Development of MoS_(2)-stainless steel catalyst by 3D printing for efficient destruction of organics via peroxymonosulfate activation

Herein,a novel MoS_(2)-stainless steel composite material was first synthetized via a 3D printing method(3DP MoS_(2)-SS)for peroxymonosulfate(PMS)activation and organics degradation.Compared with MoS_(2)-SS powder/PMS system(0.37 g/(m^(2)/min)),4.3-fold higher k_(FLO)/S_(BET)value was obtained in 3DP MoS_(2)-SS/PMS system(1.60 g/(m^(2)/min),resulting from the superior utilization of active sites.We observed that 3DP MoS_(2)-SS significantly outperformed the 3DP SS due to the enhanced electron transfer rate and increased active sites.Moreover,Mo^(4+)facilitated the Fe^(2+)/Fe^(3+)cycle,resulting in the rapid degradation of florfenicol(FLO).Quenching experiments and electron paramagnetic resonance spectra indicated that·OH,SO_(4)·^(-),O_(2)·^(-)and^(1)O_(2)were involved in the degradation of FLO.The effect of influencing factors on the degradation of FLO were evaluated,and the optimized degradation efficiency of 98.69%was achieved at 1 mM PMS and pH of 3.0.Six degradation products were detected by UPLC/MS analyses and several possible degradation pathways were proposed to be the cleavage of C-N bonds,dechlorination,hydrolysis,defluorination and hydroxylation.In addition,3DP MoS_(2)-SS/PMS system also demonstrated superior degradation performance for 2-chlorophenol,acetaminophen,ibuprofen and carbamazepine.This study provided deep insights into the MoS_(2)-SS catalyst prepared by 3DP technology for PMS activation and FLO-polluted water treatment.

Nonradical-dominated peroxymonosulfate activation through bimetallic Fe/Mn-loaded hydroxyl-rich biochar for efficient degradation of tetracycline

Biochar-based transition metal catalysts have been identified as excellent peroxymonosulfate(PMS)activators for producing radicals used to degrade organic pollutants.However,the radical-dominated pathways for PMS activation severely limit their practical applications in the degradation of organic pollutants from wastewater due to side reactions between radicals and the coexisting anions.Herein,bimetallic Fe/Mn-loaded hydroxyl-rich biochar(FeMn-OH-BC)is synthesized to activate PMS through nonradical-dominated pathways.The as-prepared FeMn-OH-BC exhibits excellent catalytic activity for degrading tetracycline at broad pH conditions ranging from 5 to 9,and about 85.0%of tetracycline is removed in 40 min.Experiments on studying the influences of various anions(HCO_(3)^(−),NO_(3)^(−),and H_(2)PO_(4)^(−))show that the inhibiting effect is negligible,suggesting that the FeMn-OHBC based PMS activation is dominated by nonradical pathways.Electron paramagnetic resonance measurements and quenching tests provide direct evidence to confirm that 1O2 is the major reactive oxygen species generated from FeMn-OH-BC based PMS activation.Theoretical calculations further reveal that the FeMn-OH sites in FeMn-OH-BC are dominant active sites for PMS activation,which have higher adsorption energy and stronger oxidative activity towards PMS than OH-BC sites.This work provides a new route for driving PMS activation by biochar-based transition metal catalysts through nonradical pathways.

NiCo_(2)O_(4)/BiOCl/Bi_(24)O_(31)Br_(10) ternary Z-scheme heterojunction enhance peroxymonosulfate activation under visible light: Catalyst synthesis and reaction mechanism

The Z-scheme heterostructure for photocatalyst can effectively prolong the lifetime of photogenerated carriers and retain a higher conduction/valence band position,promoting the synergistic coupling of photocatalysis and peroxymonosulfate(PMS) activation.In order to fully utilize the luminous energy and realize the efficient activation of PMS,this work achieved successful construction of NiCo_(2)O_(4)/BiOCl/Bi_(24)O_(31)Br_(10) ternary Z-scheme heterojunction by simultaneously synthesizing BiOCl and NiCo_(2)O_(4) with NiCl_(2) and CoCl_(2) as the precursors.The intercalated BiOCl could serve as a carrier migration ladder to further achieve the spatial separation of electron-hole pairs,so that the oxidation and reduction processes separately occurred in different regions.Compared with the reported catalysts,the as-prepared composites exhibited the enhanced removal efficiency for tetracycline hydrochloride(TCH) in the visible light/PMS system,with a degradation efficiency of 85.30%in 2 min,and possessed good stability.Z-scheme heterojunction was shown to be beneficial for maximizing the superiority of photo-assisted Fenton-like reaction system.The experimental and characterization results confirmed that both non-radicals(^(1)O_(2)) and radicals(SO_(5)^(·-) and SO_(4)^(·-)) were involved in the reaction process and the SO_(5)^(·-)generated by the oxidation of PMS played a crucial role in the TCH degradation.The possible reaction mechanism was finally proposed.This study provided new insight into the Z-scheme heterostructure to promote the photo-assisted Fenton-like reaction.

Reactive species regulation by interlayered Na^(+)/H^(+)of titanate nanotubes decorated Co(OH)_(2)hollow microsphere for peroxymonosulfate activation and gatifloxacin degradation

Emerging organic pollutants(EoPs)in water are of great concern due to their high environmental risk,so urgent technologies are needed for effective removal of those pollutants.Herein,a heterogeneous advanced oxidation process(AoP)of peroxymonosulfate(PMS)activation by functional material was developed for degradation of a typical antibiotic,gatifloxacin(GAT).The reactive species including sulfate radical(SO^(4)^(·-))and singlet oxygen(^(1)O_(2))in this AOP were regulated by interlayered ions(Na^(+)/H^(+))of titanate nanotubes that supported on Co(OH)_(2)hollow microsphere.Both the Na-type(NaTi-CoHS)and H-type(HTi-CoHS)materials achieved efficient PMS activation for GAT degradation,and HTi-CoHS even exhibited a relatively high degradation efficiency of 96.6%within 5 min.Co(OH)_(2)was considered the key component for generation of SO_(4)^(·-)after PMS activation,while hydrogen titanate nanotubes(H-TNTs)promoted the transformation of peroxysulfate radical(SO_(5)^(·-))to ^(1)O_(2) by hydrogen bond interaction.Therefore,when the interlayer ion of TNTs transformed from Na^(+) to H^(+),more ^(1)O_(2) was produced for organic pollutant degradation.H-TNTs with lower symmetry preferred to adsorb PMS molecules to achieve interlayer electron transport through hydrogen bonding,rather than electrostatic interaction of Na^(+) for Na-TNTs.In addition,the degradation pathway of GAT mainly proceeded by the cleavage of C-N bond at the 8 N site of the piperazine ring,which was confirmed by condensed Fukui index and mass spectrographic analysis.This work gives new sights into the regulation of reactive species in AoPs by the composition of material and promotes the understanding of pollutant degradation mechanisms in water treatment process.

Surface sulfur vacancies enhanced electron transfer over Co-ZnS quantum dots for efficient degradation of plasticizer micropollutants by peroxymonosulfate activation

Peroxymonosulfate(PMS)activation in heterogeneous processes is a promising water treatment technology.Nevertheless,the high energy consumption and low efficiency during the reaction are ineluctable,due to electron cycling rate limitation.Herein,a new strategy is proposed based on a quantum dots(QDs)/PMS system.Co-ZnS QDs are synthesized by a water phase coprecipitation method.The inequivalent lattice-doping of Co for Zn leads to the generation of surface sulfur vacancies(SVs),which modulates the surface of the catalyst to form an electronic nonequilibrium surface.Astonishingly,the plasticizer micropollutants can be completely degraded within only tens of seconds in the Co-Zn S QDs/PMS system due to this type of surface modulation.The interfacial reaction mechanism is revealed that pollutants tend to be adsorbed on the cobalt metal sites as the electron donors,where the internal electrons of pollutants are captured by the metal species and transferred to the surface SVs.Meanwhile,PMS adsorbed on the SVs is reduced to radicals by capturing electrons,achieving effective electron recovery.Dissolved oxygen(DO)molecules are also easily attracted to catalyst defects and are reduced to O_(2)^(·-),further promoting the degradation of pollutants.

NiCo_(2)O_(4) hollow microsphere-mediated ultrafast peroxymonosulfate activation for dye degradation

Morphology and dispersity are key factors for activating peroxymonosulfate(PMS).In this study,we designed a recyclable open-type NiCo_(2)O_(4) hollow microsphere via a simple hydrothermal method with the assistance of an NH_(3) vesicle.The physical structure and chemical properties were characterized using techniques such as scanning electron microscope(SEM),transmission electron microscope(TEM),X-ray diffraction(XRD),N2 adsorption and X-ray photoelectron spectroscopy(XPS).The test results confirm that the inner and outer surfaces of open-type NiCo_(2)O_(4) hollow-sphere can be efficiently utilized because of the hole on the surface of the catalyst,which can minimize the diffusion resistance of the reactants and products.Under optimized conditions,the total orga nic carbon(TOC) removal efficiency of rhodamine B(RhB) can reach up to 80% in 40 min,which is almost 50% shorter than the reported values.The reactive radicals were identified and the proposed reaction mechanism was well described.Moreover,the disturbances of HCO_(3)^(-),NO_(3)^(-),Cl^(-)and H_(2) PO_(4)^(-)were further investigated.As a result,HCO_(3)-and NO_(3)-suppressed the reaction while Cl-and H_(2) PO4-had a double effect on reaction.

Peroxymonosulfate activation based on Co_(9)S_(8)@N-C:A new strategy for highly efficient hydrogen production and synchronous formaldehyde removal in wastewater

Formaldehyde(FA),as an important chemical raw material,has been widely used in many fields.However,the discharge of a large amount of FA-containing wastewater poses a serious threat to the environment and human health.Recently,the in-situ hydrogen energy release technology of hydrogen-containing stable liquid has been extensively explored due to its safe storage.Exploring a robust method to achieve FA removal and synchronous in-situ hydrogen release from FA containing wastewater is of great significant for environmental protection and energy crisis alleviation.Here,we have innovatively introduced peroxymonosulfate(PMS)activation technology into FA removal and hydrogen production simultaneously.The composite of nitrogen doped carbon coating Co_(9)S_(8)nanotubes(Co_(9)S_(8)@N-C)is employed as a proof of concept for FA decomposition and simultaneously hydrogen production based on PMS activation system.As expected,the Co_(9)S_(8)@N-C/PMS system presents much superior hydrogen production efficiency and satisfactory FA removal rate towards FA wastewater than those of common catalysis,photocatalysis and Fenton reaction in the basic condition in a wide range of FA concentration.The hydrogen yield reaches a value as high as 471μmol within 60 min,corresponding to a FA degradation rate of 30%with an initial FA concentration of 0.722 mol L^(-1).Characterizations and density functional theory(DFT)calculations suggest that the free radical process dominated by superoxide radical(O_(2)·^(-))and nonradical process dominated by singlet oxygen(^(1)O_(2)),which are induced by Co_(9)S_(8)@N-C/PMS system,are responsible for highly efficient hydrogen production via FA degradation.These generated O_(2)·^(-)and ^(1)O_(2)can extract·H from FA to form·OOH intermediate,which can further combine with the·H from water to produce hydrogen.This study provides an applicable technique for environmental purification and new energy development based on FA containing wastewater.

Role of oxygen vacancies and Sr sites in SrCo_(0.8)Fe_(0.2)O_3 perovskite on efficient activation of peroxymonosulfate towards the degradation of aqueous organic pollutants

Metal-based perovskite oxides have contributed significantly to the advanced oxidation processes(AOPs)due to their diverse active sites and excellent compositional/structural flexibility.In this study,we specially designed a perovskite oxide with abundant oxygen vacancies,SrCo_(0.8)Fe_(0.2)O_(3)(SCF),and firstly applied it as a catalyst in peroxymonosulfate(PMS) activation towards organic pollutants degradation.The result revealed that the prepared SCF catalyst exhibited excellent performance on organic compounds degradation.Besides,SCF showed much better activity than La_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3)(LSCF) in terms of reaction rate and stability for the degradation of the organic compounds.Based on the analysis of scanning electron microscope,transmission electron microscope,X-ray diffraction,N_(2) adsorption-desorption,X-ray photoelectron spectroscopy and electron paramagnetic resonance,it was confirmed that the perovskite catalysts with high content of Sr doping at A-site could effectively create a defect-rich surface and optimize its physicochemical properties,which was responsible for the excellent heterogeneous catalytic activity of SCF.SCF can generate three highly active species:~1 O_(2),SO_(4)^(-)· and ·OH in PMS activation,revealing the degradation process of organic compounds was a coupled multiple active species in both radical and nonradical pathway.Moreover,it was mainly in a radical pathway in the degradation through PMS activation on SCF and SO_(4)^(-)· radicals produced were the dominant species in SCF/PMS system.This study demonstrated that perovskite-type catalysts could enrich OVs efficiently by doping strategy and regulate the PMS activation towards sulfate radical-based AOPs.

Selective activation of peroxymonosulfate to singlet oxygen by engineering oxygen vacancy defects in Ti_(3)CNT_(x) MXene for effective removal of micropollutants in water

Defect engineering is an effective strategy to boost the catalytic activity of MXene towards heterogeneous peroxymonosulfate(PMS)activation for water decontamination.Herein,we developed a facile approach to fine-tune the generation of oxygen vacancies(OVs)on Ti_(3)CNT_(x)crystals by Ce-doping(Ce-Ti_(3)CNT_(x))with the aim of mediating PMS activation for the degradation of micropollutants in water.By varying the dopant content,the OV concentrations of Ti_(3)CNT_(x)could be varied to enable the activation of PMS to almost 100%singlet oxygen(1O2),and hence the effective degradation of sulfamethoxazole(SMX,a model micropollutant).Various advanced characterization techniques were employed to obtain detailed information on the microstructure,morphology,and defect states of the catalysts.The experimental results showed that SMX removal was proportional to the OVs level.Density functional theory(DFT)models demonstrated that,in contrast to pristine Ti_(3)CNT_(x),the OVs on 10%CeTi_(3)CNT_(x)could adsorb the terminal O of PMS,which facilitated the formation of SO_(5)•−as well as the generation of 1O2.We further loaded the optimized catalysts onto a polytetrafluoroethylene microfiltration membrane and also demonstrated the efficient removal of SMX from water using a convection-enhanced mass transport flowthrough configuration.This study provides new insights into the effective removal of micropollutants from water by integrating state-of-the-art defect engineering,advanced oxidation,and microfiltration techniques.

Efficient elimination of carbamazepine using polyacrylonitrile-supported pyridine bridged iron phthalocyanine nanofibers by activating peroxymonosulfate in dark condition

The monoaminotrinitro iron phthalocyanine(FeMATNPc)is used to connect with isonicotinic acid(INA)for amide bonding and axial coordination to synthetic a unique catalyst FeMATNPc-INA,which is loaded in polyacrylonitrile(PAN)nanofibers by electrospinning.The introduction of INA destroys theπ-πconjugated stack structure in phthalocyanine molecules and exposes more active sites.The FeMATNPc-INA structure is characterized by X-ray photoelectron spectroscopy and UV-visible absorption spectrum,and the FeMATNPcINA/PAN structure is characterized by Fourier transform infrared spectroscopy and X-ray diffraction.The FeMATNPc-INA/PAN can effectively activate peroxymonosulfate(PMS)to eliminate carbamazepine(CBZ)within 40 minutes(PMS 1.5 mmol/L)in the dark.The effects of catalyst dosage,PMS concentration,pH and inorganic anion on the degradation of CBZ are investigated.It has been confirmed by electron paramagnetic resonance,gas chromatography–mass spectroscopy and free radical capture experiments that the catalytic system is degraded by·OH,SO4^(·-)and Fe(IV)=O are the major active species,the singlet oxygen(^(1)O_(2))is the secondary active species.The degradation process of CBZ is analyzed by ultra-high performance liquid chromatography-mass spectrometry and the aromatic compounds have been degraded to small molecular acids.

Design of cobalt-based catalysts with the uniformly distributed coreshell structure for ultra-efficient activation of peroxymonosulfate for tetracycline degradation

Catalysts that can rapidly degrade tetracycline(TC)in water without introducing secondary ion pollution have always been challenging.Herein,a cobalt-based catalyst(CoO_(x)@P-C)is prepared so that CoOx quantum particles(5e10 nm)are uniformly distributed on a linear substrate,and the outer layer is covered with a shell(P-C).The quantum particles of CoO_(x) provide many active sites for the reaction,which ensures the efficient degradation effect of the catalyst,and 30 mg/L TC can be completely degraded in only 5 min.The shell of the quantum particles'outer layer can effectively reduce ions'extravasation.The combination of the shell-like structure and the linear substrate greatly enhances the catalysis's stability and ensures that the catalyst is prepared into a film for practical application.The high catalytic activity of CoO_(x)@P-C is mainly due to the following factors:(1)Uniformly distributed ultra-small nanoparticles can provide many active sites.(2)The microenvironment formed by the core-shell structure enhances not only catalytic stability but also provides the driving force to improve the reaction rate.(3)The composite of CoO_(x) and P-C core-shell structure can accelerate electron transfer and generate many reactive oxygen species in a short time,which makes TC degrade extremely rapidly.

Tetracycline removal by a magnetic heterojunction Cu_(2)O/CoFe_(2)O_(4) activating peroxymonosulfate

The electron transfer mechanism in the process of peroxymonosulfate(PMS)activation using heterojunction catalyst was controversial.In this work,magnetic heterojunction Cu_(2)O/CoFe_(2)O_(4)(CC)was first synthesized to activate PMS.An innovative reaction mechanism based on built-in electric field-driven electron migration from Cu2O to CoFe2O4 and effective magnetic moment of CC for enhancing PMS activation was proposed.Meanwhile,the CC/PMS system was used for efficient removal of antibiotic tetracycline(TC).Under optimal conditions,98.0%TC could be removed using CC/PMS catalytic system after only 30 min.The catalytic activity was higher than that of Cu_(2)O/PMS and CoFe_(2)O_(4)/PMS.Meanwhile,the impact of solution pH on TC removal was insignificant,suggesting the pH-insensitive PMS activation ability of CC.Besides,the coexisting inorganic ions in the environment,such as HCO_(3)-,H_(2)PO4-,NO_(3)-,Cl-and humic acid(HA)as representative of natural organic matter,did not inhibit TC removal in CC/PMS system.Furthermore,CC/PMS system exhibited excellent reusability with more than94.0%TC removal after the 5th reuse.Electron paramagnetic resonance(EPR)tests and quenching experiments showed that O_(2)·-and 1O_(2) played vital roles in TC removal.The intermediate products and corresponding toxicity assessment revealed that this catalytic system could reduce TC toxicity.This work provided new insights into the PMS activation mechanism using heterogeneous magnetic catalysts,including transition metal oxide.

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.

Through converting the surface complex on TiO_(2) nanorods to generate superoxide and singlet oxygen to remove CN^(−)

Cyanide(CN−)is extensively used in the process of plating devices and for surface treatment in the electroplating industry and is extremely hazardous to humans and the environment.Peroxymonosulfate(PMS)-based advanced oxidation processes(AOPs)hold considerable promise for CN−removal.However,the activity of sulfate radical and hydroxyl radical generated in the PMS activation process is low in the base condition,leading to a drop in its efficiency in CN−removal.Thus,a photo-electrocatalytic system(PEC),developed using a TiO_(2) photoanode and a carbon aerogel cathode,was used to activate PMS for the removal of CN−from wastewater through the generation of radicals and non-radicals.The PEC/PMS system could effectively remove CN^(−),with the removal efficiency reaching 98.5%within 2 min,when PMS concentration was at the 0.25 mmol/L level,and the applied bias voltage was-0.5 V.The main active species in the PEC/PMS system were superoxide radicals and singlet oxygen,which was proved through electron paramagnetic resonance detection and quenching experiments.Results obtained through in-situ Raman measurements,photocurrent tests,and electrochemical impedance spectroscopy measurements indicated that the TiO2 could activate PMS to generate active species.Following many cycles of experimentation,it was discovered that the system displayed high catalytic performance and possessed satisfactory stability to remove CN−economically and efficiently.