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EFFECT OF TITANIUM SPECIES ON THE PRECIPITATION OF BOEHMITE UNDER DIGESTION CONDITIONS

Cornell, R.M. Riley, G. Clarke, P. Fletcher, S. Cornell, J.B.

Heterogeneous precipitation of boehmite in Bayer liquor under digestion conditions can be reduced by the presence of a few ppm soluble titanium.

In order for the Ti to be effective, it must be added as a solid phase – anatase or ilmenite – which gradually dissolves to some extent. If a Ti solution is added to the liquor, it forms an insoluble hydroxide which cannot affect boehmite precipitation.

It is suggested that the soluble titanium species act by adsorbing on growth sites on the boehmite. A sodium titanate gel which precipitates may also block available nucleation sites on the seed material.