Kinetics modeling of hydroboracite dissolution in nitric acid solutions

The dissolution kinetics of hydroboracite in nitric acid solutions, whose products, calcium nitrate and magnesium nitrate have important commercial applications as fertilizer was studied. The dissolution was carried out in a batch reactor at atmospheric pressure. The effects of the temperature, particle size, solid/liquid ratio and concentration of solution on the dissolution rate were investigated, and the kinetic parameters: frequency factor and activation energy were evaluated. It was found that the dissolution rate increased when the reaction temperature increased and when the particle size decreases. The dissolution rate decreases when the solid/liquid ratio increases. It was also found that an increasing in the acid concentration always increases the dissolution mineral rate. It was determined that the dissolution rate fit well to the diffusive control model and the activation energy of this dissolution process was found to be 13 KJ/mol.