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.
A stabilized zirconia oxygen probe was used to measure the oxygen partial pressure (OPP) at an electrode submerged in a copper slag melt at 1300 ℃. The OPP was controlled in the range of 10−10–10−5 atm owing to the presence or absence of a powdered carbon layer on the slag melt using a high-purity alumina crucible in argon (Ar) gas flow. Under suppression of magnetite formation at an OPP of approximately 10−10 atm, the viscosities of the copper slag and FeO-Fe2O3-SiO2-Al2O3 slag melts were measured between 1200 ℃ and 1300 ℃. The obtained values were in the range of 1.0×102–7.8×102 mPa・s. The dependences of total Fe/SiO2 mass ratio and Al2O3 concentration on viscosity were qualitatively interpreted from the aluminosilicate network structure viewpoint.