Advanced ozone treatment of heavy oil refining wastewater by activated carbon supported iron oxide

The catalytic ozonation of heavy oil refining wastewater (HORW) was investigated over activated carbon supported iron oxides (FAC) catalysts using activated carbon (AC) as the reference. The catalyst was characterized by chemical analysis, XRD, N₂ adsorption–desorption and SEM. A significant increase in COD removal efficiency was observed in FAC + ozone compared with AC + ozone due to more hydroxyl radicals, identified by tert-butyl alcohol (TBA). The composition analysis of organic pollutant in HORW by FT-ICR MS discovered organic pollutants chain scission and oxidation process during the treatment. A great improvement of biodegradability for treated HORW had been obtained. The investigation uncovered the catalytic potential of FAC catalysts for ozonation of HORW.     

Distinct synergetic effects in the ozone enhanced photocatalytic degradation of phenol and oxalic acid with Fe3+/TiO2 catalyst

In this work, phenol and oxalic acid(OA) degradation in an ozone and photocatalysis integrated process was intensively conducted with Fe~(3+)/TiO_2 catalyst. The ferrioxalate complex formed between Fe~(3+) and oxalate accelerated the removal of OA in the ozonation, photolysis and photocatalytic ozonation process, for its high reactivity with ozone and UV. Phenol was degraded in ozonation and photolysis with limited TOC removal rates, but much higher TOC removal was achieved in photocatalytic ozonation due to the generation of ·OH. The sequence of UV light and ozone in the sequential process also influences the TOC removal, and ozone is very powerful to oxidize intermediates catechol and hydroquinone to maleic acid. Fenton or photo-Fenton reactions only played a small part in Fe~(3+)/TiO_2catalyzed processes, because Fe~(3+) was greatly reduced but not regenerated in many cases.The synergetic effect was found to be highly related with the property of the target pollutants. Fe~(3+)/TiO_2 catalyzed system showed the highest ability to destroy organics, but the TiO_2 catalyzed system showed little higher synergy.     

Catalytic ozonation of azo dye active brilliant red X-3B in water with natural mineral brucite

Natural mineral brucite was used directly in catalytic ozonation of dye wastewater of active brilliant red X-3B. Compared with single ozonation, degradation of X-3B increased from 47% to 89%, and removal rate of COD increased from 9% to 32.5% in catalytic ozonation for 15 min. The catalytic ozonation of X-3B followed a direct oxidization mechanism by ozone molecule, and this was actually a homogeneous catalysis of OH⁻ due to dissolution of Mg(OH)₂ from natural brucite. As a natural mineral catalyst, brucite has supplied an economical and feasible choice for catalytic ozonation of X-3B in industrial wastewater.     

Post-Treatment of Composting Leachate by Ozonation

The post-treatment of composting leachate via an ozonation process in laboratory scale was studied in batch mode. According to the experiments, the COD removal was 47% after 30 min of ozonation via 0.4 g/h ozone (equivalent to 2.8 mg O₃/mg COD removed) at pH 9. In this circumstance, the removal of color and turbidity was also 86% and 89%, respectively. Increasing the ozone mass flow rate higher than 0.4 g/h had no considerable effect on the process variables. However, increasing the reaction time had a significant effect on both the removal of color and on COD of the leachate. Experimental data indicated that complete removal of color and 51% removal of COD were achieved after about 40 min of ozonation via 0.4 g/h ozone (equivalent to 3.3 mg O₃/mg COD removed). The ozone consumption rate increased as the reaction progressed and reached 4.1 mg O₃/mg COD removed after 60 min.     

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

In this account, highly ordered mesoporous MnO_x/TiO₂ composite 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_x was 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 O₃ or O₃ + TiO₂. Finally, the reaction mechanism of the catalyst was discussed and found to conform to pseudo-first-order reaction dynamics.     

Post-Treatment of Pulp and Paper Industry Wastewater by Advanced Oxidation Processes

The aim of this study was to investigate the effectiveness of chemical oxidation by applying ozonation, combination of ozone and hydrogen peroxide and Fenton's processes for decolorization and residual chemical oxygen demand (COD) removal of biologically pretreated pulp and paper industry effluents. The batch tests were performed to determine the optimum operating conditions including pH, O₃, H₂O_2, and Fe²⁺ dosages. H₂O₂ addition reduced the reaction times for the same ozone dosages; however combinations of ozone/hydrogen peroxide were only faintly more effective than ozone alone for COD and color removals. In the Fenton‘s oxidation studies, the removal efficiencies of COD, color and ultraviolet absorbance at 254 nm (UV₂₅₄) for biologically treated pulp and paper industry effluents were found to be about 83, 95, and 89%, respectively. Experimental studies indicated that Fenton oxidation was a more effective process for the reduction of COD, color, and UV₂₅₄when compared to ozonation and ozone/hydrogen peroxide combination. Fenton oxidation was found to have less operating cost for color removal from wastewater per cubic meter than the cost for ozone and ozone/hydrogen peroxide applications.     

Comparative Efficiency Of Three Systems (O3, O3/H2O2, and O3/TiO2) For The Oxidation Of Natural Organic Matter In Water

CATAZONE is a new process of heterogeneous catalytic ozonation in which water is ozonated in the presence of a solid catalyst composed of titanium dioxide. The efficiency of this O₃/TiO₂ system has been compared to the two well-known oxidant systems: ozone alone and ozone combined with hydrogen peroxide.

This comparison was undertaken on three models of natural organic compounds : an aquatic fulvic acid, a protein and a disaccharide. The first results showed the following order of relative efficiency: O₃/TiO₂ > O₃/H₂O₂ > O₃ as far as Total Organic Carbon (TOC) removal was concerned.     

Evaluation of water treatment sludge as a catalyst for aqueous ozone decomposition

A new, novel, efficient, and stable green catalyst has been successfully used as a catalyst in aqueous ozone decomposition in acidic medium. The catalyst was characterized by using X-ray fluorescence (XRF), transmission electron microscope (TEM), scanning electron microscope (SEM), and X-ray diffraction (XRD) techniques. The sludge mainly consists of various metal and non-metal oxides. The effect of various experimental parameters such as catalyst loading, initial ozone concentrations, and various metal oxide catalysts on the decomposition of ozone was investigated. The decomposition of dissolved ozone was substantially enhanced by increasing the catalyst loading from 125 to 750 mg and by increasing the initial ozone concentration. The ozone decomposition efficiencies of Al₂O₃, SiO₂, TiO₂, Fe₂O₃, ZnO, and sludge have been studied and the efficiencies of these catalysts were found to be in the following order: ZnO ≈ sludge > TiO₂ > SiO₂ > Al₂O₃ ≈ Fe₂O₃. The catalytic stability was also investigated for up to four successive cycles and it was found that the catalyst was stable and ozone did not affect the catalyst morphology and its composition. However, the surface area of the catalyst increased after 1st cycle then it became stable. It was concluded that the sludge powder used in this study was a promising catalyst for aqueous ozone decomposition.     

Catalytic decomposition of CH2Cl2 over supported Ru catalysts

Ru/TiO₂ and Ru/Al₂O₃ were prepared by wet impregnation of TiO₂ and Al₂O₃, and tested in the catalytic decomposition of dichloromethane (DCM). Ru/TiO₂ catalyst presents the higher activity than Ru/Al₂O₃ catalyst, with 50% and 90% conversion occurring at 235 and 267 °C, respectively. Moreover, the higher stability on Ru/TiO₂ catalyst is observed, which can be related to ready removal of Cl species produced during DCM decomposition. The chlorine uptake on Ru/TiO₂ catalyst is estimated at 240 °C to be 0.36 mmol Cl/g_cat, while on Ru/Al₂O₃, the value is 1.46 mmol Cl/g_cat.     

The Feasibility of Using a Perfluorinated Bonded Alumina Phase in the Ozonation Process

The comparison of the efficiency of three ozonation systems (ozonation alone and ozonation in the presence of alumina or PFOA) in attempting the removal of aromatic hydrocarbons from water was made. The results obtained indicate that PFOA shows a great catalytic activity, as opposed to alumina. Moreover, ozonation in the presence of PFOA results in a much higher level of ozonation efficiency in comparison to ozonation alone. The effect of ozone dosage, catalyst dosage and pH value was investigated and was found to have a great influence on hydrocarbons removal efficiency. The degradation rate was shown to decrease with increasing ozone and catalyst dosage. The efficiency of the PFOA/O₃ system was observed to be at its greatest at the lowest pH examined.     

Manganese-Based Catalysts for the Catalytic Remediation of Phenolic Acids by Ozone

Manganese-based catalysts supported on Al₂O₃, TiO₂, ZrO₂ and CeO₂ were tested for the catalytic ozonation of a simulated wastewater involving phenolic acids. Comparing the Mn-Ce catalysts preparation method, wetness impregnation and co-precipitation, the last one showed to be more active. Moreover, the increase of Mn/Ce molar proportion from 22/78 to 70/30 increased the ozonation efficiency. The catalysts stability in terms of Mn leaching, carbon adsorption and effluent biodegradability was evaluated. Mn-Ce-O (70/30) CP shows to be the most suitable catalyst to improve phenolic wastewaters catalytic remediation by ozone.     

Comparison between photocatalytic ozonation and other oxidation processes for the removal of phenols from water

Photocatalytic ozonation (1O₃ + VUV + TiO₂), ozonation (O₃), catalytic ozonation (O₃ + TiO₂), ozone photolysis (O₃ + VUV), photocatalysis (TiO₂ + VUV) and photolysis (VUV) have been compared in terms of formation of intermediates, extent of, mineralization (TOC, COD, chloride, nitrate) and kinetics in the aqueous treatment of three phenols (phenol, p‐chlorophenol and p‐nitrophenol). In all cases, photocatalytic ozonation led to lower degradation times for chemical oxygen demand and total organic carbon removal. Intermediates formed were similar in the different oxidation systems with some exceptions. They can be classified into three different types: polyphenols (resorcinol, catechol, hydroquinone), unsaturated carboxylic acids (maleic and fumaric acids) and saturated carboxylic acids (glyoxylic, formic and oxalic acids). First order kinetic equations have been checked for the oxidation processes studied in the case of the parent compound. Rate constants of these systems have also been calculated. Copyright © 2005 Society of Chemical Industry     

介质阻挡放电技术再生Pd/AC催化剂的机理探讨

利用介质阻挡放电对失活钯炭催化剂(Pd/AC)进行再生,并通过催化臭氧氧化硝基苯反应评价再生后催化剂的活性。运用扫描电镜(SEM)、比表面积测定(BET)、热重分析(TG)等测定手段对Pd/AC进行表征;并对放电过程进行臭氧产量测定和等离子体发射光谱诊断,分析了Pd/AC催化剂再生的机理。结果表明,催化剂经放电处理30 min后再生率为95%;利用在最优条件下再生的Pd/AC进行催化臭氧氧化反应,硝基苯的降解率为87%;再生过程中臭氧贡献率仅为25.6%,表明放电过程中产生的强氧化性自由基是促使催化剂再生的主要因素。     

Degradation and Transformation of Organic Compounds in Songhua River Water by Catalytic Ozonation in the Presence of TiO2/Zeolite

This paper presents experimental results of the catalytic ozonation of Songhua River water in the presence of nano-TiO₂ supported on Zeolite. The removal efficiency of TOC and UV₂₅₄, the variation of AOC and molecular weight distribution of organics was studied. Results showed that TOC and UV₂₅₄ removal efficiency by ozone was improved in the presence of TiO₂/Zeolite, and increased by 20% and 25%, respectively. The part of organic compounds less than 1000 Da increased in ozonation, but decreased in catalytic ozonation. The AOC of water increased in catalytic ozonation, and the increase of AOC was particularly obvious when ozone dose increased from 28.8 mg·L^?1 to 46.6 mg·L^?1. The degradation and transformation of organic compounds was analyzed by means of GC-MS. The total number of organic compounds was reduced from 50 in the untreated water to 36 and 20, respectively, in ozonation and catalytic ozonation. The removal efficiency of the total organic compounds peak area in ozonation and catalytic ozonation were 23.5% and 62.5%, respectively. Most of the hydrocarbons could be removed easily in ozonation and catalytic ozonation. The organic compounds having hydroxyl, carboxyl or carbonyl groups were hard to be removed in ozonation, but could be removed efficiently in the presence of TiO₂/Zeolite.     

Ozonation of Trace Nitrobenzene in Water in the Presence of a TiO2/Silica-Gel Catalyst

Heterogeneous catalytic ozonation was investigated for the degradation of nitrobenzene in the presence of TiO₂ supported on Silica-gel as a solid catalyst. The conditions in preparing the catalyst are experimentally optimized. The catalytic activity of the supported TiO₂ is strongly influenced by the calcination temperature. The TiO₂/Silica-gel calcined at 500 °C showed the highest activity for the degradation of nitrobenzene. An approximate increase of 21% in removal efficiency was achieved for catalytic ozonation compared with the case of ozonation alone. Nitrobenzene degradation was significantly influenced by the presence of carbonate and t-butanol, which confirmed that TiO₂/Silica-gel catalyzed ozonation followed a radical-type mechanism. Kinetic study demonstrated that catalytic ozonation is pseudo–first-order with no respect to the initial nitrobenzene concentration. The effect of catalyst dosage and pH on the oxidation efficiency of nitrobenzene was also investigated. Catalyst dosage exerted a positive influence on nitrobenzene removal, and nitrobenzene degraded more completely under neutral or basic conditions. Finally, the catalyst stability was tested through repeated experiments.     

Vapor phase oxidation of dimethyl sulfide with ozone over V2O5/TiO2 catalyst

The removal of volatile and odorous emissions from pulp and paper industrial processes usually generates secondary pollution which is treated further by scrubbing, adsorption, and catalytic incineration. Studies using a flow reactor packed with 10% vanadia/titania (V₂O₅/TiO₂) catalyst showed complete conversion of dimethyl sulfide (DMS) in the presence of ozone. The molar yields of partial oxidation products were only 10–20%. Small amounts of partial oxidation products, such as and dimethyl sulfone (DMSO₂), dimethyl disulfide (DMDS), and dimethyl sulfoxide (DMSO), were also formed. The results of the oxidation of DMS using ozone only, ozone plus catalyst, and oxygen plus catalyst suggest that the combined use of O₃ with catalyst is essential for the complete destruction of DMS to CO₂ and SO₂. A Box-Behnken design was used to determine the factors that have a significant effect on the conversion and selectivity of the products. It was concluded that product selectivity is strongly influenced by temperature, gas hourly space velocity (GHSV), and ozone concentration. The catalysts were characterized using XRD, surface area measurements, and SEM techniques. Time-on-stream studies carried out in a 500 ppmv gas stream held at 150 °C for 6 h, using 2 g of the catalyst, an ozone-to-DMS molar ratio of 0.9, and a GHSV of 37,000 h⁻¹, yielded 99.9% conversion of DMS. A plausible reaction mechanism has been proposed for the oxidation of DMS based on reaction product distribution and possible intermediates formed.     

Diclofenac removal from water by ozone and photolytic TiO2 catalysed processes

BACKGROUND: The aim of this work was to establish the efficiency of single ozonation at different pH levels (5, 7 and 9) and with different TiO₂ photolytic oxidizing systems (O₂/UV‐A/TiO₂, O₃/UV‐A/TiO₂ or UV‐A/TiO₂) for diclofenac removal from water, with especial emphasis on mineralization of the organic matter. RESULTS: In the case of single ozonation processes, results show fast and practically complete elimination of diclofenac, with little differences in removal rates that depend on pH and buffering conditions. In contrast, total organic carbon (TOC) removal rates are slow and mineralization degree reaches 50% at best. As far as photocatalytic processes are concerned, diclofenac is completely removed from the aqueous solutions at high rates. However, unlike single ozonation processes, TOC removal can reach 80%. CONCLUSION: In single ozonation processes, direct ozone reaction is mainly responsible for diclofenac elimination. Once diclofenac has disappeared, its by‐products are removed by reaction with hydroxyl radicals formed in the ozone decomposition and also from the reaction of diclofenac with ozone. In the photocatalytic processes hydroxyl radicals are responsible oxidant species of diclofenac removal as well as by‐products. Copyright © 2010 Society of Chemical Industry     

Catalytic ozonation process using PAC/γ-Fe2O3 to Alizarin Red S degradation from aqueous solutions: a batch study

In the catalytic ozonation process used in this study, adsorption and chemical reactions were performed at the catalyst surface. This process can increase the efficiency of plain ozonation. The main aim of this study was to investigate the efficiency of the catalytic ozonation process in removing Alizarin Red S dye from colored water by Fe₂O₃ coated on PAC. In this work, activated carbon powder/γ-Fe₂O₃ nano-composite was modified. The BET results showed that the surface area in PAC and PAC-γ-Fe₂O₃ nano-composite was 654 and 450?m² g^?1, respectively. In this study, the best pH for removal of ARS was found to be 9. At a higher pH, the efficiency of the process decreased gradually. According to studies, catalysts increase surface area and active sites for more ozone degradation. Also, the characterization of the catalyst will play a very important role in the COP. Also, the maximum removal efficiency was observed in catalyst dose 1.1?g l^?1. The study results showed that the highest mineralization rate in ARS degradation was related to O₃/PAC/γ-Fe₂O₃. The amount of mineralization in the SOP, O₃-PAC, and O₃/PAC/γ-Fe₂O₃ was 13, 25, and 40%, respectively. The finding of mineralization of ARS using the SOP reflected the low power of the ozonation process for the mineralization of pollutants.     

Catalytic Ozonation of Oxalic Acid in the Presence of Fe2O3-Loaded Activated Carbon

ABSTRACT

The activity and optimum condition of metal-loaded activated carbon catalyst (Me/AC) for oxalic acid (OA) ozonation were evaluated. Results showed that Fe-loaded activated carbon (Fe/AC) showed better activity in five kinds of Me/AC catalysts prepared by a dipping method. Fe catalyst, crystallizing as γ-Fe₂O₃, dispersed well on AC surface. Fe₂O₃/AC, with 1.12% Fe weight ratio and 450°C calcination temperature and showed better activity for OA ozonation. 89.2% of OA was removed in the Fe₂O₃/AC/O₃ process, which was higher than those in AC/O₃ (79.6%) and O₃ (3.2%) processes. The calcination process helped to promote adsorption capability and catalytic activity of AC. In addition, Surface hydroxyl groups played a key role in Fe₂O₃/AC’s catalytic activity. Acidic condition was more favorable for OA removal in the Fe₂O₃/AC/O₃ process. A hydroxyl radical (?OH) oxidation mechanism was proven in Fe₂O₃/AC/O₃. The catalytic activity of Fe₂O₃/AC remained satisfactory after several cycles, indicating that Fe₂O₃/AC had a good reusability property.     

Catalytic Ozonation of Sulfosalicylic Acid

The investigation of heterogeneous catalytic ozonation of sulfosalicylic acid (SSal) in aqueous solution is reported in this paper. It was found that catalytic ozonation in the presence of V-O supported on silica gel had a more positive effect on the removal rate (62% in 30 min) of total organic carbon (TOC) than that of ozonation alone (20% in 30 min), and the catalyst supported on TiO₂ had similar results. The experimental results also showed that the ozone dosage should be sufficient for achieving the catalytic effect. Efficient removal of TOC in catalytic ozonation was probably attributed to producing more powerful oxidants than molecular ozone.