ELECTROCHEMICAL-BEHAVIOR OF SULFATE IN SODIUM SILICATES AT 1000-DEGREES-C

The electrochemical behaviour of sulfate in Na2O . 2.5SiO(2) at 1000 d egrees C is studied by means of cyclic voltammetry, square wave voltam metry and impedance spectroscopy. It appears that the thermal decompos ition of sodium sulfate in Na2O . 2.5SiO(2) at 1000 degrees C is a com plete and fast process providing a melt containing S(IV). The voltammo grams show two reduction peaks attributed to the reduction of sulfite ions to elementary sulfur. The first peak corresponds to a reduction i nvolving strong adsorption of sulfur on the electrode. The formation o f a layer of adsorbed sulfur atoms during the prewave occurring anodic to the normal diffusion peak has a strong influence on the double lay er capacitance measured by impedance spectroscopy. (C) 1996 Elsevier S cience Ltd.