electro-Fenton Reaction Research Articles

Effect of electro‐Fenton application on azo dyes biodegradability

AbstractThe aim of this study was to examine the feasibility of combining an electro‐Fenton pre‐treatment and a biological treatment to remove azo dyes from aqueous effluents. The electro‐Fenton reaction was performed in a two‐compartment system involving a reference (saturated calomel electrode), a platinum anode and a graphite felt cathode. For the three considered dyes, high discoloration (in the range 77.1–97.8%) and low mineralization (in the range 7.7–18.8%) after 4‐h reaction were in favor of the hybrid process, which was confirmed during subsequent experiments with methyl red sodium salt (MRSS) as a model dye. When potential‐controlled electrolysis at −0.5 V/SCE was performed with a carbon‐felt cathode surface of 378 cm2 and a catalytic amount of ferric iron of 1 mmol L−1, less than 1‐h reaction was needed for an almost total discoloration (90.5%); while mineralization and oxidation remained low even after 48‐h reaction, 11.1 and 57.2%, respectively. High discoloration level concomitantly to low mineralization and oxidation for MRSS removal which were in favor of a hybrid process, confirmed by the decrease of the COD on DOC ratio (45.1%) and the increase of the average oxidation state AOS (2.1). Final BOD5 on COD ratio of 0.24 and an absence of toxicity of the treated solution (EC50 = 165%) also showed the positive impact of an electro‐Fenton pretreatment. © 2010 American Institute of Chemical Engineers Environ Prog, 2011

Electrochemical sensing the genotoxicity of Cu2O nanocubes activated by hydrogen peroxide electro-generated on the surface of Au nanoparticles

In order to investigate the genotoxicity of Cu2O nanocubes, a novel electrochemical biosensor was constructed by incorporating the mixture of Cu2O nanocubes and Au nanoparticles (AuNPs) into a multi-membrane containing natural ds-DNA. The ds-DNA was damaged in situ in the membrane and the DNA damage was monitored by DPV with two electrochemical indicators, Co(phen)33+ and Ru(NH3)63+. The mechanism studies showed that the nanoCu2O and AuNPs had synergistic effects on DNA damage and the DNA damage reagent (OH) was generated via electro-Fenton (E-Fenton) reactions on the surface of Cu2O nanocubes and Au nanoparticles. This method was very suitable to study the genotoxicity mechanisms of nanomaterials and it had potential application in studying some chemicals anti-oxidation property.

Decolorization and degradation of Ponceau S azo-dye in aqueous solutions by the electrochemical advanced Fenton oxidation

Oxidation (decolorization/degradation) of Ponceau S azo-dye in aqueous solutions by electro-generated Fenton's reagent (Fe 2+/H 2O 2) was optimized. This was carried out in a reactor containing 0.05 M Na 2SO 4 solution of pH 2.5 and a catalytic quantity of 0.1 mM FeSO 4 while a cathode potential of − 1.0 V (vs. SCE) was applied. The reactor was an undivided glass electrochemical cell with a reticulated vitreous carbon (RVC) cathode and a platinum gauze anode. Progress of oxidation of various concentrations of Ponceau S with time of electro-Fenton reaction was monitored by UV–visible absorption measurements. Mineralization of the dye solutions was examined by estimation of the chemical oxygen demand removal and HPLC analysis at various times of electro-Fenton oxidation. The complete color removal of 0.05, 0.1 and 0.3 mM Ponceau S was achieved by electro-Fenton oxidation for 30, 60 and 90 min, respectively. However, approximately 98% mineralization of 0.05, 0.1 and 0.3 mM Ponceau S was achieved due to electro-Fenton oxidation for 40, 60 and 120 min, respectively. HPLC analyses showed also that almost no aromatic compounds were remaining in the treated solutions indicating the efficiency of the electro-generated Fenton's reagent for complete decolorization and significant mineralization of the Ponceau S azo-dye in aqueous solutions.

Sensitively electrochemical detection of the DNA damage in situ by electro-Fenton reaction based on Fe@Fe 2O 3 core-shell nanonecklace and multi-walled carbon nanotube composite

An electrochemical biosensor for mimicking the metal-mediated DNA damage pathway in situ was presented. The Fenton reagents (H 2O 2 and iron ion) for the DNA damage were generated in situ with a constant rate from the sensing film. H 2O 2 and iron ion reacted further together to yield hydroxyl radical, which attacked DNA in the film. These courses of DNA damage were just like those happened in organism. The DNA damage was detected by monitoring the differential pulse voltammetric response of an electrochemical indicator, Co(phen) 3 3+. Another electrochemical indicator, Ru(NH 3) 6 3+, was also used for monitoring the DNA damage as a complementary means and the minimal detectable amount of DNA damage was 0.16 μg. The biosensor had good reproducibility. After this biosensor was used for 11 times, 90% of the first detection signal was obtained.

Photoelectrocatalysis reactivity of independent titania nanotubes

Two types of independent titania nanotube arrays with the separated tube wall structure have been fabricated by a controlled anodization process and used for photoelectrocatalysis (PEC) applications. The photocatalysis degradation efficiency of the organic pollutant is improved from 6.0 to 9.2% through increasing tube length and inter-tube space. The PEC degradation efficiency is 20.4% at an applied potential of 2.885 V for titania long nanotube array. An electro-Fenton-assisted PEC reaction system has been developed using titania long nanotube array and an iron sheet as two anodes in a parallel connection and a multiporous carbon as one cathode. The current distribution among three functional electrodes is conducted to optimize titania PEC reaction and electro-Fenton reaction. Accordingly, the degradation efficiency is improved from 20.4% in PEC to 60.2% in electro-Fenton-assisted PEC, and the mineralization efficiency is also improved from 8.1 to 37.4%. The corresponding reaction rate constant of 5.19 × 10−3 min−1 is even higher than that of 3.98 × 10−3 min−1 for the sum of individual oxidation reactions of titania PEC, electro-Fenton, and anodic electrolysis.

A Comparison of Distillery Stillage Disposal Methods

This paper compares the main stillage disposal methods from the point of view of technology, economics and energetics. Attention is paid to the disposal of both solid and liquid phase. Specifically, the following methods are considered: a) livestock feeding, b) combustion of granulated stillages, c) fertilizer production, d) anaerobic digestion with biogas production and e) chemical pretreatment and subsequent secondary treatment. Other disposal techniques mentioned in the literature (electrofenton reaction, electrocoagulation and reverse osmosis) have not been considered, due to their high costs and technological requirements.Energy and economic calculations were carried out for a planned production of 120 m3 of stillage per day in a given distillery. Only specific treatment operating costs (per 1 m3 of stillage) were compared, including operational costs for energy, transport and chemicals. These values were determined for January 31st, 2009. Resulting sequence of cost effectiveness: 1. – chemical pretreatment, 2. – combustion of granulated stillage, 3. – transportation of stillage to a biogas station, 4. – fertilizer production, 5. – livestock feeding. This study found that chemical pretreatment of stillage with secondary treatment (a method developed at the Department of Process Engineering, CTU) was more suitable than the other methods. Also, there are some important technical advantages. Using this method, the total operating costs are approximately 1 150 ??/day, i.e. about 9,5 ??/m3 of stillage. The price of chemicals is the most important item in these costs, representing about 85 % of the total operating costs.

Oxidation of Levafix CA reactive azo-dyes in industrial wastewater of textile dyeing by electro-generated Fenton's reagent

The indirect electrochemical removal of pollutants from effluents has become an attractive method in recent years. Removal (decolorization and mineralization) of Levafix Blue CA and Levafix Red CA reactive azo-dyes from aqueous media by electro-generated Fenton's reagent (Fe(2+)/H(2)O(2)) using a reticulated vitreous carbon cathode and a platinum gauze anode was optimized. Progress of oxidation (decolorization and mineralization) of the investigated azo-dyes with time of electro-Fenton's reaction was monitored by UV-visible absorbance measurements, Chemical oxygen demand (COD) removal and HPLC analysis. The results indicated that the electro-Fenton's oxidation system is efficient for treatment of such types of reactive dyes. Oxidation of each of the investigated azo-dyes by electro-generated Fenton's reagent up to complete decolorization and approximately 90-95% mineralization was achieved. Moreover, the optimized electro-Fenton's oxidation was successfully applied for complete decolorization and approximately 85-90% mineralization of both azo-dyes in real industrial wastewater samples collected from textile dyeing house at El-Mahalla El-Kobra, Egypt.

Ru-흑연 전극을 이용한 Rhodamine B의 색 제거

For the RhB removal from the wastewater, electrochemical method was adapted to this study. Three dimensionally stable anode (Pt, Ir and Ru) and graphite and Ru cathode were used. In order to identify decolorization, the effects of electrode, current density, electrolyte and air flow rate were investigated. The effects of electrode material, current, electrolyte concentration and air flow rate were investigated on the decolorization of RhB. Electro-Fenton's reaction was evaluated by added <TEX>$Fe^{2+}$</TEX> and <TEX>$H_2O_2$</TEX> generated by the graphite cathode. Performance for RhB decolorization of the four electrode systems lay in: Ru-graphite > Ru-Ru > Ir-graphite > Pt-graphite. A complete color removal was obtained for RhB (30 mg/L) at the end of 30 min of electrolysis under optimum operations of 2 g/L NaCl concentration and 2 A current. <TEX>$Fe^{2+}$</TEX> addition increased initial reaction and decreased final RhB concentration. However the effect was not high.

Pilot-plant results of the electro-Fenton treatment of olive mill wastewaters followed by anaerobic digestion

In this work, we investigated an integrated technology for the treatment of the recalcitrant contaminants of olive mill wastewaters (OMW), allowing water recovery and reuse for agricultural purposes. The method involves an electrochemical pre-treatment step of the wastewater using the electro-Fenton reaction followed by an anaerobic bio-treatment. The electro-Fenton pre-treatment process removed 66% of the total polyphenolic compounds and subsequently decreased the OMW toxicity from 100 to 66.9%, which resulted in improving the performance of the anaerobic digestion. A continuous laboratory-scale methanogenic reactor was operated at a loading rate of 10g COD/L per day without any apparent toxicity. Furthermore, in the combined process, a high overall reduction in COD, suspended solids, polyphenols and lipids content was achieved by the two successive stages. Moreover, this combined process which was experimented at a real scale (25 m3 digester) demonstrated its technical feasibility and opens promising perspectives for industrial application in the Mediterranean countries because of its easy conception and high energy (methane) production.

Pilot-plant results of the electro-Fenton treatment of olive mill wastewaters followed by anaerobic digestion

In this work, we investigated an integrated technology for the treatment of the recalcitrant contaminants of olive mill wastewaters (OMW), allowing water recovery and reuse for agricultural purposes. The method involves an electrochemical pre-treatment step of the wastewater using the electro-Fenton reaction followed by an anaerobic bio-treatment. The electro-Fenton pre-treatment process removed 66% of the total polyphenolic compounds and subsequently decreased the OMW toxicity from 100 to 66.9% which resulted in improving the performance of the anaerobic digestion. A continuous lab-scale methanogenic reactor was operated at a loading rate of 10 g COD/L day without any apparent toxicity. Furthermore, in the combined process, a high overall reduction in COD, suspended solids, polyphenols and lipids content was achieved by the two successive stages. Moreover, this combined process which was experimented at a real scale (25 m3 digester), demonstrated its technical feasibility and opens promising perspectives for industrial application in the Mediterranean countries due to its easy conception and its high energy (methane) production.

Kinetic modeling of electro-Fenton reaction in aqueous solution

To well describe the electro-Fenton (E-Fenton) reaction in aqueous solution, a new kinetic model was established according to the generally accepted mechanism of E-Fenton reaction. The model has special consideration on the rates of hydrogen peroxide (H 2O 2) generation and consumption in the reaction solution. The model also embraces three key operating factors affecting the organic degradation in the E-Fenton reaction, including current density, dissolved oxygen concentration and initial ferrous ion concentration. This analytical model was then validated by the experiments of phenol degradation in aqueous solution. The experiments demonstrated that the H 2O 2 gradually built up with time and eventually approached its maximum value in the reaction solution. The experiments also showed that phenol was degraded at a slow rate at the early stage of the reaction, a faster rate during the middle stage, and a slow rate again at the final stage. It was confirmed in all experiments that the curves of phenol degradation (concentration vs. time) appeared to be an inverted “S” shape. The experimental data were fitted using both the normal first-order model and our new model, respectively. The goodness of fittings demonstrated that the new model could better fit the experimental data than the first-order model appreciably, which indicates that this analytical model can better describe the kinetics of the E-Fenton reaction mathematically and also chemically.

Treatment of olive oil mill wastewater by combined process electro-Fenton reaction and anaerobic digestion

In this work, we investigated an integrated technology for the treatment of the recalcitrant contaminants of olive mill wastewaters (OMW), allowing water recovery and reuse for agricultural purposes. The method involves an electrochemical pre-treatment step of the wastewater using the electro-Fenton reaction followed by an anaerobic bio-treatment. The electro-Fenton process removed 65.8% of the total polyphenolic compounds and subsequently decreased the OMW toxicity from 100% to 66.9%, which resulted in improving the performance of the anaerobic digestion. A continuous lab-scale methanogenic reactor was operated at a loading rate of 10 g chemical oxygen demand (COD) l −1 d −1 without any apparent toxicity. Furthermore, in the combined process, a high overall reduction in COD, suspended solids, polyphenols and lipid content was achieved by the two successive stages. This result opens promising perspectives since its conception as a fast and cheap pre-treatment prior to conventional anaerobic post-treatment. The use of electro-coagulation as post-treatment technology completely detoxified the anaerobic effluent and removed its toxic compounds.

Treatment of Chemical–Mechanical Planarization Wastes by Electrocoagulation/Electro- Fenton Method

A method for the treatment of chemical–mechanical planaarization wastewater that utilizes the principles of electrocoagulation (EC) and electro-Fenton (EF) reactions has been investigated. The method consists of subjecting the wastewater to an applied electric field between two iron electrodes, in the presence of hydrogen peroxide. Dissolved iron is responsible for electrocoagulation, while the hydroxyl radicals produced through the reaction of dissolved iron species with hydrogen peroxide destroy dissolved organics. Over 95% of fine particles can be removed after sedimentation following exposure to electric field, and the turbidity of the clarified solution can be reduced to very low values (0.3 NTU).

Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton Reaction and Related Chemistry

Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.

Interactive oxidation of photoelectrocatalysis and electro-Fenton for azo dye degradation using TiO 2–Ti mesh and reticulated vitreous carbon electrodes

A crystallized TiO 2 thin film was prepared by electrolytic anodization of a pure Ti mesh in sulfuric acid–phosphoric acid–hydrogen peroxide and hydrofluoric acid–sodium fluorid–hydrogen peroxide electrolyte solutions. The TiO 2 particles directly grown on the Ti mesh surface had the regular anatase crystal structure. The TiO 2 thin film showed a multiporous structure and the mean micropore size was about 260 nm. The azo dye orange-G degradation reaction was studied in an undivided cell by using the air-diffusion reticulated vitreous carbon as the cathode for the H 2O 2 electrogeneration and TiO 2–Ti mesh as the photoanode for the photoelectrocatalysis under ultraviolet light irradiation. The heterogeneous photoelectrocatalysis and the homogeneous electro-Fenton reaction simultaneously occurred in one reaction system, while H 2O 2 was produced by a two-electron reduction of oxygen and the ferrous ion was supplied by the dosing or electrogeneration method. In the photo-electro-integrated oxidation reaction system, both the degradation rate and the removal ratio of total organic carbon were enhanced for orange-G dye which was ascribed to interactive oxidation processes of photoelectrocatalysis, electro-Fenton and electrooxidation reaction. Ion chromatogram results indicate that the total mineralization reaction was much delayed to produce inorganic ions and groups although the complete decolorizing degradation could be achieved for orange-G dye.

Mineralization of an azo dye Acid Red 14 by electro-Fenton's reagent using an activated carbon fiber cathode

In this paper, the comparison of activated carbon fiber (ACF) felt and graphite cathode suggested H 2O 2 might effectively be electrogenerated from O 2 reduction on the large surface area ACF felt cathode, this was more adaptive for electro-Fenton process. The removal of color and total organic carbon (TOC) from simulated dye wastewater containing Acid Red 14 (AR14) was experimentally investigated using electro-Fenton reaction with ACF cathode. After 360 min of electrolysis and under the operation conditions of 0.36 A current, 1 mM Fe 2+ at pH 3, 70% TOC was removed as well as complete decolorization occurred. The effect of Fe 2+ ion concentration and applied current were also studied in detail in the experimental runs.

Anodic oxidation, electro-Fenton and photoelectro-Fenton treatments of 2,4,5-trichlorophenoxyacetic acid

The mineralization of acidic aqueous solutions of the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in 0.05 M Na 2SO 4+H 2SO 4 at 35 °C has been studied by different electrochemical methods. Photoelectro-Fenton treatment yields a fast and complete depollution of solutions with 2,4,5-T concentrations up to about saturation within the pH range 2.0–4.0, operating at low current and with 1 mM Fe 2+. This method is carried out in an undivided cell with a Pt anode and an O 2-diffusion cathode under UV irradiation, and its great oxidative ability is due to the fast reaction of organics with the high concentration of oxidizing hydroxyl radicals produced in the medium from Fenton's reaction between added Fe 2+ and H 2O 2 electrogenerated by the cathode. Comparative treatment by an electro-Fenton reaction only leads to 60–65% of mineralization because of the formation of hardly oxidable products with hydroxyl radical. 2,4,5-T is very poorly mineralized by anodic oxidation in the absence and presence of electrogenerated H 2O 2. The herbicide decay always follows a pseudo first-order reaction. 2,4,5-Trichlorophenol, 2,5-dichlorohydroquinone, 4,6-dichlororesorcinol and 2,5-dihydroxy- p-benzoquinone have been identified and quantified as aromatic products by reverse-phase chromatography. Generated carboxylic acids such as glycolic, glyoxylic, formic, malic, maleic, fumaric and oxalic have been detected and followed by ion-exclusion chromatography. All these products are destroyed by electro-Fenton treatment, except oxalic acid which forms stable complexes with Fe 3+. These complexes are rapidly photodecarboxylated by UV light in the photoelectro-Fenton treatment.