A kinetic study on the decomposition of zircon with molten NaOH

The rate of decomposition of zircon sand with molten NaOH was investigated. A change in the reaction mechanism from chemical reaction control to mass transfer control was observed in the temperature range 5150C - 6350C. For temperatures above 6050C, the decomposition rate is limited by the rate at which the liquid NaOH defuses to the solid zircon surface. For temperatures below 5850C, the rate is, however, controlled by the slow chemical reaction at the solid surface. The rate of the chemical reaction is well explained in view of the initial nucleation at the solid surface followed by the growth of these nuclei. (author)