Abstract:The Dissolution process of synthetic gibbsite in sodium hydroxide solution was investigated by isothermal calorimetry in a conduction-type automatic calorimeter. The experiment was carried out at 75～100 ℃ . The reagent used for dissolution was 4. 19～7. 37 mol/L NaOH solution. The heat of the digestion of synthetic gibbsite was measured. By analyzing the effect of temperature and concentration on dissolution rate, a mathematical model for dissolution process was derived. The experimental result showed that the rate determining step is a chemical reaction rather than diffusion. A first-order dependence on the concentration of sodium hydroxide was observed. The apparent activation energy is 76. 85 kJ/mol, which is in fair agreement with that in references.

Key words: synthetic gibbsite; digestion; heat effect; kinetic behavior