This process occurs until the resin becomes saturated with fluoride ions, at which point the system must be regenerated using a dissolved sodium chloride salt. During regeneration, the resin is recharged with chloride ions, and the fluoride rich water is discharged.
In addition to anion exchange resins, cation exchange resins treated with alum solution can be used for defluoridation.
Because radium is a radioactive element , when consumed in high concentrations, radium can have negative health impacts. Some health impacts of radium include:. In order to avoid these effects, ion exchange can be utilized to remove radium from drinking water. Cation ion exchange, in the form of water softeners , effectively remove radium from water. However, it has a greater electron affinity, which allows it to be filtered out after hardness ions are no longer removed from water.
Despite the continued removal of radium, the unit should be regenerated once hardness ions are no longer being removed in order to prevent scale buildup. In addition, radium left on the resin can decay into radon; therefore, it is important to regenerate the unit with either sodium chloride NaCl or potassium chloride KCL periodically to purge the system.
Strontium is an alkaline earth metal that is found in the minerals strontianite and celestine. In high concentrations, strontium in drinking water has multiple negative health effects. Exposure to strontium during infancy, childhood, and adolescence can cause abnormal bone growth, as well as dental impacts. In addition, it can cause an increase in bone density in adults and has been linked to both leukemia and bone cancer. Therefore, removal of strontium from drinking water is imperative when found in high concentrations.
Water softeners, which are described above , effectively reduce strontium concentrations in drinking water. A EPA study on IE removal of strontium showed that water softening effectively removes strontium, in addition to calcium and magnesium, with similar removal percentages between the three ions.
Want more information? Reach out to Tap Score's team of water quality engineers, treatment experts, and chemists any time. Send them a message at hello gosimplelab. Entire Building Water Treatment Solutions. Ion Exchange for Dummies. Water softener FAQ. Why Do U. While the liquid is always water, the solid can be either zeolite or a resin material.
Keep in mind that resin materials can only be charged for a specific period of time. When ions are no longer able to be exchanged, the resin will need to be recharged. Resins can be properly recharged with hydrochloric acid or sodium chloride.
During the cation exchange process, any positively charged ions that touch the resin will be exchanged with other positively charged ions that are found on the surface of the resin.
These ions will usually be sodium ions. As for the anion exchange process, the same type of swap will occur, which will result in healthier negatively charged ions being placed in the water. Contaminants like fluoride and nitrate are replaced with chloride.
This article provides you with a comprehensive view of ion exchange systems and how they operate. Dissolved ionic contaminants are removed from water via a simple ion exchange process. This exchange process requires a liquid and a solid, the latter of which can either be a resin material or zeolite. When the process occurs, any ionic contaminants in the water are swapped for better ions that stick directly to the resin material. When positively charged cations are removed from your water, they will be replaced with better cations like sodium.
The same is true with the anion exchange process. These charged ions will readily bond with ions of an opposing charge, which are delivered through the application of a counterion solution. These counterions will continue to bond with the functional groups until equilibrium is reached. During an IX cycle, the solution to be treated would be added to the IX resin bed and allowed to flow through the beads.
As the solution moves through the IX resin, the functional groups of the resin attract any counterions present in the solution. If the functional groups have a greater affinity for the new counterions than those already present, then the ions in solution will dislodge the existing ions and take their place, bonding with the functional groups through shared electrostatic attraction.
In this example, the softening mechanism consists of a cation exchange resin where sulphonate anion SO 3 — functional groups are fixed to the IX resin matrix. Over time, contaminant ions bind with all available exchange sites in the IX resin. Once the resin is exhausted, it must be restored for further use through what is known as a regeneration cycle. During a regeneration cycle, the IX reaction is essentially reversed through the application of a concentrated regenerant solution.
Depending upon the type of resin and the application at hand, the regenerant may be a salt, acid, or caustic solution. These functional groups can interact with water-soluble species, especially with ions. Ions are either positively charged cations or negatively charged anions.
Since the functional groups are also charged, the interaction between ions and functional groups is exhibited via electrostatic forces. Positively charged functional groups interact with anions and negatively charged functional groups interact with cations.
The binding force between the functional group and the attached ion is relatively weak. The exchange can be reversed by another ion passing across the functional group. This process can be repeated continually, with one exchange reaction following another. The main component of ion exchange equipment is a microporous exchange resin, which is supersaturated with a loosely held solution. For water softening, this is usually done with sulfonated polystyrene beds that are supersaturated with sodium to cover the bed surface.
As water passes through this resin bed, ions attach to the resin beads releasing the loosely held solution into the water. After a time, the beds become saturated and the exchange resin must be regenerated or recharged.
To regenerate, the ion exchange resin is flushed with a salt brine solution. The sodium ions in the salt brine solution are exchanged with the ions, which are flushed out with wastewater. Maintenance of water softening equipment is somewhat dependent on the type of softener.
Some degree of monitoring or managing the regeneration process is generally required. Adequate backwashing of the resin bed is important to ensure the regeneration of the unit. However, regeneration creates wastewater.
The costs for ion exchange systems are very variable depending on scale and region. Moreover, costs depend on pretreatment requirements, discharge requirements and utilisation. People on restricted sodium diets due to health reasons should account for increased intake through softened water. Drinking and cooking with softened water is often avoided by having a cold water line to the kitchen tap that bypasses the water softener.
This provides hard water for drinking cooking and other uses. It is not recommended to repeatedly use softened water for plants, lawns or gardens due to the sodium content.
The most common applications of ion exchangers are water softening remove calcium and magnesium ions , water demineralisation removal of all ions , and de-alkalisation removal of bicarbonates. Cation exchange resins can also remove most positively charged ions in water such as iron, lead, radium, barium, aluminium and copper among others.
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