Wet Peroxide Oxidation Process Research Articles

Optimizing Oily Wastewater Treatment Via Wet Peroxide Oxidation Using Response Surface Methodology

The process of petroleum involves in a large amount of oily wastewater that contains high levels of chemical oxygen demand (COD) and toxic compounds. So they must be treated before their discharge into the receptor medium. In this paper, wet peroxide oxidation (WPO) was adopted to treat the oily wastewater. Central composite design, an experimental design for response surface methodology (RSM), was used to create a set of 31 experimental runs needed for optimizing of the operating conditions. Quadratic regression models with estimated coefficients were developed to describe the COD removals. The experimental results show that WPO could effectively reduce COD by 96.8% at the optimum conditions of temperature <TEX>$290^{\circ}C$</TEX>, <TEX>$H_2O_2$</TEX> excess (HE) 0.8, the initial concentration of oily wastewater 3855 mg/L and reaction time 9 min. RSM could be effectively adopted to optimize the operating multifactors in complex WPO process.

Phenol Degradation by UV-Enhanced Catalytic Wet Peroxide Oxidation Process

AbstractIn this study, degradation of phenol solution by the ultraviolet-enhanced catalytic wet peroxide oxidation process (UV-CWPO) were evaluated via COD removal. Six kinds of homogeneous catalysts (Fe

Regeneration of 4-Chlorophenol Exhausted GAC with a Microwave Assisted Wet Peroxide Oxidation Process

To improve the performance of wet oxidation for the regeneration of GAC, a microwave assisted wet peroxide oxidation process has been applied for the regeneration of 4-chlorophenol exhausted GAC. The effects of various factors including reaction temperature, H2O2 dosage, reaction time, and addition of catalyst have been studied. The regeneration improves with the increase in reaction temperature, H2O2 dosage, and reaction time. The addition of Cu2+ further promotes the regeneration process. Under the conditions of temperature 150°C, H2O2 dosage 15 mmol, reaction time 20 min, Cu2+ concentration 20 mg/L, the regenerated GAC recovers 93.5% of its adsorption capacity. A nearly complete degradation of 4-chlorophenol in the aqueous phase is observed based on UV-vis and high-performance liquid chromatography spectra studies.

Catalytic Wet Peroxide Oxidation of Epoxy Resin Wastewater for Reusing

To remove the organic compounds from epoxy resin wastewater which contains high concentration sodium chloride, a catalytic wet peroxide oxidation (CWPO) process was applied to treat it. The effect of different reaction conditions on total organic carbon (TOC) removal efficiency was evaluated, and the experimental results showed that the optimal H2O2 dosage, Fe2+ dosage, temperature, and pH were 0.735 M, 0.027 M, 90oC and 3.0, respectively. Multiple additive methods of H2O2 and Fe2+ significantly enhanced TOC removal than the one step addition. The TOC value of treated wastewater was lower than its limit for diaphragm electrolytic cell feed, thus it could be recycled to a chloro-alkali process for reusing.

Nanofiltration of partial oxidation products and copper from catalyzed wet peroxidation of phenol

The aim of this work is to study the combination of Catalytic Wet Peroxide Oxidation (CWPO) and nanofiltration processes in the treatment of phenol solutions. A home-made Cu-chitosan/Al2O3 catalyst was applied for this purpose. The effluent from CWPO usually contains some metal leached from the catalyst in addition to latter oxidation intermediates (short chain organic acids). Downstream nanofiltration is used to retain the metal leached from the catalyst, which would result in secondary pollution and negatively impact on a possible subsequent biological treatment step.The CWPO was performed in a batch recycle trickle bed reactor packed with the catalyst. The final distribution of intermediates was identified by HPLC. Cross flow filtration experiments using either model solutions containing phenol and the main intermediates (succinic, malonic, maleic and oxalic acid), with and without Cu(II) or the effluent of the CWPO reaction were performed using a NF90 membrane. When all intermediates were combined, the rejection of copper reached over 95% while an acceptable maximum of 10% of permeate flux loss, compared with the initial flux, was maintained.Nanofiltration of a real CWPO effluent gave a higher copper recovery of 97%. Thus, the permeate toxicity was highly reduced. In addition, after 4h of filtration, only a 5% of flux loss was observed, which guarantees a stable filtration for days.

Modulating the copper oxide morphology and accessibility by using micro-/mesoporous SBA-15 structures as host support: Effect on the activity for the CWPO of phenol reaction

This study presents an original approach to the improvement of advanced oxidation process (AOP) efficiencies through the design of highly active catalysts. Then, removal of phenol was obtained under mild conditions by catalytic wet peroxide oxidation (CWPO) process over silica supported micropore and/or mesopore confined copper oxide nanoparticles. The materials, i.e. y wt.% CuO (y ranging from 4 to 10) on SBA-15 exhibiting different pore structure properties, were entirely characterized. In this study, we took advantage from the evolution of the micropore fraction in the mesoporous silica with the autoclaving temperature of synthesis. While only mesopore nanocasted copper oxide nanoparticle formed when the support exhibits only mesoporosity, micropore silica confined nanoparticles other formed the two supports exhibiting both micropores and mesopores. In this case, mesopore nanocasted nanoparticles can be only observed when copper oxide loading reaches 10wt.%. As a consequence, the copper active surface is suggested to be higher when copper incorporates interconnected micropores, without limited pore plugging issued from mesopore confined nanoparticle formation.For the phenol removal reaction, all the materials are exhibiting interesting activity, with a complete conversion of phenol and almost 60–80% of mineralization obtained in less than 2h at 60°C. Nevertheless, the results showed that the increase in copper loading up to high values is not needed to achieve high mineralization degree, due to the typical morphology of the materials, i.e. confinement of nanoparticles inside micropores or mesopores. In addition, the prepared materials allow a continuous use in reaction with leaching of active phase (≤4.4mgL−1) which also results in no water post-purification for cation removal as in the case of the classical homogeneous Fenton process.

Supported gold nanoparticle catalysts for wet peroxide oxidation

Supported gold nanoparticles are of promising interest in wet hydrogen peroxide oxidation processes due to their efficient hydrogen peroxide consumption and adequate stability. Here, the origin of the catalytic properties of gold in this environmental process is explored by analyzing the influence of the support and the particle size on the activity of supported gold nanoparticles along with the influence of the nature of the target pollutant on the gold reactivity. The reaction mechanism for the oxidation of phenol with activated carbon-supported gold nanoparticles is proposed and the selectivity evaluated. A reaction pathway has been also proposed.The results demonstrate that wet peroxide oxidation is a support and gold size dependent reaction. Activated carbon is the preferable candidate versus TiO2 and Fe2O3 supports and small gold nanoparticles, desirably lower than 3nm, show the highest TOF values. Supports showing adsorption capacity towards the target pollutant contribute to a more efficient use of hydrogen peroxide and, improve the TOF values for the oxidation and mineralization. Organic pollutants forming intermediate complexes with gold, viz. alcohols, are more efficiently oxidized. The inclusion of gold improves substantially the selectivity towards mineralization with respect to the bare activated carbon.

Regeneration of CuZnO&lt;sub&gt;x&lt;/sub&gt;/γ-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; as a Heterogeneous Catalyst in CWPO Process

This paper evaluates the catalytic effectiveness of CuZnOx/γ-Al2O3 catalyst for the degradation of an azo dye, acid red GR, using H2O2 as an oxidant, under very mild conditions (atmospheric pressure and t = 40 ). In the catalytic wet peroxide oxidation (CWPO) process, the results show that it is possible to remove 80% of COD during the initial 30 h. But a considerable drop of catalytic activity is found after prolonged run. As characterization datas shown, the deactivation of the catalyst is caused by the depositon of intermediates on the surface and serious coverage of the active sites. However, calcination method which is possible to burn the organic species that trapped in the catalyst reaches complete restoration of the spent catalyst.

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 HYDROGEN PEROXIDE OXIDATION OF 4-CHLOROPHENOL OVER IRON-EXCHANGED CLAYS

Chlorophenols were selected for this study because most of them are toxic and difficult to biodegrade. They represent a particular group of priority toxic pollutants listed by the US EPA in the Clean Water Act and by the European Decision 2455/2001/EC. The efficiency of advanced oxidation processes for degradation of chlorophenols has been extensively documented. The catalytic wet hydrogen peroxide oxidation process, involving oxidation with H2O2 and solid catalysts in mild reaction conditions, was found to be very attractive for different pollutants; however, data regarding the degradation of chlorophenols are very scarce. The aims of this paper were: (i) to prepare and characterize a series of iron-exchanged montmorillonites and (ii) to assess their catalytic performances in a Fenton-like process for the oxidation of para-chlorophenol. DR-UV-VIS spectroscopy was tentatively used to elucidate the structure of the iron oxo sites intervening in the reaction. This approach has been used previously for ion-exchanged zeolites and was able to distinguish between isolated Fe(III) species and FexOy clusters of different nuclearity. The catalytic tests, performed at room temperature, showed that all iron-containing clays were very active, leading to the complete oxidation of parachlorophenol and a significant reduction of TOC values. 4-chlorocatechol was the major reaction intermediate found in the CWHPO of 4-CP, followed by hydroquinone and traces of benzoquinone, 5-chloro-1,2,4-benzenetriol, 1,2,4-benzenetriol and 3chloro-muconic acid. The leaching test indicates that the catalytic activity is mainly due to leached iron ions, at least in the second part of the process.

Heterogeneous catalytic wet peroxide oxidation systems for the treatment of an industrial pharmaceutical wastewater

The aim of this work was to assess the treatment of wastewater coming from a pharmaceutical plant through a continuous heterogeneous catalytic wet peroxide oxidation (CWPO) process using an Fe 2O 3/SBA-15 nanocomposite catalyst. This catalyst was preliminary tested in a batch stirred tank reactor (STR), to elucidate the influence of significant parameters on the oxidation system, such as temperature, initial oxidant concentration and initial pH of the reaction medium. In that case, a temperature of 80 °C using an initial oxidant concentration corresponding to twice the theoretical stoichiometric amount for complete carbon depletion and initial pH of ca. 3 allow TOC degradation of around 50% after 200 min of contact time. Thereafter, the powder catalyst was extruded with bentonite to prepare pellets that could be used in a fixed bed reactor (FBR). Results in the up-flow FBR indicate that the catalyst shows high activity in terms of TOC mineralization (ca. 60% under steady-state conditions), with an excellent use of the oxidant and high stability of the supported iron species. The activity of the catalyst is kept constant, at least, for 55 h of reaction. Furthermore, the BOD 5/COD ratio is increased from 0.20 to 0.30, whereas the average oxidation stage (AOS) changed from 0.70 to 2.35. These two parameters show a high oxidation degree of organic compounds in the outlet effluent, which enhances its biodegradability, and favours the possibility of a subsequent coupling with a conventional biological treatment.

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.

Use of membrane contactors as an efficient alternative to reduce effluent ecotoxicity

This works reports on the separation and recovery of copper cations from water streams from the wet peroxide oxidation process (WPO) using emulsion pertraction technology (EP) in hollow-fiber contactors as separation technology. The separation of the metal was enhanced by using LIX622N as a selective extractant, and its concentration took place in a sulphuric acid phase. The ecotoxicity characterization, according to the Vibrio fischeri bioassay of the waters coming from the WPO process, revealed that the presence of a residual copper catalyst gave the oxidized waters the character of being ecotoxic. Nevertheless, the subsequent removal of copper in the EP process produced non-ecotoxic oxidized water. Finally, the recovered copper catalyst obtained as concentrated copper sulphate solution in the emulsion pertraction process was recycled to the oxidation reactor, checking experimentally that the oxidation efficiency was maintained.

Nanocomposite of crystalline Fe 2O 3 and CuO particles and mesostructured SBA-15 silica as an active catalyst for wet peroxide oxidation processes

Crystalline Fe 2O 3 and CuO particles have been incorporated into surfactant-templated SBA-15 materials by direct synthesis. Activity and stability of this material were evaluated on the wet peroxide oxidation of phenol under mild reaction conditions. Its catalytic performance was monitored in terms of total organic carbon (TOC) conversion. The stability was determined by careful measurements of metal leaching into the aqueous solution. The presence of copper prevents the leaching of iron species and increases TOC degradation as compared with those materials containing only crystalline Fe 2O 3 particles. Moreover, the treatment of iron–copper composite materials under controlled acidic conditions in the presence of hydrogen peroxide leads to the stabilization of metallic species, maintaining TOC degradation rates similar to the fresh catalyst. Thus, this work introduces a new material with interesting properties as catalysts in advanced oxidation processes for pollutant abatement in waste waters.

Membrane contactors for the recovery of metallic compounds: Modelling of copper recovery from WPO processes

This work reports the comparative analysis of two types of separation processes aimed at the recovery of metallic compounds from residual waters by using hollow fiber modules as membrane contactors, i.e., emulsion pertraction, EPP, and non-dispersive solvent extraction, NDSX. As a representative example the recovery of the copper used as homogeneous catalyst in wet peroxide oxidation (WPO) processes is experimentally and theoretically analysed. The separation of the metal was enhanced by using LIX622N as selective extractant and its concentration took place in a concentrated sulphuric acid phase. Working with hollow fibers as membrane contactors, the mathematical modelling of the emulsion pertraction process is reported. Characteristic parameters have been determined as the membrane mass transfer coefficient, k m = 2.2 × 10 −6 m s −1, the equilibrium constant of the extraction/back-extraction reaction K EX = 22, the forward reaction kinetic constant k 1 = 2.78 × 10 −7 m s −1 and the specific area of the globules of the stripping phase A v = 2.54 × 10 4 m −1. Finally, the results of copper separation and concentration have been compared to previous results obtained working with two hollow fiber modules, one for the extraction and the second for the back-extraction process and, as expected, a good agreement was observed. Two main advantages of the EPP could be underlined: (i) reduction of the needed membrane area of the contactor and (ii) higher concentrations in the stripping phase can be obtained with the operation conditions used (at laboratory scale).

Ultrasound assisted catalytic wet peroxide oxidation of phenol: kinetics and intraparticle diffusion effects

The combination of ultrasound irradiation and catalytic wet peroxide oxidation was used as a means to degrade phenol. Direct and indirect irradiation were employed, while experiments in the absence of ultrasound were used as reference. A mixed (Al–Fe) pillared clay named FAZA, was used as a catalyst in the form of powder, extrudates and crushed extrudates. Ultrasound was found to clearly enhance the extrudates performance, increasing the conversion at 4 h by more than 6 times under direct and almost 11 times under indirect irradiation. This observation is attributed to the reduction of diffusion resistance within the catalyst pores. The overall sonication-catalytic wet peroxide oxidation process appears very promising for environmental purposes.

Application of hollow fiber membrane contactors for catalyst recovery in the WPO process.

In this work the use of a membrane based liquid extraction process for recovery of the homogeneous catalyst employed in the wet peroxide oxidation process (WPO) is studied. In the WPO process the oxidation agent is the hydroxyl radical that is obtained by using a combination of hydrogen peroxide and a mixture of Fe(II), Cu(II), and Mn(II) in aqueous solution. The mixture of metallic cations permits the almost total degradation of the refractory organic compounds, but the use of metallic salts as catalysts induces additional pollution. To recover the homogeneous catalyst of the WPO process by means of non-dispersive solvent extraction (NDSX) two hollow fiber membrane contactors are employed, one for the extraction step and the second for the back-extraction step. From the initial assays, the extractant LIX 622N was selected for Cu(II) recovery and Cyanex 272 for Fe(II) and Mn(II) recovery. Selective separation of Fe(II) and Mn(II) can be obtained by adjusting the pH of the feed aqueous phase. The three metals are stripped using sulfuric acid to give concentrated solutions of CuSO(4), FeSO(4), and MnSO(4) that can be recycled to the formulation of the catalyst solution of the WPO process. A mathematical model has been proposed to describe the recovery of Cu. Two design parameters are required: the membrane mass transport coefficient of the extraction and stripping modules (k(m) = 3.07 x 10(-7) m/sec) and the equilibrium parameter of the extraction reaction (K(Ex) = 0.0832).

Wet Oxidation of Carboxylic Acids with Hydrogen Peroxide. Wet Peroxide Oxidation (WPO®) Process. Optimal Ratios and Role of Fe:Cu:Mn Metals

The wet peroxide oxidation process (WPO®) which was developed at the laboratory uses the Fenton's reagent at high temperature. But the reaction efficiency is limited by the accumulation of volatile fatty acids such as oxalic, malonic, succinic and acetic acids (hereafter OMSA). In order to improve the efficiency of the original process, different transition metal ions are tested as catalyst. The experimental results indicate that the system using homogeneous Fe, Cu, and Mn is a promising one. The oxidation of carboxylic acids is quite completed under mild working conditions (T < 100°C, pH = 3, p = 1 atm, reaction time = 1 h, stoichiometric quantity of H2O2 = 1.5). Optimal design methodology is applied to the catalytic mixture Fe:Cu:Mn in order to determine the optimal proportions of each metal. This results in the determination of an important synergistic effect between the metals and an optimal zone. Cu(II), Mn(II) or Fe(II) alone have a slight catalytic effect while the association is very effective on ...

Wet Oxidation of Carboxylic Acids with Hydrogen Peroxide. Wet Peroxide Oxidation (WPO®) Process. Optimal Ratios and Role of Fe:Cu:Mn Metals

Wet Oxidation of Carboxylic Acids with Hydrogen Peroxide. Wet Peroxide Oxidation (WPO®) Process. Optimal Ratios and Role of Fe:Cu:Mn Metals