PREPARATION OF HIGH PURITY HYDRATED AND ANHYDROUS MAGNESIUM SULFATE FROM IRAQI DOLOMITE

Abstract

SUMMARY This work refers to a process for obtaining high purity magnesium sulfate heptahydrate and anhydrous magnesium sulfate salt from Iraqi dolomite ore. The process comprises, leaching of the starting material with dilute sulfuric acid to dissolve the magnesium compound (as magnesium sulfate) and separating it from the formed precipitate (Calcium sulfate). The optimum conditions of the leaching operation were established from the study of the main variables which effecting the leaching process namely, acid concentration, reaction temperature, reaction time and ore particle size. The magnesium sulfate solution resulted from the optimum condition where by 99.8% leachibility was achieved are (25 wt% H2SO4, 60 ˚C, 30 min reaction time and -106 micron ore particle size), was subjected to a purification to remove ferric oxide by precipitation as ferric hydroxide from Dolomite . The purified solution was evaporated and magnesium heptahydrate of 99.3% purity was obtained by cold crystallization. Anhydrous form was subsequently obtained by heat treatment of the heptahydrate at 250 ˚C for 1 hr .