Volatilization kinetics of sulphur from borosilicate melts: A correlation between sulphur diffusion and melt viscosity

Diffusion properties of sulphate dissolved into sodium silicate and borosilicate melts were studied here using Raman spectroscopy. In a first step, Raman spectroscopy led to the determination of kinetic curves of sulphate release from the melt at different temperatures. Then, assuming the fact that sulphate release was controlled by the diffusion of SO42− species, sulphate diffusion coefficients were calculated using a simple sphere diffusion model. An Arrhenius behaviour of these sulphate diffusion coefficients was systematically observed in the temperature ranges studied. A comparison of the results obtained in this study with data available in the literature, and which concern sulphur diffusion in natural and industrial melts, showed that (i) our experimental technique was efficient for the determination of sulphate diffusion coefficients and that (ii) there was a correlation between sulphur diffusion and viscosity of the melt.