How can NaCl be separated from other dissolved salts?

I want to know the easiest way to remove sodium chloride from a solution and still retain the other minerals.
sireno@netonecom.net

Dissolved salts are usually removed using either deionization or reverse osmosis. Deionization passes the water over ion exchange resins, which adsorb dissolved ions. Reverse osmosis is what Kevin Costner did in the opening scene of "Waterworld": force pressurized water across a membrane which is impermeable to dissolved salts. Neither approach will selectively remove sodium chloride, though.

The simplest approach would probably be deionization, followed by replacement of the dissolved minerals removed in the deionization.

  1. Determine the concentration of the mineral components you want to keep.
  2. Pass the water through a deionizer. This is a column packed with mixed cation and anion exchange resins. The cation exchange resin will remove the Na+ ions, replacing them with H+ ions. It will also replace the calcium and magnesium and other cations. The anion exchange resin will replace the chloride with hydroxide ions. The hydroxide ions will neutralize the hydrogen ions produced in the previous step. The anion exchange resin will also take sulfate out of the water.
  3. Replace the mineral components lost in the cation and anion removal processes.

The alternative approach, reverse osmosis, is outlined here.

Author: Fred Senese senese@antoine.frostburg.edu



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