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.
FAQs on Applications of Ion Exchange
1. What is the Ion Exchange Chromatography principle?
Charged biomolecules are separated using IEX chromatography. A crude sample comprising charged molecules makes up the liquid phase. As molecules pass along the chromatographic column, they bond to oppositely charged sites in the stationary phase.
To elute the molecules that have been separated based on their charge, a solution of varying ionic strength is utilised. When a solution like this is sent through the column, extremely selective separation of molecules based on their various charges occurs.
2. In Ion Exchange Chromatography, explain the selection of resin.
Positively or negatively charged functional groups are covalently bonded to a solid matrix in ion exchange resins. Typically, cellulose, polystyrene, agarose, and polyacrylamide are used to make matrices. Anion or cation exchanger, flow rate, weak or strong ion exchanger, resin particle size, and binding capacity are all aspects that influence resin selection. The stability of the protein of interest affects whether an anion or a cation exchanger is utilised; if stability is not an issue, any exchanger can be used.
3. How is Ion exchange used in food processing?
Both adsorption and ion exchange are employed in food processing and have comparable designs and working cycles.
Wine, fruit juice, and whey demineralization, as well as cane sugar decolourization, can all benefit from ion exchange. Ion exchange is utilised in whey demineralization to recover and convert lactose and mineral salts into more valuable compounds for usage in infant food and medications.
Ion exchange is used in fruit juice decolourization, for example, to decolourize grape must, and in wineries for demineralization.
4. What are the limitations of ion exchange?
In both industrial and municipal water treatment systems, ion exchange is commonly employed for water treatment.
The procedure has several advantages over alternative treatment options. It is environmentally friendly, has a high flow rate of purified water, and requires little maintenance.
Along with these advantages, ion exchange has some drawbacks, including calcium sulphate fouling, iron fouling, organic matter adsorption, organic contamination from the resin, bacterial contamination, and chlorine contamination.
5. What is bacterial contamination?
Ion exchange resins do not remove microorganisms such as bacteria from the feed water, but they can sometimes help them flourish.
Organic materials may build in the resin beds, providing a source of food for bacteria to continue to proliferate. When sterile water is required after treatment, heat, UV irradiation, or very fine filtration should be used to treat the demineralized water produced by the ion exchange treatment facility.
Formaldehyde or other disinfectants can be used to disinfect exchange resin beds, but not with heat or chlorine, as these can destroy the resin.
6. What are Cationic Exchangers and How do They Work?
A cation-exchange agent is made up of an insoluble salt-like or acidic material that can exchange its cation with the cation or cations of a solution passing through it, such as a natural or synthetic zeolite.
7. Why Do We Use Ion Exchange Chromatography?
Proteins, peptides, enzymes, nucleotides, DNA, antibiotics, vitamins, and other charged or ionizable molecules can all be separated and purified using ion exchange chromatography.
8. In Ion Chromatography, What Kind of Detector is Used?
Ion chromatography's standard detection approach is conductivity detection. It can detect a wide variety of analytes, including anions, cations, and amines. The Metrohm conductivity detector is the most commonly used since it "sees" all ionic components.