Patent ID: 7968066

Claim:
A method for producing a potassium chromate crystal, the method comprising the steps of: reacting chromite ore in a first aqueous solution of potassium hydroxide with an oxidant to obtain a mixture of potassium hydroxide, potassium chromate, and ferrous residue, wherein the weight of the potassium hydroxide in the first aqueous solution of potassium hydroxide is two to eight times of the weight of the chromite ore, the amount of the oxidant is equal to or above a stoichiometric amount of the oxidant required for decomposing chromite ore, water in the reaction is in a range from greater than 0 to 50% by weight of the total amount of reactants, reaction temperature is in a range from 200° C. to 350° C., reaction time is in a range from 1 to 20 hours, and said oxidant is air or oxygen; leaching the mixture with water or a second aqueous solution of potassium hydroxide with a concentration ranged from greater than 0 to 30% by weight to obtain a leached slurry having a potassium hydroxide content of 30% to 70% by weight; and separating the leached slurry to obtain a primary potassium chromate product, ferrous residue, and a third aqueous solution of potassium hydroxide.