Method of purification of the sodium aluminate liquors containing the sodium oxalate, making it possible to increase the quantity of alumina hydrate product

摘要

The invention concerns a method for removing sodium oxalate from the aluminate liquor from the Bayer process derived from the caustic attack of bauxite slightly loaded with organic matter (typically generating less than 400 grams of oxalic carbon per ton of alumina produced). Said method consists in treating a rather low proportion of non-concentrated spent aluminate liquor (typically 10 to 30%), by causing it to follow a circuit passing though a series of decomposition vessels-called cold mini-series- at low temperature around 40 DEG C, the oxalate precipitating on part of the hydrate produced which is then recuperated after washing, in a slightly greater amount than the sampled amount. The capacity of the suspension from the cold mini-series of being filtered is remarkably enhanced by the input of an additive usually designed to promote agglomeration of fines during decomposition.