Baeyer-Villiger oxidation of cyclic ketones utilizing potassium peroxydisulfate(K_2S_2O_8) or sodium perborate(NaBO_3) in acidic media

The efficient, green, facile, mild and straightforward conversion procedure for the oxidation of cyclic ketones to lactones at room temperature utilizing potassium peroxydisulfate （K2S2O8） in acidic media is satisfactory to high yields without using traditional chlorinated solvents is reported. This oxidative reagent is cheap and friendly environmental procedure for industrial purposes than use of organic peracids.

Degradation of bisphenol A using electrochemical assistant Fe(II)-activated peroxydisulfate process

Degradation of bisphenol A（BPA） in aqueous solution using sulfate radicals was investigated using the Fe（II）-activated peroxydisulfate（PDS） process, electrochemical process, electrochemical process with 2.5 mmol/L Na2S2O8 without Fe（II）, and electrochemical assistant Fe（II）-activated PDS process. It was found that the electrochemical assistant Fe（II）-activated PDS process performed best in the degradation of BPA.The variables considered to influence the degradation efficiency of BPA were the initial concentration of Fe2 t, the initial concentration of Na2S2O8, and the current density. More than 97% of the BPA removals were achieved within 120 min under the optimum operational condition.The degradation of BPA was accompanied by the formation of phenol, hydroquinone, and small-molecule compounds such as succinic acid. The electron transfer was the principal step in the oxidation of BPA.

Insights into the electron transfer mechanisms of peroxydisulfate activation by modified metal-free acetylene black for degradation of sulfisoxazole

Herein,a modified metal-free acetylene black(MMF-AB)catalyst was synthesized by a simple solvothermal-calcination method and designed successfully to activate peroxodisulfate(PDS)for the degradation of sulfisoxazole(SIZ).Due to the doping of N,S and O metal-free elements,the modified catalyst showed excellent catalytic performance with 100%SIZ removal within 30 min.Pseudo first-order reaction rate constants(evaluating catalytic efficiencies and activity)of MMF-AB(kobs=0.105 min^(−1))was 3 times higher than pure-AB(k_(obs)=0.029 min^(−1)).Interestingly,it was demonstrated that the reaction sys-tem is based on the transfer of electrons from SIZ to PDS to realize an electron-transfer-based mechanism by the evidence of premixing,electron paramagnetic resonance(EPR)spectroscopy,salt-bridge experi-ments and electrochemical analyses.The introduction of recyclable filtration device solved the secondary pollution caused by the dispersion of the powdered catalyst in the treated water,which further proved the practicality and superiority of the MMF-AB catalyst.

Synergistic effects of peroxydisulfate on UV/O_(3) process for tetracycline degradation:Mechanism and pathways

Tetracycline(TC)as a typical emerging pollutant is becoming a serious threat to the environment and human health.A combined advanced oxidation technology of UV/Ozone(O_(3))/peroxydisulfate(PDS)process was developed to explore an efficient and economic treatment process of TC in wastewater.Furthermore,the reactive sites and transformation pathways of TC were explored and the toxicity of the intermediates was quantified with a quantitative structure-activity relationship(QSAR)assessment.The degradation performance of TC was substantially enhanced in UV/O_(3)/PDS process with a kobsof 0.0949 min-1,which was 2.3 times higher than UV/O_(3)and 3.2 times than sole UV.The results demonstrated that there was a superior synergistic effect of PDS on UV/O_(3)processes for the degradation of TC.Electron paramagnetic resonance(EPR)analysis and quenching experiments show that·OH,SO_(4)·-,O_(2)·-and1O_(2)all contributed to TC degradation in the UV/O_(3)/PDS process and exhibited a synergistic effect,which inhibited the generation of harmful products.In addition,the UV/O_(3)/PDS system can effectively degrade TC in a wide range of substrate concentrations and pH,and also showed excellent adaptability to various concentrations of anions(Cl-and HCO_(3)-).This study proves the feasibility of UV/O_(3)/PDS process for treating TC contaminated wastewater with complicated water matrix.

Effective peroxydisulfate activation by CQDs-MnFe_(2)O_(4)@ZIF-8 catalyst for complementary degradation of bisphenol A by free radicals and non-radical pathways

The present study reported fabrication of novel carbon quantum dots-MnFe_(2)O_(4)@ZIF-8(CQDs-MFO@ZIF-8)by using co-precipitation hydrothermal method for activation of peroxydisulfate(PDS)to degrade bisphenol A(BPA),one of important emerging organic pollutants in water environment.CQDs-MFO@ZIF-8 served as a highly efficient thermal activated PDS catalyst with high catalytic degradation efficiency,reusability and stability.The catalyst achieved almost completely removal of 20.0 mg/L BPA within 5.0 min,and the degradation efficiency remained higher than 83%after 5 consecutive cycles.Free radicals(^(·)OH,SO_(4)^(·-)and^(·)O_(2)^(-))and non-free radicals((1)O_(2))were generated in the thermal PDS-activation system,in which singlet oxygen((1)O_(2))played a dominant role in the degradation of BPA.The potential toxicity of BPA degradation intermediates was analyzed upon the culture of E.coli and Chlorella sorokiniana by using Ecological Structure-Activity Relationship Model(ECOSAR)program.The catalytic performances of BPA degradation by CQDs-MFO@ZIF-8 were evaluated for treatment of different practical water samples to further verify the feasibility of practical applications.This study provides proof-in-concept demonstration of new nanomaterials for enhanced catalytic water decontamination.

ZnS-embedded porous carbon for peroxydisulfate activation:Enhanced electron transfer for bisphenol A degradation

Transition metal sulfides have garnered increasing attention for their role in persulfate activation,a crucial process in environmental remediation.However,the function of metal sulfides without reversible valence changes,such as ZnS,remains largely unexplored in this context.Here we report ZnS-embedded porous carbon(ZnS-C),synthesized through the pyrolysis of Zn-MOF-74 and dibenzyl disulfide.ZnS-C demonstrates remarkable activity in activating peroxydisulfate(PDS)across a wide pH range,enabling the efficient mineralization removal of bisphenol A(BPA).Through electrochemical investigation and theoretical simulations of charge density distributions,we unveil that the electron transfer from BPA to PDS mediated by the ZnS-C catalyst governs the reaction.This study,both in theory and experiment,demonstrates metal sulfide as electron pump that enhances electron transfer efficiency in PDS activation.These findings redefine the role of metal sulfide catalysts,shedding new light on their potential for regulating reaction pathways in PDS activation processes.

Efficient piezocatalytic activation of peroxydisulfate over Bi_(2)Fe_(4)O_(9):thickness-dependent synergy effect between peroxydisulfate activation and piezocatalysis

Piezocatalytic activation of persulfate(PS) has great application potential in environmental remediation;however,the relationship between piezocatalyst thickness and catalytic activity is not clear,limiting the further improvement of catalytic activity and application of the technology.Herein,the Bi_(2)Fe_(4)O_(9)(BFO) piezocatalysts with tunable thickness were prepared through a facile hydrothermal method by tuning the molar ratio of Bi(NO_(3)),5H_(2)O and FeCl_(3)·6H_(2)O for piezocatalytic activation of peroxydisulfate(PDS).The BFO with the smallest thickness exhibits excellent catalytic activity,and the SO_(4)^(·-)and ·OH are the major reactive oxygen species for degrading organic pollutants.Further XPS investigations and finite element analyses demonstrate that the decreased thickness of BFO not only exposes more Fe^(2+)sites for PDS activation,but also improve the piezoelectric effect to accelerate the regeneration of Fe^(2+),thus enabling an enhanced synergy effect between PDS activation and piezocatalysis for outstanding catalytic activity.This work provides an understanding of the relationship between thickness of piezocatalysts and its catalytic activity over PDS activation,facilitating the development of more efficient piezocatalysts and PS-based advanced oxidation processes.

Natural siderite derivatives activated peroxydisulfate toward oxidation of organic contaminant: A green soil remediation strategy

Natural siderite(FeCO_(3)),simulated synthetic siderite and nZVI/FeCO_(3) composite were used as green and easily available iron-based catalysts in peroxydisulfate activation for remediating 2-chlorophenol as the target contaminant and this technique can effectively degrade organic pollutants in the soil.The key reaction parameters such as catalysts dosage,oxidant concentration and pH,were investigated to evaluate the catalytic performance of different materials in catalytic systems.The buffering property of natural soil conduced satisfactory degradation performance in a wide pH range(3-10).Both the main non-radical of ^(1)O_(2) and free radicals of SO_(4)^(-) and OH·were evidenced by quenching experiment and electron paramagnetic resonance.The reduction of nZVI on FFC surface not only has the advantage for electronic transfer to promote the circulation of Fe(Ⅲ)to Fe(Ⅱ),but also can directly dechlorinate.Furthermore,the intermediates were comprehensively analyzed by GC-MS and a potential removal mechanism of three oxidant system for 2-CP soil degradation was obtained.Briefly,this research provides a new perspective for organic contaminate soil treatment using natural siderite or simulated synthetic siderite as efficient and environmental catalytic material.

A green strategy for porous biochar fabrication with superior capacity for peroxydisulfate activation to degrade sulfadiazine:the cooperative role of C-sp^(3) and specific surface area

Metal-free porous biochars are popularly utilized as catalysts for peroxydisulfate(PDS)activation.The enhancement effect of PDS activation of porous biochars fabricated by employing both hard template and alkali metal activating agent has not been explored completely.In addition,the role of the inherent carbon defect in PDS activation has not been clearly elucidated.Hence,a series of carbonaceous catalysts were fabricated using a sole template(KCl),a sole activating agent(Na_(2)S_(2)O_(3))or a combination of template and activating agent(KCl/Na_(2)S_(2)O_(3),KCl/KHCO_(3),KCl/NaHCO_(3),and KCl/Na_(2)C_(2)O_(4)),to systematically investigate the effect of specific surface area(SSA)and intrinsic defect of porous biochar on its PDS activation ability.The biochar synthesized by KCl and Na_(2)S_(2)O_(3)(SK-C)exhibited the optimum degradation performance.The SK-C was found to possess an interconnected hollow cage with three-dimensional mesh structure showing the largest surface area,pore volume and C-sp^(3) edge defect content among all the catalysts,which explained its paramount catalytic ability.The SSA and C-sp^(3) content together can determine the catalytic performance in a quantitative relationship.The single electron transfer pathway from SDZ to inner-sphere bound SK-C/PDS*was the protagonist of pollutant oxidation.The degradation intermediates were detected and recognized and their toxicities were evaluated.This study for the first time comprehensively identified the synergistic effect between the SSA and inherent defects on improving the catalytic performance of biochar for PDS activation to removal contaminants.

Application of heat-activated peroxydisulfate process for the chemical cleaning of fouled ultrafiltration membranes

Na Cl O has been widely used to restore membrane flux in practical membrane cleaning processes,which would induce the formation of toxic halogenated byproducts.In this study,we proposed a novel heatactivated peroxydisulfate(heat/PDS)process to clean the membrane fouling derived from humic acid(HA).The results show that the combination of heat and PDS can achieve almost 100%recovery of permeate flux after soaking the HA-fouled membrane in 1 mmol/L PDS solution at 50℃ for 2 h,which is attributed to the changes of HA structure and enhanced detachment of foulants from membranes.The properties of different treated membranes are characterized by scanning electron microscopy(SEM),atomic force microscope(AFM),attenuated total reflection Fourier transform infrared spectroscopy(ATRFTIR),and X-ray photoelectron spectroscopy(XPS),demonstrating that the reversible and irreversible foulants could be effectively removed by heat/PDS cleaning.The filtration process and fouling mechanism of the cleaned membrane were close to that of the virgin membrane,illustrating the good reusability of the cleaned membrane.Additionally,heat/PDS which can avoid the generation of halogenated byproducts shows comparable performance to Na Cl O on membrane cleaning and high performance for the removal of fouling caused by sodium alginate(SA),HA-bovine serum albumin(BSA)-SA mixture and algae,further suggesting that heat/PDS would be a potential alternative for membrane cleaning in practical application.

Improving sludge dewaterability via Fe^(2+) chelated citrate activated peroxydisulfate oxidation

Citrate (Ct) was chosen as a typical chelator used in the Fe^(2+)-peroxydisulfate (PDS) process to improve sludge dewaterability.The PDS-Fe^(2+)-Ct process exhibited better performance in sludge dewatering than PDS-Fe^(2+).Specifically,with a PDS dosage of 1.2 mmol/g VS,the molar ratio of PDS/Fe^(2+)and Ct/Fe^(2+)were 4:5 and 1:4,respectively,the capillary suction time decreased from 155.8 to 24.8sec,and the sludge cake water content decreased from 82.62%to 64.11%(-0.06MPa).The oxidation led to a reduced negative charge and a decrease in particle size.The enhanced sludge dewaterability and changes of sludge properties were attributed to the decomposition of extracellular polymeric substances,and it was explored by protein,polysaccharide,3D-EEMs,and FT-IR.Additionally,the quenching experiments of radical species demonstrated that SO_(4)-·played a more important role than·OH,and its productivity was improved with the addition of Ct.Moreover,the reasons for the improved productivity of radicals with the addition of Ct were discussed.The results of this study could serve as a basis for improving sludge dewatering using the PDS-Fe^(2+)-Ct process and suggest that the addition of Ct may improve the productivity of SO_(4)-·in the activation o PDS via Fe^(2+).

Modification strategies on 2D Ni-Fe MOF-based catalysts in peroxydisulfate activation for efficient organic pollutant removal

This study reports several modification strategies to optimize and enhance the performance of twodimensional(2D) metal organic frameworks(MOFs)-derived catalysts in peroxydisulfate(PDS) activation.The raw 2D Ni-MOF and 2D Ni-Fe-MOF without modification show poor catalytic activities for PDS activation and high metal ion leaching. The carbonization of 2D MOF can increase the activity of the catalyst but cannot solve the metal leaching problem. The further acid treatment of carbonization products can further improve the catalytic activity and decrease the metal ion leaching. The in-situ growth of2D MOF on graphene oxide(GO) support with subsequent carbonization and acid treatment offers the best performance in PDS activation for organic pollutant removal with low metal ion leaching. Compared with other PDS systems, the Ni-Fe-C-acid/GO system displays much lower catalyst and PDS dosages for p-chloroaniline degradation. This study presents new insights in the modification strategies of 2D MOFbased catalysts in PDS activation.

Topological defects strengthened nonradical oxidation performance of biochar catalyzed peroxydisulfate system

Nonradical oxidation based on peroxydisulfate(PDS)activation has attracted increasing attention for selective degradation of organic pollutants.Herein,topological defects were introduced into biochar(BC)via removing N atoms in N-doped BC(NBC)in an attempt to improve the nonradical catalytic performance.Compared to the pristine BC and NBC,the introduction of topological defects could achieve up to 36.6-and 8.7-times catalytic activity enhancement,respectively.More importantly,it was found that the catalytic activity was dominated by topological defects,which was verified by the significant positive correlation between the pseudo-first-order rate constants and the content of topological defects.Theoretical calculations suggested that topological defects enhanced the electrondonating ability of BC by reducing the energy gap,which made the electrons transfer to PDS molecules more easily.As a result,holes were generated after the carbon defects lost electrons,and induced a nonradical oxidation process.Benefiting from the merits of nonradical oxidation,the developed BC/PDS system showed superior performance in removing electron-rich contaminants in the presence of inorganic anions and in the actual environments.This study not only provides a potential avenue for designing efficient biochar-based catalysts,but also advances the mechanism understanding of nonradical oxidation process induced by carbon defects.

Involvements of chloride ion in decolorization of Acid Orange 7 by activated peroxydisulfate or peroxymonosulfate oxidation

The effects of chloride anion （Cl-） （up to 1.0 mol/L） on the decolorization of a model compound,azo dye Acid Orange 7 （AO7）,by sulfate radical （SO4-） based-peroxydisulfate （PS） or peroxymonosulfate （PMS） oxidation under various activated conditions （UV 254 nm /PS,Thermal （70°C/PS,UV 254 nm /PMS,Co 2＋ /PMS） were investigated.Methanol and NH4 ＋ were used as quenching reagents to determine the contributions of active chlorine species （dichloride radical （Cl2-.） and hypochlorous acid （HClO））.The results indicated that the effects of Cl- on the reaction mechanism were different under various activated conditions.For UV/PS and Thermal/PS,the inhibition tendency became more clear as the Cl- concentration increased,probably due to the reaction between Cl- and SO4-.and the generation of Cl2-.or HClO.For UV/PMS,Cl- did not exhibit inhibition when the concentration was below 0.1 mol/L.As Cl- concentration reached to 1.0 mol/L,the decolorization rate of AO7 was,however,accelerated,possibly because PMS directly reacts with Cl- to form HClO.For Co2＋ /PMS,Cl- exhibited a significant inhibiting effect even at low concentration （ 0.01 mol/L）.When Cl- concentration exceeded 0.1 mol/L,the activation of PMS by Co 2＋ was almost completely inhibited.Under this condition,HClO maybe played a major role in decolorization of AO7.The results implicated that chloride ion is an important factor in SO4-.-based degradation of organic contamination in chloride-containing water.

Enhanced activation of peroxydisulfate by strontium modified BiFeO3 perovskite for ciprofloxacin degradation

A series of Sr-doped BiFeO3 perovskites(Bi1-xSrxFeO3,BSFO)fabricated via sol-gel method was applied as peroxydisulfate(PDS)activator for ciprofloxacin(CIP)degradation.Various technologies were used to characterize the morphology and physicochemical features of prepared BSFO samples and the results indicated that Sr was successfully inserted into the perovskites lattice.The catalytic performance of BiFeO3 was significantly boosted by strontium doping.Specifically,Bi0.9Sr0.1FeO3(0.1 BSFO)exhibited the highest catalytic performance for PDS activation to remove CIP,where 95%of CIP(10 mg/L)could be degraded with the addition of 1 g/L 0.1 BSFO and 1 mmol/L PDS within 60 min.Moreover,0.1 BSFO displayed high reusability and stability with lower metal leaching.Weak acidic condition was preferred to neutral and alkaline conditions in 0.1 BSFO/PDS system.The boosted catalytic performance can be interpreted as the lower oxidation state of Fe and the existence of affluent oxygen vacancies generated by Sr doping,that induced the formation of singlet oxygen(^1O_(2))which was confirmed as the dominant reactive species by radical scavenging studies and electron spin resonance(ESR)tests.The catalytic oxidation mechanism related to major ^1O_(2) and minor free radicals was proposed.Current study opens a new avenue to develop effective A-site modified perovskite and expands their application for PDS activation in wastewater remediation.

Efficient degradation of sulfamethoxazole by acetylene black activated peroxydisulfate

Acetylene black(AB),as a kind of carbon material with large specific surface area,low density,strong electron transferability,is supposed to have great potential for application in advanced oxidation processes(AOPs).In this study,AB was utilized as a peroxydisulfate(PDS)activator for the catalytic degradation of sulfamethoxazole(SMX)in aqueous media.Scanning electron microscopy(SEM),X-ray diffraction(XRD),Brunauer-Emmett-Teller(BET)techniques,zeta potential and Raman spectra were employed to characterize the features of AB.To verify the excellent performance of AB/PDS systems,a series of control experiments were carried out.Compared to graphite/PDS and biochar/PDS system,AB/PDS system could complete degradation of SMX within 15 min.Besides,the effects of key factors including AB dosage,PDS dosage,initial pH and SMX concentration on SMX degradation in AB/PDS system were elucidated systematically.Furthermore,through the radical quenching experiments,it was proved that singlet oxygen(1 O_(2))was dominantly responsible for the degradation of SMX.Finally,based on the experiment results and compre hensive analysis,a probable reaction mechanism of AB/PDS system for SMX degradation was proposed.This work suggests that AB has a good potential for tackling the hazardous pollutants in environmental remediation.

Ultrasound enhanced heterogeneous activation of peroxydisulfate by bimetallic Fe-Co/GAC catalyst for the degradation of Acid Orange 7 in water

Bimetallic Fe-Co/GAC （granular activated carbon） was prepared and used as heterogeneous catalyst in the ultrasound enhanced heterogeneous activation of peroxydisulfate （PS, S2O8 2-） process. The effect of initial pH, PS concentration, catalyst addition and stirring rate on the decolorization of Acid Orange 7 （AO7） was investigated. The results showed that the decolorization efficiency increased with an increase in PS concentration from 0.3 to 0.5 g/L and an increase in catalyst amount from 0.5 to 0.8 g/L. But further increase in PS concentration and catalyst addition would result in an unpronounced increase in decolorization efficiency. In the range of 300 to 900 r/min, stirring rate had little effect on AO7 decolorization. The catalyst stability was evaluated by measuring decolorization efficiency for four successive cycles.

Effective removal of chlorinated organic pollutants by bimetallic iron-nickel sulfide activation of peroxydisulfate

Chlorinated organic pollutants(COPs)have caused serious contaminants in soil and groundwater,hence developing methods to remove these pollutants is necessary and urgent.By a simple hydrothermal method,we synthesized the bimetallic iron-nickel sulfide(FeNiS)particles which exhibited excellent catalytic property of COPs removal.FeNiS was chosen as the peroxydisulfate(PDS)activator to removal COPs including 4-chlorophenol(4-CP),1,4-dichlorophenol(1,4-DCP)and 2,4,6-trichlorophenol(2,4,6-TCP).The results show that FeNiS can efficiently activate PDS to produce sulfate radical(SO4·-)which plays major role in the oxidative dechlorination and degradation due to its strong oxidizing property and the ability of producing hydroxyl radicals(·OH)in the alkaline condition.Meanwhile,the Cl-abscised from COPs during the dechlorination can turn into the chlorine radicals and enhance the degradation and cause further mineralization of intermediate products.This bimetallic FeNiS catalyst is a promising PDS activator for removal of chlorinated organics.

Visible light-assisted peroxydisulfate activation via hollow copper tungstate spheres for removal of antibiotic sulfamethoxazole

The contamination of antibiotics in aqueous environment causes increasing concerns recently.Lightassisted activation of peroxydisulfate(PDS)has been demonstrated as an efficient technology for re moval of contamination in water.Herein,a hollow sphere of CuWO_(4)(h-CuWO_(4))was employed as a visible lightactivated photocatalyst for the activation of PDS,and following with high removal efficiency(98%)of antibiotic sulfamethoxazole(SMX).Under visible light irradiation,the degradation rate on hollow structures system is nearly 2 times higher than the traditional solid CuWO_(4) spheres.Furthermore,the underlying mechanism and detailed pathway of SMX degradation were proposed based on density functional theory(DFT)calculations and liquid chromatography-mass spectrometry(LC-MS).This work provides a new feasible way for advanced oxidation processes to remove antibiotics SMX in heterogeneous system,and open up new application possibilities of CuWO_(4)-based materials.

Ordered mesoporous carbon as an efficient heterogeneous catalyst to activate peroxydisulfate for degradation of sulfadiazine

Catalytic potential of carbon nanomaterials in peroxydisulfate(PDS)advanced oxidation systems for degradation of antibiotics remains poorly understood.This study revealed ordered mesoporous carbon(type CMK)acted as a superior catalyst for heterogeneous degradation of sulfadiazine(SDZ)in PDS sys-tem,with a first-order reaction kinetic constant(k)and total organic carbon(TOC)mineralization efficiency of 0.06 min^(–1) and 59.67%±3.4%within 60min,respectively.CMK catalyzed PDS system exhibited high degradation efficiencies of five other sulfonamides and three other types of antibiotics,verifying the broad-degradation capacity of antibiotics.Under neutral pH conditions,the optimal catalytic parameters were an initial SDZ concentration of 44.0mg/L,CMK dosage of 0.07g/L,and PDS dosage of 5.44mmol/L,respectively.X-ray photoelectron spectroscopy and Raman spectrum analysis confirmed that the defect structure at edge of CMK and oxygen-containing functional groups on surface of CMK were major active sites,contributing to the high catalytic activity.Free radical quenching analysis revealed that both SO_(4)•−and•OH were generated and participated in catalytic reaction.In addition,direct electron transfer by CMK to activate PDS also occurred,further promoting catalytic performance.Configuration of SDZ molecule was optimized using density functional theory,and the possible reaction sites in SDZ molecule were calculated using Fukui function.Combining ultra-high-performance liquid chromatography(UPLC)–mass spectrometry(MS)/MS analysis,three potential degradation pathways were proposed,including the direct removal of SO_(2)molecules,the 14S-17N fracture,and the 19C-20N and 19C-27N cleavage of the SDZ molecule.The study demonstrated that ordered mesoporous carbon could work as a feasible catalytic material for PDS advanced oxidation during removal of antibiotics from wastewater.