Sea salt: Difference between revisions

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| ||0.002||{{#Chem: HCO3<sup>-</sup>}}
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| ||0.00082||{{#Chem: Br<sup>-</sup>}}
| ||0.00082||[[Bromine|Br<sup>-</sup>]]
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Revision as of 20:48, 23 December 2019

Dissolved ions in seawater over 50mg/L
Cation Molarity Anion
0.535 Cl-
Na+ 0.459
0.009 {{#Chem:SO4}}
Mg2+ 0.051
Ca2+ 0.009
K+ 0.009
0.002 {{#Chem: HCO3-}}
0.00082 Br-

Seawater contains just about every element in some small quantity. The materials over 50mg/L is a shorter list.

Character

For seawater and many brines, the order of deposition is:[1]

  1. calcium carbonate
  2. calcium sulfate
  3. sodium chloride
  4. magnesium sulfate
  5. potassium magnesium chloride hexahydrate ({{#Chem:KCl*MgCl2*6H2O}})
  6. 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.

{{#Chem: CaO + NaHCO3 = CaCO3 + NaOH}}
{{#Chem: Ca(OH)2 + NaHCO3 = CaCO3 + NaOH + H2O}}
{{#Chem: CaO + Na2SO4 + H2O = CaSO4 + 2NaOH}}
{{#Chem: Ca(OH)2 + Na2SO4 = CaSO4 + 2NaOH}}

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.

{{#Chem: (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

  1. Hills, John M.; Wood, Frank Osborne (2019) "Salt: Salt Manufacture"
    Encyclopedia Britannica 
    link courtesy Encyclopedia Britannica.