Catalytic Wet Peroxide Oxidation Process Research Articles

Comparative Study Using Chemical Wet Oxidation for Removal of Reactive Black 5 in the Presence of Activated Carbon

The objective of this study was to assess the feasibility of various chemical wet oxidation techniques to remove azo dyes from wastewater. The performances of three different catalytic wet oxidation techniques were evaluated: catalytic wet air oxidation (CWAO), catalytic wet peroxide oxidation (CWPO), and hydrogen peroxide promoted wet air oxidation (PCWAO), using activated carbon as a catalyst to evaluate the degradation and decolorization of Reactive Black 5 in aqueous solution. The experiments were also conducted to investigate the optimum operating conditions of the processes, such as temperature, pH, activated carbon loading, H2O2 loading, and reaction time. This investigation revealed that all of the wet oxidation techniques showed similar results and rather high removal efficiencies, but at different operating conditions. At the optimized conditions, the degradation was generally approximately 85% and decolorization was nearly 95% in each case. The operating conditions were as follows: in the CWAO process, higher temperature (70°C) and higher activated carbon loading (0.5 g/L) were used; in the CWPO process, a lower temperature (0.25 g/L) was used but a high amount of H2O2 was added (0.1 mL/250 mL solution); and in the PCWAO process, a lower amount of H2O2 was added (0.01 mL/250 mL solution) and higher temperature (70°C) was necessary to achieve the required performance.

The treatment of azo dyes found in textile industry wastewater by anaerobic biological method and chemical oxidation

The treatment of synthetic wastewater containing azo dyes found in textile industry wastewater was carried out by anaerobic biological method and chemical oxidation. The main target of this study was to compare different treatment methods and to evaluate the effect of different parameters on treatment effectiveness. In the microbial process, the results have shown that increasing the residence time, the amount of yeast extract and the addition of microorganisms originally growing on forest residues had positive effects on the dye removal. In the catalytic wet peroxide oxidation process, CWPO, the reaction conditions were optimized at 0.5 g/L activated carbon loading with 2 mL H 2O 2/300 mL solution (35 wt%), at 80 °C, in 2 h with pH = 3. At the optimum conditions, approximately 93% of the dye was removed. At these optimized conditions, the CWPO process was tested with real textile industry wastewater. The percentage of dye removal with this wastewater was 50%. The adsorption effect of the activated carbon was also investigated. At pH = 7, the removal by just adsorption was around 15%. But in acidic conditions (pH = 3) and at higher temperatures the adsorption effect of activated carbon increased. Adsorption and oxidation performances were compatible at 80 °C, however, at lower temperatures the adsorption effect was more considerable than the oxidation. It can be concluded that, generally the decolorization was accomplished by 60% adsorption and by 40% oxidation.

Catalytic Wet Peroxide Oxidation Process for the Continuous Treatment of Polluted Effluents on a Pilot Plant Scale

AbstractCatalytic Wet Peroxide Oxidation (CWPO) for the continuous treatment of a phenolic aqueous solution has been studied on a pilot scale process. The pilot plant has been designed by integration of a catalytic fixed bed reactor (FBR) with a continuous stirred tank reactor (CSTR). The CSTR is used as reservoir for the continuous delivering of a recirculation stream through the catalytic bed. The main part of phenol mineralization takes place by catalytic oxidation in the FBR. The mesoporous SBA-15 silica-supported iron oxide (Fe

Reuse of a dyehouse effluent after being treated with the combined catalytic wet peroxide oxidation process and the aerated constructed wetland

A catalytic wet peroxide oxidation process was combined with the aerated constructed wetland in order to treat the raw dyehouse wastewater to in acceptable level for reuse as washing process water. More than 90% of BOD and CODs could be removed with the wet peroxide oxidation reactor and the remaining pollutants in the treated water were transformed into biodegradable ones which could have been successfully treated at the following aerated constructed wetland. The highest values of BOD5, CODMn, CODCr, SS and T-N in the treated water were 1.6, 1.8, 2.1, 0.5 and 12.8 mg/L, respectively. These values were low enough for the treated water to be reused at the washing process.

Crystallization mechanism of Fe-MFI from wetness impregnated Fe 2O 3–SiO 2 amorphous xerogels: Role of iron species in Fenton-like processes

The crystallization mechanism of Fe-MFI zeolite synthesized from amorphous Fe 2O 3–SiO 2 xerogels wetness impregnated with aqueous TPAOH solutions has been studied. Samples with different degrees of crystallinity were prepared and characterized by means of conventional techniques. Activity and stability of these iron-containing samples has been tested in the catalytic wet peroxide oxidation (CWPO) of phenolic aqueous solutions. The crystallization mechanism involves a partial dissolution of the initial xerogel to yield an amorphous material. Nucleation and growth of the MFI phase is effected by reorganisation of the amorphous phase, although crystal growth also involves the incorporation of iron and silicon species during the last stage of the crystallization. A highly crystalline Fe-silicalite material is obtained after 3 h of synthesis at 170 °C. Spectroscopic studies reveal that iron species are in framework positions (isomorphously substituted) in this highly crystalline material. In addition, the environment of Fe atoms as well as textural properties of the samples is dramatically modified along the crystallization affecting significantly to their catalytic activity and stability in CWPO processes.