Starch-based flocculating reagent - for flocculating red mud in aq. alkaline aluminate soln.

摘要

Starch-based reagent is prepd. for flocculation of solids suspended in aq. alkaline aluminate soln. which are formed in treatment of bauxite by the Bayer process. Method comprises subjecting starch in an aq. suspension in presence of 1-3 wt.% Na tetraborate and 3-30 wt.% water soluble Mg salt calculated as water free salt referred to starch, to a simultaneous heating and drying treatment. The reagent has improved flocculating properties and is used for the flocculation of red mud formed when treating bauxite with aq. alkaline soln. according to the Bayer process. Flocculation of red mud is effected with a smaller quantity of starch than the known starch based reagents, which is desirable since the liquor, after sepn. of red mud and pptn. of alumina hydrate, is recycled to the Bayer process.