Cadmium removal from dilute aqueous solutions under galvanostatic mode in a flow-through cell

Abstract

Cadmium electrodeposition at reticulated vitreous carbon cathode from dilute aqueous solutions in a flow-through cell under galvanostatic mode is accomplished. The influence of different parameters such as background electrolyte, initial cadmium concentration, initial pH of the catholyte, and applied current density is studied. Cadmium concentration is detected by differential pulse stripping voltammetry technique using calibration curves built for each background electrolyte tested. The concentration decay is predicted based on a batch recycle reactor operating under mass transport control. The prediction of the concentration decay of cadmium ions is in good agreement with the experimental data. The current efficiency at pH 6 is influenced by the anion present in the working solution and decreases in the sequence Cl− > SO42- > NO3-. Also, the lowest current efficiency is observed in nitrate media at pH 6, sulfate electrolyte at pH 2, and when 3.2 × 10−4 mol L−1 cadmium concentration is used. Cadmium removal efficiency increases with the increase in applied current density, with the subsequent increase in the specific energy consumption. The efficiency of cadmium removal is within 81–99%, which is also influenced by the initial pH, initial cadmium concentration, and the applied current density. The current efficiency is within 12–34% with specific energy consumption between 3.9 and 11.1 kW h kg−1 depending on the operational parameters.