LABORATORY STUDY OF MgO PREPARATION FROM IRAQI DOLOMITE BY LEACH-PRECIPITATION – PYROHYDROLYSIS PROCESS
In this study, a three-process approach was applied for the extraction of Magnesia (MgO) from Iraqi dolomite. The first process comprises leaching of (– 2 mm) raw dolomite in 25% solid by 22% HCl aqueous solution for 10 minutes at room temperature, extracts 99.68% of MgO in the dolomite ore. The second process, which is a separation process, includes two-steps (hydration and carbonation) for the separation of calcium as Precipitated Calcium Carbonate (PCC, 1st stage) of 90.1% purity and a magnesium recovery of 92.8% as dissolved MgCl2. Hydration was carried out by adding 55% by weight ratio of calcined dolomite (dolime)/ leached dolomite at 70 °C for 60 minute; this was followed by carbonation of the slurry formed by CO2 gas at a pressure of 2 bars for 100 minutes at room temperature. The MgCl2 solution produced was subjected for evaporation to remove the dissolved Calcium Bicarbonate by precipitation as (PCC, 2nd stage) with a purity of 97%. The purified brine was further evaporated till dry salt of MgCl2.6H2O (Bischofite) was obtained, and then subjected for pyrohydrolysis, which was the third process, at 650 °C for 60 minutes. 22% HCl was regenerated with a product of 95.48% MgO purity after washing with water and drying.