Alkali metal chromates from chrome ore - with high recovery even from low grades using relatively low temps

摘要

Alkali metal chromates are prepd. a chrome ore by (a) reacting the ore at 400-700 degrees C with 2 moles molten alkali metal hydroxide per mole are Cr2O3, in the presence of 1-2.5 moles alkali metal salt of a nitrogen oxyacid per mole Cr2O5, and (b) leaching the resulting alkali metal chromate from the reaction prod. using water or a dilute aq. soln. of the chromate of the same alkali metal hydroxide and (c) opt. reslurrying the residue with nitrogen oxyacid to recover remaining alkali metal values as nitrogen oxy-acid salts for re-use in (a). SiO2 may also be present in (a), providing a SiO2/Al2O3 molar ratio of 1-3, based on Al2O3 in the ore.