Dissolution of boehmite in sodium hydroxide at ambient pressure: Kinetics and modelling

The kinetics of the digestion rate of pure boehmite in concentrated sodium hydroxide solutions was studied experimentally and modelled mathematically. The experiments were performed under ambient pressure and at 60 °C–85 °C in the kinetic regime. The changes in morphology of the solid phase were studied during the reaction by particle size, porosity and surface area measurements as well as SEM imaging. The reaction rate was observed to be strongly dependent on temperature and hydroxide concentration. The kinetics was determined for the solid–liquid reaction by taking into account the morphological changes during the reaction. The influence of boehmite on the dissolution kinetics of gibbsite was investigated, too. Moreover, the boehmite model was compared to experimental data from literature on the leaching of boehmite from actual high level nuclear waste.