Premium
Hydration of calcium sulphate hemihydrate in the presence of phosphoric acid and calcium oxide: III. Phosphogypsum
Author(s) -
Beretka Julius,
Brown Trevor
Publication year - 1986
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.280361103
Subject(s) - phosphogypsum , lime , calcination , gypsum , slurry , phosphoric acid , calcium oxide , chemistry , calcium , nuclear chemistry , mineralogy , kinetics , metallurgy , materials science , inorganic chemistry , raw material , biochemistry , organic chemistry , composite material , catalysis , physics , quantum mechanics
Abstract The kinetics of hydration and physical properties of plaster slurries and cast gypsums of three calcined industrial phosphogypsums containing 0.09, 0.38 and 0.73% ‘soluble’ P 2 O 5 , respectively, were investigated. The materials were neutralised with lime as in industry, and the lime addition was expressed in terms of CaO/P 2 O 5 wt ratio from 0 to 5. It was found that the presence of 0.09% P 2 O 5 had relatively little effect on the kinetics of hydration and physical properties of calcined phosphogypsum. However, with the material containing 0.38% P 2 O 5 the rate of hydration of the slurry was severely retarded within the CaO/P 2 O 5 wt ratio range of 1 to 2; the setting time increased, the strength was reduced, and all the other physical properties of the slurries and cast gypsums were greatly affected. Similar findings were observed with the material containing 0.73% P 2 O 5 , except that these changes took place within the higher and broader weight ratio range of 1.5 to 3.5 CaO/P 2 O 5 . The practical implications of these findings on the industrial conversion of phosphogypsums to good quality plaster of Paris and cast gypsum are discussed.