Abstract
Porous inert SnO2-based anodes rammed inside a mullite tube, for an initial study of their depolarization effect applying reducing gas, have been prepared. The anodes were prepared by using commercial SnO2 materials which were crushed down and mixed with a SnO2-CuO-Sb2O3 binder phase and sintered at 1200-1300 ° C in air. The anodes were characterized for electrical and mechanical properties and used as depolarizing inert anodes applying H2 as reducing gas in electrowinning of Ag in NaCl-CaCl2 melts at 680 ° C. The mechanical and electrical properties were found suitable for applications as inert anodes. The depolarizing effect was confirmed by a reduction of cell voltage and electrode potentials while introducing H2 through the inert anodes. However, reactions between the melt and anode resulted in a Ca-SnO2 phase reducing the electrical conductivity of the anodes and increasing the anode potential during electrolysis compared to the initial potential.