Kinetics of AlOOH dissolving in caustic solution studied by high-pressure DSC

Abstract

Mechanism functions and kinetic parameters of AlOOH (boehmite or diaspore) dissolving in sodium hydroxide solution were researched. The mixture of boehmite or diaspore and caustic solution was scanned by high-pressure differential scanning calorimetry (DSC) instrument with heating rate of 10 °C/min, and differential equation method was used to analyse the DSC curves, combining with iterative method and linear least square method. The most probable mechanism functions for both boehmite or diaspore and caustic solution reactions were logically selected from 30 types of non-isothermal kinetics differential equations, according to the calculated results obtained by Matlab program. The most probable differential mechanism function of boehmite dissolving in caustic solution is f(α)=1-α, which reveals the first-order reaction with apparent activation energy of 79.178 kJ/mol and the preexponential constant 1.031×10 8 s −1. The function, f(α)=2(1-α) 3/2, can describe the dissolution of diaspore sample in sodium hydroxide solution. The calculated results of kinetic parameters are apparent activation energy of 73.858 kJ/mol, preexponential constant of 5.752×10 7 s −1 and reaction order of 1.5.