Removal of oxalate from Bayer process liquor
AssigneeAlcan Research and Development Limited
InventorGordon Lever
Life of this patent
Estimating the term…
Abstract
Sodium oxalate in supersaturated solution in Bayer spent liquor stabilized by the presence of humic material is precipitated by the treatment with cationic sequestrants which interact with the humic material to give an insoluble product, thus removing it from solution and destabilizing the solution with respect to precipitation of sodium oxalate. Preferred cationic sequestrants are quaternary nitrogen compounds including medium or long chain alkyl groups. Precipitation of sodium oxalate can be expidited by addition of seed crystals and/or addition of sodium oxalate solution which is supersaturated at a temperature higher than that of the spent liquor.
Claims15
A method for controlling the level of sodium oxalate present in the process liquor in the Bayer process for the production of alumina trihydrate which method comprises the steps of treating spent liquor which contains in excess of 1 gram per liter (as organic carbon) of humic matter and is supersaturated with regard to sodium oxalate, with a cationic sequestrant in an amount to remove sufficient of the said humic matter but not more than 0.5 gram per liter from the said liquor and thereby destabilizing the said liquor with regard to precipitation of sodium oxalate, said sequestrant being an organic cationic sequestrant having a cationic center that interacts with a weakly acidic anionic center in the humic matter to form a product sufficiently insoluble in the Bayer liquor to be physically separable therefrom, holding the said liquor to allow precipitation of sodium oxalate, separating the precipitated sodium oxalate and spent cationic sequestrant and returning the said liquor to the Bayer process.
Dependencies are inferred from the claim text.