Removal of Inorganic Solutes

The most widely used techniques for removing dissolved inorganic solids are boiling, addition of washing soda, lime-soda softening, complexation, sodium ion exchange, demineralization, reverse osmosis, electrodialysis, adsorption onto suspended solids, and aeration. 

Boiling. Boiling will remove temporary hardness, but the resulting precipitation of CaCOs may be precisely what one is trying to avoid. 

Addition of washing soda. Washing soda (Na2CO3-10H2O) precipitates most of the MgCOa and CaCOs by the common ion effect, that is, by forcing up the concentration of C03 (aq)  

This is fairly costly, as substantial excesses of Na2C03 are needed, and furthermore the solution is left quite alkaline (and hence likely to transport silica)  

Lime-soda softening. Lime-soda softening involves removal of the temporary hardness by adding the calculated amount of hydrated lime (Section 11.1)  

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