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.

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 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.

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.

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.

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.

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.

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.

Development, dilemma and potential strategies for the application of nanocatalysts in wastewater catalytic ozonation: A review

With the continuous development of nanomaterials in recent years,the application of nanocatalysts in catalytic ozone oxidation has attracted more and more researchers’attention due to their excellent catalytic properties.In this review,we systematically summarized the current research status of nanocatalysts mainly involving material categories,mechanisms and catalytic efficiency.Based on summary and analysis,we found most of the reported nanocatalysts were in the stage of laboratory research,which was caused by the nanocatalysts defects such as easy aggregation,difficult separation,and easy leakage.These defects might result in severe resource waste,economic loss and potentially adverse effects imposed on the ecosystem and human health.Aiming at solving these defects,we further analyzed the reasons and the existing reports,and revealed that coupling nano-catalyst and membrane,supported nanocatalysts and magnetic nanocatalysts had promising potential in solving these problems and promoting the actual application of nanocatalysts in wastewater treatment.Furthermore,the advantages,shortages and our perspectives of these methods are summarized and discussed.

Heterogeneous catalytic ozonation by amorphous boron for degradation of atrazine in water

As one of the most promising and practical advanced oxidation processes(AOPs),the catalytic ozonation is triggered by the active components of catalyst,which are usually derived from metals or metal oxides.To avoid the metal pollution from catalyst,here the amorphous boron(A-boron)is used as a metalfree catalyst for catalytic ozonation to produce free radicals for effective degradation of atrazine(ATZ),the world-widely used herbicide and also a widespread pollutant in environment.A-boron exhibits an outstanding performance for catalytic ozonation to remove ATZ from water.As A-boron is introduced into ozonation,the degradation efficiency in 10 min is promoted to 97.1%,much higher than that of 15.1%under ozonation.The mechanism is that the B-B bonds and internal suboxide B in A-boron serve as the main active sites to donate electrons to accelerate ozone decomposition to produce reactive oxygen species(ROS),including·O_(2)^(-)and^(1)O_(2),and further enhance ATZ degradation via ROS reactions.Moreover,the A-boron is still highly active with a degradation efficiency of ATZ over 95%in 10 min even after four successive cycles.This work shows A-boron could be an alternative for the active components of metal or metal oxide in catalytic ozonation.

Fe_(3)C@C/C for catalytic ozonation of silicon-containing wastewater:Dual improvement of silicon resistance and catalytic effect

The improvement of catalysts’stability under harsh reaction conditions is vital for their practical applica-bility.Herein,iron carbide(Fe_(3)C)nanoparticles were encapsulated in graphitic carbon in situ and a carbon ball served as the carrier.The synthesized Fe_(3)C@C/C was first utilized to treat an m-cresol wastewater containing Si via catalytic ozonation.Compared with the commercial Fe/Al_(2)O_(3)catalyst,the resistance to Si of the Fe_(3)C@C/C was improved 22.68 times,while the TOC removal rate increased by a factor of 2.9,and it remained stable during 10 cycles and 12000 min of continuous reaction,which further demon-strated its potential for diverse applications.The catalyst exhibits improved resistance to Si because of the dual protection from the carbon-encapsulated structure and carbon carrier.Density functional theory calculations show that the encapsulation of Fe_(3)C using carbon significantly increases the resistance to adsorption of Si on its active sites.In addition,the activation of O_(3)is unimpeded on the Fe_(3)C adsorption sites by the protection from C,thus the generation of reactive oxygen species(ROS)by ozone is largely promoted.The mechanism associated with the resistance of the Fe_(3)C@C/C catalyst to Si and its elevated activity are also elucidated.

Catalytic ozonation in advanced treatment of kitchen wastewater:multi-scale simulation and pilot-scale study

Catalytic ozonation is regarded as a promising technology in the advanced treatment of refractory organic wastewater.Packed-bed reactors are widely used in practical applications due to simple structures,installation and operation.However,mass transfer of packed-bed reactors is relatively restrained and amplified deviations usually occurred in scale-up application.Herein,a multi-scale packed-bed model of catalytic ozonation was established to guide pilot tests.First,a laboratory-scale test was conducted to obtain kinetic parameters needed for modeling.Then,a multi-scale packed-bed model was developed to research the effects of water distribution structure,catalyst particle size,and hydraulic retention time(HRT)on catalytic ozonation.It was found that the performance of packed bed reactor was increased with evenly distributed water inlet,HRT of 60 min,and catalyst diameter of about 3-7 mm.Last,an optimized reactor was manufactured and a pilot-scale test was conducted to treat kitchen wastewater using catalytic ozonation process.In the pilot-scale test with an ozone dosage of 50 mg/L and HRT of 60 min,the packed-bed reactor filled with catalysts I was able to reduce chemical oxygen demand(COD)from 117 to 59 mg/L.The performance of the catalytic ozonation process in the packed-bed reactor for the advanced treatment of actual kitchen wastewater was investigated via both multi-scale simulation and pilot-scale tests in this study,which provided a practical method for optimizing the reactors of treating refractory organic wastewater.

Catalytic ozonation treatment of papermaking wastewater by Ag-doped NiFe2O4 : Performance and mechanism

The catalytic ozonation treatment of secondary biochemical effluent for papermaking wastewater by Ag-doped nickel ferrite was investigated.Ag-doped catalysts prepared by sol-gel method were characterized,illustrating that Ag entirely entered the crystalline of Ni Fe2O4 and changed the surface properties.The addition of catalyst enhanced the removal efficiency of chemical oxygen demand and total organic carbon.The results of gas chromatography-mass spectrometer,ultraviolet light absorbance at 254 nm and threedimensional fluorescence excitation-emission matrix suggested that aromatic compounds were efficiently degraded and toxic substances,such as dibutyl phthalate.In addition,the radical scavenging experiments confirmed the hydroxyl radicals acted as the main reactive oxygen species and the surface properties of catalysts played an important role in the reaction.Overall,this work validated potential applications of Ag-doped Ni Fe2O4 catalyzed ozonation process of biologically recalcitrant wastewater.

Pretreatment of cyanided tailings by catalytic ozonation with Mn^(2+)/O^3

The increasing amount of cyanided tailings produced as a by-product has gained significant attention in recent years because of the rapid development of the gold industry and extensive exploitation of gold mineral resources. The effective use of these secondary resources is becoming an important and urgent problem for all environmental protection staff. Manganese-catalyzed ozonation for the pre-oxidation of cyanided tailings was studied and the effects of Mn2＋dosage, initial sulfuric acid concentration, ozone volume flow, temperature and agitation speed on pretreatment were examined. The optimum reaction conditions were observed to be： ore pulp density 2.5%, agitation speed 700 r/min,temperature 60°C, Mn2＋dosage 40 g/L, ozone volume flow 80 L/hr, initial sulfuric acid concentration 1 mol/L, and reaction time 6 hr. Under these conditions, the leaching rate of Fe and weight loss could reach 94.85% and 48.89% respectively. The leaching process of cyanided tailings by Mn2＋/O3 was analyzed, and it was found that the leaching of pyrite depends on synergetic oxidation by high-valent manganese and O3, in which the former played an important part.

Catalytic ozonation performance and surface property of supported Fe304 catalysts dispersions

Fe304 was supported on mesoporous A12O3 or SiO2 （50 wt.%） using an incipient wetness impregnation method, and Fe304/A12O3 exhibited higher catalytic efficiency for the degradation of 2,4-dichlorophenoxyace- tic acid andpara-chlorobenzoic acid aqueous solution with ozone. The effect and morphology of supported Fe304 on catalytic ozonation performance were investigated based on the characterization results of X-ray diffraction, X-ray photoelectron spectroscopy, BET analysis and Fourier transform infrared spectroscopy. The results indicated that the physical and chemical properties of the catalyst supports especially their Lewis acid sites had a significant influence on the catalytic activity. In comparison with SiO2, more Lewis acid sites existed on the surface of A12O3, resulting in higher catalytic ozonation activity. During the reaction process, no significant Fe ions release was observed. Moreover, Fe304/A12O3 exhibited stable structure and activity after successive cyclic experiments. The results indicated that the catalyst is a promising ozonation catalyst with magnetic separation in drinking water treatment.

Catalytic ozonation-biological coupled processes for the treatment of industrial wastewater containing refractory chlorinated nitroaromatic compounds

A treatability study of industrial wastewater containing chlorinated nitroaromatic compounds （CNACs） by a catalytic ozonation process （COP） with a modified Mn/Co ceramic catalyst and an aerobic sequencing batch reactor （SBR） was investigated. A preliminary attempt to treat the diluted wastewater with a single SBR resulted in ineffective removal of the color, ammonia, total organic carbon （TOC） and chemical oxygen demand （COD）. Next, COP was applied as a pretreatment in order to obtain a bio-compatible wastewater for SBR treatment in a second step. The effectiveness of the COP pretreatment was assessed by evaluating wastewater biodegradability enhancement （the ratio of biology oxygen demand after 5 d （BOD5） to COD）, as well as monitoring the evolution of TOC, carbon oxidation state （COS）, average oxidation state （AOS）, color, and major pollutant concentrations with reaction time. In the COP, the catalyst preserved its catalytic properties even after 70 reuse cycles, exhibiting good durability and stability. The performance of SBR to treat COP effluent was also examined. At an organic loading rate of 2.0 kg COD/（m^3.d）, with hydraulic retention time （HRT）=10 h and temperature （30±2） ℃, the average removal efficiencies of NH3-N, COD, BOD5, TOC, and color in a coupled COP/SBR process were about 80%, 95.8%, 93.8%, 97.6% and 99.3%, respectively, with average effluent concentrations of 10 mg/L, 128 mg/L, 27.5 mg/L, 25.0 mg/L, and 20 multiples, respectively, which were all consistent with the national standards for secondary discharge of industrial wastewater into a public sewerage system （GB 8978-1996）. The results indicated that the coupling of COP with a biological process was proved to be a technically and economically effective method for treating industrial wastewater containing recalcitrant CNACs.

Catalytic ozonation of reactive red X-3B in aqueous solution under low pressure： decolorization and OH. generation

Catalytic ozonation of Reactive Red X-3B in aqueous solution had been carried out in an ozone oxidation reactor where Mn-Fe-ceramic honeycomb was used as the catalysts. The presence of Mn-Fe-ceramic honeycomb catalyst could obviously improve the deco- loration efficiency of Reactive Red X-3B and the utilization efficiency of ozone compared to the results from non-catalytic ozonation. Adsorption of Reactive Red X-3B had no obviously influence on the degradation efficiency. Addition of tert-butanol significantly decreased the degradation efficiency, indicating that the degradation of Reactive Red X-3B followed the mechanism of hydroxyl radical （OH.） oxidation. The operating variables such as reaction pressure and ozone supply had a positive influence on the degradation efficiency, mainly attributing to facilitate the ozone decomposition and OH. formation.

Catalytic ozonation of NH_(4)^(+)-N in wastewater over composite metal oxide catalyst

Large amounts of water containing-ammonium nitrogen(NH_(4)^(+)-N)have attracted increasing attention.Catalytic ozonation technology,involving the generation of hydroxyl radical(OH)with strong oxidation ability,was originally utilized to degrade organic-containing wastewater.In this paper,Ce/MnOx composite metal oxide catalysts prepared with different preparation conditions were used to degrade wastewater containing inorganic pollutant(NH_(4)^(+)-N).The as-prepared catalyst features were characterized using X-ray diffraction(XRD),Brunauer-Emmett-Teller method(BET),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and H_(2)-temperature programmed reduction(H_(2)-TPR)techniques.The results show that the catalyst,prepared by conditions with precipitant Na_(2)CO_(3) and Ce/Mn molar ratio 1:2 calcined at 400℃for 3 h in pH 11.0,displays the optimal performance,with the removal rate of NH_(4)^(+)-N and selectivity to gaseous nitrogen,88.14 wt%and 53.67 wt%,respectively.The effects of several operating factors including solution pH,initial NH_(4)^(+)-N concentrations and scavengers were evaluated.In addition,XRD patterns of catalyst with the best performance and the comparative study on decontamination of NH_(4)^(+)-N by various processes(O_(3),catalyst and catalyst/O_(3))show that the primary metal oxides are CeO_(2) and MnO_(2) in Ce/MnOx composite metal oxide catalysts,which have a synergistic effect on the catalytic ozonation of NH_(4)^(+)-N,and the new phase MnO_(2) plays a great role.After 5 consecutive use cycles,the degradation efficiency is declined slightly,and can still achieve better than 70 wt%over 1 h reaction.Additionally,the application of catalytic ozonation for actual wastewater on the removal rate of NH_(4)^(+)-N was investigated.Possible mechanism and degradation pathway of NH_(4)^(+)-N were also proposed.In a word,the application of CeO_(2)-MnO_(2) composite metal oxide catalysts in catalytic ozonation can be regarded as an effective,feasible and promising method for the treatment of NH_(4)^(+)-N.

Interlayer-confined two-dimensional manganese oxide-carbon nanotube catalytic ozonation membrane for efficient water purification

Catalytic ozonation technology has attracted copious attention in water purification owing to its favorable oxidative degradation of pollutants and mitigation of membrane fouling capacity.However,its extensive industrial application has been restricted by the low ozone utilization and limited mass transfer of the short-lived radical species.Interlayer space-confined catalysis has been theoretically proven to be a viable strategy for achieving high catalytic efficiency.Here,a two-dimensional MnO_(2)-incorporated ceramic membrane with tunable interspacing,which was obtained via the intercalation of a carbon nanotube,was designed as a catalytic ozonation membrane reactor for degrading methylene blue.Benefiting from the abundant catalytic active sites on the surface of two-dimensional MnO_(2) as well as the ultralow mass transfer resistance of fluids due to the nanolayer confinement,an excellent mineralization effect,i.e.,1.2 mg O_(3)(aq)mg^(-1) TOC removal(a total organic carbon removal rate of 71.5%),was achieved within a hydraulic retention time of 0.045 s of pollutant degradation.Further,the effects of hydraulic retention time and interlayer spacing on methylene blue removal were investigated.Moreover,the mechanism of the catalytic ozonation employing catalytic ozonation membrane was proposed based on the contribution of the Mn(III/IV)redox pair to electron transfer to generate the reactive oxygen species.This innovative twodimensional confinement catalytic ozonation membrane could act as a nanoreactor and separator to efficiently oxidize organic pollutants and enhance the control of membrane fouling during water purification.

A magnetic-void-porous MnFe_(2)O_(4)/carbon microspheres nano-catalyst for catalytic ozonation:Preparation,performance and mechanism

Wastewater treatment is essential to guarantee human health and ecological security.Catalytic ozonation with nanocatalysts is a widely studied and efficient treatment technology.However,this method has always been limited by nanocatalysts disadvantages such as easily loss,difficult to separate and reuse,and catalytic ability decay caused by aggregation,which could cause severe resources waste and potential risk to human health and ecosystem.To remedy these challenges,a magnetic-void-porous MnFe_(2)O_(4)/carbon microsphere shell nanocatalyst(CMS-MnFe_(2)O_(4))was successfully synthesized using renewable natural microalgae.The separation test showed CMS-MnFe_(2)O_(4) was rapidly separated within 2 min under an external magnetic field.In catalytic ozonation of oxalic acid(OA),CMS-MnFe_(2)O_(4) showed efficient and stable catalytic efficiency,reaching a maximum total organic carbon removal efficiency of 96.59% and maintained a 93.88% efficiency after 4 cycles.The stable catalytic efficiency was due to the supporting effects of the carbon microsphere shell,which significantly enhanced CMS-MnFe_(2)O_(4) chemical stability and reduced the metal ions leaching to 10-20% of MnFe_(2)O_(4) through electron transfer.To explore the catalytic mechanism,radical experiments were conducted and a new degradation pathway of OA involving superoxide anions rather than hydroxyl radicals was proposed.Consequently,this study suggests that an efficient,recyclable,stable,and durable catalyst for catalytic ozonation could be prepared.