Electrochemical Peroxidation Process Research Articles

A Fenton-based approach at neutral and un-conditioned pH for recalcitrant COD removal in tannery wastewater: Experimental test and sludge characterization

The combination of raw animal skin manufacturing processes involves the use of large amounts of chemicals, resulting in the generation of complex and highly polluted tannery wastewater. In this context, the high concentration of chloride in tannery wastewater represents a crucial bottleneck. Indeed, sodium chloride, commonly used in tannery industry to prevent skin rot, increases the concentration of chlorides up to 50 %. At the same time, most of the advanced oxidation processes usually employed in tannery wastewater treatment to remove recalcitrant COD involve the use of conditioning agents, thus increasing the overall concentration of chlorides in the treated effluent. The aim of this study was to evaluate the electrochemical peroxidation process (ECP) efficiency in the treatment of tannery wastewater without changing pH, to improve Fenton technology by avoiding the use of chemicals. The influence of different electric currents on COD and color removal was investigated. The characterization of the produced sludge was conducted through FTIR, SEM and XRD analysis, exploring the morphology and composition of precipitate, depending on the applied current. Although an electrical current of 750 mA yields the highest COD and color removal efficiency (69.7 % and 97.8 %, respectively), 500 mA can be considered the best compromise because of energy consumptions. Iron oxides and hydroxides were generated during the ECP process, playing the role of coagulants through the absorption of organic and inorganic contaminants. The consumption of energy increased as a function of time and applied current; however, cost analysis showed that the electrodes contributed the most to the total cost of the process. In authors' knowledge, the application of ECP process as a tertiary treatment for the removal of recalcitrant COD in tannery wastewater represents a novelty in the literature and the results obtained can be considered as the basis for scaling up the process in future research.

Solar photo-assisted electrochemical peroxidation process for the sustainable treatment of tannery industry wastewater

Abstract Tannery wastewater is a complex mixture of organic and inorganic components from various processes with high concentrations of Cr, BOD, COD, TDS, strong colour and pH. The goal of the present work was to determine the optimal solar photo-assisted electrochemical peroxidation process (SPECP) experimental conditions for the treatment of tannery wastewater. Experiments were conducted in a bench-scale stirred tank SPECP reactor of 5 L with iron plates as anode and cathode in a contact effective area of 218 cm2. In the stirred tank reactor at optimal conditions, the SPECP yielded 97% COD, 98% of colour and 92% of chromium (III) removal after 60 min at 15 mA/cm2. SPECP improved the biodegradability (BOD5/COD) of tannery wastewater from 0.4 to 0.6 in 15 min. These results showed that wastewater from tannery industries could be treated up to the level of the minimal national standards of India for waste disposal; COD=90 mg/L, BOD=30 mg/L and chromium (III)=1.2 mg/L at a treatment time of 60 min. The operating cost of the best economic condition with maximum degradation was $8.2/m3.

Box-Behnken design-based biodiesel wastewater treatment using sequential acid cracking and electrochemical peroxidation process: Focus on COD, oil-grease and volatile fatty acids removals

Box-Behnken design-based biodiesel wastewater treatment using sequential acid cracking and electrochemical peroxidation process: Focus on COD, oil-grease and volatile fatty acids removals

Decolorization of industrial wastewater using electrochemical peroxidation process

In this study, decolorization of wastewater samples taken from the paper industry is investigated using electrochemical peroxidation process. The electrochemical peroxidation process is a part of electrochemical advanced oxidation processes, which is based on the Fenton’s chemical reaction, provided by addition of external H2O2 into reaction cell. In this study, iron is used as anode and graphite as cathode put at the fixed distance of 30 mm in a glass reaction cell. The cell was filled with the solution containing wastewater and sodium chloride as the supporting electrolyte. Factors of the process such as pH, current intensity, hydrogen peroxide concentration, and time of treatment were studied. The results illustrate that all these parameters affect efficiencies of dye removal and chemical oxygen demand (COD) reducing. The maximal removal of wastewater contaminants was achieved under acid (pH 3) condition, with the applied current of 1 A, and hydrogen peroxide concentration of 0.033 M. At these conditions, decolorization process efficiency reached 100 and 83 % of COD removal after 40 minutes of wastewater sample treatment. In addition, the electrical energy consumption for wastewater treatment by electrochemical peroxidation is calculated, showing increase as the current intensity of treatment process was increased. The obtained results suggest that electrochemical peroxidation process can be used for removing dye compounds and chemical oxygen demand (COD) from industrial wastewaters with high removal efficiency.

Electrochemical Peroxidation Method for Reduction of Chemical Oxygen Demand (COD) Carbofuran in Furadan 3GR Pesticides

Carbofuran is a pollutant compound derived from the pesticide Furadan 3GR which is widely used in agriculture. Various methods of carbofuran degradation have been carried out, one of which is the conventional electrochemical method. This study used an electrochemical peroxidation process to degrade Carbofuran in the pesticide Furadan 3GR. This study aims to determine the optimum conditions (time, Na2SO4 concentration, and volume addition of H2O2) for electrochemical peroxidation and to compare the effectiveness of electrochemical and electrochemical peroxidation methods by measuring the parameter of carbofuran COD reduction. The significance of the electrochemical peroxidation method and the conventional electrochemical method was compared as a preliminary test. The COD reduction of Carbofuran using traditional electrochemical methods and electrochemical peroxidation was 45.76% and 88.70%, respectively. Batch carbofuran electrochemical peroxidation process was accomplished to ascertain the optimum conditions under various operation times, the concentration of Na2SO4, and the additional volume of H2O2. The largest COD reduction of 93.78% was obtained at 10 minutes, 75 mM Na2SO4, and 2 mL H2O2. The UV-Vis spectrophotometric absorption of Carbofuran at a wavelength of 274 nm was significantly reduced from 1.377 to 0.131 at optimum conditions. The IR spectrum measurement results indicate a reduction in absorbance for the N-H group (3383 cm-1) and the C=O group (1643 cm-1) at optimum conditions. Overall, the electrochemical peroxidation process proved to be an appropriate technique for COD reduction of Carbofuran in Furadan 3GR pesticides.

Treatment of municipal solid waste landfill leachate by aeration assisted electrochemical peroxidation process using aluminium and iron electrodes

Treatment of municipal solid waste landfill leachate by aeration assisted electrochemical peroxidation process using aluminium and iron electrodes

Arsenic Removal by Advanced Electrocoagulation Processes: The Role of Oxidants Generated and Kinetic Modeling

Arsenic (As) is a naturally occurring element in the environment that poses significant risks to human health. Several treatment technologies have been successfully used in the treatment of As-contaminated waters. However, limited literature has explored advanced electrocoagulation (EC) processes for As removal. The present study evaluates the As removal performance of electrocoagulation, electrochemical peroxidation (ECP), and photo-assisted electrochemical peroxidation (PECP) technologies at circumneutral pH using electroactive iron electrodes. The influence of As speciation and the role of oxidants in As removal were investigated. We have identified the ECP process to be a promising alternative for the conventional EC with around 4-fold increase in arsenic removal capacity at a competitive cost of 0.0060 $/m3. Results also indicated that the rate of As(III) oxidation at the outset of electrochemical treatment dictates the extent of As removal. Both ECP and PECP processes reached greater than 96% As(III) conversion at 1 C/L and achieved 86% and 96% As removal at 5 C/L, respectively. Finally, the mechanism of As(III) oxidation was evaluated, and results showed that Fe(IV) is the intermediate oxidant generated in advanced EC processes, and the contribution of •OH brought by UV irradiation is insignificant.

Electrochemical treatment of sunflower oil refinery wastewater and optimization of the parameters using response surface methodology

Combined electrocoagulation (EC) + electrooxidation (EO) process was compared with electrochemical peroxidation (ECP) treatment process to treat sunflower oil refinery wastewater. The effect of applied current density, pH/H2O2 dosage, and operation time in the removal of chemical oxygen demand (COD), soluble COD, total organic carbon, and dissolved organic carbon (DOC) were studied using Box Behnken Design. In EC process, decrease in organic concentration was observed as the time and current density increased. The optimized conditions for EC process were achieved at pH 6.07 when a current density of 5.69 mA cm−2 was applied for 18 min. The EO removed about 90% of DOC at an optimized pH of 5.27 and current density of 11.56 mA cm−2 when operated for 400 min. The combined EC + EO process was successful compare to ECP process in removing between 90 and 95% of organic pollutant from the sunflower oil refinery wastewater. The energy consumption was calculated to compare between the process efficiency of EC + EO and ECP and found that EC + EO was more efficient process. The reaction rate followed a first order kinetics validated with a high R2 value (0.96).

Treatment of canola-oil refinery effluent using electrochemical methods: A comparison between combined electrocoagulation + electrooxidation and electrochemical peroxidation methods

A comparative study of combined electrocoagulation (EC) + electrooxidation (EO) and electrochemical peroxidation (ECP) treatment processes were carried out to treat canola oil refinery (COR) wastewaters. The effect of applied current density and operation time in the removal of organic pollutants were investigated and discussed. Total chemical oxygen demand (TCOD), soluble chemical oxygen demand (sCOD), total organic carbon (TOC), dissolved organic carbon (DOC) and total suspended solids (TSS) were measured. Using only EC process was found to be significantly successful in removing suspended and colloidal pollutants and could remove more than 90% TCOD and 80% of TOC at current densities between 0.91 and 13.66 mA cm−2. From the statistical model, the optimized conditions for TCOD at a current density of 7.61 mA cm−2 and TOC at 7.99 mA cm−2 under 40 min operation, validated to remove 93.45% and 94.5% respectively. However, the maximum removal of dissolved organic pollutants was relatively low in EC process and reported to be 75% for sCOD and 74% for DOC. Therefore, EC + EO process were run to increase the removal of sCOD and DOC to 99 and 95%, respectively. On the other hand, treatment using ECP process achieved a removal of sCOD and DOC between 77 and 86%. TSS were removed completely in both EC + EO and ECP processes. A statistical model was applied to compare the performance of two methods and found that the combined EC + EO process provided lightly better treatment compared to ECP method.

Electrochemical peroxidation using iron nanoparticles and anodic iron dissolution to remove selenium from oil refinery wastewater

AbstractExperimental results for selenium removal from oil refinery wastewater applying the electrochemical peroxidation process (ECP) using either graphite electrodes with iron nanoparticles (nZVI) or carbon steel electrodes with anodic iron dissolution (AD) on laboratory scale are presented. Operating parameters were: current density, iron‐selenium molar ratio and treatment time. It was found that when applying ECP and nZVI, selenium removal reached 93%. On the contrary, when the ECP and AD process was applied, selenium removal only reached 64%. Therefore, the ECP process and use of iron nanoparticles could be a feasible technology to remove selenium from oil refinery wastewater.

Removal of chromium(III) from tannery wastewater by electrochemical peroxidation process in a bench scale reactor

Removal of chromium(III) from tannery wastewater by electrochemical peroxidation process in a bench scale reactor

Degradation of ciprofloxacin by the Electrochemical Peroxidation process using stainless steel electrodes

The performance of the electrochemical peroxidation (EP) process on the degradation of ciprofloxacin (CIP) was investigated. Different EP process conditions were assessed using an electrolytic cell based on stainless steel electrodes and O2 injection. Parameters, such as H2O2 (25–1000 mg L−1), electrical current density (ECD) (19.71–164.26 A m−2), Fe2+ (0.5 and 2.0 mg L−1), initial solution pH (2.5–9.0), and electrolysis treatments (5–90 min), were varied to determine the best EP performance. Changes in CIP, total organic carbon, and residual H2O2, as well as solution pH, were monitored during the EP performance analysis. Additionally, a set of intermediary by-products and chemical element concentrations was identified and quantified. The toxicity levels of the samples, in terms of the median lethal concentration (LC50), were assessed with Lactuca sativa-based bioassays tests. By setting the ECD, initial H2O2 concentration, initial pH, and electrolysis treatment to 32.85 A m−2, 100 mg L−1, 3, and 30 min, respectively, the optimal EP performance on CIP removal was attained. Conversely, low toxicity levels were observed for shorter electrolytic treatments (<45 min), with LC50 reduced to 40% of their initial values due to a strong drop in intermediate by-products and metals, and 30 min electrolytic treatments being more suitable for yielding efficient EP process performance. Finally, it is recommended that this EP process is considered as a complementary treatment to assist in reducing the negative impacts of the inappropriate discharge of pharmaceuticals in water bodies.

Application of electrochemical peroxidation (ECP) process for waste-activated sludge stabilization and system optimization using response surface methodology (RSM).

In this study, the performance of the electrochemical peroxidation (ECP) process for removing the volatile suspended solids (VSS) content of waste-activated sludge was evaluated. The Fe2+ ions required by the process were obtained directly from iron electrodes in the system. The performance of the ECP process was investigated in various operational conditions employing a laboratory-scale pilot setup and optimized by response surface methodology (RSM). According to the results, the ECP process showed its best performance when the pH value, current density, H2O2 concentration and the retention time were 3, 3.2 mA/cm2, 1,535 mg/L and 240 min, respectively. In these conditions, the introduced Fe2+ concentration was approximately 500 (mg/L) and the VSS removal efficiency about 74%. Moreover, the results of the microbial characteristics of the raw and the stabilized sludge demonstrated that the ECP process is able to remove close to 99.9% of the coliforms in the raw sludge during the stabilization process. The energy consumption evaluation showed that the required energy of the ECP reactor (about 1.8-2.5 kWh (kg VSS removed)-1) is considerably lower than for aerobic digestion, the conventional waste-activated sludge stabilization method (about 2-3 kWh (kg VSS removed)-1). The RSM optimization process showed that the best operational conditions of the ECP process comply with the experimental results, and the actual and the predicted results are in good conformity with each other. This feature makes it possible to predict the introduced Fe2+ concentrations into the system and the VSS removal efficiency of the process precisely.

Modeling and kinetics study of electrochemical peroxidation process for mineralization of bisphenol A; a new paradigm for groundwater treatment

To remove the bisphenol A (BPA) effectively from groundwater great attempts made in the current work to optimize the operating parameters of electrochemical peroxidation (ECP) process using response surface methodology (RSM) based on central composite design (CCD). The obtained data from ANOVA analysis revealed the significance of experimental variables. The obtained removal efficiency of BPA demonstrated that the predicted quadratic model is highly adequate and applicable. According to the experimental data, it found that the best removal efficiency of 100% achieved at initial concentrations BPA of 5.0 mg·L−1, hydrogen peroxide amount of 55.0 μL, pH 3.0, reaction time 12.0 min, and current density 6.0 mA·cm−2. The rate of the oxidation process of BPA reduced by increasing the amount of H2O2 and Fe2+ ions, which might be due to the reducing the amount of hydroxyl free radicals involved in the scavenging reaction. The kinetics of the process follows the pseudo first-order model with rate constants of 0.596 min−1 (R2 = 0.9908). Since, most of the reported studies are based on one factor at the time method, in the current study, RSM was used to evaluate the main effects of parameters, their simultaneous interactions and quadratic effect to achieve the optimum condition for EC process. The kinetics studies of ECP process provide valuable information on the mechanism of the degradation process that attributes to the presence of free hydroxyl radicals.

Treatment of pretreated coke wastewater by electrocoagulation and electrochemical peroxidation processes

In this study, treatment of pretreated real coke wastewater by Electrocoagulation process (EC) and Electrochemical Peroxidation process (ECP) using direct pulse current was investigated. Air stripping process of ammonia was used as a physicochemical process for the pretreatment of wastewater. In the present study, ECP process has been offered to remove chemical oxygen demand (COD), total organic carbon (TOC), phenol, cyanide (CN−) and thiocyanate (SCN−) from coke wastewater. The efficiency of the process and settling characteristic of waste sludge were investigated through changing some operating parameters such as initial pH, initial H2O2 concentration and current density. Direct pulse current (DPC) was used to prevent the passivity or polarization of electrodes and to increase removal efficiency. Under the optimum operation conditions at the EC and ECP process (pH 3, current density 200A/m2, initial H2O2 10g/L (for ECP), operation time 20min.), the removal efficiencies of COD, TOC, phenol, CN− and SCN− were observed to be 26%, 20%, 9%, 9.2% and 8.2% (for EC) and to be 92.0%, 90.0%, 97.6%, 90.0% and 93.6% (for ECP), respectively. Operating costs for the EC and ECP process were calculated as 1.46€/m3 and 5.64€/m3. These results asserted that ECP process was more effective than EC process for removal efficiencies of pollutions. But, the ECP process was more expensive than EC process.

Electrochemical peroxidation using iron nanoparticles to remove arsenic from copper smelter wastewater

In the present work a study of the electrochemical peroxidation process (ECP) was carried out by using carbon electrodes and iron nanoparticles. Arsenic removal from synthetic and real wastewater from copper pyro-metallurgical industry was analyzed. The experiments were carried out in a 2L batch reactor with agitation by air injection with airflow of approximately 5Lmin−1. A fixed current density of 171.7A·m−2 was used and a drop wise 30% (w/w) hydrogen peroxide dosage of around 0.5–1mL·min−1 was supplied to the wastewater solution. The evaluated operating parameters were: initial pH of the wastewater that was in the range of 2.0 to 6.5 and the treatment time that was varied from 30 to 180min. The results when the ECP process was applied for 1h, in the pH range of 2.0 to 6.5, to treat As(III) synthetic wastewater, showed that the maximum removal of arsenic was 62.4% at a pH of 6.5; being approximately constant when more treatment time was applied. On the other hand, when treating As(V) wastewater, the maximum removal was 99.7% at a pH of 5.0. When working with real wastewater in the pH range of 3.5 to 6.5; the arsenic maximum removal was 96% at pH 6.5. This removal was approximately constant when more treatment time was applied. The ECP process using carbon electrodes and iron nanoparticles showed to be a capable technology to remove high concentrations of arsenic (1300 to 3000mg·L−1).

The performance of electrochemical peroxidation process for COD reduction and biodegradability improvement of the wastewater from a paper recycling plant

This study investigated pretreatment and biodegradability of wastewater from a paper recycling plant using the electrochemical peroxidation process in a bench scale reactor. The influence of wastewater pH, H2O2 concentration, current density, and reaction time was evaluated for the removal of COD from the wastewater. The COD of wastewater from paper recycling decreased from the initial level of 4300mg/L in raw wastewater to 106mg/L (95.7% removal) in wastewater treated by the electrochemical peroxidation process at optimum pH, H2O2 concentration, current densities of 4, 15 and 5mA/cm2, and a reaction time of 30min. The optimum ratio of H2O2 (mM) to Fe2+ (mM) was found to be 2. The biodegradability of wastewater increased from an initial level of 0.12 to 0.43 after treatment by the electrochemical peroxidation process under optimum experimental conditions at a reaction time of 30min. Overall, the electrochemical peroxidation process proved to be an efficient and appropriate technique for COD reduction and enhancement of biodegradability of the industrial effluents containing high concentrations of recalcitrant organic compounds.

Pretreatment of coking wastewater by acid out, micro-electrolysis process with in situ electrochemical peroxidation reaction

The coking wastewater was pretreated by acid out, micro-electrolysis process with in situ electrochemical peroxidation (ECP) (approximately 0.013–0.015M H2O2) reaction to reduce the subsequent processing load. The results showed that the acidification process brought about changes not only in organic species of contaminants but also in decrease of COD, NH3N in wastewater through precipitation and some special reactions, resulting in 33% of COD and 9.7% of NH3N removal. Then Fe/C micro-electrolysis (ME) with in situ ECP reaction exhibited a stronger ability to remove the COD and NH3N than that with ex situ Fenton reaction, because at this stage, for the two reaction models, the total COD and NH3N removal were 65%, 26% and 43%, 25% in sequence, but in view of the contribution of only Fenton reaction to the whole COD and NH3N removal, they were 26%, 4.2% (the former was about six times as strong as the latter) and 9.3%, 8.1%, respectively. So it was reasonable to deduce that there was a prominent synergistic effect on COD removal between the dynamic Fe/C micro-electrolysis and the Fenton reaction; furthermore, the Fenton reaction in in situ ECP process was not only high-efficient but also low-cost. These advantages might mainly be attributed to the technique of dynamic Fe/C ME with in situ ECP reaction, as it was presumed that the technique might promote some favorable reactions involved, but inhibit those unfavorable ones. The major degradation mechanism of organic contaminants in effluent had been proposed.

Electrochemical peroxidation of contaminated aqueous leachate

The landfill process for disposal of domestic waste produces a large volume of contaminated aqueous leachate. This study was aimed at investigating the feasibility of using electrochemical peroxidation (ECP) for the treatment of this leachate. ECP is a process by which aqueous, or suspended organic matter, is oxidised by the action of hydroxyl free radicals, produced using hydrogen peroxide and cast iron or mild steel electrodes. The effectiveness of the ECP process was quantified by measuring reductions in leachate biological oxygen demand (BOD) and chemical oxygen demand (COD) as a result of treatment. Optimisation of the process was carried out by varying electrode voltage, polarity switching rate, leachate pH and hydrogen peroxide concentration. This resulted in an observed BOD reduction of 36% and COD reduction of 52%, which was achieved by adjusting the pH to 4.0, applying an electrode voltage of 1.9V and switching speed of 5 cycles per minute. The optimum hydrogen peroxide concentration was found to be 100ppm. In addition to reductions in BOD and COD, reductions in chloride and ammonium levels were measured and found to be 15% and 18% respectively. The results of the investigation indicate that the ECP process is effective in the treatment of landfill leachate, and suggest that with further optimisation, ECP may serve as an attractive alternative to current biological leachate treatment methods.

Retention of arsenic on hydrous ferric oxides generated by electrochemical peroxidation.

Electrochemical peroxidation (ECP), an emerging remediation technology, with direct electric current applied to steel electrode and small addition of H2O2, was used to remove As(III) from contaminated aqueous solutions. Bench scale experiments were conducted to evaluate the sorption and distribution of arsenic between the soluble and solid state hydrous ferric oxides (HFO) formed as part of the ECP process. ECP was effective in removing arsenic from the aqueous solution, with >98% of the applied As(III) adsorbed on HFO. Removal was complete within 3 min of ECP treatment and apparently independent of the initial pH of the water (3.5-9.5). In the absence of H2O2 more As(III) was adsorbed by solid state iron at pH 9.5 than at 3.5 (2600 vs. 1750 microg l(-1)). Thus H2O2 was crucial to oxidize As(III) to As(V) which is more strongly retained by HFO. Removal of As was not significantly affected by the concentration of H2O2 or by current processing time. The optimal operating conditions were pH < 6.5, H2O2 concentration of 10 mg l(-1) and current process time not exceeding 3 min. X-ray diffraction (XRD), diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy and transmission electron microscopy (TEM) were applied to study the HFO deposits. The XRD data indicated the prevalence of poorly ordered Fe minerals in the suspended ECP solids with a dominance of 5 line ferrihydrite in the absence of H2O2. At pH 3.5 and with 100 mg H2O2 l(-1), akaganeite was formed, whereas an incipient hematitic phase, reflection at 0.39 nm, occurred at pH 6.5. DRIFT data indicate that both As(III) and As(V) were specifically adsorbed onto HFO at acid and neutral pH. TEM observations indicated the presence of spherical shape ferrihydrite and provided evidence for possible formation of subrounded hematite and acicular shape goethite.