METHOD FOR PREPARING PURE MAGNESIUM OXIDE Russian patent published in 2003 - IPC

FIELD: inorganic chemistry, chemical technology. SUBSTANCE: natural serpentinite is ground to particles size 0.5 mm, not above, dissolved in H₂SO₄, H₂O₂ is added and cooled. Crystallized mixture is washed out with water to MgSO₄ concentration 290-330 g/l and unsolved residue is separated from prepared sulfate solution. Then NaOH solution with concentration 40-50% is added to filtrate to pH = 5-7. Compounds of impurity metals are precipitated as hydroxides. Precipitate is separated, NaOH solution with concentration 40-50% is added to filtrate to pH = 10-12, heated to 30-40 C, prepared precipitate Mg(OH)₂ is filtered off and washed out with water up to MgSO₄ content in washing out waters 0.5-4 g/l. Washed out product is dried at 350-400 C to moisture 2%, not above, and subjected for thermal treatment at 800-850 C for 40 min to yield magnesium oxide. Finally, magnesium oxide is washed with water and filtered off. Magnesium oxide comprises, wt.-%: MgO, 97, not less; Fe, 0.100-0.254; MnO, 0.059-0.14; total impurity of other metal oxides, the balance. EFFECT: improved preparing method. 3 ex