Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers


Anion Exchange

Last updated: July 18, 2017

What Does Anion Exchange Mean?

Anion exchange is the process in which anions in the form of acids are adsorbed by a basic substance. It describes the exchange of ions in which one anion (as chloride or hydroxide) is substituted for one or more other anions (as sulfate).

It is highly effective on negatively charged ions such as:

  • Bicarbonate
  • Nitrates
  • Sulfate
  • Selenium
  • Arsenic compounds

However, anion exchange is ineffective on ions with positive charges like iron and magnesium.


Corrosionpedia Explains Anion Exchange

Ion exchange is a chemistry separation technique that lets selectively retains various ionic matters on an ion for resin exchange. In this regard, resins are polymeric ionic material which is water insoluble, yet its ions can be exchanged in various locations on the polymer chain in locations referred to as exchange sites.

Water passes through these exchange sites through a device that aids ionization. With this, all unwanted ions are exchanged for desirable ones. There are two types of exchange units: anions and cations. In the latter, resin beads are usually saturated with potassium or sodium. In anion exchange, the beads are saturated through ions that are negatively charged in replacement of contaminants.

Anion exchange is great tool to exchange or eliminate contaminants in low concentrations and can help in identifying the ion exchange unit that is most effective for treatment.

Control of scale and corrosion is most commonly achieved by calcium removal, which is the main action associated with the formation of scale. This process reduces the tendency for scale to form. Removal of calcium ions is usually carried out using a base exchange water softener.

Base exchange water softeners contain ion exchange resins that can replace ions of calcium with ions of sodium when associated with water. It is completely automated with the use of highly reliable control valves that regenerate the softener automatically, according to the operation time or treated water volume.


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