Thermal decomposition of aqueous manganese nitrate solutions and anhydrous manganese nitrate. Part 4. Non-isothermal kinetics

Abstract

Kinetic parameters for the decomposition of aqueous manganese nitrate solutions were derived from non-isothermal experiments in air. First, most of the water evaporates to a solution containing approximately equimolar quantities of water and manganese nitrate which then decomposes in two steps to MnO 2. The first step can be described by a model valid for two-dimensional growth of a constant number of nuclei, viz. g(α) = [−ln-(1 − α)] 1 2 , and the second by a model based on a surface reaction, viz. g(α) = 1 − (1 − α) 1 3 . The decomposition of anhydrous manganese nitrate most probably occurs via nuclei formation with a decreasing rate and one-dimensional growth of the nuclei formed. The model g(α) = [ −ln(1 − α)] 0.6 described the measurements satisfactorily. The parameters in the above models closely agree with results from isothermal experiments.