Electrochemical Reduction of Lead Sulphide in NaCl-KCl and NaCl-KCl-%2Na2S

Abstract

In this study, the lead production from lead sulfide (PbS) by molten salt electrolysis was investigated under potentiostatic and galvanostatic conditions using NaCl-KCl and NaCl-KCl-2%Na2S electrolytes. Stable cell voltage and current were aimed with the addition of Na2S to the NaCl-KCl electrolyte. Reduction experiments were carried out at constant 700 °C temperature and for 15 min. duration. The current density was set to 250 mA/cm2 for the galvanostatic reduction experiments. It was observed that there was an increase in cell voltage in both electrolytes due to the decrease in the amount of PbS in galvanostatic experiments. In these experiments, it was determined that the reduction occurred at higher cell voltages in the NaCl-KCl electrolyte compared to the NaCl-KCl-2%Na2S electrolyte. Although the cell voltage was aimed to remain constant with the Na2S addition, the cell voltage decreased slightly compared to the NaCl-KCl electrolyte, but increased with the experiment duration as in the NaCl-KCl electrolyte. Potentiostatic reduction experiments carried out at a constant cell voltage of 3.0 V under the electrolyte decomposition voltage. The morphology of the cathode products was examined by SEM-EDS analysis and, the phases were examined by X-ray diffractometry. Higher current values were obtained in the NaCl-KCl-%2Na2S electrolyte compared to the NaCl-KCl electrolyte. Current variation with electrolysis duration showed similar trends in both electrolytes. According to structural characterization, it was determined that the metallic lead mass did not contain any impurities.

Keywords

• Molten salt electrolysis
• electrochemical-reduction
• lead extraction
• lead sulphide

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