Ion exchange is the reversible exchange of one type of ion on an insoluble solid with another of a similar charge present in a solution surrounding the solid.
It is accomplished through the use of a process for water softening or demineralization, chemical purification, and material separation.
Ion exchange is a term used to describe a method of purifying aqueous solutions utilising solid polymeric ion-exchange resin. More exactly, the phrase refers to a wide range of processes involving the exchange of ions between two electrolytes.
The process is frequently used for the purification and separation of several industrially and medicinally significant compounds, in addition to drinking water purification. Although the phrase is most commonly associated with the use of synthetic (man-made) resins, it can also apply to a variety of different materials, such as soil.
Ion Exchange Process
A microporous exchange resin supersaturated with a loosely held solution is the main component of ion exchange equipment. Sulfonated polystyrene beds that have been supersaturated with sodium to cover the bed surface are commonly used for water softening. Ions attach to the resin beads as water travels through the resin bed, releasing the loosely contained solution into the water.
The exchange resin must be replenished or recharged after the beds get saturated. The salt brine solution flushes the ion exchange resin to revive it. The ions in the wastewater are exchanged with the sodium ions in the salt brine solution.
Water softening (removal of calcium and magnesium ions), water demineralization (removal of all ions), and de-alkalinization are the most prevalent uses of ion exchangers (removal of bicarbonates).
Iron, lead, radium, barium and copper can all be removed from water using cation exchange resins. Nitrate, sulphate, and other negatively charged atoms can be removed by anionic exchange units (called anions). Researchers are working on resins that will allow them to extract nitrate more selectively than is currently possible.
In the chemical sector, ion exchangers are also used to extract or recover metal ions from effluent. Due to the poor selectivity of the resins, some pollutants (such as arsenic, fluoride, and lithium ions) are difficult to remove using ion exchange.