Method for the removal of organic substances from alkali metal aluminate solution

A method for removing organic substances from an alkali aluminate solution in the production of alumina from alumina-containing ores by the Bayer process or improved processes thereof, characterized by contacting the alkali aluminate solution containing organic substances with molecular oxygen gas or a molecular oxygen-containing gas of at least an amount corresponding to an oxygen amount necessary for oxidizing a required amount of organic substances contained in said aluminate solution under a pressure of 20 to 150 kg/cm.sup.2 and under such conditions that at least a pair of said aluminate solution is maintained in a liquid state and at a temperature of 180.degree. to 300.degree. C. in the presence of at least 100 mg/l, based on the amount of said aluminate solution of copper ions, thereby oxidizing the organic substances, adding to the resultant aluminate solution a chemical substance, which reacts with the copper ions to form a water-insoluble precipitate, precipitating the water-insoluble precipitate and separating the produced preciptate from the aluminate solution, and recycling the separated precipitate as a copper source to the above oxidation step.