Dissolution kinetics and mechanism of pandermite in acetic acid solutions

In this study, the dissolution kinetics and mechanism of pandermite mineral was investigated using a batch reactor employing the parameters of particle size, acid concentration, solid/liquid ratio, stirring speed and reaction temperature. From experimental data, it was determined that the conversion rate of pandermite to boric acid was increased with decreasing particle size, solid/liquid ratio and increasing reaction temperature. Conversion rate increased up to 3 M, acid concentration then decreased with increasing acid concentration. It was observed that there was no important effect of stirring speed on the dissolution rate. Furthermore, it was observed that the dissolution mechanism was dependent on acid concentration due to restriction of dissolution in acetic acid solutions. The dissolution rate of pandermite mineral in acetic acid solution was examined according to homogeneous and heterogeneous chemical reaction model. It was determined from graphical and statistical methods that the reaction kinetics fitted to model in the form of first order pseudo homogeneous model [- ln (1 - X)] = kt and activation energy for the dissolution process was found to be 28.496 kj/mol. A mathematical model, which indicated the dissolution process was established.