Ion Exchange Process

CATION EXCHANGE PROCESS

• Ion exchange describes a specific chemical process in which unwanted dissolved ions are exchanged for other ions with a similar charge.
• Ions are atoms or molecules containing a total number of electrons that are not equal to the total number of protons.
• There are two different groups of ions, cations, which are positively charged, and anions, which are negatively charged.
• Cations (+vely charged particles) are attracted to the cathode (-vely charged electrode) and the anions (-vely charged particles) are attracted to the anode (+vely charged electrode) in a galvanic device.
• This attraction is used to remove dissolved ionic contaminants from water.
• The exchange process occurs between a solid (resin or a zeolite) and a liquid (water).
• In the exchange of cations during water treatment, positively charged ions that come into contact with the ion exchange resin are exchanged with positively charged ions available on the resin surface, usually sodium.
• Resin materials have a finite exchange capacity. Each of the individual exchange sites will become full with prolonged use. When unable to exchange ions any longer, the resin must be recharged or regenerated to restore it to its initial condition. The substances used for this can include sodium chloride, as well as hydrochloric acid, sulfuric acid, or sodium hydroxide.