What is ion exchange in water treatment?
Ion exchange is a water treatment process commonly used for water softening or demineralization, but it also is used to remove other substances from the water in processes such as dealkalization, deionization, denitrification, and disinfection.
What is the purpose of the ionic exchange process?
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 process, the less desired compounds are swapped for those that are considered more desirable.
What are the applications of ion exchange membranes?
Ion-exchange membranes have been used in a wide range of applications, from water treatment to treating industrial effluents in the food, manufacturing, and pharmaceutical industries. Ion-exchange membranes have recently been widely used in battery applications.
What are the ion exchange cations of ion exchange?
The common appli cations of ion exchange are water softening (removal of "hardness" ions such as CA2+ and Mg2+) and nitrate removal in advanced wastewater treatment operations. These ion exchange resins are either naturally occurring inorganic zeolites or synthetically produced organic resins.
How does ion exchange occur?
The ion exchange chemical process works by removing dissolved ionic contaminants from the water. These ions are swapped for better ones that won't degrade the quality of your water. Water softeners are very similar to ion exchange systems since both systems can remove magnesium and calcium ions from the water.
Where does ion exchange chromatography work?
Ion chromatography (or ion-exchange chromatography) separates ions and polar molecules based on their affinity to the ion exchanger. It works on almost any kind of charged molecule—including large proteins, small nucleotides, and amino acids.
How does ion exchange work in water treatment?
Ion exchange is a water treatment method where one or more undesirable ionic contaminants are removed from water by exchange with another non-objectionable, or less objectionable ionic substance.
What are the rules of ion exchange?
The two requirements for ion exchange—fixed ionic charges on a supporting material and permeability of the material to a solution—are met in a surprisingly large number of materials. The fixed charges may be negative, as in the above example, or they may be positive.
How does ion chromatography work?
How Does Ion Chromatography Work? Ion chromatography, a form of liquid chromatography, measures concentrations of ionic species by separating them based on their interaction with a resin. Ionic species separate differently depending on species type and size.
What is an ion exchange column How does it work?
Ion exchange chromatography is used to separate charged molecules. In an anion exchange column, the packing is positively charged and therefore retains negatively charged molecules by coulombic interaction. The bound molecules are eluted with an anion gradient.
Why is ion exchanger used?
Ion exchange resins are useful for the removal of water problems including hard water, scale buildup, nitrates and arsenic. Ion exchange resins are useful for the removal of water problems including hard water, scale buildup, nitrates, arsenic and more.
When should I replace ion exchange resin?
As a general rule, you can expect an ion exchange resin to last about 10 to 15 years in water treatment (as opposed to four to eight years for anion exchange resins).
How do you activate ion exchange resin?
The resin can be recharged by washing it with a solution containing a high concentration of sodium ions (e.g. it has large amounts of common salt (NaCl) dissolved in it). The calcium and magnesium ions migrate from the resin, being replaced by sodium ions from the solution until a new equilibrium is reached.
What are the important characteristics of a good ion exchanger?
Basic Characteristics of Ion Exchange ResinsAppearance. ... Particle Size. ... Reversible Swelling. ... Moisture. ... Density. ... Total capacity.
What is ion exchange?
Ion exchange can be defined as the reversible exchange of ions between a liquid phase and a solid phase (ion-exchange resin) which is not accompanied by any radical change in the solid structure.
What are the advantages of ion exchange?
Advantages of ion exchange are low energy usage, no further degradation of the amine during reclaiming, and removal of only the solution contaminants.
How does a sorption and elution process work?
Continuous operation of a sorption and elution process is achieved by processing the feed through a series of columns . Here, the lead column is taken off-line and eluted when the contaminant concentration in the product rises to a target value. Feed is then directed to the lag column, which becomes the lead column and a previously regenerated column is taken on-line into the lag position. A major factor affecting the number of columns is the mass transfer rate of contaminant ions. For a slow mass transfer rate, a large number of small columns may be preferable to maximize the quantity of contaminant loaded onto the lead column. However, system complexity increases with increasing number of columns since column positions are switched by means of valves.
How do cations and anions exchange?
The cations and anions can be exchanged for anions or cations in a solution that is passed through the ion exchange material. Contact between the solution and the ion exchange material is usually achieved within a column, with the solution flowing either upwards or downwards though the ion exchange bed.
When did ion exchange begin?
The modern history of ion exchange began in about 1850 when two English chemists, Thompson(4) and Way(5), studied the exchange between ammonium ions in fertilisers and calcium ions in soil. The materials responsible for the exchange were shown later to be naturally occurring alumino-silicates(6).
What is an esix?
Electrically switched ion exchange (ESIX) technology combines ion exchange and electrochemistry to provide a selective, reversible method for the removal of target species from wastewater. In this technique, an electroactive ion exchange layer is deposited on a conducting substrate, and ion uptake and elution are controlled directly by modulation of the potential of the layer. ESIX offers the advantages of no secondary waste generation. We have improved upon the ESIX process by modifying the conducting substrate with carbon nanotubes (CNTs) prior to the deposition of the electroactive ion exchanger. The nanomaterial-enhanced electroactive ion exchange technology will remove cesium-137, chromate, and perchlorate rapidly from wastewater. The high porosity and high surface area of the electroactive ion exchange nanocomposites results in high loading capacity and minimizes interferences for nontarget species. Since the ion adsorption/desorption is controlled electrically without generating a secondary waste, this electrically active ion exchange process is a novel technology that will greatly reduce operating costs.
What is ion exchange?
Ion exchange is a water treatment process commonly used for water softening or demineralization, but it also is used to remove other substances from the water in processes such as dealkalization, deionization, denitrification, and disinfection. With many other overlapping technologies available, it is important to determine whether ion exchange is ...
What is the process of exchange of ions?
Ion exchange describes a specific chemical process in which unwanted dissolved ions in water and wastewater — like nitrate, fluoride, sulfate, and arsenic — 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.
What is the exchange process between a solid and a liquid?
In the process, the less desired compounds are swapped for those that are considered more desirable. These desirable ions are loaded onto the resin material. These resins can be used alone or in concert to remove ionic contaminants from water.
What is the exchange of cations during water treatment?
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. In the anion exchange process, negatively charged ions are exchanged with negatively charged ions on the resin surface, ...
How much is the ion exchange resin market?
The global market for ion exchange resins, which was estimated at $1.54 billion in 2014, was projected in 2016 to be $2.46 billion by 2022, a compound annual growth rate of roughly 6%, according to Stratistics MRC, a Maryland-based market research firm. Their analysts see increased nuclear power demand and stringent environmental regulations driving the market. This is particularly seen in the power generation and wastewater treatment markets.
What can be removed by anion exchange?
Various contaminants — including nitrate, fluoride, sulfate, and arsenic — can all be removed by anion exchange. Compared to other technologies, including continuous electrodeionization (CEDI), chromatography, ultrafiltration, and biological treatments, ion exchange is particularly suitable when trying to remove a specific low concentration ...
What is resin exchange capacity?
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.
What is the purpose of ion exchange systems?
Ion exchange systems are used for efficient removal of dissolved ions from water.
What is the use of a weak acid cation exchange resin?
Weak acid cation exchange resins derive their exchange activity from a carboxylic group (-COOH).
What is the difference between cation anion demineralization and zeolite softening?
The primary difference is that the vessels, valves, and piping must be made of (or lined with) corrosion-resistant materials. Rubber and polyvinyl chloride (PVC) are commonly used for ion exchange vessel linings. The controls and regenerant systems for demineralizers are more complex, to allow for such enhancements as stepwise acid and warm caustic regenerations.
How does a demineralizer work?
In a conventional demineralizer system, regenerant flow is in the same direction as the service flow, down through the resin bed. This scheme is known as co-current operation and is the basis for most ion exchange system designs. During the regeneration of a co-current unit, the contaminants are displaced through the resin bed during the regeneration. At the end of the regeneration, some ions, predominately sodium ions, remain in the bottom of the resin bed. Because the upper portion of the bed has been exposed to fresh regenerant, it is highly regenerated. As the water flows through the resin during service, cations are exchanged in the upper portion of the bed first, and then move down through the resin as the bed becomes exhausted. Sodium ions that remained in the bed during regeneration diffuse into the decationized water before it leaves the vessel. This sodium leakage enters the anion unit where anion exchange produces caustic, raising the pH and conductivity of the demineralized water.
Why should a regenerant distributor be secured to the tank structure?
The regenerant distributor should be secured to the tank structure to prevent breakage and subsequent channeling of the regenerant. Water is softened by the bed of strong acid cation exchange resin in the sodium form.
What is the process of demineralization of water?
Demineralization of water is the removal of essentially all inorganic salts by ion exchange.
Where is the underdrain system located?
The underdrain system, located at the bottom of the vessel, retains ion exchange resin in the tank, evenly collects the service flow, and evenly distributes the backwash flow. Uneven collection of water in service or uneven distribution of the backwash water can result in channeling, resin fouling, or resin loss.
What is ion exchange resin?
Ion exchange is a process in which ions of a particular species in solution are replaced by ions with a similar charge but of different species attached to an insoluble resin. In essence, ion exchange is a sorption process and can also be considered a reversible chemical reaction. The common appli cations of ion exchange are water softening (removal of "hardness" ions such as CA2+ and Mg2+) and nitrate removal in advanced wastewater treatment operations. These ion exchange resins are either naturally occurring inorganic zeolites or synthetically produced organic resins. The synthetic organic resins are the predominant type used today because their characteristics can be tailored to specific applications.
What is the exchange capacity of weak base resins?
Consequently, weak base resins exhibit minimum exchange capacity above a pH of 7.0. These resins merely sorb strong acids: they cannot split salts.
What is the ionizable group in HCL?
In a weak acid resin, the ionizable group is a carboxylic acid (COOH) as opposed to the sulfonic acid group (SO3H) used in strong acid resins.
Is sulfate an ion exchanger?
Sulfate. Greater preference for a particular ion, however, will result in increased consumption of chemicals for regeneration. Ion exchange resins are classified as cation exchangers that have positively charged mobile ions available for exchange, and anion exchangers, whose exchangeable ions are negatively charged.
Is a resin with sulfonic acid groups a strong cation exchange resin?
Accordingly, a resin with sulfonic acid groups would act as a strong cation exchange resin.
Do weak acid resins have a higher affinity for hydrogen ions than strong acid resins?
Weak acid resins exhibit a much higher affinity for hydrogen ions than do strong acid resins. This characteristic allows for regeneration to the hydrogen form with significantly less acid than is required for strong acid resins. Almost complete regeneration can be accomplished with stoichio-metric amounts of acid.
What is the ion exchange process?
The Ion Exchange process can be used in a variety of ways when it comes to water purification and softening. Although different water treatment products utilize this process in different ways, the action itself remains the same: unwanted ions that are dissolved in the water are replaced with new beneficial or harmless ions of an equivalent charge.
What is the process of replacing unwanted ions that are dissolved in water with beneficial or harmless ions of an equivalent
Ion Exchange is the process of replacing unwanted ions that are dissolved in water with beneficial or harmless ions of an equivalent charge.
What is the difference between a cation and an anion?
A Cation is an atom with a positive charge, whereas an Anion is an atom with a negative charge. When it comes to the resins used, their composition is normally made up of microbeads that are very permeable. Typically, the microbeads are created out of different polymers like polystyrene.
What is magnetic exchange resin?
Also, resins known as magnetic exchange are often utilized when organic compounds need to be separated from the water, such as with waste water treatment. A Cation Resin can be used in ion exchange systems for dealkalization or demineralization, depending on whether it’s a weak acid cation or a strong acid cation.
What is the EPA regulated cation?
Barium and radium removal. Barium and radium, two divalent cations, are regulated by the U.S. Environmental Protection Agency (EPA) for National Primary Drinking Water Standards and can be removed by standard SAC resin.
What is the IX process?
Specialized IX resins address these challenges. The IX process removes soluble ionized contaminants such as hardness ...
What is a negatively charged anion resin?
Negatively charged anion resins remove negatively charged ionic contaminants in water. Included in this category of resins are strong base/strong anion (SBA) and weak base/weak anion (WBA) resins. These anion resins can be used to remove the contaminants described in this section.
What are the two main categories of IX resins?
IX resins’ two main categories are cation and anion. Cation IX resins include strong/weak cation, (H+ and Na+). Anion IX resins include a strong/weak anion, such as OH- and Cl-. Acting together or alone, these types remove many ionic contaminants from water. Neither type removes non-ionic contaminants such as benzene.
What is TOC in water?
TOC. Total organic carbon (TOC) or naturally occurring organic matter can be oxidized by secondary chlorine disinfection and create DBPs, such as THMs and HAAs. These DBPs are suspect carcinogens and regulated by the EPA in drinking water. Municipal treatment plants sometimes remove TOC to limit the formation of DBPs.
Is resin a finite exchange?
Hardness levels are reduced and sodium levels are increased. All resin has a finite exchange capacity. Individual exchange sites on the resin beads will eventually become full and incapable of exchanging further hardness, so the resin must be recharged.
What is ion exchange?
Ion exchange methods are often used to filter water when impurities are soluble and ionized. Soluble: Any substance that can be readily dissolved in another substance (usually water). Ionized: Any atom or molecule with a positive or negative charge (as opposed to being uncharged).
Why do you need two separate tanks for cation exchange resin?
Because the fixed ions can only be either cations or anions, in order to remove both cation and anion contaminants from water, you would have to have two separate tanks for each resin. Often, cation exchange resins have sulphonates (SO3-) as their fixed ions, with sodium cations (Na⁺) as their mobile counterions.
What happens when water flows through an IE filter?
When water flows through an IE filter, impurities, which are dissolved as ions, are attracted to the fixed ions on the resin beads with a higher affinity than the counterions. This attraction causes the impurities to attach to the fixed ions, replacing the counterions.
How are ions created in water?
In water, ions are created when water’s own polar bonds break ionic bonds of other atoms, causing them to lose or gain an electron. This results in positively charged ions, called cations, and negatively charged ions, called anions.
What is an IE system?
Typically, IE systems have a pressure tank that is filled with ion exchange resin. Ion exchange resin consists of very small (often, polystyrene) beads. These beads, which are about ½ millimeter in diameter, are highly porous and are engineered to have special ions permanently attached to their structure.
Why is water neutral?
Because water is electrically neutral, the amount of positive and negative charges present in the water is equal. Water’s ability to dissolve ionic bonds allows it to hold many nutrients, chemicals, and minerals imperative to life on Earth. However, it also allows for dissolution of undesired impurities, like fluoride, radium, and strontium.
Why is RO used in water?
Because pathogens are comparatively larger in size than water molecules, RO is an effective means of bacterial reduction, and is used especially for applications requiring high purity water. Other types of membrane filtration, such as ultrafiltration, are also effective for reduction and are generally more cost-effective than RO. ...
Is disinfection effective for bacterial reduction?
IX is not effective for bacterial reduction purposes.
What is the attraction between an ion exchanger and analyte?
This form of chromatography relies on the attraction between oppositely charged stationary phase , known as an ion exchanger, and analyte. The ion exchangers basically contain charged groups covalently linked to the surface of an insoluble matrix. The charged groups of the matrix can be positively or negatively charged.
What is an ionic exchanger?
Anionic exchangers have positively charged groups that will attract negatively charged anions. These are also called “Basic ion exchange” materials. Ion exchange chromatography is most often performed in the form of column chromatography. However, there are also thin-layer chromatographic methods that work basically based on the principle ...
Why are cationic exchangers called acidic ion exchangers?
These exchangers are also called “Acidic ion exchange” materials, because their negative charges result from the ionization of acidic group.
What is the separation of a mixture of compounds into its individual components based on their relative interactions with an iner
Chromatography is the separation of a mixture of compounds into its individual components based on their relative interactions with an inert matrix. Ion exchange chromatography (or ion chromatography) is a process that allows the separation of ions and polar molecules based on their affinity to ion exchangers.
What buffers are used for ion exchangers?
The tris-buffer, pyridine buffer, acetate buffer, citrate and phosphate buffers are widely used. The particles which have high affinity for ion exchanger will come down the column along with buffers. In next step using corresponding buffer separates the tightly bound particles.
What are the advantages of ion exchange chromatography?
Advantages of ion exchange chromatography. It is one of the most efficient methods for the separation of charged particles. It can be used for almost any kind of charged molecule including large proteins , small nucleotides and amino acids.
What is a suppressor in a separation column?
Suppressor. The suppressor reduces the background conductivity of the chemicals used to elute samples from the ion-exchange column which improves the conductivity measurement of the ions being tested.
What Exactly Is Ion Exchange?
Removing Ionic Contaminants
Recharging Resins
Exchange Resins Market
Ion Exchange in Drinking Water Treatment
Food Processing
Is Ion Exchange Right For Your Needs?
- Although ion exchange and biological treatmentare widely recognized as the two leading technologies for denitrification, ion exchange is typically used to treat for nitrates in groundwater, while biological treatment is typically used to treat surface water. Ion exchange can also be used in the removal of arsenicand other metalloids and metals. Oth...
Strong Acid Cation Resins
Strong Base Anion Resins
Weak Base Anion Resins
- Weak base resins are like weak acid resins in that the degree of ionization is strongly influenced by pH. Consequently, weak base resins exhibit minimum exchange capacity above a pH of 7.0. These resins merely sorb strong acids: they cannot split salts.
Evaluation of Resins
Ion Exchange Systems
References