Indium electrowinning kinetics on titanium, aluminum and copper supports from sulfate solution

Indium electrowinning process from sulfate solution on copper, titanium and aluminum cathodes (Cu, Ti and Al) were studied using the methods of cyclic voltammetry (CV) and chronoamperometry (CA). Voltammogram features indicated the irreversible behavior of indium discharge on each cathode. The heterogeneous charge transfer rate constant (k0) has been evaluated on Cu, Ti and Al cathodes and their values were 7.1·10−5 cm/s, 6.2·10−5 cm/s and 5.4·10−5 cm/s, respectively. The indium ions electro-reduction seems to be quite different on these diverse cathodic supports: a nucleation process appears on Cu and Al cathodes, while is absent on Ti cathode due to the hydrogen evolution overlapping at high cathodic overpotentials. CV and CA techniques allowed to calculate the diffusion coefficient (D0) of indium ion in sulfate solution. Furthermore, calculating the roughness coefficient (φ) by CV technique on each metal surface, it was possible to establish the real surface area of Cu, Ti and Al cathodic supports. The charge transfer coefficient values (α) calculated by Tafel curves agreed those obtained by CV results, while the k0 value and the exchange current density (i0) showed a similar trend for each cathode. By these results, the exchange current density was equal to 1.20 mA/cm2, 0.30 mA/cm2 and 0.075 mA/cm2 for Cu cathode Ti and Al cathodes, respectively. The findings of this investigation can provide an understanding of the indium electrowinning process on three different support electrodes (Cu, Ti and Al) from sulfate solution.