Home – Home – Jornals – Chemistry for Sustainable Development 2009 number 4

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 : CaO_акт > 2.1 almost the whole CaO_act 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 CaO_act 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.