(VII) oxidation process was ascribed to the oxidation of the phenolic organics by MnO2 colloids. The influence of pyrophosphate on the oxidation of different organic contaminants by MnO2 colloids suggests that Mn(III) was also responsible for the autoaccelerating oxidation of organic contaminants by Mn(VII) under specific reaction conditions. The kinetic models revealed that the overall contributions of MnO2 colloids and Mn(III) ranged within 6.6-67.9% during the autoaccelerating oxidation of phenolic contaminants by Mn(VII). These findings advance the understanding of the roles of MnO2 colloids and Mn(III) in the Mn(VII) oxidation process.

Insight into mechanism of peroxydisulfate activation by natural pyrite: Participation of Fe(IV) and regulation of Fe(III)/Fe(II) cycle by sulfur species

In this study, natural pyrite (NP) was used to activate peroxydisulfate (PDS) for imidacloprid (IMD) degradation. NP was characterized by X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Effects of key reaction parameters (NP dosage, PDS concentration and initial pH) and co-existing ions on IMD degradation in the NP/PDS system were investigated. Quenching experiments and electron spin resonance (ESR) tests identified the existence of sulfate radical (SO4•−), hydroxyl radical (•OH), singlet oxygen (1O2) and superoxide radical (O2•−). The cumulative concentration of SO4•− and •OH were quantified by the formation of benzoquinone (BQ) and p-hydroxybenzoic acid (HBA), respectively. Meanwhile, more than 60% of methylphenyl sulfoxide (PMSO) was selectively converted to methylphenyl sulfone (PMSO2), revealing that Fe(IV) was dominant in the NP/PDS system. The order of contribution of the three reactive species in the NP/PDS system was Fe(IV) > •OH > SO4•− (contributions of 1O2 and O2•− were negligible). Fe(II) released from NP played a crucial role in PDS activation, and sulfur species in NP could also boost Fe(III)/Fe(II) cycle and contribute to the generation of reactive species. Further, the possible degradation pathways of IMD have been proposed based on the detected intermediates using high-performance liquid chromatography-mass spectrometry (HPLC-MS), and the toxicity (including acute toxicity, developmental toxicity and mutagenicity) of these intermediates have been predicted using Toxicity Estimation Software Tool (T.E.S.T). Moreover, NP/PDS system was applied in four natural water bodies and IMD degradation efficiency reached more than 97% after adjusting the pH to 3. The fluorescence excitation–emission matrix (EEM) spectra showed that in addition to IMD, NP/PDS system could also remove other impurities.

Photoelectrochemical oxidation of methyl phenyl sulfide with oxygen atom transfer way on Mo-BiVO4 photoanode

Photoelectrochemical oxidation of methyl phenyl sulfide with water as the only oxygen source on Mo-BiVO 4 photoanode. Mo-BiVO 4 photoelectrode performs oxygen transfer reaction in PEC oxidation of MPS. • Mo-BiVO 4 photoelectrode was applied to oxidation of methyl phenyl sulfide. • PEC oxygen atom transfer (OAT) reaction was achieved on Mo-BiVO 4 photoelectrode. • Isotopic labelling experiment with H 2 18 O revealed oxygen atoms in MPSO were mainly from water. Photoelectrochemical (PEC) selective oxidation is an environment-friendly strategy to obtain value-added chemicals. Herein, we report the PEC oxidation of methyl phenyl sulfide (MPS) into methyl phenyl sulfoxide (MPSO) with 85.7% selectivity and 36.2% conversion on molybdenum doped bismuth vanadate (Mo-BiVO 4 ) photoelectrode under simulated sunlight illumination (AM 1.5 G, 100 mW cm -2 ). Isotopic labelling experiment with H 2 18 O was conducted to clearly reveal that the oxygen atoms in the MPSO were mainly from water. Based on these results, the application of Mo-BiVO 4 has been extended to PEC selective oxidation.

Activation of peroxymonosulfate by sulfonated cobalt (II) phthalocyanine for the degradation of organic pollutants: The role of high-valent cobalt-oxo species

Sulfate radicals (SO4•−) are typically regarded to be the dominant active species in the cobalt-activated peroxymonosulfate (PMS) processes. In this study, a water-soluble sulfonated cobalt (II) phthalocyanine (CoPcS) was applied as a molecular catalyst to activate PMS and break down organic contaminants. The CoPcS/PMS system was shown to be dominated by high-valent cobalt-oxo species (Co(IV)) rather than the conventional SO4•− and hydroxyl radical (•OH) based on methyl phenyl sulfoxide (PMSO) chemical probe, radical quenching experiments, and electron paramagnetic resonance (EPR). The nonradical oxidation process was found to be predominant in acid conditions (pH 3–5), whereas the radical oxidation pathway co-occurred in neutral or alkaline medium conditions (pH 7–8). Organic contaminants with low ionization potential (IP) can be effectively and selectively removed by the CoPcS/PMS system. More notably, the removal of organic pollutants in the CoPcS/PMS system was not significantly impacted by the ubiquitous inorganic anions (such as SO42−, HCO3−, H2PO4− and HPO42−) or dissolved organic matter (e.g., humic acid). The promoting effect for the removal of levofloxacin was observed under the high concentration of HPO42- conditions. The CoPcS/PMS system demonstrated resistance to the environmental matrix and maintained its oxidation capacity at the practical aqueous substrates (tap water and secondary effluent).

Combination of peroxymonosulfate and Fe(Ⅵ) for enhanced degradation of sulfamethoxazole: The overlooked roles of high-valent iron species

Sulphate radicals (SO4−) has been widely considered as the predominant active species for pollutants degradation by the combination of ferrate (Fe(VI)) and peroxymonosulfate (PMS). However, this study for the first time revealed the important roles of high-valent iron species in the degradation of sulfamethoxazole (SMX) by Fe(VI)/PMS system. The competitive oxidation kinetics results indicated that when the molar ratio of PMS/Fe(VI) was 1:1 at neutral pH, the contributions of high-valent iron species and free radicals to SMX degradation were 49.3% and 50.7%, respectively. By comparing the Fe(VI)/PMS and Fe(VI) systems, it was found that PMS could promote the production of high-valent iron species. Density functional theory calculations showed that SMX was more susceptible to electrophilic attack initiated by high-valent iron species rather than free radicals. Because of their different oxidative reactivities toward different organic contaminants, the high-valent iron species and free radicals contributed differently to abating different organic contaminants. Significantly, using methyl phenyl sulfoxide (PMSO) as a probe of high-valent iron species indicated that the dominant ROS changed from high-valent iron species to free radicals with an increase in the PMS/Fe(Ⅵ) molar ratio at pH 7.0. The results of this work may facilitate the process regulation and application of Fe(VI)/PMS systems in water/wastewater treatment.

KuQuinone as a Highly Stable and Reusable Organic Photocatalyst in Selective Oxidation of Thioethers to Sulfoxides.

A chemoselective photocatalytic system to perform thioether oxidation to sulfoxide is presented. The light-induced oxidation process is here promoted by a metal-free quinoid catalyst, namely 1-hexylKuQuinone (KuQ). Reactions performed in a fluorinated solvent (i.e., HFIP), using O2 as the oxidant, at room temperature, lead to complete thioanisole conversion to methyl phenyl sulfoxide in 60 min. Remarkably, the system can be recharged and recycled without a loss of activity and selectivity, reaching turnover numbers (TONs) higher than 4000. Excellent catalytic performances and full selectivity have also been obtained for the photocatalytic oxidation of substituted thioanisole derivatives, aliphatic, cyclic, and diaryl thioethers. Likewise, the oxidation of heteroaromatic organosulfur compounds can be accomplished, with longer reaction times.

Nephrotoxicity of gasoline fumes in male albino rat: a mechanism-based approach study

Nephrotoxicity of gasoline fumes has been documented, but the mechanisms underlying the toxicity remain vague. This study determined the residue of gasoline components in the kidney of 72 male albino rats with a view to providing the basis for a detailed understanding of the nephrotoxicity of gasoline fumes. The rats were randomized into 6 groups and daily exposed to distilled water (control) or gasoline fumes for 1, 3, 5, 7 and 9 h for 10 weeks. Some standard clinical blood biochemistry, activities of some kidney antioxidant and membrane-bound ATPase enzymes and kidney histological changes were examined. Gasoline hydrocarbons were extracted, identified and quantified in the kidney of rats with Gas Chromatography-Mass Spectrometry (GC-MS). Significant (p < 0.05) changes were observed in the biochemical parameters examined in the blood and kidney of the exposed rats compared to the control. Residues of some gasoline metabolites including 2,3-diphenylcyclopropyl) methyl phenyl sulfoxide; Cyclotrisiloxane and 2.2-Paracyclophane were identified in the kidney of rats exposed to gasoline fumes. The kidney of the exposed rats also displayed mild histological changes. Retention of some hydrocarbons in the kidney of rats exposed to gasoline fumes could potentially result in oxidative stress capable of inducing renal dysfunction. Key policy highlights Continuous exposure to gasoline fumes for varying hours over a period of time may result in the retention of some gasoline hydrocarbons and metabolites in the kidney of the exposed animal. Presence of gasoline hydrocarbons and metabolites in the kidney may induce a high production of reactive oxygen species and consequently lead to oxidative damage to the organ. Metabolic process of gasoline hydrocarbons in the kidney of the exposed animal varies with the hours of exposure.

Two pseudo-polymorphic porous POM-pillared MOFs for sulfide-sulfoxide transformation: Efficient synergistic effects of POM precursors, metal sites and microstructures

Developing sustainable and powerful heterogeneous catalytic systems to convert sulfides into high-value sulfoxide products has become a particularly appealing field and an arduous challenge. In this work, two porous polyoxometalate-pillared metal-organic frameworks, formulated as H3n[Cu3(pidc)2(H2O)2.5]2[PW12O40]n·xH2O (n = 1.5, x = 6 for 1, n = 1, x = 12 for 2; and H3pidc = 2-(3-pyridinyl)-1H-imidazole-4,5-dicarboxylic acid), were consciously manufacture and employed for heterogeneously catalyzed sulfide-sulfoxide transformation. Structural analysis shows that 1 and 2 exhibit similar porous frameworks with nearly identical two-dimensional metal-organic layers further pillared by tetradentate POM ligands with different coordination modes, which also result in the porosity of 1 being almost twice that of 2. In catalyzing the conversion of methyl phenyl sulfide (MPS) to methyl phenyl sulfoxide (MPSO), 1 can convert nearly 100% of MPS into MPSO within 30 min, while 2 achieved the similar results requires 50 min. The higher activity of 1 may be attributed to its larger channel that can provide more active sites and more efficient mass transfer process. Systematic structure-activity analyses and mechanistic studies revealed dual-reaction pathways driven by POM sites and metal sites assisted by the structural microenvironment.

Simultaneous oxidation of trace organic contaminant and Mn(II) by Mn(VII): Accelerating role of dissolved oxygen

Permanganate (Mn(VII)) is a widely used oxidant in water treatment, which can oxidize trace organic contaminants (TrOCs) and Mn(II). Interestingly, this study found that presence of Mn(II) could accelerate the abatement of bisphenol A by Mn(VII) only under oxic condition. Herein, the effects of Mn(II) and dissolved oxygen (DO) on the abatement of TrOCs by Mn(VII) oxidation and the related mechanism were investigated. Results indicate that DO was involved in the Mn(VII)/Mn(II) reaction, with the reaction stoichiometry of Δ[Mn(VII)]:Δ[Mn(II)] determined to be 1:2 and 1:1.5 in the presence and absence of DO, respectively. Quenching and electron paramagnetic resonance tests verified that both superoxide radicals (O2•−) and reactive Mn species contributed to the accelerated abatement of TrOCs (bisphenol A, methyl phenyl sulfoxide, and methyl phenyl sulfone) in the Mn(VII)/Mn(II) process. Specifically, O2•− was produced through the one-electron reduction of DO and made an important contribution (32.4%–100%) to the abatement of selected TrOCs. This study reveals that Mn(II) could enhance TrOC abatement by Mn(VII) oxidation, and DO played a pivotal role in the Mn(VII)/Mn(II) process.

Insight into a strategy to improve charge carrier migration in lead-free bismuth-based halide perovskite for efficient selective oxidation of thioanisole under visible light

Lead-free halide perovskites have attracted a lot of attention as a new type of photoelectric conversion material in various solar energy-related applications involving photocatalysis. However, the perovskite photocatalysts still face the problem of insufficient performance arising mainly from the weak charge carrier migration currently. Exploring the strategies to promote the carrier separation efficiency maintains an urgent need. Different from the previous surface modification and construction of heterojunction, herein, we report a new lead-free perovskite solid solution of Cs3(BixSb1−x)2Br9 with tunable band gap prepared via a facile and efficient co-precipitation method. The introduction of Sb atoms in Cs3Bi2Br9 has obviously broadened the absorption of visible light, and making it to be a prominent visible-light photocatalyst for the selective oxidation of thioanisole to methyl phenyl sulfoxide in n-hexane. The single-particle PL study proves that the obtained CBSB (Cs3(BixSb1−x)2Br9) solid solution has a longer carrier lifetime than Cs3Bi2Br9 (CBB). In-situ ESR spectra demonstrate that O2− plays an important role during the oxidization process. The CBSB also has a superb stability, showing no apparent decrease in the catalytic activity in a five-cycle experiment. We believe our work can provide new understanding in promoting carrier lifetime of the lead-free perovskite materials, present a new approach for selective photo-oxidation, and may shed light on other solar energy conversion areas related to halide perovskites.

Expeditious degradation of SMX by high-valent cobalt-oxo species derived from cobalt-doped C3N5-activated peroxymonosulfate with the assistance of visible light

With excellent photoelectric properties and catalytic stability, carbon nitride and its derivatives are drawing increasing interest in persulfate activation for treating emerging pollutants in wastewater. In the present work, the synthesized cobalt-doped C3N5 (C3N5-Co) has well-defined surface properties and excellent performance in SMX degradation by activating peroxymonosulfate (PMS) with the assistance of visible light, and the removal rate can reach 99.57 % within 20 min. Moreover, the system shows superior operability over a wide pH range with promising catalytic stability and environmental suitability. Quenching experiments and EPR spectroscopic indicated that high-valent cobalt oxide (Co(IV)) species, SO4•-, •OH, O2•-, and 1O2 work in C3N5-Co0.59/PMS/SMX-vis combined system. The conversion of the oxidation product phenyl methyl sulfoxide (PMSO2) > 98 % using phenyl methyl sulfoxide (PMSO) as a probe agent demonstrated that high-valent cobalt oxide (Co(IV)) species as the major active species dominated the degradation process of SMX. The Co(II) species on the surface of C3N5-Co0.59 worked as a direct driver to rapidly and efficiently activate the PMS, producing various active species involved in the degradation process, while the photo-carriers generated by visible radiation act as another contributing force to regenerate Co(II) species and activate PMS. This study presented the heterogeneous C3N5-Co0.59/PMS/SMX-vis system is an effective strategy for the degradation of emerging pollutants and provides a promising novel ideal for the treatment of various organic pollutants in wastewater.

An efficient Fe2+ assisted UV/electrogenerated-chlorine process for carbamazepine degradation: The role of Fe(IV)

To improve the performance and solve the restrictions of UV/chlorine process (e.g., the narrow pH application range and high disinfection by-products (DBPs) formation), a Fe2+ assisted advanced oxidation process with electrochemically generated chlorine (UV/E-Cl/Fe2+) was proposed for carbamazepine (CBZ) degradation, which eliminated CBZ (5 mg/L) within 4 min under the optimal conditions. Compared with UV/electro-generated chlorine (UV/E-Cl) and anodic oxidation-chlorination/Fe2+ (AO-Cl/Fe2+) processes, the apparent first-order kinetics constant in UV/E-Cl/Fe2+ increased by 2.56 and 3.18 times respectively, and the energy consumption was lower (1.15 kWh/m3-log). Simultaneously, the pH application range could be expanded to 9, and DBPs formed in this process were 17.1% less than those in UV/E-Cl. Through quenching tests, electron paramagnetic resonance (EPR) experiments, measurement of •OH concentration, quantification of methyl phenyl sulfoxide (PMSO) and benzosulfone (PMSO2) and processes comparison, possible CBZ degradation pathways and mechanism of UV/E-Cl/Fe2+ were proposed, in which Fe(IV) played the dominant role in the early stage, while the production of radicals (i.e., •OH and Cl•) was enhanced with the increase of chlorine generation, accelerating the CBZ removal. Furthermore, this process demonstrated wide application prospect in treating various contaminants and real wastewaters. In conclusion, this study offers an effective and energy-efficient method for organic pollutants degradation.

Nano- and micro-scale zerovalent iron-activated peroxydisulfate for methyl phenyl sulfoxide probe transformation in aerobic water: Quantifying the relative roles of SO4·−, Fe(IV), and ·OH

Multiple reactive intermediates have been proposed to be involved in peroxydisulfate (PDS) activation by zerovalent iron (ZVI), including sulfate radical (SO4·−) produced via iron-oxide shell mediated electron transfer, ferryl ion species (Fe(IV)) formed from Fe(II)-PDS interaction, and hydroxyl radical (·OH) generated by ZVI aerobic oxygenation. In this study, evolution of the relative role of these intermediates in microscale and nanoscale ZVI (mZVI vs. nZVI) activated PDS processes is comparatively investigated by using a methyl phenyl sulfoxide (PMSO) probe that selectively reacts with Fe(IV) to produce methyl phenyl sulfone (PMSO2). Interestingly, during PMSO transformation by mZVI/PDS process, yields of PMSO2 (η(PMSO2)) exhibit three-stage behavior that they first increase to a maximum (∼80% but lower than 100%) (Stage I) and then plateau for a period (Stage II) followed by a decrease phase (Stage III). Accordingly, the relative role of Fe(IV) in PMSO transformation is unceasingly improved in Stage I and subsequently reaches equilibrium with that of free radicals in Stage II, while it finally decreases in Stage III. Similar η(PMSO2) evolution trends are obtained in nZVI/PDS process, except that the η(PMSO2) increase in Stage I is negligible, possibly due to the exceptional fast nZVI dissolution. It was further clarified by tert-butyl alcohol scavenging assay that, in addition to Fe(IV), the free radical involved in Stages I and II is SO4·−, while ·OH was dominant in Stage III. Moreover, studies on O2 effect reveal that ZVI aerobic oxygenation participates in mZVI corrosion during the entire process, while it is only involved in nZVI corrosion when PDS content is reduced to a low concentration, indicating that the reactivities of PDS and O2 are similar in mZVI corrosion, but differ greatly in nZVI corrosion. Additionally, effects of reactant dose and pH on η(PMSO2) evolution are also explored. Dynamics of the relative role of different reactive oxidants should be taken into account in further applications of ZVI/PDS in situ chemical remediation technology considering their different chemistries.

L-cysteine boosted Fe(III)-activated peracetic acid system for sulfamethoxazole degradation: Role of L-cysteine and mechanism

Sulfamethoxazole (SMX), a widely used and frequently detected antibiotics, may pose threat to water safety and environmental sustainability. In this study, L-cysteine (L-Cys) was used to boost the Fe(III)/peracetic acid (PAA) system for SMX degradation. After the addition of L-Cys, the degradation efficiency of Fe(III)/PAA system for SMX increased from 26.2% to 96.7%. Appropriate increase in initial concentration of Fe(III), L-Cys or PAA promoted the SMX degradation. The role of L-Cys, including the promotion of Fe(III)/Fe(II) cycle and the improvement of pH suitability by complexation, in boosted SMX degradation was proposed. Results of methyl phenyl sulfoxide probe assays, electron paramagnetic resonance tests and quenching experiments showed that FeIVO2+ as well as HO play major roles while carbon-centered radicals hardly contribute in SMX degradation. Degradation intermediates identified by LC/MS showed that SMX was degraded to less toxic small molecules through SN bond breaking, SC bond breakage, self-coupling and hydroxylation. Besides, L-Cys/Fe(III)/PAA system showed ideal tolerance to Cl– and humic acid, while HCO3– significantly inhibited the SMX degradation. Further, the satisfactory degradations of SMX were obtained in three real waters. This study provides a feasible strategy for enhancing the oxidation capacity of the Fe(III)/PAA system and an effective technique for the treatment of SMX in real waters.

Methyl phenyl sulfoxide (PMSO) as a quenching agent for high-valent metal-oxo species in peroxymonosulfate based processes should be reconsidered

Nowadays, the possible appearance of high-valent metal-oxo species (like Co(IV)) in transition metals activated peroxymonosulfate (PMS) processes was explored by sulfoxides type quenching agent (e.g. methyl phenyl sulfoxide (PMSO)), as corresponding sulfones (e.g. methyl phenyl sulfone (PMSO2)) would be selectively produced by the attack of high-valent metal-oxo species on PMSO. However, the confirmed reactive oxygen species like hydroxyl radical (•OH), sulfate radical (SO4•−), single oxygen (1O2) or superoxide (O2•−) in PMS based processes shows highly aggressive and non-selective characteristics towards organic compounds. We therefore designed this work to examine whether PMSO conversion to PMSO2 would be interfered by those reactive oxygen species. By the comparison of PMSO degradation and PMSO2 formation in heat/PMS and Co2+/PMS systems, we found PMSO was easily converted to PMSO2 without Co2+. Scavenging experiments demonstrated that 1O2 or O2•− directly resulted in PMSO to PMSO2 while •OH and SO4•− also made contributions as they helped generate 1O2 and O2•−. Four common products of PMSO were found in heat/PMS and Co2+/PMS systems and more hydroxylated products were formed in the latter. Theoretical calculations further proved that 1O2 played a leading role in the conversion of PMSO to PMSO2. All these results indicated that in PMS based processes, PMSO was not an appropriate quenching agent for high-valent metal-oxo species like Co(IV). This work hoped to deepen the understanding of the formation and transformation mechanisms of reactive species in PMS based processes.

Peroxymonosulfate oxidation via paralleled nonradical pathways over iron and nitrogen doped porous carbons.

Hierarchically porous iron/nitrogen-doped carbons (Fe-N-PC) were developed for the oxidation of ibuprofen (IBP) with peroxymonosulfate (PMS). The incorporation of trace-level iron and nitrogen dopants promoted the catalytic performance remarkably, leading to 4.8, 16.4 and 22.9-fold enhancement over N-doped carbon (N-PC), porous carbon (PC), and Fe-doped carbon (Fe-PC), respectively. Fe(III) was anchored in nitrogen-coordinated pots (Fe-Nx) in the sp2-hybridized carbon network, and graphitic-N could synergistically boost the catalysis. Notably, methyl phenyl sulfoxide (PMSO) transformation, quenching tests, in situ electrochemical analysis and Raman spectroscopy verified high-valent iron-oxo species and direct electron transfer pathway accounted for pollutant oxidation. The relationship between the kinetic constants (lnkobs) and the oxidation peak potential (Eop) of pollutants was established with good correlation, manifesting particular selectivity toward oxidizing electron-rich pollutants and great immunity to background inorganic ions and natural organic matters (NOMs) for real wastewater treatment. The deactivation mechanisms of Fe-N-PC were revealed via surface oxidation and dopant refabrication. This work delicates to deepen the understanding of the nonradical mechanisms and structure-oriented PMS activation by engineered carbonaceous materials.

Peracetic Acid Enhances Micropollutant Degradation by Ferrate(VI) through Promotion of Electron Transfer Efficiency.

Ferrate(VI) and peracetic acid (PAA) are two oxidants of growing importance in water treatment. Recently, our group found that simultaneous application of ferrate(VI) and PAA led to much faster degradation of micropollutants compared to that by a single oxidant, and this paper systematically evaluated the underlying mechanisms. First, we used benzoic acid and methyl phenyl sulfoxide as probe compounds and concluded that Fe(IV)/Fe(V) was the main reactive species, while organic radicals [CH3C(O)O•/CH3C(O)OO•] had negligible contribution. Second, we removed the coexistent hydrogen peroxide (H2O2) in PAA stock solution with free chlorine and, to our surprise, found the second-order reaction rate constant between ferrate(VI) and PAA to be only about 1.44 ± 0.12 M-1s-1 while that of H2O2 was as high as (2.01 ± 0.12) × 101 M-1s-1 at pH 9.0. Finally, further experiments on ferrate(VI)-bisulfite and ferrate(VI)-2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic)acid systems confirmed that PAA was not an activator for ferrate(VI). Rather, PAA could enhance the oxidation capacity of Fe(IV)/Fe(V), making their oxidation outcompete self-decay. This study, for the first time, reveals the ability of PAA to promote electron transfer efficiency between high-valent metals and organic contaminants and confirms the benefits of co-application of ferrate(VI) and PAA for alkaline wastewater treatment.

A benzimidazole‐linked porphyrin covalent organic polymers as efficient heterogeneous catalyst/photocatalyst

Porphyrins are selected as building units to synthesize porphyrin‐based covalent organic polymers (COPs), which can combine the excellent properties of covalent organic polymers with the fantastic catalytic effect of porphyrin to obtain a heterogeneous catalyst with excellent catalytic activity. In this work, the novel benzimidazole‐linked porphyrin COPs MPp‐BTA (M = 2H, Zn, Co) were synthesized using a new porphyrin with aldehyde group peripherally MPp (M = 2H, Zn, Co) and 1,2,4,5‐tetraminobenzene tetrahydrochloride (BTA) as monomers. The synthesized MPp‐BTA were carefully characterized by FT‐IR, UV–vis, SEM, TEM, TG, and PXRD. As heterogeneous catalyst, MPp‐BTA (M = Zn, Co) shows the high catalytic activity and stability for cycloaddition of CO2 with phenyl glycidyl ether (PGE) under mild conditions (80°C, 0.1 MPa CO2), and the yield of cyclocarbonate can reach 95% and 92% respectively. In addition, the recycling stability of ZnPp‐BTA was investigated, and the yield of cyclocarbonate was still remained at 86% after five cycles. Furthermore, MPp‐BTA (M = 2H, Zn, Co) can be used directly as heterogeneous photocatalysts for selective oxidation of thioanisole to methyl phenyl sulfoxide. To our delight, H2Pp‐BTA shows satisfactory photocatalytic performance, and the yield of methyl phenyl sulfoxide can reach 93% in 4 h.