Chemical processing of dolomite associated with the phosphorites for production of magnesium sulfate heptahydrate

M.M. Rashad*, H.M. Baioumy

Central Metallurgical Research and Development Institute, P.O. Box: 87 Helwan, Cairo, Egypt

Accepted 25 January 2005


Egyptian dolomite (CaMg(CO3)2) associated with Abu-Tartur phosphorites, New Valley was leached with sulfuric acid to produce magnesium sulfate heptahydrate and calcium sulfate dihydrate (gypsum). Magnesium sulfate heptahydrate containing 16.23% MgO was obtained at the following optimum conditions The particle size was100% -150m, temperature of the reaction was 60oC, time of reaction 50.0 minute, solid/liquid ratio 1:4g/ml and mole ratios of sulfuric acid to calcium oxide and magnesium oxide was 1.0 and pH 8.5 for removal of precipitated iron, manganese, aluminum. The magnesium sulfate was separated from calcium sulfate dihydrate by filtration. The factors affecting on the filtration rate was studied and the filtered magnesium sulfate was concentrated at density from 1.35-1.45g/ml at temperature 103-110oC and then crystallized as MgSO4.7H2O by cooling at room temperature. The purity of the produced magnesium sulfate heptahydrate was 99.2%.

Keywords: Magnesium sulfate heptahydrate, Dolomite, Leaching

* Corresponding author
   E-mail : rashad133@yahoo.com