Wet Peroxide Research Articles

Treatment of an agrochemical wastewater by integration of heterogeneous catalytic wet hydrogen peroxide oxidation and rotating biological contactors

The treatment of a non-biodegradable agrochemical wastewater has been studied by coupling of heterogeneous catalytic wet hydrogen peroxide oxidation (CWHPO) and rotating biological contactors (RBCs). The influence of the hydrogen peroxide dosage and the organic content of the wastewater (dilution degree) were studied. The CWHPO of the raw wastewater at 80°C and using a moderate amount of oxidant (0.23gH2O2/gTOC) reduced significantly its total organic carbon content and increased its biodegradability. Likewise, the iron leaching of the heterogeneous catalyst (Fe2O3/SBA-15) was less than 2mg/L in the treated effluent. Under the best operating conditions, the resultant CWHPO effluent was successfully co-treated by rotating biological contactors (RBCs) using a simulated municipal wastewater with different percentages of the CWHPO effluent (2.5, 5 and 10%v/v). The RBCs showed high stability for the treatment of the highest percentage of the CWHPO effluent, achieving total organic carbon (TOC) and total nitrogen (TN) reductions of ca. 78% and 50%, respectively. The integration of both processes on a continuous mode has been successfully accomplished for the treatment of the as-received agrochemical wastewater.

Magnetically Separable Fe3O4 Nanoparticles-Decorated Reduced Graphene Oxide Nanocomposite for Catalytic Wet Hydrogen Peroxide Oxidation

Fe3O4 nanoparticles-decorated reduced graphene oxide magnetic nanocomposites (Fe3O4/rGO NCs) were prepared by a facile one-step strategy, and further used as heterogeneous Fenton-like catalysts for catalytic wet hydrogen peroxide oxidation (CWHPO) of methylene blue (MB) at 25 °C and atmospheric pressure. The effects of variables such as the Fe3O4/rGO with the mass ratio of rGO, initial pH, MB concentration and H2O2 dosage were investigated. The Fe3O4/rGO NCs with rGO mass ratio of 10.0 wt % showed the highest H2O2-activating ability, which was six-fold than that of pure Fe3O4 nanoparticles (NPs). The resulting catalysts demonstrated high catalytic activity in a broad operation pH range from 5 to 9, and still retained 90.5 % catalytic activity after reuse in five cycles. Taking advantage of the combined benefits of rGO and magnetic Fe3O4 NPs, these Fe3O4/rGO NCs were confirmed as an efficient heterogeneous Fenton-like catalyst for CWHPO to treat organic pollutants. And a reasonable catalytic mechanism of Fe3O4/rGO NCs was proposed to interpret the degradation process.

Study on Catalytic Wet Oxidation of H-Acid Containing Water over Fe/SiO<sub>2</sub> Catalyst

This study has investigated the degradation of H-acid (1-amino-8-naphthol-3, 6-disulfonic acid) containing water by catalytic wet hydrogen peroxide oxidation method, in which the catalyst of Fe/SiO2 was prepared by impregnation technology. The effect of catalyst dosage, initial pH value, amount of hydrogen peroxide and reaction temperature on the degradation process have been discussed, and the results indicated that wet hydrogen peroxide oxidation is an effective method for treating the wastewater containing H-acid, under the conditions that: catalyst dosage was 2 g, initial pH value was 7, amount of hydrogen peroxide was 10 mL (0.83 time of theoretical required amount) and reaction temperature was 80 °C, the COD and color removal rate can reach 87.3% and 96.5%, respectively.

Catalytic oxidation with Al–Ce–Fe–PILC as a post-treatment system for coffee wet processing wastewater

The effluent from the anaerobic biological treatment of coffee wet processing wastewater (CWPW) contains a non-biodegradable compound that must be treated before it is discharged into a water source. In this paper, the wet hydrogen peroxide catalytic oxidation (WHPCO) process using Al-Ce-Fe-PILC catalysts was researched as a post-treatment system for CWPW and tested in a semi-batch reactor at atmospheric pressure and 25 °C. The Al-Ce-Fe-PILC achieved a high conversion rate of total phenolic compounds (70%) and mineralization to CO(2) (50%) after 5 h reaction time. The chemical oxygen demand (COD) of coffee processing wastewater after wet hydrogen peroxide catalytic oxidation was reduced in 66%. The combination of the two treatment methods, biological (developed by Cenicafé) and catalytic oxidation with Al-Ce-Fe-PILC, achieved a 97% reduction of COD in CWPW. Therefore, the WHPCO using Al-Ce-Fe-PILC catalysts is a viable alternative for the post-treatment of coffee processing wastewater.

Development of a Predictive Model for Removal of Organic Matter from Leachate Landfill by Catalytic Oxidation Using Response Surface Methodology

In this work the heterogeneous Fenton catalytic experiments were arranged in a CCF experimental design and analyzed by response surface methodology, for every peroxide concentration. These response surfaces were the representation of a quadratic predictive model developed for improving of biochemical o xygen demand at five days/chemical o xygen demand (BDO5/COD) ratio, trough the optimizat ion parameters of reaction. For this proposal 18 catalytic tests were carried out evaluating three main factors: pero xide concentration, catalyst loading and the peroxide addition rate. The results in confronting with the experimental data showed that fro m 60 minutes the catalytic wet pero xide oxidation (CWPO) react ion was stationated in focusing the chemical COD removal, inclusively in any opportunities these values were decreased maybe because new co mpounds had been formed and we supposed that these new co mpounds were with biodegradable character because this behavior was perfect ly answered by the prediction model, hence with this new and enhancent ratio there are possibilities to get in to the biological process again for the refine the effluent and co mply with the actual regulation. The best conditions predicted for the model are at 4.68M pero xide concentration, catalyst loading charge (CL) (0.5 - 0.6%) and pero xide addit ion rate (PAR) (7.5 - 10 mL/h) to imp rove its biodegradability to 0.30, thus this effluent might come back to the begin of plant fo r refin ing the treatment.

Combination of wet disk milling and hydrogen peroxide treatments for enhancing saccharification of sugarcane bagasse

A pretreatment method using wet disk milling (WDM) and hydrogen peroxide (HP) was investigated to produce a saccharified solution with a high glucose concentration from sugarcane bagasse. The chemical composition of the bagasse was uninfluenced by WDM treatment alone, whereas a slight reduction in the contents of lignin and xylan was effected by HP treatment alone performed at neutral pH. The combination of WDM treatment and HP treatment (WDM–HP treatment) significantly increased the removal of lignin and xylan. A cellulose-rich material containing 87% glucan was obtained by performing the HP treatment at 70°C using 2.5% biomass, after WDM treatment. By using 15% WDM, HP- and WDM–HP-treated bagasse, glucose concentrations of 28g/L, 27g/L, and 98g/L, respectively, were obtained from the various saccharification processes, suggesting the feasibility of the WDM–HP treatment for the production of a saccharified solution with high glucose concentration. Moreover, WDM–HP-treated bagasse was shown to be a good substitute for cellulose in cellulase production by Acremonium cellulolyticus. Under the same conditions, the treated bagasse provided a cellulase activity of 8.2FPU/mL compared with the value of 7.9FPU/mL provided by the commercial cellulose, SF 40.

Synthesis of stable Cu-supported pillared clays for wet tyrosol oxidation with H2O2

In the present paper the synthesis of stable Cu-containing pillared clays catalysts (Cu-PILCs) is described. These catalysts were prepared by the solid-state reaction of Al-pillared clay with copper nitrate. The resultant materials were then treated with an oxalic acid solution in order to improve the dispersion of metal species on the alumina pillars. Characterization studies were performed by use of X-ray diffraction, nitrogen adsorption at 77K, chemical analysis, temperature-programmed reduction (H2-TPR) and transmission electron microscopy (TEM). The texture of the copper catalysts showed a high specific surface area and microporosity (197m2g−1 and 0.081cm3g−1 respectively for the catalyst Cu5.6Al-PILC), with high loading of copper (up to 4.72Cuwt%). TPRprofiles of catalysts show the presence of isolated copper species with high interaction with the alumina pillars.The properties of copper-based catalysts have been studied in the wet hydrogen peroxide oxidation of an aqueous solution of tyrosol, a molecule which constitutes more than half of the light fraction of the olive mill wastewater. The reaction was conducted in batch and flow reactors. Performance of catalysts remained quite excellent; total removal of tyrosol with high TOC abatement (around 65%) was obtained after 2h reaction. Furthermore, the Cu5.6Al-PILC(t) catalyst showed very high stability and performance in the flow reactor: 90% of tyrosol conversion and 78% of TOC removal are obtained in 192h on stream, without the detection of any change in the activity.

A lumped kinetic model based on the Fermi's equation applied to the catalytic wet hydrogen peroxide oxidation of Acid Orange 7

A catalytic wet hydrogen peroxide process was applied for the degradation of an azo dye – Acid Orange 7, also called Orange II (OII) – using as catalyst a pillared saponite clay impregnated with 21wt.% of iron. Tests were carried out in a slurry batch reactor, following along time the OII degradation, the dye mineralization and the iron leaching from the support. A detailed parametric study was done, changing one variable at a time, while keeping the others constant. Among the variables studied (temperature, catalyst dose, and initial concentration of oxidant – H2O2 – or dye), temperature revealed to have a marked effect, increasing reaction rate but also iron leaching from the support (which was in all cases still negligible, thus allowing to comply with legislated standards and evidencing the heterogeneous character of the process). A previously developed semi-empirical kinetic model, based on the Fermi's equation (the mirror image of the logistic function), was used to successfully describe the evolution of the OII concentration in this complex process. Such equation was extended in the present work by developing a lumped model proposed to predict the evolution of the total organic carbon along time; this model also showed very good adherence to the experimental data.

Phenol Degradation by Catalytic Wet Hydrogen Peroxide Oxidation on Fe/Active Carbon Catalyst

A catalyst based on Fe/active carbon (Fe/AC) and H2O2 as oxidant for the catalytic wet hydrogen peroxide oxidation of phenol in aqueous solution was investigated. The results indicate that the degradation rate of phenol(20mg/L) reach 90.5% in the presence of Fe/AC(2g/L) and hydrogen peroxide (0.5 %) at pH value 7 after 5 hours under normal temperature and atmospheric pressure. Kinetic studies of the degradation reaction show that the degradation rate of phenol nearly follows the first-order reaction. The reaction rate constant and activity energy are 0.4162 min-1 and 23.64 kJ/mol at 25°C, respectively.

Development of Pillared Clays for Wet Hydrogen Peroxide Oxidation of Phenol and Its Application in the Posttreatment of Coffee Wastewater

This paper focuses on the use of pillared clays as catalysts for the Fenton-like advanced oxidation, specifically wet hydrogen peroxide catalytic oxidation (WHPCO). This paper discusses the limitations on the application of a homogeneous Fenton system, development of solid catalysts for the oxidation of phenol, advances in the synthesis of pillared clays, and their potential application as catalysts for phenol oxidation. Finally, it analyzes the use of pillared clays as heterogeneous Fenton-like catalysts for a real wastewater treatment, emphasizing the oxidation of phenolic compounds present in coffee wastewater. Typically, the wet hydrogen peroxide catalytic oxidation in a real effluent system is used as pretreatment, prior to biological treatment. In the specific case of coffee wet processing wastewater, catalytic oxidation with pillared bentonite with Al-Fe is performed to supplement the biological treatment, that is, as a posttreatment system. According to the results of catalytic activity of pillared bentonite with Al-Fe for oxidation of coffee processing wastewater (56% phenolic compounds conversion, 40% selectivity towards CO2, and high stability of active phase), catalytic wet hydrogen peroxide oxidation emerges as a viable alternative for management of this type of effluent.

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.

Catalytic Oxidation of Industrial Wastewater Under Mild Conditions

Cerium–zirconia-supported ruthenium and activated carbon catalysts were used in catalytic wet air (CWAO) and wet peroxide (CWPO) oxidation of industrial wastewater. Both catalysts were active in the removal of TOC and COD from the wastewater. The degree of biodegradation of organic matter increased during CWAO. Therefore, the CWAO process could be considered as a potential pre-treatment process integrated with subsequent biological treatment to achieve the required level of purification of wastewater.

Catalytic wet hydrogen peroxide oxidation of para-chlorophenol over Al/Fe pillared clays (AlFePILCs) prepared from different host clays

In this work, three AlFePILCs prepared from different host clays were synthesized, characterized and tested in the catalytic wet hydrogen peroxide oxidation of 4-chlorophenol. Two reference clays, with widely different cation exchange capacities (1.2meq/g for SAz-1 and 0.87meq/g for SWy-2), and a Romanian montmorillonite (Mt) were used for the preparation of the catalysts, their structural and textural properties being determined by X-ray diffraction and nitrogen adsorption-desorption isotherms. The catalyst based on SAz-1 has a more ordered structure and a higher surface area than the other two catalysts, prepared from SWy-2 and Mt, and this was attributed to its higher layer charge. The 4-chlorophenol oxidation proceeds with the formation of 4-chlorocatechol (main reaction intermediate) and hydroquinone. Other chlorinated benzenediols and triols as well as dimerization products have been also identified by derivatization and GC–MS analysis. All the catalysts allowed the total elimination of 4-chlorophenol and significant removal efficiencies for the total organic carbon, of 60, 52 and 45%, for Mt, SWy-2 and SAz-1 based catalysts, respectively. The iron leaching was very low, but the most active catalyst produced the higher amount of dissolved iron (1ppm), as compared with AlFePILCs based on SWy-2 and SAz-1 (0.5ppm). To explain the differences in the catalytic properties, Mössbauer and diffuse-reflectance UV–vis spectroscopies were used to investigate the nature of the active sites. Both methods suggested the presence of two iron species: low-nuclearity ferric oxides and well-ordered hematite-like nanoparticles. The low-nuclearity ferric oxides seem to be responsible for the iron leaching and for the differences in the catalytic activity.

Catalytic wet hydrogen peroxide oxidation of H-acid in aqueous solution with TiO 2–CeO 2 and Fe/TiO 2–CeO 2 catalysts

TiO 2–CeO 2 and Fe/TiO 2–CeO 2 catalysts were prepared by the methods of co-precipitation and impregnation, respectively, and evaluated through the catalytic wet peroxide oxidation treatment of H-acid solution in the high concentration aqueous medium under mild experimental conditions. Furthermore, the catalysts were characterized by BET, XRD, SEM-EDX and TEM. The results showed that iron-containing samples were comparatively more active, Fe/TiO 2–CeO 2 (Ti/Ce 9/1, 2 wt.% Fe) was a very efficient catalyst to oxidize the pollutants of dye industry such as H-acid into biodegradable species and doping cerium into TiO 2 obviously restrained the growth of crystal, greatly enhancing the surface areas of the catalysts. At the reaction temperature of 100 °C, initial pH of 5.0, the atmospheric pressure and the theoretical dosage of peroxide, 98.1% color removal, 89.6% COD and 65.4% TOC reduction with Fe/TiO 2–CeO 2 catalyst were obtained.

Degradation of Acid Orange 7 using a saponite-based catalyst in wet hydrogen peroxide oxidation: Kinetic study with the Fermi's equation

In the current work, the degradation of Acid Orange 7 (also called Orange II – OII) by a heterogeneous catalytic wet hydrogen peroxide process has been described by a simple semi-empirical kinetic model, based on the Fermi's equation, which captures simultaneously the influence of all the reaction conditions with few adjustable parameters. Complete decolorization was reached in less than 4h, using as catalyst a pillared saponite clay impregnated with Fe(II) acetylacetonate (16wt.% of iron) in a slurry batch reactor. The model was fitted to the dye concentration histories, being the kinetic parameters determined by non-linear regression. The adherence of the model to the data was remarkable, and the effect of the operating conditions (temperature, catalyst dose and both pollutant and hydrogen peroxide concentration) on the fitting parameters – apparent rate constant and transition time – was analyzed.

A compact process for the treatment of olive mill wastewater by combining wet hydrogen peroxide catalytic oxidation and biological techniques

A system based on combined actions of catalytic wet oxidation and microbial technologies for the treatment of highly polluted OMW containing polyphenols was studied. The wet hydrogen peroxide catalytic oxidation (WHPCO) process has been investigated in the semi-batch mode at atmospheric pressure, using aluminium–iron-pillared inter layer clay ((Al–Fe)PILC), under two different catalytic processes: ((Al–Fe)PILC/H 2O 2/ultraviolet radiations) at 25 °C and ((Al–Fe)PILC/H 2O 2) at 50 °C. The results show that raw OMW was resistant to the photocatalytic process. However ((Al–Fe)PILC/H 2O 2), system operating at 50 °C reduced considerably the COD, colour and total phenolic contents, and thus decreased the inhibition of the marine photobacteria Vibrio fischeri luminescence by 70%. This study also examined the feasibility of coupling WHPCO and anaerobic digestion treatment. Biomethanisation experiments performed with raw OMW or pre-treated OMW proved that pre-treatments with ((Al–Fe)PILC/H 2O 2) system, for more than 2 h, resulted in higher methane production. Both untreated OMW as well as 2-h pre-treated OMW revealed as toxic to anaerobic bacteria.

Cu−Zn−(Mn)−(Fe)−Al Layered Double Hydroxides and Their Mixed Metal Oxides: Physicochemical and Catalytic Properties in Wet Hydrogen Peroxide Oxidation of Phenol

Cu−Zn−Mn−Fe−Al layered double hydroxides (LDHs) with Cu/Zn/Mn/Fe/Al atomic ratios of 1/1/0/0/1, 1/1/1/0.3/0.7, and 1/0.7/0.3/0.3/0.7, respectively, in synthesis mixture were prepared by coprecipita...

Copper hydroxyphosphate as catalyst for the wet hydrogen peroxide oxidation of azo dyes

Copper hydroxyphosphate was synthesized hydrothermally and characterized by XRD and SEM. The peroxide degradation of azo dye on this material was evaluated by examining initial pH, catalyst loading, H 2O 2 dosage, initial dye concentration and temperature. Although copper hydroxyphosphate is a low surface area material without micropores or mesopores, it shows considerable activity for oxidative degradation of azo dyes under near-neutral pH conditions. A catalyst with such simple and clear structure may be a suitable model material for research on the mechanism of generating hydroxyl radicals and heir destruction of organic molecules.

Catalytic wet hydrogen peroxide oxidation of a petrochemical wastewater

Continuous Catalytic Wet Hydrogen Peroxide Oxidation (CWHPO) for the treatment of a petrochemical industry wastewater has been studied on a pilot plant scale process. The installation, based on a catalytic fixed bed reactor (FBR) coupled with a stirred tank reactor (STR), shows an interesting alternative for the intensification of a continuous CWHPO treatment. Agglomerated SBA-15 silica-supported iron oxide (Fe(2)O(3)/SBA-15) was used as Fenton-like catalyst. Several variables such as the temperature and hydrogen peroxide concentration, as well as the capacity of the pilot plant for the treatment of inlet polluted streams with different dilution degrees were studied. Remarkable results in terms of TOC reduction and increased biodegradability were achieved using 160 degrees C and moderate hydrogen peroxide initial concentration. Additionally, a good stability of the catalyst was evidenced for 8 hours of treatment with low iron leaching (less than 1 mg/L) under the best operating conditions.

Synthesis of polymer-supported copper complexes and their evaluation in catalytic phenol oxidation

Polymer-supported metal complexes have been used as catalysts for the catalytic wet hydrogen peroxide oxidation (CWPO) of phenol. The synthesis of six catalysts derived from three polymer-supports (a polybenzimidazole resin and two poly(styrene-divinylbenzene) resins) and two Cu(II) salts. The catalytic oxidation of phenol with initial phenol concentration of 1 g L −1 was performed in a 200 mL batch stirred tank reactor at 30 °C and atmospheric pressure. Under these conditions, phenol conversion and total organic carbon conversion were evaluated. The highest phenol conversion was 93% obtained for poly(DVB-co-VBC) functionalised with iminodiacetic acid (IMDA) and loaded with copper acetylacetonate, however metal leaching was very unsatisfactory. If metal leaching was taken into consideration, it was found that polybenzimidazole loaded with copper sulphate appeared to be the most stable yielding 54% of mineralisation and 0.75 TOC/phenol conversion efficiency with simultaneously low release of metal during the oxidation.