What Is Ion Exchange?

Ion exchange is a chemical process in which ions in a solution are replaced with ions of a similar charge from an insoluble solid (called a resin). This process involves exchanging one type of ion for another, which can result in the removal of impurities from a solution or the separation of different ions. The process is commonly used in water treatment, where ion exchange resins are used to remove dissolved ions such as calcium, magnesium, or heavy metals from water. Learn more about ion exchange technology.

Structure of Ion Exchange Resin

Understanding the structure of ion exchange resins is a necessary prerequisite for understanding ion exchange. The unit structure of ion exchange resin consists of two parts. One part is an immobile network skeleton with a three-dimensional structure, and the other part is active ions that can migrate freely between the network skeleton and the solution.

Structure of Ion Exchange Resin

The network skeleton is made up of a network of cross-linked polymer chains with ionic functional groups attached to them. The functional groups are responsible for exchanging ions between the resin and the surrounding solution.

The resin is typically composed of small beads or grains that are packed into a column or vessel. The beads have a high surface area and are porous, allowing the solution to flow through and interact with the functional groups.

Most ion exchange resins are composed of a styrene-divinylbenzene copolymer matrix, with various functional groups attached to the benzene rings. Common functional groups include sulfonic acid, carboxylic acid, and amine groups.

Ion Exchange Mechanism

The ion exchange process can be divided into the following steps:

Ion Exchange Mechanism

  • A+ diffuses from the solution to the resin surface;
  • A+ is an active group that re-diffuses from the surface of the resin to the interior of the resin;
  • A+ undergoes an exchange reaction in the active group inside the resin;
  • The exchanged B+ diffuses from the active groups inside the resin to the surface of the resin;
  • B+ diffuses from the resin surface into the solution.

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