Constructing fast mass-transfer channels with efficient catalytic ozonation activity in 2D manganese dioxide membranes by intercalating Fe/Mn bimetallic MOF

Two-dimensional(2D)catalytic ozonation membranes are promising for the treatment of micropollutants in wastewater due to simultaneous ozone-catalyzed degradation and membrane filtration processes.However,it remains challenging for 2D catalytic ozonation membranes to efficiently degrade micropollutants due to low mass-transfer efficiency and poor catalytic activity.Herein,Fe/Mn bimetallic metal-organic framework(MOF)intercalated lamellar MnO_(2) membranes with fast and robust ozone-catalyzed mass-transfer channels were developed on the surface of the hollow fiber ceramic membrane(HFCM)to obtain 2D Fe/Mn-MOF@MnO_(2)-HFCM for efficiently degrading micropollutants in wastewater.The intercalation of Fe/Mn-MOF expanded the interlayer spacing of the MnO_(2) membrane,thereby providing abundant transport channels for rapid passage of water.More notably,the Fe/Mn-MOF provided enriched reactive sites as well as high electron transfer efficiency based on the redox cycling between Mn^(3+)/Mn^(4+) and Fe^(2+)/Fe^(3+),ensuring the effective catalytic oxidative degradation of micropollutants including tetracycline hydrochloride(TCH),methylene blue,and methyl blue.Moreover,the carboxyl groups on the MOF formed covalent bonds(-COO-)with the hydroxyl groups in MnO_(2) between layers,which increased the interaction between MnO_(2) nanosheets to form stable interlayer channels.Specifically,the optimal composite membrane achieved a high removal rate of TCH micropollutant(93.4%),high water treatment capacity(282 L·m^(-2)·h^(-1)·MPa^(-1)),and excellent longterm stability(1200 min).This study provides a simple and easily scalable strategy to construct fast,efficient,and stable 2D catalytic mass-transfer channels for the efficient treatment of micropollutants in wastewater.

A novel process of ozone catalytic oxidation for low concentration formaldehyde removal

To reduce energy costs,minimize secondary pollution from undecomposed ozone,and improve the efficiency of ozone use,a novel process of cycled storage‐ozone catalytic oxidation(OZCO)was employed to remove formaldehyde(HCHO)at low concentrations in air.We applied Al2O3‐supported manganese oxide(MnOx)catalysts to this process,and examined the HCHO adsorption capacity and OZCO performance over the MnOx catalysts.Owing to the high dispersion of MnOx and low oxidation state of manganese,the MnOx/Al2O3catalysts with a manganese acetate precursor and10%‐Mn loading showed good performance in both storage and OZCO stages.The presence of H2O led to a decrease of the HCHO adsorption capacity owing to competitive adsorption between moisture and HCHO at the storage stage;however,high relative humidity(RH)favored complete conversion of stored HCHO to CO2at the OZCO stage and contributed to an excellent carbonbalance.Four low concentration HCHO storage‐OZCO cycles with a long HCHO storage period and relatively short OZCO period were successfully performed over the selected MnOx/Al2O3catalyst at room temperature and a RH of50%,demonstrating that the proposed storage‐OZCO process is an economical,reliable,and promising technique for indoor air purification.

Degradation of Organic Pollutants in Water by Catalytic Ozonation

Different series of transition metal catalysts supported on Al2O3 were prepared by the impregnation method. The catalytic activity was measured in a batch reactor with ozone as the oxidizing reagent. The experimental results indicate that Cu/Al2O3 has a very effective catalytic activity during the ozonation of organic pollutants in water. The optimum conditions for preparing Cu/Al2O3 were systematically investigated with the orthogonal testing method. Furthermore, the results also show that the surface properties of catalyst are not compulsory for effective oxidation.

Catalytic ozonation of phenol and oxalic acid with copper-loaded activated carbon

A novel heterogeneous catalytic ozonation process in water treatment was studied, with a copper-loaded activated carbon （Cu/AC） that was prepared by an incipient wetness impregnation method at low temperature and tested as a catalyst in the ozonation of phenol and oxalic acid. Cu/AC was characterized using XRD, BET and SEM techniques. Compared with ozonation alone, the presence of Cu/AC in the ozonation processes significantly improves the degradation of phenol or oxalic acid. With the introduction of the hydroxyl radical scavenger, i.e., turt-butanol alcohol （t-BuOH）, the degradation efficiency of both phenol and oxalic acid in the Cu/AC catalyzed ozonation process decreases by 22% at 30 min. This indicates that Cu/AC accelerates ozone decomposition into certain concentration of hydroxyl radicals. The amount of Cu（II ） produced during the reaction of Cu/AC-catalyzed ozonation of phenol or oxalic acid is very small, which shows that the two processes are both heterogeneous catalytic ozonation reactions.

Heterogeneous Catalytic Ozonization of Sulfosalicylic Acid

This paper describes the potential of heterogeneous catalytic ozonization of sulfo-salicylic acid (SSal). It was found that catalytic ozonization in the presence of Mn-Zr-O (a modified manganese dioxide supported on silica gel) had significantly enhanced the removal rate (72%) of total organic carbon (TOC) compared with that of ozonization alone (19%). The efficient removal rate of TOC was probably due to increasing the adsorption ability of catalyst and accelerating decomposition of ozone to produce more powerful oxidants than ozone. .

Optimization and Effects of Catalytic Ozonation of Actual Phenolic Wastewater by CuO/Al2O3

In order to improve the ability of ozone to catalyze the degradation of phenolic pollutants in wastewater,the CuO/Al2O3 catalysts was prepared by the impregnation precipitation method and an ozone catalytic oxidation system was constructed.The actual phenolic sewage was used as the treatment object.And the reaction conditions of the system were optimized,and the treatment effect was determined,while the non-catalytic system was used as a control group.At the same time,the influence of salt and ammonia nitrogen related water quality on the system was studied.The optimal reaction conditions for the treatment of phenolic wastewater covered:a catalyst dosage of 30 g/L,an ozone flow rate of 0.3 m3/h,a pH value of 8.80,and a reaction time of 15 minutes.Under these conditions,the phenol and COD removal rates of the system reached 98.7%and 49.4%,respectively,which were by 31.3 percentage points and 16.2 percentage points higher than that of the ozonation system alone.The salt and ammonia nitrogen in the sewage can reduce the oxidation effect of the system.When the salinity reached 10%and the ammonia nitrogen content reached 13 000 mg/L,the removal rate of phenol could be reduced by about 20%.The results of this paper have a reference value for phenol wastewater treatment engineering.

Catalytic ozonation of volatile organic compounds(ethyl acetate)at normal temperature

Catalytic treatments of VOCs at normal temperature can greatly reduce the cost and temperature of processing,and improve the safety factor in line with the requirements of green chemistry.Activated carbon fiber(ACF)was pretreated with 10%H_(2)SO_(4)by single factor optimization to increase specific surface area and pore volume obviously.The catalytic ozonation performance of ACF loaded with Au,Ag,Pt and Pd noble metals on ethyl acetate was investigated and Pd/ACF was selected as the optimal catalyst which had certain stability.Pd is uniformly distributed on the surface of ACF,and Palladium mainly exists in the form of Pd0 with a amount of Pd+2.The specific surface area of the catalysts gradually decreases as the loading increases.The activation energy of ethyl acetate calculated by Arrhenius equation is 113 kJ mol 1.With 1%Pd loading and the concentration ratio of ozone to ethyl acetate is 3:1,catalytic ozonation performance is maximized and the conversion rate of ethyl acetate reached to 60%in 3050℃Cat 15,00030,000 h^1.

CuO-containing multi-walled carbon nanotubes:a novel catalyst for the catalytic ozonation of humic acid in water

CuO particles were attempted to fill in the channel of multi-walled carbon nanotubes (MWCNTs) as novel catalytic materials CuO@MWCNTs used for ozonation of humic acids (HA) in aqueous solution.Catalyst samples were characterized by transmission electron microscopy (TEM),X-ray diffraction (XRD),thermogravimetric analysis (TG) and X-ray photoelectron spectroscopy (XPS).The removal efficiency of HA was promoted in the presence of CuO@MWCNTs compared with that of Al2O3-supported CuO catalyst (CuO/Al2O3) and CuO-coating MWCNTs catalyst (CuO/MWCNTs).The strong synergetic effect in the confinement environment on CuO nanoparticles can attribute to the locally higher pressure due to the lower potential energy of reactants in the channels.Strong interaction happened between the catalyst and reactants,which promoted the decomposition of ozone and the generation of OH.The results of experimental and theoretical investigation confirmed that CuO@MWCNTs promotes the initiation and generation of OH,hence accelerating the degradation of organic pollutants.

Study on CeO_2/CuFe_2O_4 Catalytic Ozonation of Resorcinol

In order to improve the catalytic ozonation effect of resorcinol, the spinel CuFe_2O_4 was modified by doped CeO_2, and X-ray diffraction(XRD) and scanning electron microscopy(SEM) were used for characterization analysis. The effects of composite catalyst CeO_2/CuFe_2O_4 dosage, ozone dosage, initial pH and reaction temperature on degradation were studied, and the stability of the catalyst was tested. The results showed that the composite effect of CeO_2/CuFe_2O_4 prepared by combustion method was good, and the catalyst presented a laminated structure, in which 30 wt% CeO_2/CuFe_2O_4 degradation effect was significant. The removal rate of resorcinol using CeO_2/CuFe_2O_4 composite catalyst was higher than that using ozone or CuFe_2O_4 separately by 41.8% and 11.9%, respectively. In a reaction with resorcinol concentration of 100 mg/L, the catalyst dosage of 1.0 g/L, the ozone dosage of 2.5 mg/(L·min), at pH=9, temperature of 20 ℃, for reaction time of 40 min, the resorcinol removal rate was 88.5%. The catalyst CeO_2/CuFe_2O_4 still showed good degradation effect after repeatedly using for 10 times, and the dissolution rate of metal ions was lower than that of CuFe_2O_4.

Synthesis of ordered mesoporous manganese titanium composite oxide catalyst for catalytic ozonation

In this account,highly ordered mesoporous MnO_x/TiO_2composite catalysts with efficient catalytic ozonation of phenol degradation were synthesized by the sol–gel method.The surface morphology and properties of the catalysts were characterized by several analytical methods,including SEM,TEM,BET,XRD,FTIR,and XPS.Interestingly,Mn doping was found to improve the degree of order,and the ordered mesoporous structure was optimized at 3%doping.Meanwhile,MnO_xwas highly dispersed in the ordered mesoporous materials to yield good catalytic ozonation performance.Phenol could completely be degraded in 20 min and mineralized at 79%in 60 min.Thus,the catalyst greatly improved the efficiency of degradation and mineralization of phenol when compared to single O_3or O_3+TiO_2.Finally,the reaction mechanism of the catalyst was discussed and found to conform to pseudo-first-order reaction dynamics.

Discoloration on Methylene Blue Solutions by Direct and Catalytic Ozonation

During textile manufacturing, huge amounts of wastewaters characterized by removed impurities and high concentrations of dye are produced. These wastewaters cause several problems when they are discharged to the environment. The use of ozone in wastewater treatment results of interest. In this work we propose to assess the discoloration rate of different synthetic wastewaters as a function of pH, dye concentration (methylene blue (MB)) and reaction time. A comparison of discoloration rate between conventional ozonation and catalytic ozonation salts of copper, zinc, silver and nickel was also performed. For the optimization of the ozonation process of colored solutions, it was used a central composite experimental design with five replicates of the center point resulting to evaluate the influence of the independent variables at different ranges of pH, [MB] and time. In the catalyst-assisted ozonation, [MB], pH and the reaction time were fixed to 100 mg/L, 5.5 and 15 min, respectively. The optimized experimental conditions to provide maximum discoloration were pH=3.3;[MB]=8.6 mg/L and time=74.3 min. Regarding the catalyst-assisted ozonation, it was found that CuSO4 catalyst gave better color reduction if compared with other catalysts assayed.

Pilot study on combined process of catalytic ozonation and biological activated carbon for organic pollutants removal

A combined process of catalytic ozonation in the presence of a novel heterogeneous catalyst and biological activated carbon was investigated for the removal of priority control organic pollutants, the reduction of genotoxicity, and the improvement of biodegradable dissolved organic carbon (BDOC). Results confirm that the catalytic ozonation has higher effectiveness for the removal of refractory harmful organic pollutants, the reduction of genotoxicity and the increase of bio-degradability of organics than ozonation alone, which results in lower pollution load for subsequent biological activated carbon process, and then leads to less organic pollutants penetrating biological activated carbon. The novel catalytic ozonation with this combined process exhibits excellent performance to guarantee the safety of drinking water.

The progress of catalytic technologies in water purification:A review

Catalytic technologies have been paid increasing attention in refractory pollutants abatement due to its practical and potential values in water purification. As effective and efficient approaches for water purification, Fenton＇s reagent, ozonation, electrochemical and photocatalytic methods have been widely studied and applied in different aspects and have been reviewed by several articles. In recent years, some novel catalytic processes based on above processes have been developed for enhancing the efficiency of removing the organics from water. This review emphasized on the recent development of heterogeneous catalytic ozonation, electrocatalysis in respect of novel electrodes and electro-Fenton method, photoelectrocatalysis process and photoelectron-Fenton in water purification. It was also an attempt to propose general ideas about mechanism and principle enhancing the catalytic efficiency for the degradation and the mineralization of organics in water.

Degradation of nitrobenzene in aqueous solution by ozone-ceramic honeycomb

The degradation of nitrobenzene by ceramic-honeycomb catalyzed ozonation was investigated. The results showed that the presence of ceramic honeycombs significantly increased the oxidation rate of nitrobenzene by ozone compared to the case of ozone oxidation alone. In this paper, the effects of various factors on the catalytic oxidation were investigated, such as the amount of catalysts, the ozone dosage, the temperature, the pH value and the presence of tert-butanol. With the addition of tert-butanol the removal of nitrobenzene decreased sharply, which appeared to support that, the degradation of nitrobenzene by ozonation followed a radical type mechanism. The EPR experiments verified that higher nitrobenzene removal rate was attributed to more OH radicals generated in the catalyzed ozonation than ozonation alone.

Direct and Indirect Applications of Dielectric Barrier Discharge Plasma to Catalytic Reduction of Nitrogen Oxides from Exhaust Gas

Dielectric barrier discharge （DBD） plasma was utilized to oxidize NO contained in the exhaust gas to NO2, ultimately improve the selective catalytic reduction of nitrogen oxides （NOx）. In the one case, DBD was created directly in the exhaust gas （direct application）, and in the an other case, ozone produced by DBD was injected into the exhaust gas （indirect application）. A comparative study between such direct and indirect applications of DBD plasma was made in terms of the NOx removal efficiency and the energy consumption. The NO2 content in the exhaust gas was changed by the voltage applied to the DBD device （for direct application） or by the amount of ozone added to the exhaust gas （for indirect application）. In both cases, NO was easily oxidized to NO2, and the change in NO2 content largely affected the NOx removal performance of the catalytic reactor placed downstream, where both NO and NO2 were reduced to N2 in the presence of ammonia as the reducing agent. The experiments were primarily concerned with the effect of reaction temperature on the catalytic NOx reduction at various NO2 contents. The direct and indirect applications of DBD were found to remarkably improve the catalytic NOx reduction, especially at low temperatures.

Catalysts for decomposing ozone tail gas

The preparation of immobilizing-catalysts for decomposing ozone by using dipping method was studied. XRD, XPS and TEM were used to characterize the catalysts. The three kinds of catalysts were selected preferentially, and their catalytic activities were investigated. The results showed that the catalyst with activated carbon dipping acetate(active components are Mn:Cu=3:2, active component proportion in catalyst is 15%, calcination temperature is 200℃) has the best catalytic activity for ozone decomposing. One gram of catalyst can decompose 17.6 g ozone at initial ozone concentration of 2.5 g/m 3 and the residence time in reactor of 0.1 s. The experimental results also indicated that humidity of reaction system had negative effect on catalytic activity.

Photothermal Catalytic Selective Oxidation of Isobutane to Methacrylic Acid over Keggin-Type Heteropolyacid

Thermal and photothermal catalytic selec-tive oxidation of isobutane to methacrylic acid(MAA)are comparatively studied over a keggin-type Cs2.9Cu0.34V0.49PMo12O40 het-eropolyacid acid.An introduction of light was observed to enhance both the i-C4H10 conversion and the MAA selectivity,and consequently the MAA formate rate,particularly at low temperatures.Characterization re-sults show that oxidation of methacrolein(MAL)to MAA is the rate-limiting step while UV light illumination promotes the oxidation ofσ-bonded MAL with OH groups toσ-bonded MAA on the catalyst surface.These results demonstrate a synergistic effect of thermal cataly-sis and photocatalysis in selective oxidation of isobutane to MAA,which suggests photother-mal catalysis as a promising strategy to catalyze the selective oxidation of higher hydrocar-bons at relative mild reaction conditions.

A novel insight of degradation ibuprofen in aqueous by catalytic ozonation with supported catalyst:Supports effect on ozone mass transfer

Catalytic ozonation is an effective wastewater purification process.However,the low ozone mass transfer in packed bubble columns leads to low ozone utilization efficiency(OUE),poor organic degradation performance,and high energy consumption.Therefore,there is an urgent need to develop efficient supported catalysts that can enhancemass transfer and performance.However,the reaction mechanism of the support on ozone mass transfer remains unclear,which hinders the development of catalytic ozonation applications.In this study,lava rocks(LR)-supported catalysts,specifically CuMn_(2)O_(4)@LR and MnO_(2)–Co_(3)O_(4)@LR,were proposed for catalytic ozonation of IBP degradation due to their superior catalytic activity,stability,and high OUE.Addition of CuMn_(2)O_(4)@LR or MnO_(2)–Co_(3)O_(4)@LR increased IBP removal efficiency from 85%to 91%or 88%,and reduced energy consumption from 2.86 to 2.14 kWh/m^(3)or 2.60 kWh/m^(3),respectively.This improvement was attributed to LRsupported catalysts enhancing mass transfer and promoting O3 decomposition to generate•OH and•O_(2)^(−),leading to IBP degradation.Furthermore,this study investigated the effects of ozone dose,supporter sizes,and catalyst components on ozone-liquid mass transfer.The results revealed that the size of the supporter influenced stacked porosity and consequently affected ozone mass transfer.Larger-sized LR(kLa=0.172 min^(−1))exhibited better mass transfer compared to smaller-sized supports.Based on these findings,it was concluded that both CuMn_(2)O_(4)@LR and MnO_(2)–Co_(3)O_(4)@LR are potential catalysts for catalytic ozonation in residual IBP degradation of pharmaceutical wastewater,and LR showed good credibility as a catalyst supporter.Understanding the effects of supporters and active components on ozone mass transfer provides a fundamental principle for designing supported catalysts in catalytic ozonation applications.

In-situ sludge reduction based on Mn^(2+)-catalytic ozonation conditioning:Feasibility study and microbial mechanisms

To improve the sludge conditioning efficiency without increasing the ozone dose,an in-situ sludge reduction process based on Mn^(2+)-catalytic ozonation conditioning was proposed.Using ozone conditioning alone as a control,a lab-scale sequencing batch reactor coupled with ozonated sludge recycle was evaluated for its operating performance at an ozone dose of 75 mg O_(3)/g VSS and 1.5 mmol/L Mn^(2+)addition.The results showed a 39.4%reduction in MLSS and an observed sludge yield of 0.236 kg MLSS/kg COD for the O_(3)+Mn^(2+)group compared to the O_(3)group (15.3%and 0.292 kg MLSS/kg COD),accompanied by better COD,NH_(4)^(+)-N,TN and TP removal,improved effluent SS and limited impact on excess sludge properties.Subsequently,activity tests,BIOLOG ECO microplates and 16S rRNA sequencing were applied to elucidate the changing mechanisms of Mn^(2+)-catalytic ozonation related to microbial action:(1) Dehydrogenase activity reached a higher peak.(2) Microbial utilization of total carbon sources had an elevated effect,up to approximately 18%,and metabolic levels of six carbon sources were also increased,especially for sugars and amino acids most pronounced.(3) The abundance of Defluviicoccus under the phylum Proteobacteria was enhanced to 12.0%and dominated in the sludge,they had strong hydrolytic activity and metabolic capacity.Denitrifying bacteria of the genus Ferruginibacter also showed an abundance of 7.6%,they contributed to the solubilization and reduction of sludge biomass.These results could guide researchers to further reduce ozonation conditioning costs,improve sludge management and provide theoretical support.