Sea salt
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Concentration of cation in sea water | Molarity | Concentration of anion in sea water |
---|---|---|
0.535 | Cl- | |
Na+ | 0.459 | |
0.009 | SO4 | |
Mg2+ | 0.051 | |
Ca2+ | 0.009 | |
K+ | 0.009 | |
0.002 | HCO3- |
Seawater contains just about every element in some small quantity. The materials over 1mmol/L is a shorter list.
Character
For seawater and many brines, the order of deposition is:[1]
- calcium carbonate
- calcium sulfate
- sodium chloride
- magnesium sulfate
- potassium magnesium chloride hexahydrate (KCl•MgCl2•6H2O)
- magnesium chloride
Purification
Removal of sulfate and bicarbonate
To remove the 0.011 mol of these, add a small amount soluble calcium. (0.5g/L calcium oxide or 0.75g/L of calcium hydroxide) This will cause calcium carbonate and calcium sulfate to precipitate.
Removal of calcium and magnesium
With Calcium and Magnesium combined for 0.06 mol/L, adding 0.06mol of soluble ash (7-8g/L) should precipitate most of the alkali earth metal content.
- (Ca/Mg)Cl2(aq) + (Na/K)2CO3(aq) → (Ca/Mg)CO3(s) + 2 (Na/K)Cl(aq)
This leaves sodium/potassium chloride/sulfate/carbonate in solution, which can be more easily separated by crystallization
See Also
References
- ↑ Hills, John M.; Wood, Frank Osborne (2019) "Salt: Salt Manufacture"
Encyclopedia Britannica
link courtesy Encyclopedia Britannica.