Precipitation of Magnesium Carbonate from Bicarbonate Solution

1 Precipitation of Magnesium Carbonate from Bicarbonate Solution 

The precipitation of hydrated magnesium carbonate, such as hydromagnesite, from the filtered leachate, can be achieved using air sparging and/or heating to remove excess carbon dioxide. Since magnesium bicarbonate is not stable in the absence of dissolved carbon dioxide, the following precipitation occurs at temperatures above 55°C see reaction (9.13)  

The form of magnesium carbonate precipitated from solution is dependent upon temperature, and the following transformation between the forms of magnesium carbonate can occur (Langmuir, 1965 Davies and Bubela, 1973) see reaction (9.14)  

High-purity MgO ( 99%) can be reclaimed from the carbonates by calcination, liberating carbon dioxide and water in the process. 

Canterford, J. H., and Moorrees, C. (1985). Bull. Proc. Austras. Inst. Min. Metall. 290, 67-70. 

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