Sea salt

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Dissolved ions in seawater over 1mmol/L
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.

Purification

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. Hypothetically just bubbling carbon dioxide through the material for a brief period should do it.

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 bicarbonate, calcium carbonate, and calcium sulfate to precipitate. Use the same soda ash/carbon dioxide system as before to remove any remaining calcium hydroxide.

Alternatively, use fractional crystallization. Potassium and Sodium bicarbonate are less than one tenth as soluble as the chlorides, so they will precipitate first. The sulfates are almost 2/3 as soluble, so it will be more difficult. doing it very very slowly might grow large enough crystals to physically sort them.

See Also

References