Lead Electrodeposition from Highly Concentrated Calcium Chloride Aqueous Solutions

Abstract

CaCl2 is a low-toxic, inexpensive reagent that dissolves in large amounts in water to form highly concentrated aqueous solutions, or hydrate melts electrolyte. In this work, it was investigated that the concentrated CaCl2 aqueous solutions (aq) as novel lead (Pb) electrodeposition baths. While PbCl2 is poorly soluble in water at room temperature, PbCl2 dissolved up to 0.452 mol kg−1 ([Pb(II)] = 93.7 g kg−1) by the formation of PbCl42− complexes in the concentrated CaCl2 aq due to its high Cl− activity. Electrochemical measurements confirmed that the apparent exchange current density and the limiting current density of Pb electrodeposition decreased with increasing CaCl2 concentration. Since the diffusion of Pb(II) species was limited due to the high viscosity and ionic strength of the solution, agitation was effective in improving ion transport and electrodeposition rate. The presence of chloride ions in Pb electrolysis is usually detrimental due to the low solubility of PbCl2, however, the highly concentrated CaCl2 solution can be a potential candidate electrolyte for PbCl2-based electrolytic processes.

Keywords

• lead electrolysis
• concentrated aqueous solution
• calcium chloride
• lead chloride
• chloride solution