Dissolution Kinetics of Silicon Nitride in Aqueous Suspension.

A general system of equations describing the dissolution of polydisperse solids having a porous particulate structure is set up and applied to study the hydrolysis and subsequent dissolution of silicon nitride powder in aqueous suspensions. The latter process has been found to follow a simple kinetic equation, c(t) = c(s)[1 - exp(-kt)], with the dissolution rate constant k = 2.3 x 10(-6) s(-1) (or 2.5 x 10(-11) mol m(-2) s(-1)) and the saturation concentration c(s) = 3.2 mmol dm(-3) at room temperature and pH 9. The role of diffusion is unimportant, so the concentration of soluble species in pore water changes almost simultaneously with their concentration in the surrounding solution. Copyright 1999 Academic Press.