CO-PRECIPITATION OF ORGANICS WITH HYDROTALCITE

Seawater was added to high oxalate Bayer liquor to evaluate the precipitation of organics, including oxalate solids. Laboratory trials have shown that coloured organic species may co-precipitate with hydrotalcite talcs formed upon addition of the seawater. The precipitates formed upon stepwise addition of seawater to plant liquors were analysed using a Cerium (IV) redox back titration to quantify the oxalate fraction. Results show that the coloured organics precipitate out early, during the initial formation of hydrotalcite talcs, while much of the oxalate precipitates out later, after formation of hydrotalcite. The species of oxalate changes throughout the course of liquor neutralisation and very little oxalate is removed through intercalation into hydrotalcite.