Variation Of CO2 contained in an apatitic phosphate calcined and then, recarbonated by gaseous CO2

The phenomena of decarbonatation and recarbonatation of the apatite have be en studied on calcareous phosphate (Kasrik, Turkey) characterized by low co ntents of phosphate (14.6 % P2O5), sulfur (traces), organic matter (0.15 % C) chlorine (0.01 %) and magnesium (0.5 % MgO). The phosphate phase is made up of a carbonatofluoroapatite in which parameter a of the apatite lattice is equal to 9.341 Angstrom. Thermograms show an important endothermicity, due to the loss of water and to the dissociation of carbonate. The exotherm icity effect, connected with the burning of organic matter, compensates par tly the endothermicity (the ore samples are crushed to a grain size of 400 pm). The calcination is operated in a muffle furnace at 950 degrees and 100 0 degreesC for about 1 h. After roasting, quenching, washing and attriting, the calcined product is treated by gaseous CO2. During the calcination, pa rameter a increases from 9.341 to 9.351 Angstrom. and after recarbonatation decreases from 9.351 to 9.347 Angstrom. corresponding to a decrease of the apatitic CO2 from 3.8 to 1.1 % and then to an increase to 2.1 %. In final analysis. it appears that the phenomena of thermal decarbonatation and, the n, of recarbonatation after cooling, present important consequences on ore beneficiation technologies. (C) 2001 Academie des sciences / Editions scien tifiques et medicales Elsevier SAS.