Electro-oxidation Method Research Articles

Central composite experimental design for Indigo Carmine dye removal from solutions by applying electro-coagulation and electro-oxidation processes

Textile and food industries produce toxic or harmfull dye-containing wastewaters that should be treated for safely discharge. The electro-coagulation (EC) and the electro-oxidation (EO) methods for removal of dyes from wastewaters are being investigated nowadays by researchers. In this study, the Indigo Carmine, a textile and food coloring agent, removal was investigated by applying the electro-coagulation and the electro-oxidation methods. For this purpose, aluminum electrodes for EC and graphite plates for EO were used. The central composite experimental design was applied as the optimization method for the EC and the EO processes. The optimization parameters were selected as time (10-30 minutes), current density (0.4-2 Ampere/500 mL) and concentration (50-250 mg/L), natural pH (5.78-6.90) and room temperature (20-25 °C). The EO process was determined to be effective than the EC process. Statistically important parameters were concentration and time-current density interaction for the EC, but all the parameters were statistically unimportant for the EO. Dye removal percentages by the EC were calculated between 82.75% and 98.38%, and dye removal percentages by the EO were calculated between 46.88% and 100% for the determined experimental matrix. Electrical consumptions were almost equal for the EO and the EO prosesses. A column ion exchange process (Selion SBA 2000 resin) was applied to the dye residue after the EO treatment. From the oxidation reduction measurements, the treated solutions were determined as dischargeable.

Deciding on the priority of process parameters using the analytical hierarchy process in electrochemical wastewater treatment and investigation of paint wastewater treatability

In planning electrochemical treatment processes, it is thought that decision-making tools should be used in the selection of the main parameters that are likely to affect pollutant removal. According to detailed research in the literature, no previous study has systematically prioritized process parameters in electrochemical wastewater treatment using the analytical hierarchy process (AHP). In this study, published articles in the literature on the subject were used to determine which parameters were used in the treatment processes and with what frequency. Using the obtained results, the priorities of the process parameters were estimated with the help of AHP within the scope of the removal efficiencies and treatment cost criteria. According to the AHP analysis results, it was determined that the most effective parameters for both electrocoagulation and electrooxidation processes were pH (0.241), current density (0.171), voltage (0.171), conductivity (0.107), concentration (0.105) and reaction time (0.094). Four of the independent parameters were selected and treatability studies were carried out using both electrocoagulation (with Al electrode pair and Fe electrode pair) and electro oxidation (with Graphite electrode pair and Ti electrode pair) methods for different levels of each parameter. The pH, current density, voltage, and reaction time were chosen as independent parameters based on decision making process. Unit costs for removal of chemical oxygen demand with Al, Fe, graphite, and Ti electrodes were obtained as 1.05, 2.56, 0.074, and 14 USD per m3 wastewater, respectively. Unit costs for removal of color with Al, Fe, graphite, and Ti electrodes were obtained as 0.68, 1.20, 0.074, and 14 USD per m3 of wastewater, respectively. In addition, nine batch kinetic studies were conducted for optimum conditions obtained from pre-treatment studies with Al and Fe electrodes. Removal of chemical oxygen demand was achieved at 64 % with aluminum and iron electrodes at 40 and 70 min, respectively. The results obtained from kinetic studies showed that adsorption of organic substances fit the 2nd-order kinetic model and the correlation coefficient was 0.95 and 0.96 for aluminum and iron electrodes, respectively.

Electroplating wastewater treatment by electro-oxidation using synthesized new electrode: Experimental, optimization, kinetics, and cost analysis

The present work studied electroplating wastewater treatment by the electro-oxidation (EO) method through a new Ti/TiO2-GO-SnO2 electrode in a once-through continuous mode. The Ti/TiO2-GO-SnO2 electrode was synthesized using an anodic oxidation technique and characterized by electrochemical characterizaftion. Response Surface Methodology (RSM) employing a Box-Behnken Design (BBD) model was utilized to optimize pH (3−7), current density (j = 16.72–50.16 mA/cm2), and time (t = 30–130 min) for removal of electroplating effluents and energy consumption. At the optimum condition, the values of the responses R1 (% Cr(VI) removal), R2 (% Zn removal), R3 (% COD removal), and R4 (energy consumption) were found to be 97.55%, 95.66%, 87.32%, and 14.97 kWh/m3, respectively. The effect of reactive species scavengers on removing electroplating effluents has been studied. The kinetics and cost analysis were also carried out under optimal conditions. Once-through continuous experiments were carried out at different flow rates to determine the viability of the process at industrial or pilot scale applications. The synthesized electrode proved highly reusable, maintaining durability even after sixty cycles of usage. Toxicity analysis showed that EO has the potential to detoxify electroplating effluents. The observed results confirm that the EO with Ti/TiO2-GO-SnO2 electrode is low-cost and effective for removing electroplating effluents.

Colour removal from wastewaters by an electrooxidation method

This study examined the potential of electrooxidation techniques for treating Rhodamine B dyestuff from aqueous solutions made from synthetic wastewater. The Rhodamine B dyestuff was electro-oxidized by using five anodes coated with "Ti/IrO2/RuO2" as anode material and five stainless steel cathodes as cathode material. The initial concentration of Rhodamine B, the type of support electrolyte, the current density, and the initial pH of the wastewater were evaluated. KCl, NaCl, NaNO3 and Na2SO4 were used as supporting electrolytes. Colour removal performance was optimum when the initial pH was approximately 5, the current density was 1.78 mA cm-2, and the supporting electrolyte was NaCl at a concentration of 10 mM. Under ideal circumstances, colour removal was shown to be 99.72% effective.

Technoeconomic analysis of fine chemical electrosynthesis: a case study using electrooxidation of 2-methylnaphthelene to vitamin K3

A cerium-mediated electrooxidation method was developed for synthesizing vitamin K3 in a green and efficient manner. A systematic technoeconomic analysis was provided to understand its potential for practical implementation.

Treatment and optimization of high-strength egg-wash wastewater effluent using electrocoagulation and electrooxidation methods

Egg-washing wastewater contains a high concentration of nutrition and organic matter since eggs are broken during the washing and cleaning processes. Moreover, the wastewater contains small amounts of detergents or sanitizing agents. These contaminants may pose environmental challenges when they are not properly managed or treated. The study scrutinizes the efficiency of electrocoagulation (EO) and electrooxidation (EO) approaches for egg-wash wastewater treatment. The response surface methodology was employed to optimize the operational parameters. The removal efficiencies of soluble chemical oxygen demand (sCOD 90%), ammonia (NH3–N 91%), nitrate (NO3−-N 97%), nitrite (NO2−-N 89.3%), total dissolved nitrogen (TDN 91%), and phosphate (90%) were measured under various treatment conditions. The optimum treatment conditions achieved in the combined EC + EO process were pH 6.0, current density 20 mA cm−2, and electrolysis time of 60 min, respectively. Degradation kinetics of the egg-wash pollutants showed a significant reduction in half-life (t1/2) with EO (after EC-Aluminum) at 15 min, 12 min, 17 min, and 15 min for sCOD, NO2−-N. NO3−-N, and TDN, respectively. Whereas the half-life of NH3–N (18 min) and phosphate (17 min) reduced significantly with the EO (after EC-iron). Al and Fe electrodes coupled with boron-doped diamond were found efficient for pollutant removal.Environmental implication.Egg-wash wastewater has a high protein content and contains nutrients that are essential for living organisms. While these compounds can be valuable for agricultural use by increasing soil phosphate concentration, they can also become an issue if the excess nutrients are not properly managed. The soil has a threshold limit for holding phosphate, and any excess amount may be transported through surface runoff or contaminate groundwater through leachate, potentially affecting aquatic ecosystems and water quality. This study explores the efficiency of electrocoagulation and electrooxidation methods in treating egg-wash wastewater. These methods aim to remove pollutants and reduce their environmental impact.

Reversible surface modification of PAN-based carbon fibers by a ferrocene-based surfactant

The surface of carbon fibers (CFs) was modified by a surfactant (ferrocenemethyl)dodecyldimethylammonium bromide (FDDA) to enhance the interfacial ashesion between the CFs and surrounding matrix. Results showed that it could be electrochemically desorbed by a potentiostatic electro-oxidation method. The FDDA adsorption isotherm was attributed to the formation of multi-molecular layers mainly by non-electrostatic interactions. The adsorption and desorption of FDDA on the CFs have little effect on their tensile strength. The effects of FDDA modification on the interfacial properties of CF/epoxy composites were evaluated by a single-filament fragmentation test. Compared with the un-modified CFs, the FDDA-modified ones had significantly improved interfacial adhesion properties in the composites. This method provides a potential approach for preparing recyclable CF/resin composites.

Synthesis and characterization of cylindrical electrode with sucrose binder as advanced electrode materials for copper 3D-electro-oxidation.

This study produced a biomass-based cylindrical electrode containing sucrose (an organic binder). The Cu2+ removal performance of the synthesized sucrose-bonded cylindrical electrode was evaluated in a 3-phase 3-dimensional electro-oxidation reactor (3D-EO) and the classical electro-oxidation method (2D-EO). Sodium Dodecyl Sulfate (SDs) was grafted onto activated carbon and used as microelectrode in 3D-EO reactors. SDs grafting resulted in a 57% reduction in the micropores of activated carbon. Therefore, the surface area of carbon after grafting decreased from 1328 m2/g to 580 m2/g. The sucrose-bonded cylindrical electrode has a rich carbon structure and consists of 84.04 wt% C, 12.10 wt% O and 3.20 wt%Si. According to CV measurement, the sucrose-bonded cylindrical electrode gives a surface reaction against Cu2+ at voltages lower than -0.62 V. Increasing the potential difference from 1V to 3V in 2D-EO and 3D-EO processes led to the removal of Cu2+ from the solution. The 3D-EO reactor achieved a removal rate of 87.12% at 3V. The 100 ppm solution was treated with a 3D-EO reactor containing 6 g/L of PC/SDs400Ws for 60 min, successfully removing 91.22% of Cu2+.

Investigation of the effect of supporting electrolyte type and pH parameters on electrooxidation color removal from Direct Blue 86

In this study, color removal and electrical consumption from Direct Blue 86 (DB86) dyestuff, commonly used in the textile industry, were investigated using the electrooxidation method. A jacketed glass reactor with a volume of 2000 mL was preferred for the electrooxidation process. Five anode and five cathode electrodes with dimensions of 70 x 100 mm were used. Ti/IrO2/RuO2 was chosen as the anode material, and stainless steel (plate type) electrodes were preferred as the cathode. The effects of the supporting electrolyte type and pH parameters on color removal were investigated. NaCl, KCl, NaNO3, and Na2SO4 were used as supporting electrolytes. Experiments were conducted at pH 3, 5, 7, 9, and 11 with an applied current density of 0.325 mA/cm2. The results showed that KCl as the supporting electrolyte provided the highest color removal efficiency with 99.76%. The optimum pH value was found to be pH 9. The minimum energy consumption was calculated as 3.39 kW-h/m3 for pH 11. Based on the obtained results, it was concluded that the electrooxidation method is effective in color removal and can be preferred due to its ease of use and process control advantages.

Evaluation of Ti/Pt Anode Efficiency and Energy Consumption in Turbidity and Suspended Solids Removal from Paper Industry Wastewater: The Effect of pH and Support Electrolyte Type

In the research, different experimental setups were used to examine the treatment of wastewater from the paper industry using the electrooxidation method, one of the electrochemical treatment methods in the batch system. In the 2000 mL volume jacketed glass reactor utilized for the treatment of wastewater from the paper industry, 4 anode and 4 cathode sieve type plates of 7 cm x 10 cm dimensions were positioned at 0.5 cm intervals, and 1200 mL wastewater was used in the tests. Coated sieve type Ti/Pt electrodes were employed as the anode in the electrooxidation studies, and uncoated sieve type Ti electrodes were used as the cathode. It was determined that the active anodic wet surface area was 1078 cm2 . The removal rates of pollutant parameters such as turbidity and SS (Suspended Solids) in the experiments; the effects of wastewater initial pH value and supporting electrolyte type parameters were investigated. According to the results, the most effective pH value for Ti/Pt anode type at 400 rpm mixing speed was determined to be waste water natural pH (7.5), and 0.50 M NaCl was the most successful supporting electrolyte type. 96.92% Suspended Solids removal efficiency and 95.38% turbidity removal efficiency for Ti/Pt anode were achieved under ideal conditions. In addition, 312.05 kW-hour/kg COD is determined as the energy consumption value.

The experimental design approach to removal of endocrine disrupting compounds from domestic wastewater by electrooxidation process

In this study, the treatment performance of the process in the removal of Endocrine Disrupting Compounds (EDCs) from domestic wastewater by a laboratory-scale electrooxidation process using Ti/IrO2/RuO2 electrodes as an anode was evaluated using the response surface method (RSM). The effect of pH (3.00–9.00), current density (10–20 A), and flow rate (8–16 mL/min) on the electrochemical removal of 17α-ethinylestradiol, β-estradiol, triclosan, and estrone has been studied. The Box-Behnken Design (BBD) was used to optimize the parameters that affect the removal efficiencies of the Electrooxidation process (EOP), and second-order quadratic models were developed for the EOP process. Under optimum conditions of current density = 10 A, pH = 3.00 and flow rate = 13.93 mL/min, the maximum removal efficiencies of triclosan, 17α-ethinylestradiol and β-estradiol, and minimum energy consumption are 91.65, 96.43 and 96.65% and 41.606 kWh/m3, respectively. The Response Surface Method predicted values that reasonably agreed with the experimental values. At the same time, the electrooxidation method is not successful in completely removing estrone from wastewater.

Evaluation of the Efficiency of Ti/IrO2/RuO2 Anode in COD Removal from Paper Industry Wastewaters by Electrooxidation Method

In the research, the electrooxidation method of the electrochemical treatment methods in thebatch system was explored a variety of experimental conditions for the treatment of wastewater from thepaper sector. 4 anodes and 4 cathodes sieve type plates with dimensions of 7 cm x 10 cm were positionedat 0,5 cm intervals in the 2000 mL volume jacketed glass reactor used for the treatment of wastewater fromthe paper industry, and 1200 mL wastewater was used in the testing. 4 coated Ti/IrO2/RuO2 electrodes ofthe sieve type were used as the anode material and 4 uncoated Ti electrodes of the sieve type were utilizedas the cathode material in the electrooxidation of effluent from the paper industry. In the experiments, theremoval rate of the COD (Chemical Oxygen Demand) pollutant parameter; The effects of supportingelectrolyte types and concentrations such as KCl, NaCl, NaNO3, and Na2SO4, and parameters such as initialpH value and current density of wastewater without supporting electrolyte were investigated. According tothe results obtained; In the experiments conducted at the natural pH value of wastewater, 18.55 mA/cm2was the most effective current density, 0.50 M NaCl was the most effective supporting electrolyte type andconcentration. The COD removal rate at the best conditions (37.11 mA/cm2current density) was 90.62%.In optimum conditions; 73.20% COD removal efficiency has been achieved.

Direct Electrochemical Leaching Method for High-Purity Lithium Recovery from Spent Lithium Batteries.

Recovering lithium from lithium batteries (LIBs) is a promising approach for sustainable ternary lithium battery (T-LIB) development. Current lithium recovery methods from spent T-LIBs mainly concentrated on chemical leaching methods. However, chemical leaching relying on the additional acid seriously threatens the global environment and nonselective leaching also leads to low Li recovery purity. Here, we first reported a direct electro-oxidation method for lithium leaching from spent T-LIBs (Li0.8Ni0.6Co0.2Mn0.2O2); 95.02% of Li in the spent T-LIBs was leached under 2.5 V in 3 h. Meanwhile, nearly 100% Li recovery purity was also achieved, attributed to no other metal leaching and additional agents. We also clarified the relationship between lithium leaching and other metals during the electro-oxidation of spent T-LIBs. Under the optimized voltage, Ni and O maintain the electroneutrality in the structure assisting Li leaching, while Co and Mn maintain their valence states. A direct electro-oxidation Li leaching approach achieves high Li recovery purity and meanwhile overcomes the secondary pollution problem.

Modified W, Ti-doped IrO2 anode for efficient organic contaminant oxidation in livestock wastewater

The treatment of livestock wastewater is a major environmental challenge due to the presence of antibiotics from animal excreta, which may pass through conventional biological oxidation treatment and pose a threat to public health. Electro-oxidation method presents an opportunity to remove antibiotics in the livestock wastewater at the source of generation, and titanium-based IrO2 anode has been shown to have excellent electro-catalytic activity and stability. However, the soaring price of iridium limits the practical application. In this work, we showed that W, Ti-doped IrO2 anodes largely preserved the electro-catalytic activity while reducing the cost of electrode fabrication. The prepared Ti/Sb-SnO2/(Ir0.6W0.2Ti0.2)Ox anode was shown to achieve 94 % conversion of sulfadiazine in 1 min and 100 % conversion in 15 min. Additionally, complete removal of chemical oxygen demand (COD0 = 700–800 mg/L) was achieved in 1–3 h of electrolysis at 40 mA/cm2. Chlorine-mediated oxidation was demonstrated to be the main mechanism for organic contaminant degradation. The COD removal during galvanostatic electrolysis exhibited zero-order kinetics, indicating that the reaction rate was controlled by the heterogeneous reaction at the anode surface. In the stability test, >95 % COD removal was maintained after 5 cycles of electro-oxidation experiments. The accelerated life of the anode was tested to be 352 h (1000 mA/cm2, 1 M H2SO4 electrolyte, 60 °C).

Degradasi Pewarna Tekstil Remazol Violet 5R Dengan Metode Elektrooksidasi Menggunakan Elektroda Grafit

Remazol Violet 5R textile dye degradation experiment has been carried out by electrooxidation method using graphite electrodes. The electrooxidation device consists of a plastic tub with a size (p x l x h) = 20 x 20 x 25 cm which is equipped with an electric stirrer and graphite electrodes using a used battery anode. Graphite electrodes consist of 3 pairs arranged in parallel. This dye degradation experiment was carried out using a batch system (not continuous) with variations in stirring time of 15, 30, 45, and 60 minutes, while the other variables were fixed, namely the concentration of dye 100.24 mg/liter, electrolyte NaCl 2.06 g/liter, 12 V voltage, and a stirring speed of 250 rpm. The dye solution before degradation and after degradation was measured for absorbance using a UV-Vis spectrophotometer at the maximum wavelength, to determine the percentage decrease in absorbance and optimum contact time. The experimental results showed that the percentage decrease in absorbance was constant after a contact time of 30 minutes with an absorbance of 98.36%. This indicates that the optimum contact time for the degradation of Remasol Violet 5R dye is 30 minutes. From the experiments that have been carried out, it can be concluded that the electrooxidation method using graphite electrodes can be used as an alternative waste treatment method, especially in terms of removing dyes in textile industry wastewater.

Formation and Stabilization of NiOOH by Introducing α-FeOOH in LDH: Composite Electrocatalyst for Oxygen Evolution and Urea Oxidation Reactions.

NiOOH is considered as the most active intermediate during electrochemical oxidation reaction, however, it is hard to directly synthesize due to high oxidation energy. Herein, theoretical calculations predict that α-FeOOH enables a decline in formation energy and an improvement in stabilization of NiOOH in NiFe-based layered double hydroxide (LDH). Inspiringly, a composite composed of α-FeOOH and LDH is well-designed and successfully fabricated in hydrothermal treatment by adding extra Fe3+ resource, and stable NiOOH is obtained by the following electro-oxidation method. Benefiting from strong electron-capturing capability of α-FeOOH, it efficiently promotes charge redistribution around the Ni/Fe sites and activates Ni atoms of LDH, verified by X-ray photoelectron spectra (XPS) and X-ray absorption spectra (XAS). The d-band center is optimized that balances the absorption and desorption energy, and thus Gibbs free energy barrier is lowered dramatically toward oxygen evolution reaction (OER) and urea oxidation reaction (UOR), and finally showing an outstanding overpotential of 195mV and a potential of 1.35V at 10mA cm-2 , respectively. This study provides a novel strategy to construct highly efficient catalysts via the introduction of a new phase for complex multiple-electron reactions.

Removal and recovery of aqueous uranium using photocatalytic reduction method: Performance and implication

The effective extraction and recovery of uranium (U) from aqueous systems are pivotal to the sustainable development of the nuclear power industry and environmental protection. In this study, immobilized photocatalyst TiO2 nanotube arrays (TNAs) were synthesized and characterized, and the photocatalytic extraction of hexavalent U (U(VI)) from wastewater was investigated. The anodization voltage and annealing temperature used for the synthesis influenced the surface morphology and crystallographic composition characteristics of the obtained TNAs, which were found to impose a crucial influence: TNAs with an anodization voltage of 15 V and annealing temperature of 600 ℃ enabled rapid U(VI) extraction. Other factors, such as the solution pH, initial U(VI) concentration, inorganic ions, and EDTA, which could influence the photocatalytic extraction performance of TNAs, were also investigated. The efficiency of U(VI) extraction was found to be >54 % after 3-cycles over 120 min of UV-light irradiation. A possible mechanism was proposed to explain the photocatalytic extraction of U(VI). Furthermore, an electrooxidation method for recovering U from TNAs was also proposed investigated, and the efficiency in 3-cycles was all higher than 83 %. The recovery product of U was found as a mixture of UO3 and UO3·H2O. Finally, a photocatalytic U recovery process was designed to remove and recover U from U-containing wastewater. This work potentially helps opening a new avenue for cost-effective U removal and recovery from U-containing wastewater.

Fluorine-doped nickel oxyhydroxide as a robust electrocatalyst for oxygen evolution reaction

Fluorine (F) anion doping has recently emerged as a promising approach for boosting the activity of earth-abundant metal catalysts for the oxygen evolution reaction (OER). But many key questions concerning this new approach remain unanswered, including the nature of F-doping, the mechanistic understanding of F-doping effects as well as the long-term stability of F-doped catalysts. Herein, we report a case study of F-NiOOH/Ni(OH)2/NF catalyst that was fabricated using a simple anodic electrooxidation method in a F-containing alkaline solution. A combination of experimental and computational studies revealed that F anions substitute for OH groups in the NiOOH surface layer and such a substitutional F-doping results in significant improvement of OER activity. In particular, the F-doped catalyst possesses outstanding stability when operated in a F-containing electrolyte. For instance, F-NiOOH/Ni(OH)2/NF showed an overpotential fluctuation of only ±4 mV in a 100-h constant current test at 100 mA cm−2 in a 0.01 M KF alkaline solution. Furthermore, our study found that this simple F-doping method is applicable to other transition metal oxide/hydroxide catalysts for boosting OER activity.

Scalable Electrosynthesis of Formamide through C-N Coupling at the Industrially Relevant Current Density of 120 mA cm-2.

The scalable and durable electrosynthesis of high-valued organonitrogen compounds from carbon- and nitrogen-containing small molecules, especially operating at a high current density, is highly desirable. Here, a one-pot electrooxidation method to synthesize formamide (HCONH2 ) from methanol and ammonia over a commercial boron-doped diamond (BDD) catalyst is reported. The formamide selectivity from methanol and formamide Faradaic efficiency (FE ) achieve 73.2 % and 41.2 % at the current density of 120 mA cm-2 with high durability. The C-N bond originates from the nucleophilic attack of ammonia on an aldehyde-like intermediate. Impressively, an 8 L electrolyzer is employed for the pilot plant test over a 2200 cm2 BDD electrode, which exhibits 33.5 % FE at 120 mA cm-2 (current: 264 A) with a yield rate of 36.9 g h-1 , demonstrating the potential of this technique for large-scale electrosynthesis of formamide.

Scalable Electrosynthesis of Formamide through C−N Coupling at the Industrially Relevant Current Density of 120 mA cm−2

AbstractThe scalable and durable electrosynthesis of high‐valued organonitrogen compounds from carbon‐ and nitrogen‐containing small molecules, especially operating at a high current density, is highly desirable. Here, a one‐pot electrooxidation method to synthesize formamide (HCONH2) from methanol and ammonia over a commercial boron‐doped diamond (BDD) catalyst is reported. The formamide selectivity from methanol and formamide Faradaic efficiency (FE ) achieve 73.2 % and 41.2 % at the current density of 120 mA cm−2 with high durability. The C−N bond originates from the nucleophilic attack of ammonia on an aldehyde‐like intermediate. Impressively, an 8 L electrolyzer is employed for the pilot plant test over a 2200 cm2 BDD electrode, which exhibits 33.5 % FE at 120 mA cm−2 (current: 264 A) with a yield rate of 36.9 g h−1, demonstrating the potential of this technique for large‐scale electrosynthesis of formamide.