Fundamental studies of the anodic behavior of thiourea in copper electrorefining

The behavior of thiourea in the anodic process of copper electrorefining was investigated using various advanced electrochemical techniques with a view to establishing an accurate method to determine its effect on the anode process in certain highly concentrated copper sulfatesulfuric acid electrolytes. It was found that thiourea acted as an inhibitor hindering the anodic dissolution of copper. Combination measurements of chronoamperometry and rotating disk electrode were sensitive to the addition of trace concentration of thiourea and were able to quantify the characteristics of the inhibition effect on the anodic dissolution process. The various techniques used - linear sweep voltammetry, chronoamperometry combined with the use of the rotating disk electrode, chronopotentiometry measurements and AC impedance provided results which exhibited excellent agreement. Together the measurements provided detailed information about the inhibition effect on the interfaces of the copper electrodes. An interaction mechanism was proposed to describe the inhibition. The effects of cupric ions, protons, and thiourea were determined. The influence of formamidine disulfide, one of decomposition products of thiourea, on the anodic dissolution of copper was also investigated. The chronopotentiometry technique demonstrated the most promise as an experimental method as it provided a simple measurement of copper passivation at various concentrations of thiourea.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat