Heterogeneous Fenton Oxidation Research Articles

EDTA enhanced heterogeneous Fenton oxidation of dimethyl phthalate catalyzed by Fe3O4: Kinetics and interface mechanism

It has been noticed that some chelating agents can enhance heterogeneous Fenton reactions, as well as homogeneous Fenton reactions. However, the mechanism of the enhanced heterogeneous Fenton reactions remains speculative, due to the ambiguous concurrence of homogeneous and heterogeneous reactions. In the present work, ethylene diamine tetraacetic acid (EDTA) was introduced to study the role of the chelating agent in the oxidation of dimethyl phthalate (DMP) in nano-Fe3O4/H2O2 system. The addition of EDTA in solution dramatically accelerated DMP removal partly due to the induced homogeneous Fenton reaction by enhanced dissolution of Fe3O4. Meanwhile, the adsorbed EDTA on the catalyst could also enhance DMP removal. Effects of EDTA surface loadings, initial H2O2 concentrations, initial DMP concentrations, and initial pHs on the reaction kinetics in EDTA modified Fe3O4/H2O2 system were investigated, together with the reusability of the EDTA modified Fe3O4. Results showed that the surface complexed EDTA (FeII/III-EDTA) inhibited H2O2 decomposition by competition for surface active sites. However, the generation of OH and HO2/O2−was not suppressed according to the ESR results. The enhanced DMP removal by FeII/III-EDTA was probably due to the efficient use of reactive oxygen species (ROS). A possible EDTA enhanced heterogeneous Fenton mechanism was further proposed.

Highly active iron-containing silicotungstate catalyst for heterogeneous Fenton oxidation of 4-chlorophenol

Polyoxometalates (POMs) have been a class of attractive redox catalysts and photocatalysts, but so far, there have been few reports on application of POMs in Fenton (or Fenton-like) oxidation processes. In this context, an iron-containing silicotungstate (FeIIIAspSiW) was synthesized using ferric chloride (FeCl3, FeIII), aspartic acid (C4H7NO4, Asp) and silicotungstic acid (H4SiW12O40·xH2O, SiW) as raw materials and employed as a heterogeneous catalyst for Fenton oxidizing 4-chlorophenol (4-CP). The chemical formula of FeIIIAspSiW is speculated as [Fe(C4H5NO4)]3.5H0.5SiW12O40·14H2O with Keggin-structured SiW12O404− anion. The FeIIIAspSiW catalyst showed high activity for oxidation of 4-CP by H2O2 ranging from acidic to circumneutral pHs under both the dark and irradiated conditions. Besides, the catalyst also exhibited good regenerability without significant performance drop. The catalytic mechanism in non-irradiated system was related to the Fenton-like catalysis of ferric iron in FeIIIAspSiW. Moreover, the enhanced degradation of 4-CP under irradiation was attributed to the synergistic effect of Fenton-like catalysis of ferric iron and photocatalysis of SiW12O404− anions in FeIIIAspSiW.

Advanced treatment of biologically pretreated coal gasification wastewater by a novel heterogeneous Fenton oxidation process

Sewage sludge from a biological wastewater treatment plant was converted into sewage sludge based activated carbon (SBAC) with ZnCl2 as activation agent, which was used as a support for ferric oxides to form a catalyst (FeOx/SBAC) by a simple impregnation method. The new material was then used to improve the performance of Fenton oxidation of real biologically pretreated coal gasification wastewater (CGW). The results indicated that the prepared FeOx/SBAC significantly enhanced the pollutant removal performance in the Fenton process, so that the treated wastewater was more biodegradable and less toxic. The best performance was obtained over a wide pH range from 2 to 7, temperature 30°C, 15mg/L of H2O2 and 1g/L of catalyst, and the treated effluent concentrations of COD, total phenols, BOD5 and TOC all met the discharge limits in China. Meanwhile, on the basis of significant inhibition by a radical scavenger in the heterogeneous Fenton process as well as the evolution of FT-IR spectra of pollutant-saturated FeOx/BAC with and without H2O2, it was deduced that the catalytic activity was responsible for generating hydroxyl radicals, and a possible reaction pathway and interface mechanism were proposed. Moreover, FeOx/SBAC showed superior stability over five successive oxidation runs. Thus, heterogeneous Fenton oxidation of biologically pretreated CGW by FeOx/SBAC, with the advantages of being economical, efficient and sustainable, holds promise for engineering application.

Simple and high-efficient degradation of methylene blue on impregnated Fe/KIT-6: combined homogeneous and heterogeneous Fenton oxidation

A novel mesoporous Fe/KIT-6 catalyst was prepared by simple wetness impregnation technique. The impregnation of metal species did not alter the well-ordered three-dimensional cubic Ia3d mesostructure of KIT-6. This novel impregnated Fe/KIT-6 catalyst showed high degradation efficiency for methylene blue. The effects of catalyst loadings, pH, Fe content and H2O2 dosage were investigated. At neutral pH, 2600 mg L−1 of H2O2 dosage and initial 30 mg L−1 of methylene blue concentration, over 90% methylene blue degraded in 80 minutes with 15 wt-% Fe/KIT-6. With increasing of Fe loading from 5 to 20 wt-%, degradation efficiency decreased after increasing. The reason may lie in the confinement of nanoparticles inside micropores or mesopores with high Fe content. The degradation of methylene blue might be due to the heterogeneous Fenton oxidation of Fe/KIT-6 catalyst and homogeneous Fenton of leached iron ions from the catalyst.

Advanced treatment of biologically pretreated coal gasification wastewater by a novel integration of heterogeneous Fenton oxidation and biological process

Laboratorial scale experiments were conducted in order to investigate a novel system integrating heterogeneous Fenton oxidation (HFO) with anoxic moving bed biofilm reactor (ANMBBR) and biological aerated filter (BAF) process on advanced treatment of biologically pretreated coal gasification wastewater (CGW). The results indicated that HFO with the prepared catalyst (FeOx/SBAC, sewage sludge based activated carbon (SBAC) which loaded Fe oxides) played a key role in eliminating COD and COLOR as well as in improving the biodegradability of raw wastewater. The surface reaction and hydroxyl radicals (OH) oxidation were the mechanisms for FeOx/SBAC catalytic reaction. Compared with ANMBBR–BAF process, the integrated system was more effective in abating COD, BOD5, total phenols (TPs), total nitrogen (TN) and COLOR and could shorten the retention time. Therefore, the integrated system was a promising technology for engineering applications.

Highly Porous Fe2O3/KIT-6 with Mg Substitution for Heterogeneous Fenton Oxidation of Imidacloprid with Enhanced Catalytic Activity

Abstract A highly porous Fe2O3/KIT-6 with Mg substitution (MgO@Fe2O3/KIT-6) has been synthesized through a coincipient wetness impregnation of Fe and Mg into ordered mesoporous KIT-6 silica. The postreaction catalyst showed higher degradation efficiency than as-prepared catalyst for imidacloprid (IMI). Higher BET surface area, broader pore size distribution of postreaction catalyst and Mg leaching during the reaction processes might be responsible for the enhanced catalytic activities of MgO@Fe2O3/KIT-6 for the heterogeneous Fenton oxidation of IMI.

In situ generation of hydroxyl radical by cobalt oxide supported porous carbon enhance removal of refractory organics in tannery dyeing wastewater

In this study, cobalt oxide doped nanoporous activated carbon (Co-NPAC) was synthesized and used as a heterogeneous catalyst for the Fenton oxidation of organic dye chemicals used in tannery process. The nanoporous activated carbon (NPAC) was prepared from rice husk by precarbonization followed by chemical activation at elevated temperature (600°C). The cobalt oxide was impregnated onto NPAC and characterized for UV–visible, Fluorescence spectroscopy, FT-IR, HR-TEM, XRD, BET surface area and XPS analyses. The hydroxyl radical generation potential of Co-NPAC from hydrogen peroxide decomposition was identified (λexi, 320nm; λemi, 450nm) by Excitation Emission Spectra (EES) analysis. The conditions for the degradation of tannery dyeing wastewater such as, Co-NPAC dose, concentration of H2O2, and temperature were optimized in heterogeneous Fenton oxidation process and the maximum percentage of COD removal was found to be 77%. The treatment of dyes in wastewater was confirmed through UV–Visible spectra, EES and FT-IR spectra analyses.

Hydrophilic modification of ordered mesoporous carbon supported Fe nanoparticles with enhanced adsorption and heterogeneous Fenton-like oxidation performance

Ordered mesoporous carbon with Fe nanoparticles (Fe/meso-C) underwent hydrophilic surface modification with hydrogen peroxide, which shows enhanced adsorption and heterogeneous Fenton oxidation performance for methylene blue.

Heterogeneous Fenton oxidation of 2,4-dichlorophenol using iron-based nanoparticles and persulfate system

Nanoscale zero-valent iron (nZVI) has received attention for its potential applications in contaminated site remediation due to its reactivity. However, it is still unclear how nZVI acts as a catalyst to generate sulfate radicals in heterogeneous Fenton oxidation of 2,4-dichlorophenol (DCP). In this paper, various Fe materials such as Fe2+, nano-ZVI, and nano-Fe3O4 (nFe3O4) were used as heterogeneous catalysts, where the removals of DCP by Fe2+, nZVI, and nFe3O4 were 11.9%, 9.0%, and 5.5%, while the degradation of DCP in the presence of persulfate increased to 34.4%, 37.8%, and 5.8%, respectively. These data indicate nZVI can potentially generate sulfate radicals. UV, SEM, EDS and XRD demonstrated that changes on the surface of nZVI occurred owing to the Fe2+ leaching. It was further observed that DCP degradation increased when the dosage of nZVI and persulfate concentration also increased. However, it decreased when the initial pH and DCP concentration increased. More than 98% of DCP degradation was achieved within 180min under optimum conditions, but less than 40% of chemical oxygen demand (COD) was removed. The degradation of DCP follows the pseudo-first-order kinetics and it is a chemical control reaction with an activation energy of 91.5kJmol−1. Finally, a possible mechanism of DCP degradation using the nZVI/PS system was proposed.

Fenton-like oxidation of 2,4-DCP in aqueous solution using iron-based nanoparticles as the heterogeneous catalyst

In this report, various iron-based nanoparticles (nZVI, n-Ni/Fe, n-Pd/Fe) were used for both heterogeneous Fenton oxidation of 2,4-dichlorophenol (2,4-DCP) and reductive dechlorination of 2,4-DCP in order to understand their roles in the Fenton oxidation and the reductive degradation of 2,4-DCP. The dechlorination efficiency of 2,4-DCP using nZVI, n-Ni/Fe, n-Fe/Pd and Fe2+ was 6.48%, 6.80%, 15.95%, 5.02%, while Fenton oxidation efficiency of 2,4-DCP was 57.87%, 34.23%, 27.94%, 19.61% after 180min, respectively. The new findings included a higher dechlorination using n-Fe/Pd due to Pd effective catalysis and the effective heterogeneous Fenton oxidation using nZVI depending on reductive dechlorination and heterogeneous Fenton oxidation occurs simultaneously. However, nZVI as the potential catalyst for heterogeneous Fenton was observed, and SEM, EDS and XRD demonstrate that change on the nZVI surface occurred due to the Fe2+ leaching, and Total Organic Carbon (TOC) (30.71%) shows that 2,4-DCP was degraded. Furthermore, the experiment indicates that the pH values and concentration of 2,4-DCP significantly impacted on the heterogeneous Fenton oxidation of 2,4-DCP and the data fits well with the pseudo first-order kinetic model, which was a diffusion-controlled reaction. Finally, a possible mechanism for degradation of 2,4-DCP was proposed.

Magnetic Nd<sub>2</sub>Fe<sub>14</sub>B Actived Carbon: Fabrication and Heterogeneous Fenton Oxidation of Congo Red <sup></sup>

Magnetic Nd2Fe14B activated carbon, a new kind of heterogeneous Fenton catalyst has been synthesis to treat the dyestuff wastewater. The obtained catalysts were characterized by X-raydiffraction (XRD) and vibrating sample magnetometer (VSM), and the catalytic activity in heterogeneous Fenton oxidation of Congo red was evaluated. Experiments show that the Nd2Fe14B activated carbon has hard magnetic properties. The saturated magnetization, remanence and coercive force were 15.93emu/g, 6.0emu/g, and 1313Oe, respectively. The results also indicated that Nd2Fe14B activated carbon has good performance on azo dye Congo red oxidation with heterogeneous Fenton process. Under the optimum conditions ([NdFeB-AC-FC]0=20g/L, [H2O2]0= 8mmol/L and pH=7.0), Congo red degradation rate could reach 83.4%. The pH had few effects on heterogeneous Fenton process degraded Congo red. The kinetics studied shown that Congo red degraded followed the pseudo-first-order reaction by heterogeneous Fenton process.

Heterogeneous Fenton oxidation of catechol and 4-chlorocatechol catalyzed by nano-Fe3O4: Role of the interface

The nano-Fe3O4 catalyzed Fenton oxidations of catechol and 4-chlorocatechol in aqueous solution were comparably investigated to elucidate the interface reaction mechanism of the heterogeneous Fenton reactions. Nano-Fe3O4 were synthesized as quasi-spherical particles with specific surface areas of 57.84 m2/g. Almost all the catechol or 4-chlorocatechol was oxidized within 3 h after the addition of H2O2, while about only 10% of the parent compounds adsorbed onto nano-Fe3O4 without H2O2. And the oxidation curves followed the pseudo-second order kinetic model. 4-Chlorocatechol was oxidized faster than catechol, but with only 40% of mineralization. The contribution of homogeneous reaction induced by the leaching iron was limited. The surface generated reactive oxygen species were OH and HO2/O2-, which were further reacted to generate oxygen-centered radicals in both systems, and carbon-centered radicals only in catechol system. In-situ flow-cell ATR-FTIR spectroscopy further confirmed that the adsorbed catechol or 4-chlorocatechol remained on the nano-Fe3O4 surface, indicating an Eley–Rideal mechanism. Meanwhile, the generated carboxyl acids and some intermediates like ethers or dimers were also adsorbed. Accordingly, schematic diagrams of oxidation mechanisms of catechol and 4-chlorocatechol in nano-Fe3O4/H2O2 system were proposed.

Heterogeneous Fenton degradation of bisphenol A by carbon nanotube-supported Fe3O4

In this study heterogeneous Fenton oxidation using Fe3O4 amended onto multi-walled carbon nanotube (Fe3O4/MWCNT) showed effective degradation of aqueous bisphenol A (BPA). The Fe3O4/MWCNT exhibited an octahedron crystal structure of Fe3O4 (100–150nm) which was well-dispersed onto the MWCNT with little agglomeration. The Fe3O4/MWCNT catalyst-driven Fenton oxidation achieved high removal of BPA (97% removal in 6h) at the selected operating conditions (pH of 3, 0.5gcatalyst/L, [H2O2]:[BPA] of 4 (mol/mol), 50°C). The Fenton oxidation of BPA demonstrated similar removal of BPA at 0.5–1gcatalyst/L while showing significant removal of BPA at the initial pH of 3. The [H2O2]:[BPA] of 4 in this study was found to be the cost-effective condition to achieve high removal of BPA at low concentration of H2O2. Besides, the intermediates and oxidation products produced by the Fenton oxidation of BPA at the [H2O2]:[BPA] of 4 did not show any biological toxicity. The [H2O2]:[BPA] ratio of 4 was much lower than that for other heterogeneous Fenton of BPA (54mol H2O2/mol BPA) and comparable to those for homogeneous Fenton of BPA (2–9mol H2O2/mol BPA). The Fenton oxidation rate of BPA using the catalyst was enhanced by the factor of 3.5 as the reaction temperature increased from 20°C to 50°C. The five cycles of the Fenton oxidation using the same catalyst resulted in the steady removal of BPA confirming high stability of the Fe3O4/MWCNT catalyst over the multiple Fenton reactions. The scavenging tests of the hydroxyl radicals suggested that the hydroxyl radical-driven oxidation was the major step among the multiple reactions in the heterogeneous Fenton oxidation. The findings from this study suggest that the Fenton oxidation using Fe3O4/MWCNT would highly efficient solution for the removal of bisphenol A from water.

Nanoscale zero-valent iron as a catalyst for heterogeneous Fenton oxidation of amoxicillin

Abstract Nanoscale zero-valent iron (nZVI) was used as the catalyst to remove amoxicillin (AMX) using a heterogeneous Fenton-like system, where 86.5% of AMX was oxidized using nZVI/H 2 O 2 , while only 25.2% of AMX was removed when nZVI was used. The surface change in nZVI before and after reaction was characterized by various techniques. Scanning electron microscopy (SEM) showed that aggregation and corrosion of nZVI had occurred. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) confirmed the existence of Fe 0 and the presence of iron oxide and iron oxohydroxide Fe(II), Fe(III), as well as UV–visible demonstrated that the absorption peak of AMX had disappeared after the reaction. To understand the degradation mechanism, LC–MS analysis of the degraded products shows that the LC–MS spectra found a new peak at m/z 301 (C 8 H 14 O 9 NS), and the mechanism for Fenton oxidation of AMX was proposed. Removal efficiency depended on the nZVI dosage, initial pH, initial H 2 O 2 concentration and the temperature, where 86.5% of AMX was degraded and 71.2% of COD was removed after 25 min at conditions of H 2 O 2 6.6 mM, nZVI 500 mg/L, AMX 50 mg/L, pH 3.0 and temperature 30 °C. Kinetics for the oxidation of AMX fitted well to the pseudo first-order model and the rate constant k obs increased as temperature increased with an apparent activation energy of 30.1 kJ/mol. Finally, nZVI demonstrated its capacity as a catalyst for heterogeneous Fenton oxidation of AMX from wastewater, and the removal percentage was 80.5%.

Three different clay-supported nanoscale zero-valent iron materials for industrial azo dye degradation: A comparative study

For evaluation of oxidative degradation of industrial azo dye Rosso Zetanyl B-NG (RZ B-NG), three clay supported nanoscale zero-valent iron materials were synthesized: bentonite, kaolin and native clay-supported nanoscale zero-valent iron (B-nZVI, K-nZVI and NC-nZVI). All clays used as a support material not only dispersed and stabilized nanoscale zero valent iron (nZVI) but also improved the adsorption and degradation of dye as they consequently improved heterogeneous Fenton oxidation. Under the optimal conditions, for the used nanomaterial concentrations of 112, 168 and 224mg/L for B-nZVI, NC-nZVI and K-nZVI, the decolourization efficiencies achieved were 92.7, 92.1 and 91.6% and appropriate TOC removals were 57.8, 57.2 and 50.7% in the same order. The best catalytic performance was exhibited when B-nZVI was used. These results correlate with the specific surface area and mesoporous structure of the synthesized materials. They contributed to Fenton reaction enhancement by generating effective reaction sites for potential adsorption and subsequent oxidative degradation of the azo dye. Based on these results, all clay supported nanomaterials have proved to be superior heterogeneous Fenton-like catalysts for removing azo dyes from wastewater.

Synthesis and characterization of Co-NPAC and in situ hydroxyl radical generation for the oxidation of dye laden wastewater from the leather industry

Cobalt oxide supported on nanoporous activated carbon (Co-NPAC) could be utilized as a catalyst in the heterogeneous Fenton oxidation of organic dye chemicals in tannery wastewater.

Decolorization of Direct Orange 26 by heterogeneous Fenton oxidation

In this work, the decolorization of Direct Orange 26 (DO26) was conducted using Fe(III)-sepiolite catalyst in the presence of hydrogen peroxide (H2O2) in a batch process. The catalyst was prepared by ion exchange. All experiments were performed on a laboratory-scale setup. The effects of different parameters such as solution pH, catalyst concentration, initial concentration of H2O2 and DO26, stirring speed on the decolorization efficiency of the process were studied. The best reaction conditions were found to be an initial pH of 2.0 when the concentration of catalyst was 1.5 g/L with [H2O2]o of 35 mM, [DO26]o of 40 mg/L, and a stirring speed of 250 rpm at a temperature of 25°C. Under optimal conditions, a 98% decolorization efficiency of DO26 was achieved within 60 min of the reaction. The kinetics of decolorization of DO26 followed second-order reaction kinetics. Stability and reuse of the catalyst were also tested. This catalyst successfully overcomes the two problems faced by the heterogeneous Fenton process. The catalyst is reusable and the high effectivity of the catalyst in a wide range of pH.

Monitoring of ORP, pH and DO in heterogeneous Fenton oxidation using nZVI as a catalyst for the treatment of azo-dye textile wastewater

The nanoscale zero valent iron-Fenton (nZVI-Fenton) process combines the advantages of nZVI reduction and Fenton oxidation, was regarded as a very effective process for the treatment of azo-dye/textile wastewater. In this paper, we present the results of the investigation of the on-line monitoring of oxidation–reduction potential (ORP), pH, and dissolved oxygen (DO) to evaluate the effectiveness of the nZVI-Fenton process for the removal of color and chemical oxygen demand (COD) from azo-dyes textile wastewater. The experimental results indicated that the optimal doses of nZVI and H2O2 for color removal were 60–80mg/L and 300–400mg/L, respectively. The nZVI reduction removed around 80–90% of the color; however, less than 15% of the COD was removed. To attain the desired removal of COD, much higher doses of nZVI and H2O2 were required, i.e., 200–225mg/L and 1000–1125mg/L, respectively. ORP, pH, and DO had direct and meaningful correlations with the removal efficiencies of both color and COD. Thus, regression models and artificial neural networks (ANN) models were used to predict the color and COD removal efficiencies using the monitoring data acquired for ORP, pH, and DO. The ANN model provided very precise prediction results with R2 values in the range of 0.96–0.99. The predictions provided by the regression model had R2 values in the range of 0.92–0.95. These results indicated that on-line ORP, DO, and pH monitoring data can be used as input to either model to obtain a reliable evaluation of the effectiveness of the nZVI-Fenton process for the removal of color and COD from azo-dyes textile wastewater.

Heterogeneous Fenton oxidation of paracetamol using iron oxide (nano)particles

100mgL−1 paracetamol aqueous solutions were treated by heterogeneous Fenton oxidation at acidic pH (2.6). Three types of iron oxides – nano- and submicro-structured magnetite, nanostructured maghemite – were tested as catalysts for that purpose. For each system, the paracetamol conversion and mineralization yield (Total Organic Carbon removal) were evaluated, as well as the catalyst stability upon recycling.The influence of reaction parameters such as temperature, iron amount, and hydrogen peroxide dosage was also investigated. Paracetamol mineralization was improved by high temperature and low oxidant dosage due to radical scavenging effects. In best conditions (two times the stoichiometric amount of H2O2, a temperature of 60°C, a catalyst concentration of 6gL−1), paracetamol was fully degraded after 5h, but total mineralization was not yet achieved: TOC removal reached about 50% when magnetite powders were used as catalysts. All iron oxides exhibited low iron leaching (<1%) and stable catalytic activity upon first recycling.

Heterogeneous Fenton oxidation of Direct Black G in dye effluent using functional kaolin-supported nanoscale zero iron

This study investigated kaolin-supported nanoscale zero-valent iron (nZVI/K) as a heterogeneous Fenton-like catalyst for the adsorption and oxidation of an azo dye, Direct Black G (DBG). New findings suggest that kaolin as a support material not only reduced the aggregation of nanoscale zero-valent iron (nZVI) but also improved the adsorption of DBG. It consequently improved Fenton oxidation by increasing the local concentration of DBG in the vicinity of nZVI. This was confirmed by scanning electron microscopy and X-ray diffraction for the surface morphology of nZVI/K before and after the Fenton-like reaction. Furthermore, nZVI/K proved to be a catalyst for the heterogeneous Fenton-like oxidation of the DBG process in the neutral pH range. More than 87.22 % of DBG was degraded, and 54.60 % of total organic carbon was removed in the optimal conditions: 0.6 g/L dosage of nZVI/K, 33 mM H2O2, 100 mg/L initial DBG concentration, temperature of 303 K and pH of 7.06. Finally, it was demonstrated that nZVI/K removed DBG from dye wastewater through the processes of adsorption and oxidation.