Comparative Study of Electrocoagulation and Electrooxidation Processes for the Degradation of Ellagic Acid From Aqueous Solution

A comparative study of electrocoagulation and electrooxidation processes for the degradation of ellagic acid from aqueous solution was carried out. For the electrocoagulation process, metallic iron was used as electrodes whereas graphite and RuO₂/IrO₂/TaO₂ coated titanium electrodes were used for the electrooxidation processes. The effect of the process variables such as initial pH, concentration of the supporting electrolyte, applied current density, electrolysis time, and anode materials on COD removal were systematically examined and discussed. Maximum COD removal of 93% was obtained at optimum conditions by electrocoagultion using an iron electrode. The ellagic acid was degraded completely by electrooxidation using graphite electrodes under the optimum conditions. During electrooxidation, the chloride ion concentration was estimated and the effect of the Cl^? ion was discussed. The finding of this study shows that an increase in the applied current density, NaCl concentration, and electrolysis time enhanced the COD removal efficiency. The UV–Vis spectra analysis confirms the degradation of ellagic acid from aqueous solution.     

Influence of Experimental Parameters in the Treatment of Distillery Effluent by Electrochemical Oxidation

The electrochemical oxidation of distillery effluent was studied in a batch reactor in the presence of supporting electrolyte NaCl using Mixed Metal Oxide (MMO) electrode. The effect of operating parameters such as current density, initial pH, and initial electrolyte concentration on the percentage of Chemical Oxygen Demand (COD) removal, power consumption, and current efficiency were studied. The maximum percentage removal of COD was observed to be 84% at a current density of 3 A/dm²at an electrolyte concentration of 10 g/l with an effluent COD concentration of 1000 ppm and at an initial pH of 6. The operating parameters for the treatment of distillery effluent by electrochemical process were optimized using response surface methodology by CCD. The quadratic regression models with estimated coefficients were developed for the percentage removal of COD and power consumption. It was observed that the model predictions matched with experimental values with an R² value of 0.9504 and 0.9083 for COD removal and power consumption respectively. The extent of color removal and oxidation of organic compounds were analyzed using UV spectrophotometer and HPLC.     

Treatment of Polyvinyl Alcohol from Aqueous Solution via Electrocoagulation

This study investigates the feasibility of removing the chemical oxygen demand (COD) from a solution containing polyvinyl alcohol (PVA) by electrocoagulation. Several parameters—including the current density, supporting electrolyte, and temperature—were evaluated in terms of COD removal efficiency. The effects of these parameters on the electrical energy consumption were also investigated. The optimum current density, supporting electrolyte concentration, and temperature were found to be 5 mA/cm², 0.012 N NaCl, and 298 K, respectively. The experimental data were also tested against different adsorption isotherm models to describe the electrocoagulation process; the COD adsorption studied here best fit the Freundlich adsorption isotherm model. Thermodynamic parameters, including the Gibbs free energy, enthalpy, and entropy, indicated that the adsorption of COD on metal hydroxides was feasible, spontaneous, and endothermic in the temperature range of 288 K to 318 K.     

Pre-Treatment of Pistachio Processing Industry Wastewaters (PPIW) by Electrocoagulation using Al Plate Electrode

The objective of the present study is to assess the efficiency of electro-coagulation treatment of pistachio processing industry wastewaters (PPIW) using an aluminum plate electrode. The effect of some of the parameters was examined on the removal of chemical oxygen demand (COD), total organic carbon (TOC), and total phenols (TP) removal efficiency. The treatment was carried out in a batch system. The influences of current density (from 1 to 6 mA cm^?2), initial pH of wastewater (from 2 to 8), constant pH of wastewater (from 3 to 7), stirring speed (from 100 to 500 rpm), and supporting electrolyte concentration (from 10 to 50 mg L^?1 NaCl) on removal efficiency were investigated to determine the best experimental conditions. The evaluation of the physico-chemical parameters during the treatment by electrocoagulation showed that the best removal efficiency was obtained under the conditions of 180 min electrolysis time, wastewater with constant pH of 6, and 6 – mA cm^?2 current density. Under such experimental conditions, COD, TOC, and TP removal efficiency were found to be 60.1%, 50.2%, and 77.3%, respectively, while energy consumption was 39.6 kW-h m^?3. The results of the study show that the electrocoagulation can be applied to PPIW pre-treatment.     

Characterization of the removal of Chromium(VI) from groundwater by electrocoagulation

A batch electrocoagulation system has been evaluated for the removal of Cr(VI) from brackish groundwater under different operating conditions. The influence of electrode type, applied current density, initial pH, initial chromium concentration, conductivity and temperature were evaluated. The experimental results indicated that chromium removal increased with increasing the applied current density and conductivity. The efficiency of different electrode arrangements (iron, aluminum) was also assessed, and indicated that Fe–Fe electrode pair was the most efficient arrangement and was able to achieve 100% Cr removal at an electrocoagulation time of 5 min, a current density of 7.94 mA/cm², and pH of 8 at room temperature 25 °C. The generated sludge for the iron electrodes was characterized using EDS, X-ray fluorescence (XRF) and FE-SEM. The analysis confirmed the formation and precipitation of Fe(OH)₃ and Cr(OH)₃ as solids. Overall, the study affirmed that electrocoagulation is a reliable technique for the purification of groundwater with an estimated energy consumption of 0.6 kWh/m³.     

Treatment of dairy wastewater by electrocoagulation process: Advantages of combined iron/aluminum electrodes

ABSTRACT

The objective was to assess the efficiency of electrode material in an electrocoagulation (EC) process for wastewater treatment by comparing the efficiency of aluminum (Al–Al), iron (Fe–Fe) and combined Fe–Al electrodes. The treatment of synthetic dairy wastewater, characterized by high levels of 5-day biological oxygen demand (BOD₅) and chemical oxygen demand (COD), was used to compare electrode materials. Experimental results showed that all electrodes materials achieved the same final removal yield in the range of current studied (55% COD, 60% total organic carbon, 90% total nitrogen, and nearly 100% turbidity) when equilibrium was achieved. But at fixed current density and initial concentration of dairy waste, the Al–Al assembly exhibited the fastest elimination, whereas the slowest removal rate was observed with the Fe–Fe electrodes, even though adsorption was always the main removal mechanism. Finally, an Fe–Al system using an Fe anode with an Al cathode emerged as a techno-economic trade-off because of the low price of iron: both metals contributed to the removal of dairy waste, and the treatment time to achieve equilibrium values was closer to the Al–Al assembly at fixed current density. Moreover, experimental results proved the additivity of the mechanisms reported for Al–Al and Fe–Fe systems with Fe–Al.     

Performance evaluation of electrocoagulation process using zinc electrodes for removal of urea

ABSTRACT

This study investigated the ability of the electrocoagulation process to remove urea from synthetic and real wastewater using zinc electrodes. The electrocoagulation cell was operated under various conditions of current density, initial pH, electrode spacing, and electrolytes. The results indicated that the maximum urea removal reached was 66%, which occurred at a current density of 21 mA/cm², initial pH = 7.0, 4 cm electrode spacing, and using magnesium chloride as the electrolyte. By-products were analyzed using FTIR. The anode’s morphology was examined using a scanning electron microscope. Results were compared with chemical coagulation using zinc sulfate as the coagulant.     

铝阳极电凝聚处理活性红241染料模拟废水

本文考察了电流密度、初始pH值、电解质浓度及种类、温度、染料浓度因素对铝阳极电凝聚处理活性红241模拟废水的影响。结果表明,在一定实验条件下,电流强度、染料浓度、电解液初始pH值、NaCl电解质浓度、温度对染料溶液脱色效率的影响明显,而Na2SO4电解质浓度对脱色效率的影响不显著;在电凝聚处理过程中,主要作用机理是以Al3 的单核水解产物与染料络合作用占主导地位;活性红241在阴极上发生了还原反应。     

Investigation of shipyard wastewater treatment using electrocoagulation process with Al electrodes

In this study, shipyard oily wastewater treatment was investigated by electrocoagulation (EC) using aluminum electrodes in a batch reactor by evaluating different operation conditions. The maximum chemical oxygen demand (COD) removal efficiency of 88.83% was obtained at current density of 3 mA/cm². The removal efficiency was gradually improved with increasing current density and decreased with increasing COD concentration. However, initial pH value was not determinant factor for this process. Total energy and electrode cost were calculated as $0.88 per m³ treated wastewater. The result of this research shows that EC process seems to be an efficient method for the oily wastewater treatment.     

Electrochemical removal of the insecticide imidacloprid from water on a boron-doped diamond and Ta/PbO<Subscript>2</Subscript> anodes using anodic oxidation process

The removal of pesticides from water is a major environmental concern. This study investigates the electrochemical removal of the insecticide imidacloprid (IMD) from aqueous solutions on a boron-doped diamond (BDD) and Ta/PbO₂ anodes under galvanostatic electrolysis. The influence of operating parameters, such as applied current density (50–100 mA cm^?2), initial chemical oxygen demand COD (0) (281–953 mg L^?1), temperature (25–65 °C) and pH (3.0–10.0) on COD and instantaneous current efficiency (ICE), was studied using the BDD electrode. The degradation efficiency of IMD increased by increasing current density and temperature, but noticeably decreased by the increase of initial pH value and initial concentration of IMD. The COD decay follows a pseudo-first-order kinetic, and the process was under mass transport control. COD removal reaches 90% when using an apparent current density of 100 mA cm^?2, initial COD of 953 mg L^?1, pH of 3.0 and at 25 °C after 4.5 h electrolysis time. Compared with Ta/PbO₂, BDD anode has shown better performance and rapidity in the COD removal using the same electrolysis device.     

Electrochemical Treatment of Simulated Textile Effluent

Electrooxidation of simulated Acid Blue 113 dye effluent has been carried out using a RuO₂/Ti electrode. The influence of the initial concentration of dye, supporting electrolyte, current densities and pH on COD reduction has been critically studied. Electrochemical analysis such as Instantaneous Current Efficiency (ICE) and Electrochemical Oxygen Demand (EOD) were used.     

臭氧强化电絮凝处理直接耐晒大红4BS模拟染料废水

采用臭氧强化电絮凝法处理直接耐晒大红4BS模拟染料废水,研究了染料脱色的影响因素及其COD_Cr去除动力学。考察了电流密度、溶液初始pH 值、染料初始浓度、支持电解质浓度、反应温度和臭氧流量对臭氧强化电絮凝法处理4BS染料脱色效率的影响。结果表明,电流密度15 mA·cm^-2,pH值10.0,4BS染料初始浓度100 mg·L^-1,支持电解质浓度3000 mg·L^-1,臭氧流量06 L·h^-1,20 ℃下反应50 min后4BS脱色率达94％以上。COD_Cr去除符合拟二级动力学。     

Indirect Electrochemical Oxidation of Phenol in the Presence of Chloride for Wastewater Treatment

Electrochemical oxidation of phenol using a Ti/TiO₂‐RuO₂‐IrO₂ anode in the presence of chloride as the supporting electrolyte was investigated. The experiments were performed in an undivided batch reactor. Preliminary investigations showed that only a small fraction of phenol was oxidized by direct electrolysis, while complete degradation of phenol was achieved by indirect electrochemical oxidation using chloride as a supporting electrolyte. The effect of operating parameters such as initial pH, supporting electrolyte concentration, phenol concentration, and charge input was studied using Box‐Behnken second order composite experimental design. The effect of current density on COD removal was studied separately. TOC removal and AOX formation were studied for selected conditions. It was found that the formation of chlorinated organic compounds was pronounced at the beginning of electrolysis, but it was reduced to lower levels by extended electrolysis.     

Electrochemical oxidation of Crystal Violet in the presence of hydrogen peroxide

BACKGROUND: The combination of electrochemical oxidation using a Ti/RuO₂? IrO₂ anode with hydrogen peroxide has been used for the degradation of Crystal Violet. The effect of major parameters such as initial pH, hydrogen peroxide concentration, current density, electrolyte concentration and hydroxyl radical scavenger on the decolorisation was investigated. RESULTS: The decolorisation rate increased with initial pH and hydrogen peroxide concentration, but decreased with electrolyte and radical scavenger concentration. The decolorisation rate increased with current density, but the increase became insignificant after current density exceeded 47.6 mA cm^?2. On the other hand, hydrogen peroxide decomposition rate increased with initial pH and current density, but decreased with electrolyte and radical scavenger concentration. The amount of hydrogen peroxide decomposed during 30 min reaction increased linearly with hydrogen peroxide dosage. The main intermediates were separated and identified by gas chromatography–mass spectrometry (GC–MS) technique and a plausible degradation pathway of Crystal Violet was proposed. At neutral pH, the electrochemical process in the presence of hydrogen peroxide was more efficient than that in the presence of Fenton's reagent (electro‐Fenton process). CONCLUSION: The anodic oxidation process could decolorise Crystal Violet effectively when hydrogen peroxide was present. Almost complete decolorisation was achieved after 30 min reaction under the conditions 2.43 mmol L^?1 hydrogen peroxide, 47.6 mA cm^?2 current density and pH₀ 7, while 62% COD removal efficiency was obtained when the reaction time was prolonged to 90 min. Copyright © 2010 Society of Chemical Industry     

Electrochemical degradation of 17β-estradiol (E2) at boron-doped diamond (Si/BDD) thin film electrode

Electrochemical degradation of aqueous solutions containing 17β-estradiol (E2), concentrations range of 250-750 μg dm⁻³, has been extensively studied using boron-doped diamond (BDD) anode with a working solution volume of 250 ml under galvanostatic control. Cyclic voltammetric experiments were performed to examine the redox response of E2 as a function of cycle number. The effect of operating variables such as initial concentration of E2, applied current density, supporting medium (Na₂SO₄, NaNO₃, and NaCl) and initial pH of the electrolyte (pH 2-10) were systematically examined and discussed. Electrolysis at high anodic potential causes complex oxidation of E2 that leads to form the final sole product as CO₂. A pseudo first-order kinetics for E2 decay was found against varying applied current density. Also, kinetic analysis suggests that electrooxidation reaction of E2 undergo the control of applied current density. It was observed that electrolyte pH and supporting medium have a vital role on E2 degradation. From a comparison study with other anode materials such as platinum (Pt) and glassy carbon (GC), the superiority of the BDD anode was proved. Total organic carbon results have shown that almost complete mineralization could be accomplished at higher applied current density with specific electrical charge 22.5 × 10⁻² A h dm⁻³. Mineralization current efficiency was comparatively lower with increasing applied current density.     

Study on the treatment of waste metal cutting fluids using electrocoagulation

Electrocoagulation (EC) technique is applied for the treatment of waste metal cutting fluids (WMCFs) characterized by high COD and TOC concentration, discharged from metal manufacturing facilities including automotive engine, transmission, and stamping plants. The effects of initial pH, current density and operating time on the performance of EC are investigated by using sacrificial Al and Fe electrodes. Upon treatment by EC, the COD of WMCF is reduced by 93% and the TOC is reduced by 78% for Al electrode at pH 5.0, current density of 60 A/m² and operating time of 25 min. For Fe electrode, the reduction in COD is 92% and reduction in TOC is 82% at pH 7.0, current density of 60 A/m² and operating time of 25 min. Under optimal operating conditions, the operating costs are calculated as 0.497 $/m³ (0.023 $/kg removed COD or 0.144 $/kg removed TOC) for Fe electrode, and 0.768 $/m³ (0.036 $/kg removed COD or 0.228 $/kg removed TOC) for Al electrode. Fe electrode is found to be more efficient than Al electrode in terms of parameters such as COD and TOC removal efficiencies and operating costs.     

Use of a PbO2 electrode of a lead-acid battery for the electrochemical degradation of methylene blue

In this work, the electrochemical degradation efficiency of synthetic azo dye, methylene blue, at positive electrode PbO₂ of lead-acid battery was investigated. The structure and morphology of the electrode was investigated by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectrometry. The influence of several operating parameters on electro-oxidation of 100 mL of methylene blue solution 100 mg/L was studied. Results indicated that lead-acid battery electrode is effective for removing color and chemical oxygen demand (COD). It is found that current density, the stirring speed, and the supporting electrolyte concentration have a positive effect on decolorization and mineralization, and no significant effect of the distance between the electrodes on methylene blue degradation and COD removal was observed. By contrast, the percentage of color and COD removal decreases with increasing of pH. Kinetic analysis of the results revealed that the COD removal follows a pseudo-first-order kinetics.     

Electrochemical treatment of a graphitic forging lubricant effluent: The effect of chloride concentration and current density

The graphite removal and the chemical oxygen demand (COD) reduction by the electrochemical treatment of an effluent containing a lubricant (oil in water emulsion with graphite) was investigated. The electrochemical cell used a pair of aluminum plates. Since the effluent conductivity was very low, NaCl was used as supporting electrolyte and different current densities as well as different distance between the electrodes were applied. In lower current densities, higher chloride concentrations implied in smaller COD values. The same behavior was observed when electrode distance was decreased. All the tested conditions presented significant graphite removal and COD reductions larger than 94%.     

Optimization of the Iron Electro-Coagulation Process of Cr,Ni, Cu,and Zn Galvanization By-Products by Using Response Surface Methodology

An electrocoagulation laboratory scale system was studied for the removal of inorganic pollutants from a mixture of galvanic process-based by-products. Response surface methodology based on a five-level, four-variable central composite rotatable design was employed for optimization with respect to four important variables—reaction time, agitation velocity, current density, and pH. The electrocoagulation process response was evaluated on the basis of chemical oxygen demand (COD), turbidity, total suspended solid, and element concentration values. Interaction effects between reactor operating variables and response variables were evaluated by using 3-D response surface analysis Second-order models were validated by ANOVA. Predicted yields were in a good agreement with the experimental ones. The reactor optimal performance was achieved at 35 min reaction time, 170 rpm agitation velocity, 97.7 Am^?2 current density, and 6.5 initial pH. Under these conditions 100% color and turbidity, 90% COD and total suspended solids, 100% chromium and nickel, and almost 99% zinc and copper were removed. A pseudo-first-order rate model was applied to describe the metal removal kinetics. The EC treatment of heavy metal solutions proved to be more cost-effective than the conventional one, indicating clearly that the method of electro-coagulation is a very promising alternative for industrial applications.     

Treatment of olive mill wastewater by the combination of ultrafiltration and bipolar electrochemical reactor processes

The main purpose of this study was to investigate the removal of the chemical oxygen demand (COD) from olive mill wastewater (OMW) by the combination of ultrafiltration with electrocoagulation process. Ultrafiltration process equipped with CERAVER membrane was used as pre-treatment for electrochemical process. The obtained permeate from the ultrafiltration process allowed COD removal efficiency of about 96% from OMW. Obtained permeate with an average COD of about 1.1 g dm⁻³ was treated by electrochemical reactor equipped with a reactor with bipolar iron plate electrodes. The effect of the experimental parameters such as current density, pH, surface electrode/reactor volume ratio and NaCl concentration on COD removal was assessed. The results showed that the optimum COD removal rate was obtained at a current density of 93.3 A m⁻² and pH ranging from 4.5 to 6.5. At the optimum operational parameters for the experiments, electrocoagulation process could reduce COD from 1.1 g dm⁻³ to 78 mg dm⁻³, allowing direct discharge of the treated OMW as that meets the Algerian wastewater discharge standards (<125 mg dm⁻³).