Dissolution kinetics of single fluoroapatite crystals in phosphoric acid solution under the conditions of the wet-process phosphoric acid production

The dissolution process for natural single fluoroapatite (FAP) crystals is studied in phosphoric acid solutions, containing the main inorganic impurities present in the industrial wet-process phosphoric acid production. A special flow device providing constant dissolution conditions was used far this purpose. The device gave the possibility to obtain new information about the dynamics concerning shape and size of each individual FAP crystal during its dissolution. Dissolution rates for the FAP crystals were measured under various conditions. The process of epitaxial coating of the FAP crystal surface by CaSO4 . 0.5H(2)O was also studied. Without coating formation the single FAP crystals always dissolved with continuously increasing rates for all crystal faces. The measured values of dissolution rates are applied to computer simulation of industrial reactors.