Diffusion coefficient of cupric ion in a copper electrorefining electrolyte containing nickel and arsenic

Abstract

Diffusion and convection are the main modes of mass transport that occur during copper electrorefining. Diffusion determines the rate of copper transfer across the diffusion layer, which in turn, affects the dissolution of the anode and deposition on the cathode. The diffusion coefficient of cupric ion (DCu(II)) is a typical property that can be defined from the limiting current density (jlim) values. In this work, the limiting current densities were measured for 24 different synthetic copper electrolytes over a temperature range of 50-70 °C using a rotating disc electrode (RDE). From this data, a model for jlim and the corresponding models for DCu(II) were constructed using Levich (Model L), Koutecký-Levich (Model K) and mixed-control Newman equations (Model M). The models for jlim and DCu(II) were designed, refined and analyzed using the modeling and design tool MODDE, with the temperature, copper, nickel, arsenic and sulfuric acid concentrations as variables. Results from this research show for the first time that an increase in arsenic concentration has a reciprocal effect on the DCu(II) under copper electrorefining conditions. Furthermore, the models were validated with 11 industrial electrorefining electrolytes with known compositions. Model L (DCu(II) based on Levich equation) was shown to provide the highest correlation with the industrial solutions when compared to the other models (Model K and M) considered and previously published diffusion coefficient models. Overall, this work provides an explanation for the previously observed data variances in the literature, investigates for the first time the combined effect of parameters on DCu(II) value in industrial copper electrolysis and clarifies the effect of arsenic on the DCu(II) of copper electrorefining electrolytes.

Electrochemical codeposition of arsenic from acidic copper sulfate baths: The implications for sustainable copper electrometallurgy

“…The experimentally obtained values for the limiting current density seem to be reasonably in line with theoretical values (i.e. 58 mA cm − 2 in our conditions (Kalliomäki et al, 2019)).…”

“…As, Bi, Sb) are present in e-waste and accumulate in the acidic sulfate electrolyte used for the electrolytic production of high purity copper (i.e. electrorefining or electrowinning) (Forsén et al, 2017;Kalliomäki et al, 2019). The standards for the chemical purity of electrolytic copper are strict to ensure excellent drawability and electrical conductivity (Kato, 1995;David, 2017).…”

Direct copper recovery from pregnant leaching solutions (PLS), using a custom electrolytic cell, based on reactive electrodialysis (RED)

“…Considering that in present practice, the average copper electrowinning efficiency ranges between 90% and 95% and the specific energy consumption is close to 2 Wh/kg. Cu (Price and Davenport 1980; Kalliomäki et al 2019), this cell is capable of reaching the operational parameters of conventional copper electro-winning plants without the need to implement the solvent extraction stage.…”

Selective Recovery of Tellurium from the Tellurium-Bearing Sodium Carbonate Slag by Sodium Sulfide Leaching Followed by Cyclone Electrowinning

“…Moreover, the tellurium recovery followed a similar trend as that for current efficiency. These could be attributed to the fact that with the increase in electrolyte flow rate, the mass transfer is effectively enhanced, leading to a decrease in the diffusion layer thickness and concentration polarization [46].…”