Patent Number: 6,168,767

Title: Production of alumina

Abstract: A process of recovering alumina from a pregnant Bayer process liquor by crystallisation after adding to the liquor a crystallisation modifier characterised in that the crystallisation modifier comprises: (a) a polyalkoxylated non-ionic surfactant, (b) a surfactant, or precursor thereof, which is not a polyalkoxylated non-ionic surfactant and (c) water. In a further aspect of the invention the composition may contain water but preferably contains substantially no water. Preferred compositions for the crystallisation modifier for use in this process contain a surfactant blend which consists essentially only of the polyalkoxylated non-ionic surfactant (a) and the surfactant (b) or precursor thereof. The process consistently gives excellent improvement in crystal size without decreased yield. Specifically the process results in a reduction in the percentage of undersized crystals.

Inventors: Welton; Roger (Beverley, GB), McColl; Philip (Huddersfield, GB)

Assignee: Ciba Specialty Chemicals Water Treatments Limited

International Classification: C01F 7/14 (20060101); C01F 7/00 (20060101); C01F 007/02 ()

Expiration Date: 01/02/2018