Process for the removal of oxalate and/or sulphate from Bayer liquors
US6743403B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 18, 2001 |
| Grant date | Jun 1, 2004 |
| Priority date | — |
| Expiry date | Sep 18, 2021 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC01F7/473
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A process for the removal and causticisation of sodium oxalate and/or sodium sulphate from a Bayer process liquor containing sodium carbonate and one or both of sodium oxalate and sodium sulphate in an alumina refinery is described. The process is based on the observation that to efficiently causticise sodium oxalate solutions, it is first necessary to remove the aluminate ion from solution, optionally with recovery of the aluminate ion in some later step. This is effected by removing aluminate ions from the Bayer liquor through the formation of a carbonate-bearing hydrocalumite and/or sulphate-hearing hydrocalumite. The liquor may then be treated with sufficient lime to remove and causticise any residual carbonate ions and some or all of the oxalate ions present so that any reacted lime solids thus formed can be separated and safely disposed of. The process may include a pre-causticisation step in which the Bayer liquor is first causticised to reduce the concentration of carbonate ions, prior to the step of removing aluminate ions. The invention provides an effective process for the removal of sodium sulphate and a practical method for the recovery of soda from sodium sulphate. Th…
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