Batch Electrochemical Reactor Research Articles

Direct electrochemical regeneration of the enzymatic cofactor 1,4-NADH employing nano-patterned glassy carbon/Pt and glassy carbon/Ni electrodes

A glassy carbon electrode surface was patterned with electrochemically deposited platinum and nickel nano-particles, with the aim of increasing the electrode efficiency in the process of in situ electrochemical regeneration of enzymatically active 1,4-NADH from NAD+, in a batch electrochemical reactor. The role of Pt and Ni was to provide ‘active’ adsorbed hydrogen (Pt–Hads or Ni–Hads) for the fast protonation of electrochemically formed NAD-radical. The effect of nano-particle size, surface coverage, and the electrode potential on the percentage of 1,4-NADH recovered from NAD+ was investigated. It was demonstrated that up to a 100% recovery of 1,4-NADH from NAD+ was possible on the produced electrodes at relatively low electrode potentials, making them excellent candidates for regeneration of 1,4-NADH in industrial bioreactors.

Binary system dye removal by electrocoagulation from synthetic and real colored wastewaters

In this study, binary system dye removal by electrocoagulation (EC) process using aluminum electrode was studied in a batch electrochemical reactor. Acid Black 52 and Acid Yellow 220 were used as model dyes. The effect of operating parameters such as conductivity, current density, initial dye concentration and pH on the electrocoagulation process was studied and the electrical energy consumption was calculated. Also the wool dyeing process has been performed and the dye removal from real colored wastewater by the electrocoagulation process has been studied. It was found that the increasing of the current density up to 40A/m2 had increased the dye removal efficiency and the optimum pH for EC process was 5. The increasing of electrolyte concentration from 0 to 8g/L had a negligible effect on the color removal but it has decreased the electrical energy consumption. Data for single and binary systems of dye removal and the results for the synthetic solutions and the real colored wastewater were too close and it can be concluded that the electrocoagulation process is an effective method to remove dyes from colored wastewaters.

Electrochemical treatment of simulated sugar industrial effluent: Optimization and modeling using a response surface methodology

The removal of organic compounds from a simulated sugar industrial effluent was investigated through the electrochemical oxidation technique. Effect of various experimental parameters such as current density, concentration of electrolyte and flow rate in a batch electrochemical reactor was studied on the percentage of COD removal and power consumption. The electrochemical reactor performance was analyzed based on with and without recirculation of the effluent having constant inter-electrodes distance. It was found out that the percentage removal of COD increased with the increase of electrolyte concentration and current density. The maximum percentage removal of COD was achieved at 80.74% at a current density of 5A/dm2 and 5g/L of electrolyte concentration in the batch electrochemical reactor. The recirculation electrochemical reactor system parameters like current density, concentration of COD and flow rate were optimized using response surface methodology, while COD removal percents were maximized and power consumption minimized. It has been observed from the present analysis that the predicted values are in good agreement with the experimental data with a correlation coefficient of 0.9888.

Application of electrochemically dissolved iron in the removal of tannic acid from water

Effects of some experimental parameters (supporting electrolyte, initial pH and current density) on the performance of electrocoagulation process using iron electrodes were investigated. Results of experiments showed that dissolution of iron is purely electrochemical and fits well with Faraday's law and leads to Fe2+ which are chemically oxidized into Fe3+ in aerated conditions. In neutral and alkaline conditions, the reaction between hydroxyl ions generated at the cathode and dissolved iron ions forms insoluble hydroxo-iron species. Potentiodynamic polarization tests showed that the formation of passive film on iron anode limits the continuous electrochemical dissolution of iron. Corrosion and pitting potentials largely depend on the nature of supporting electrolyte. The dissolution of iron is facilitated by pitting corrosion with chloride ions, but it is inhibited in the presence of phosphate ions. However, fluctuations between pitting and passivity were observed in the presence of sulfate ions but this can be eliminated by the addition of small amount of chloride ions. Electrocoagulation using iron electrodes was applied to remove tannic acid (TA) from water. The obtained results have shown that the efficiency of this electrochemical technology depends largely on certain operating parameters including initial pH, current density and nature of supporting electrolyte. Almost complete COD removal can be achieved in batch electrochemical reactor using iron electrodes under optimized operating conditions after consumption of 1Ahdm−3. The elimination of TA from water involves a primary mechanism leading to the formation of stable black organometallic complexes and a second mechanism through sweep coagulation.

Boron removal from seawater by electro-chemical treatment as part of water desalination

Significant decrease of boron concentration during seawater desalination is one of the more difficult, consuming and expensive tasks. Average boron concentration in the Mediterranean Sea is 4 mg/l, and due to heavy use of wastewater in irrigation the Israeli Water Authority (Ministry of Health) demands boron reduction to 0.4 mg/l maximum. The current boron removal procedure is based on two-pass reverse osmosis (RO) membrane treatment that requires pH adjustment to dissociate boric acid into borate ion. The operation is expensive, energy consuming and calls for cheaper and reliable alternatives. The current research was initiated to explore the abilities of electro-flocculation (EF) to remove boron from seawater. The EF experiments were performed under batch electro-chemical reactor conditions with iron electrodes. Settling time and pH of the solution were selected as two main independent parameters. The obtained results suggest that significant boron reduction can be achieved without membrane separation technologies. The obtained drop from 4.2 to 0.8 mg/l boron after 10 min EF and 60 min sedimentation suggests that RO can be applied as a polishing stage only, needed to achieve the goal of 90% B retention. At the same time, the average 80% boron retention achieved by EF/sedimentation is encouraging and can be viewed as a valuable alternative to currently applied RO-based technology. The studies were performed on seawater from the Palmachim beach (near Rishon-Le-Zion, Israel) and were an important step in detection of possible boron removal mechanisms.

Degradation studies for textile reactive dye by combined electrochemical, microbial and photocatalytic methods

The main objective is to reduce the chemical oxygen demand of the effluent containing Procion blue by combined electrochemical, microbial and photocatalytic methods and testing the degradation capability of different microorganisms. First, pretreatment was performed for 4 h prior to microbial oxidation using batch electrochemical reactor. Microbial degradation was carried out for the treated effluent in sequence in aerobic batch reactor for 5 days using bacterial ( Pseudomonas putida and Bacillus cereus) and fungal strains ( Pleurotus ostreatus, Fusarium oxysporum and Trichoderma viridae). Post electrolysis was done for 5 h on the treated effluent to meet the required standards as well as colour developed during microbial oxidation. Finally, Photocatalysis process was carried out for 5 h to remove the microbes present in it. The results indicate the overall performance in these schemes of operation is successful.

Removal of arsenic from drinking water by the electrocoagulation using Fe and Al electrodes

A novel technique of electrocoagulation (EC) was attempted in the present investigation to remove arsenic from drinking waters. Experiments were carried out in a batch electrochemical reactor using Al and Fe electrodes with monopolar parallel electrode connection mode to assess their efficiency. The effects of several operating parameters on arsenic removal such as pH (4–9), current density (2.5–7.5Am−2), initial concentration (75–500μgL−1) and operating time (0–15min) were examined. Optimum operating conditions were determined as an operating time of 12.5min and pH 6.5 for Fe electrode (93.5%) and 15min and pH 7 for Al electrode (95.7%) at 2.5Am−2, respectively. Arsenic removal obtained was highest with Al electrodes. Operating costs at the optimum conditions were calculated as 0.020€m−3 for Fe and 0.017€m−3 for Al electrodes. EC was able to bring down aqueous phase arsenic concentration to less than 10μgL−1 with Fe and Al electrodes. The adsorption of arsenic over electrochemically produced hydroxides and metal oxide complexes was found to follow pseudo second-order adsorption model. Scanning electron microscopy was also used to analyze surface topography of the solid particles at Fe/Al electrodes during the EC process.

Electrochemical regeneration of NADH on a glassy carbon electrode surface: The influence of electrolysis potential

The communication reports a surprising finding on the influence of electrode potential on the percentage of enzymatically active 1,4-NADH produced by reduction of NAD + in a batch electrochemical reactor, using a glassy carbon electrode. At the lowest cathodic electrolysis potential studied (− 1.4 V vs. MSE), only 32% of 1,4-NADH was found in the product mixture. However, at the highest cathodic electrolysis potential (− 2.3 V vs. MSE), a surprisingly high amount (98%) of 1,4-NADH was produced. The work demonstrates that, a batch electrochemical reactor employing a glassy carbon working electrode operated at high cathodic electrolysis potentials, represents a good candidate system for the regeneration of 1,4-NADH in industrial bioreactors.

Electrochemical decolorization of textile dyes and removal of metal ions from textile dye and metal ion binary mixtures

The electrochemical textile dye decolorization and removal of metal ions from [textile dye|metal ion] binary mixtures of [AB29|Cu(II)], [RR2|Cu(II)], [AR97|Ni(II)], and [RB4|Ni(II)] were investigated using iron anodes and Na 2SO 4 electrolyte in a batch electrochemical reactor. The independent parameters of current density, electrolyte concentration, initial solute concentrations, and reaction temperature were operated in the range of 0.8–4.0 mA/cm 2, 0–2 g/L, 0–400 mg/L, and 25–45 °C, respectively. The experimental data were optimized using response surface methodology (RSM), the approximation functions were obtained and the optimum operating conditions for the electrochemical decolorization and metal ions removal from [textile dye|metal ion] binary mixtures were determined. The quadratic models for textile dye decolorization and metal ion removal responses were well satisfied the assumptions of the analysis of variance (ANOVA). At optimized reaction conditions, the operating regions were determined for the efficiencies over 95% textile dye decolorization along with metal ion removal in [AB29|Cu(II)], [RR2|Cu(II)], [AR97|Ni(II)], and [RB4|Ni(II)] binary mixtures. The mean energy consumption values were evaluated between 29.2–38.1 kWh/kg dye decolorization and 14.2–22.5 kWh/kg metal ion removal at response surface optimized operating conditions.

Investigation for the possibility of nitrogen removal from industrial effluent of bone glue industry using a batch electrocoagulation unit with monopolar horizontal electrodes

The aim of the present work is to investigate the possibility of using the electrocoagulation technique (EC) for the treatment of wastewater generated from bone glue industry especially for the removal of nitrogen as pollutant. A batch electrochemical reactor with monopolar horizontally oriented aluminum electrodes was used. Variables studied were initial nitrogen concentration measured as total Kjeldahl nitrogen (TKN), applied current density distance between the electrodes, sodium chloride concentration, electrode area ratio (cathode/anode) and time of electrolysis. The results show that up to 90% of TKN of a synthetic waste can be removed within 60 min. In addition, a real wastewater sample from a bone glue factory located in Alexandria, Egypt, was investigated under different current densities. The results show that 60–80% of TKN can be removed within 120 min depending on the operating conditions. At the same time, a reduction in BOD, COD, and TSS of about 68%, 61% and 85% respectively can be achieved...

Electrochemical oil/water demulsification and purification of bilge water using Pt/Ir electrodes

The electrochemical oil/water demulsification and purification of bilge water were investigated using Pt/Ir electrodes in a batch electrochemical reactor. Bilge water is a corrosive mixture of seawater containing a variety of constituents including cleaning agents, solvents, fuel, lubricating oils and hydraulic oils. It is resulted mainly by the leakage from the machinery and fresh water washdowns, which are allowed to drain to the lowest inner part of the ship's hull. In this study, the influence of operating parameters as bilge water composition, seawater/fresh water composition, current density, and reaction temperature on the removal efficiency of COD, oil/grease and turbidity was analyzed. Experimental results were optimized using response surface methodology in order to maximize the removal rates while minimizing current density and mean energy consumption. The optimized conditions under specified constraints were obtained for the highest desirability at 100% bilge water composition (COD o = 3080 mg/L), 50/50% seawater/fresh water composition, 12.8 mA/cm 2 current density and 32 °C reaction temperature. Kinetic studies resulted in first order overall electrochemical conversion rate of pollutants based on COD concentration with the activation energy of 26.2 kJ/mol.

Electrocoagulation of Textile Effluent: RSM and ANN Modeling

This investigation attempts to study electrocoagulation of Acid Blue 113 textile effluent in a batch electrochemical reactor covering wide range in the operating conditions. Experiments were designed using statistical tool of Response Surface Method (RSM) to analyze the combined effect of operating parameters on the efficiency of electro coagulation process. The level of importance of the experimental parameters on the percentage COD removal has been determined by using analysis of variance (ANOVA). Further, the percentage COD removal was also modeled using artificial neural network (ANN).

Optimisation of Electro-Fenton denitrification of a model wastewater using a response surface methodology

Electro-Fenton denitrification of a model wastewater was studied using platinised titanium electrodes in a batch electrochemical reactor. The model wastewater was prepared from components based on the real aquaculture effluent with nitrate concentrations varying from 200 to 800 mg L −1. The technical as well as scientific feasibility of the method was assessed by the relationship between the most significant process variables such as various Fenton’s reagent to hydrogen peroxide ratios (1:5; 1:20 and 1:50) and current densities (0.17 mA cm −2, 0.34 mA cm −2 and 0.69 mA cm −2) and their response on denitrification efficiency in terms of nitrate degradation using central composite Box-Behnken experimental design was determined. The goodness of the model was checked by the coefficient of determination R 2 (0.9775), the corresponding analysis of variance P > F and a parity plot. The ANOVA results indicated that the proposed model was significant and therefore can be used to optimize denitrification of a model wastewater. The optimum reaction conditions were found to be 1:20 Fenton’s reagent/hydrogen peroxide ratio, 400 mg L −1 initial nitrate concentration and 0.34 mA cm −2 current density. Treatment costs in terms of electricity expenditure at 0.17, 0.34 and 0.69 mA cm −2 was 7.6, 16 and 41.8 €, respectively, per kilogram of nitrates and 1, 2 and 4 €, respectively, per cubic meter of wastewater.

Arsenic removal through electrocoagulation: Kinetic and statistical modeling

Arsenic removal from water/wastewater has been the subject of top priority among researchers/industries in recent years due its notorious characteristics. A novel technique of electrocoagulation has been attempted in the present investigation to remove arsenic from aqueous solution. Experiments were carried out in a batch electrochemical reactor using aluminum and mild steel sacrificial anodes. The mechanism of electrocoagulation has been modeled using adsorption isotherm kinetics. Experimental runs were designed by response surface methodology and the influence of combined effects of operating parameters on arsenic removal has been critically examined.

Electrochemical synthesis of coenzymes Q n by oxidation of tetramethoxy precursors

The electrochemical oxidation of tetramethoxy precursors (2) to coenzymes Qn (1) at a carbon anode was investigated both in a bench-scale batch electrochemical reactor and in a continuous recirculation reaction system equipped with a parallel-plate electrochemical divided cell. High faradic efficiency (>60%) and excellent selectivity (>90%) in coenzymes Qn were obtained in CH3CN or CH3CN/CH2Cl2 + 0.15 M Bu4NBF4 under potentiostatic or amperostatic alimentation.

전기분해와 UV 조사에 의한 수중의 Rhodamine B의 제거(I)

The feasibility study for the application of the removal and mineralization of Rhodamine B (RhB) was performed in a batch electrochemical reactor. The electro/UV process was consisted of DSA (dimensionally stable anode) electrode and UV-C or ozone lamp. The experimental results showed that RhB removal by the ozone lamp was higher than that of the UV-C lamp. Optimum current of the electro/UV process was 1 A. The electrochemical, UV and electro/UV process could completely degrade RhB, while a prolonged treatment was necessary to reach a high level RhB mineralization. It was observed that RhB removal in electro/UV process is similar to the sum of the UV and electrolytic decolorization. However, it was found that the COD of RhB could be degraded more efficiently by the electro/UV process (90.2 %) than the sum of the two individual oxidation processes [UV (19.7%) and electrolytic process (50.8%)]. A synergetic effect was demonstrated between the UV and electrolysis.

Potassium Ferrate and/or Sodium Ferrate Generation Using a Prototype of Electrochemical Reactor without Membrane

In this work, electrochemical generation of ferrate ion (FeO4-2) using a prototype of batch electrochemical reactor with agitation was studied. The anode used was a piece of steel tube (ASTM-A53) of 2 inches of nominal diameter and the cathode used was a steel bar of 0.5 inches. In the electrochemical reactor we did not use membranes, in order to diminish production costs and to make it a much more competitive and attractive process. Two different electrolytes were tested as reactant medium in the system: NaOH (10 M) and KOH (10 M). A current density of 53.62 mA/cm2 was applied with respect to the anode during a period of time of two hours. Afterwards the concentration of ferrate was determined in function of time using a spectroscopy method. It was found that the concentration of ferrate is higher in NaOH as reactant medium than KOH.

Electrocatalytic carboxylation of chloroacetonitrile at a silver cathode for the synthesis of cyanoacetic acid

The electrocatalytic carboxylation of chloroacetonitrile to cyanoacetic acid performed at silver cathodes was investigated both theoretically and experimentally. Silver exhibits powerful electrocatalytic activities towards the reduction of chloroacetonitrile. In CO 2-saturated CH 3CN, reduction of NCCH 2Cl occurs at potentials that are about 0.7 V more positive than those observed at glassy carbon and gives cyanoacetic acid in good yields. Theoretical considerations on the effect of operative parameters on the performances of the process were confirmed by electrocarboxylation experiments performed in undivided cells equipped with sacrificial anodes both in a bench-scale electrochemical batch reactor and in a continuous batch recirculation reaction system equipped with a parallel plate electrochemical cell. Selectivities and Faradic efficiencies higher than 80% were obtained by working under anhydrous conditions both under amperostatic and potentiostatic alimentation at proper values of either current density or applied potential.

Optimal time-varying potential profile for electro-hydro-dimerization reactions

Optimal time-varying potential profile for batch electrochemical reactor is evaluated for a major industrial electro-organic synthesis, the electro-hydro-dimerization of acrylonitrile to adiponitrile. The control vector iteration technique is used for computing the optimal profiles. As the technique is continuous on both state and adjoint variables, it can give more accurate profile with no need for any polynomial approximation. A heterogeneous model of the reactor is uniquely used for the formulation of dynamic optimization problem statements by expressing the differential constraints in terms of concentration variations in bulk as well as at the electrode surface. In addition to taking an account of surface concentration variations, the separation of total current as faradic and non-faradic currents is also considered as an additional equality constraint. A path constraint on the electrode potential is imposed for safe reactor function and economical operation. The results of optimum time-varying potential profile are compared with those of applying a steady potential.

Electrolytic recovery of silver from low concentrated silver cyanide spent plating solutions

Cyanide silver solution containing 200 to 1000 mg L−1 silver ions were used for recovery studies. The nature of the silver deposit was studied using a Hull cell, and the current density range was selected for electrolysis to recover silver. A batch electrochemical reactor, consisting of a planar stainless steel cathode and platinum anode was used and silver was recovered at 0˙04 to 0˙2 A dm−2. The effect of different initial silver concentrations on the electrochemical recovery of the metal was investigated as a function of electrolysis duration at various current densities. The cathode current efficiency and the energy consumption were determined for the solutions for various experimental conditions. Surface morphology and structure of the silver deposit was also studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that irrespective of the initial silver concentration, higher current efficiency and lower energy consumption can be achieved at a low current density. For a given current density, the energy consumption to recover silver is lower from relatively concentrated than from dilute solutions.