Nowadays cobalt is mostly produced through the ELECTROWINNING process of sulfate solutions. Regarding to the competition between the precipitation of cobalt ions and evolution of hydrogen gas on the cathode surface during the reduction process in a sulfate bath, investigation on the mechanism of metal precipitation is of great importance. In the present work, study on the kinetics of cobalt ELECTROWINNING and the mechanism of the involved reactions have been carried out. The obtained results, confirm the mechanism of cobalt precipitation by depletion of hydroxides. The effects of temperature and scan rate parameters were studied on ELECTROWINNING of cobalt by cyclic voltammetry technique. The diffusion coefficient and rate constant of the reactions were measured and calculated by performed experiments.

ELECTROWINNING is the process of copper deposing from the intracellular electrolyte solution to the cathode by creating an electric current. In the present study, the hydrodynamic simulation of the ELECTROWINNING cell of Miduk Copper Complex is studied using computational fluid dynamics. Ansys-CFX software is used for this modeling. Navier Stokes and continuity equations are considered as the two-phase fluid and gas, turbulent, incompressible and steady states and the equation for copper concentration in the electrolyte will be solved with consideration of its specific boundary condition. Turbulence will be modeled using the k-ω method. The general and local simulations have been used together due to the large variation in the properties, close to the cathode and anode, and the large volume of the cell, to create a good mesh and increase the speed and accuracy of the solution. First, in general simulation, the entire geometry of the cell is modeled by creating a suitable mesh. Then in the local simulation, only the volume between the two cathodes of the cell is considered and modeled with higher precision. Data on boundary conditions in the local simulation of interface boundary are obtained with general simulation data, which increases the accuracy of modeling. Comparison of the results of general and local simulations shows an accuracy of up to 30% in close to the electrodes. The results of this simulation are the velocity vector, the concentration of acid and copper, the turbulence intensity, pressure and the volume fraction of the oxygen phase in the whole of the ELECTROWINNING cell. Finally, the model has been validated by experiments on the real cells. The results show the high accuracy of this modeling technique with less than 2. 5% deviation.

In this research, the electrodeposition of antimony was studied in alkaline sulfide solution. The effect of time and temperature of ELECTROWINNING step on antimony recovery, current efficiency and specific energy in the temperature range of 45-65 °C for 0-6 h was investigated. Furthermore, the kinetics of electrodeposition was studied, and the results were used in developing mathematical model. Results show that increasing the temperature of ELECTROWINNING decreases antimony recovery, current efficiency and increases energy consumption. Hydrogen evolution at the cathode at low concentration of antimony in the solution and occurrence of harmful reactions at the electrodes lead to energy consumption and decrease current efficiency and antimony recovery. Maximum antimony recovery was 70 % after 6 h electrodeposition at 45 °C and maximum current efficiency was 90 % after one hour electrodeposition at the same temperature. The energy consumed per one kilogram of deposited antimony in the temperature range of the experiments was in the range of 1.35-2.28 kWh. Minimum value of consumed energy was achieved at 45 °C. The kinetic investigation shows that Avrami- Erofeyev equation can be used for prediction of antimony recovery with high accuracy.

In this study, effect of some parameters on chathodic current efficiency, consumption of energy per kg of produced zinc and surface morphology has been investigated. Based on obtained results, the optimum values of electrolyte flow rate, concentration of Sulfuric acid and Zinc and, current efficiency have been determined in the presence of addition values of gummy Arabic and Potassium Permanganate. The suitable conditions for the parameters of specific electrolyte flow rate, current density, sulfuric acid concentration and zinc concentration found equal to, 16.6x10-3 /min, Max 400 amp/m2, 120-140 gr/L and 50-60 gr/L, respectively.

ELECTROWINNING is the process of depositing copper of the electrolyte solution inside the cell to the cathode. In the present study, the hydrodynamic simulation of the ELECTROWINNING cell of Miduk Copper Complex is studied using computational fluid dynamics. The software used is Ansys CFX. The Navier-Stokes and continuity equations are considered in the form of two phases of fluid and gas, turbulent, incompressible and steady state, and the equation for copper concentration in the electrolyte is solved with consideration of its specific boundary condition. The flow turbulence is modeled using K-ω relationships. Due to large variations in the properties near cathode and anode, and also the large size of the ELECTROWINNING cell, to create a good grid, and increase the speed and accuracy of the results, global and local simulations are used together. First, in global simulation, the entire geometry of the cell is modeled by creating an appropriate grid, then, in the local simulation, the volume between two cathodes of the cell only is considered and modeled with a much smaller mesh. Data on boundary conditions of the common border plates in the local simulation are obtained from global simulation data, which increases the accuracy of modeling. The results of this simulation are the velocity vectors, the concentrations of acid and copper, turbulence Intensity, the amount of pressure, and the volume ratio of the oxygen phase in the entire ELECTROWINNING cell domain. Finally, for model validation, the model is compared with experiments conducted on actual cells in the industry. Results show high accuracy with less than 2. 5% deviation of this modeling technique. Then, the mass transfer coefficient values for the different electrode intervals are obtained by this modeling and the results are validated using the results of the experimental relations, indicating a deviation of only 0. 5%. In the next step, the electrolyte mixture containing different mass fractions of oxygen is sprayed into the ELECTROWINNING cell from the inlet of the simulated cell. The results demonstrate that spraying 16 liters per second of oxygen at the inlet can increase the overall mass transfer coefficient of the electrode plates up to 7%. The effect of changing inlet temperature and flow rate of the electrolyte on the mass transfer coefficient is also investigated by the obtained model.

Nowadays cobalt is mostly produced through ELECTROWINNING process of sulfate solution. Regarding competitive cobalt precipitation and hydrogen evolution in the cathode during reduction in a sulfate bath, investigation on the mechanism of metal precipitation is of great importance. In the present work, study on the kinetics of cobalt ELECTROWINNING and the mechanism of involved reactions have been carried out. The obtained results, represent that the cobalt precipitation by depletion of hydroxides. The effects of temperature and scan rate parameters were studied on ELECTROWINNING of cobalt by cyclic voltammetry technique. The diffusion coefficient and rate constant of the reaction were measured and calculated by performed experiments.

In this study, the ELECTROWINNING process was investigated in the production of metal cobalt from a low chloride solution concentration by both response surface methodology and artificial neural network. Initially, the solvent extraction process from two different feeds was performed to recover cobalt ions by dithiophosphinic acid to the organic phase and transferring it to the aqueous phase with HCl solution (1 M). Then, the metal production process was performed using the ELECTROWINNING method and examining the effective parameters such as time, pH of solution, ion concentration and current ampere. The optimization conditions for pH of aqueous solution, time, cobalt ion concentration, and ampere were obtained equal to 4, 40, 0.008 mol/L, 1 A, respectively. The results showed that the temperature of 15 ◦ C was more favorable for the process. Increasing the current ampere, time, and concentration of ions in the solution helps to increase the current efficiency. The acidity values ​​in the aqueous phase are essential for the ELECTROWINNING process and depend on the system’s conditions. The XRF and EDX analysis results showed that in optimum conditions, metal cobalt with purity above 99.8% was accumulated on the cathode surface. The modeling results of two methods showed that the artificial neural network is in better agreement with the experimental results than the response surface methodology.