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Chemistry for Sustainable Development

2009 year, number 4

Technology of Processing Technical-Grade Calcium Carbonate Obtained from Phosphogypsum into Pure Calcium Carbonate and Concentrate of Rare-Earth Elements

V. A. Kolokolnikov, M. I. Kovalev
Keywords: phosphochalk, phosphogypsum, conversion, rare-earth elements, strontium
Pages: 393-399


Results of laboratory investigation of thermal decomposition of technical-grade calcium carbonate (phosphochalk) obtained by conversion of phosphogypsum with sodium carbonate and calcium leaching by ammonium chloride into solution are presented. It is established that phosphochalk completely decomposes to form aO at a temperature of 900 oC. As a result of leaching for the molar ratio NH4Cl : CaOакт > 2.1 almost the whole CaOact passes into solution. Carbonization of the resulting CaCl2 solution allows one to obtain high-quality calcium carbonate. Rare-earth elements and strontium get concentrated during CaOact leaching in the insoluble residue; their content increases to 4-5 and 10-11 %, respectively. Therefore, the insoluble residue may be considered as a raw material to obtain the compounds of REE and strontium.