Selective Organic Removal from the Alumina Industrial Liquor: Wet Oxidation and Catalytic Wet Oxidation of Disodium Malonate

The wet oxidation and catalytic wet oxidation of a key organic component, particularly disodium malonate (the salt of propanedioic acid) found in the alumina industrial liquor have been investigated. The wet oxidation and catalytic wet oxidation of the disodium malonate in highly alkaline media was carried out at 165 °C in a high-pressure reaction system. The main carbon-containing species detected as products from disodium malonate oxidation were sodium carbonate and sodium oxalate produced in similar quantities during wet oxidation and catalyzed wet oxidation. The amounts of ketomalonic acid hydrate detected during disodium malonate oxidation were up to 20 mg/L. Mechanisms for both wet oxidation and copper-catalyzed wet oxidation of disodium malonate are proposed, with ketomalonic acid (hydrate) as a key intermediate organic species.