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US 4,786,482 AGranted
Bayer process for producing aluminum hydroxide having improved whiteness
AssigneeAluminum Company of America
InventorsPaul J. The, Chanakya Misra
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Abstract
A process for producing aluminum hydroxide product having an improved level of whiteness is disclosed. In the process, a caustic solution having dissolved aluminum hydroxide is subjected to purification to remove color producing humate material. Purification includes passing the caustic solution through a semi-permeable membrane. The solution purified of humate material is treated to precipitate aluminum hydroxide therefrom.
Claims8
A process for producing an improved aluminum hydroxide product characterized by an improved level of whiteness, the process comprising the steps of:
- (a) subjecting a caustic solution containing dissolved aluminum hydroxide to a purification step to remove dissolved impurities including color producing humate material therefrom, the purification comprising passing said caustic solution through a semi-permeable membrane substantially inert to a highly caustic solution and capable of separating said humate material from said solution:
- and
- (b) treating the purified solution to precipitate aluminum hydroxide therefrom, the aluminum hydroxide having an improved level of whiteness.
Dependencies are inferred from the claim text.