Abstract
Current density plays a major role in deciding the plant size, current efficiency, and energy consumption in electrorefining cells. In general, operating current density will be 40% of the limiting current density. Forced circulation of the electrolyte in the presence of promoters improves the mass transfer coefficient. In the present study, rectangular turbulence promoters are fitted at the bottom side of the cell to improve the mass transfer coefficient at the cathode support plate. The limiting current density technique is used to measure the mass transfer coefficient. The variables covered in the present study are the effects of flow rate, promoter height, and spacing among the promoters. The electrolyte consists of copper sulfate and sulphuric acid. At a regulated flow rate, the electrolyte is pumped from the recirculation tank to the cell through an intermediate overhead tank. The limiting current density increased with an increasing flow rate in the presence of promoters, and thus the overall mass transfer coefficient on the cathode support plate also improved. With an increase in the flow rate of the electrolyte from 6.67 × 10−6 to 153.33 m3/s, limiting current density increased from 356.8 to 488.8 A/m2 for spacing of 0.30 m, with a promoter height of 0.01 m. However, it is noteworthy that when the promoter height is increased from 0.01 to 0.07 m, the overall mass transfer coefficient is found to increase up to 60%, but with the further increase in the promoter height to 0.30 m the mass transfer coefficient starts to decrease. Therefore, the optimized cell parameters are established in this work. The current sustainable concept of employing rectangular turbulence promoters will bring benefits to any precious metal refining or electrowinning tank house electrolytes.
Highlights
Electrochemical processes include electrodeposition/electrowinning, and electrorefining techniques, in which precious metals are either recovered or purified from the solutions containing cations of the metal in an electrolytic cell [1,2]
All these previous studies in the past and in present invariably suggest that electrochemical reaction kinetics are often influenced by electrolytic cell design for industrial production
The overall aim of the current work is the improvement of the ionic mass transfer coefficient of point electrodes located at the cathode support plate at specified locations due to the presence of rectangular promoters, which has been successfully demonstrated to lead to more sustainable and cleaner production of precious metals such as copper
Summary
Electrochemical processes include electrodeposition/electrowinning, and electrorefining techniques, in which precious metals are either recovered or purified from the solutions containing cations of the metal in an electrolytic cell [1,2]. Another study by Chandralekha et al [24] showed that mass transfer coefficients decrease as the height increases and depend on the characteristic length of the promoter, typically a single pentagonal plate assembly All these previous studies in the past and in present invariably suggest that electrochemical reaction kinetics are often influenced by electrolytic cell design for industrial production. Rectangular promoters were employed, and their sustainable concepts, which could be beneficial for electrorefining tank house electrolytes in terms of operation feasibility, and cost-effectiveness, are reported Both the rectangular and cylindrical promoters will enhance the limiting current density while improving the mass transfer coefficients. The overall aim of the current work is the improvement of the ionic mass transfer coefficient of point electrodes located at the cathode support plate at specified locations due to the presence of rectangular promoters, which has been successfully demonstrated to lead to more sustainable and cleaner production of precious metals such as copper
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