Deionization is the process of removing certain contaminants and minerals from water by exchanging certain undesirable ions for other, less harmful ions. The process generally involves water passing through resin beads that have a charge opposite from the charge of the substance being removed from the water. The process removes nearly all total dissolved solids (TDS), however, as with any filtration process, a few may remain.
Each ion has protons or electrons that will give either a positive charge or a negative charge. If the ion has a positive charge, it is known as a cation, if it has a negative charge, it is referred to as an anion. In general, strongly acidic synthetic cation resin exchanges hydrogen ions (H) for positive ions, and strongly basic anion resin exchanges hydroxide ions (OH-) for negative ions. When both are applied, the result is pure water (H2O).
What should be kept in mind, however, is that the water is chemically pure; deionization resins do not filter uncharged impurities like solids, bacteria, and viruses. This is one of the reasons that DI water is often not recommended for drinking water.
The terms deionization and demineralization are often used interchangeably, however there is a slight difference. Deionization is the process as described above; the removal of ions from water using charged resins. Deionization is a way to create demineralized water. While deionization is a type of demineralization, demineralization can be achieved in a number of different ways as it is simply the removal of minerals, whether all or only partially. Some other examples of demineralization include reverse osmosis, water softeners, and distillation.
There are many different grades of deionization filtration that can vary by manufacturer. Different grades are created by using different resins that are coated with different functional groups of cations and anions to focus on the reduction of particular ions. The resins tend to be spherical, tiny plastic beads usually made up of a combination of styrene and divinyl-benzene (DVB). the DVB acts as a hardener, and different combinations of the ingredients can create different grades of resins with different properties.
The three main categories can be separated by the resin charge:
From these three base categories, more grades of deionization can be made with different applications in mind. Changes to factors such as the capacity, resin swelling, ion selectivity, speed of process, and resin stability and integrity can create the different grades. Some of these include:
The SpiroPure SP-ID200QC inline deionization filter is a mixed-bed filter for general DI applications. The ready-to-use mixed-bed resin employs a 2:3 canion to anion volume ratio, allowing you to use it in countertop RO systems, attached directly to a hose, or other other water filtration applications to get water free of ions like sodium, magnesium, and calcium, resulting in the perfect choice for aquariums, CPAP machines, humidifiers, and spot-free cleaning for cars, windows, glass, and more. This filter also employs a color-changing indicator resin.
Color-changing indicator type resins are resins that begin as one color and then change color overtime as the resin loses its charge and thus its filtration abilities. This allows for a visual indication of when it is time to replace the cartridge or filter media. For example, the SpiroPure SP-ID200QC begins as a green resin, but becomes purple once the filter media is exhausted. This color-changing process is achieved by a dye that is stable at either high or low pH levels depending upon the resin type, but slowly changes as the pH of the resin becomes more neutral and the media is exhausted.
Because DI water creates a chemically pure water, it is often used in specific industries that require ultra-pure water that won’t change the final product, cause oxidation, affect the pH balance, that can act as a semiconductor, and more. Some of the industries that use DI water include for pharmaceuticals; biotech applications; sugar refining and production; food and beverage production like beer, wines, and juices; medical industry; dentistry; laboratories; makeup and other cosmetics; nuclear plants; electrical and other power industries; electronic manufacturing; aquariums; glass cleaning; the automotive industry; and more.
Common applications for the SpiroPure SP-ID200QC inline filter cartridge include:
It should be noted that it is strongly recommended that you do not use DI water for drinking water. Mostly this is due to the fact that it removes many of the healthy minerals from water, that it does not remove bacteria and other solids, and is generally not a cost effective solution for filtered drinking water. For more information, view our article, “Do You Have a Water Filter System with Deionization?"
How long the resin lasts in your deionization cartridge depends on a number of factors, including the quality of water you are treating, water temperature and pressure, and if you are using the filter in addition to other filtration methods. Here are a few common problems and what you can do to help minimize the issue.
High CO2 Levels - High levels of carbon dioxide in your water can use up the ion exchange sites on the resin more quickly. A good range for carbon dioxide levels is around 15-35 ppm. If you have high levels of CO2 in your water, adding a RO system before the DI cartridge can provide more time for the CO2 to disperse and let off extra amounts before reaching your DI cartridge. You can also divert water into a storage tank before the DI cartridge and use an air stone to disperse fine air bubbles before pumping water through the DI resin.
High Chlorine and Chloramine Levels - Chlorine and chloramine will break down resin, creating more of a mush instead of the individual, spherical beads. As a result, the resin will be unable to hold its charge, making it incapable of performing the ion exchange process. Using a carbon filter before the DI cartridge will reduce chlorine levels and extend resin life.
High Iron Levels - While ferrous irons are soluble and can be removed from water through deionization, ferric irons and other contaminants like manganese and other insoluble debris can cause fouling of the resin, reducing its capacity for ion reduction. Some of these insoluble particles can be reduced from your water by installing a sediment filter before your DI resin cartridge.
High Levels of TDS - If your water has a large amount of total dissolved solids, your DI cartridge may require frequent changes. To help minimize the load on your DI resin, you may consider a RO system prior to the DI cartridge. An RO system will significantly reduce TDS levels, leaving your DI resin to perform as a polishing filter to ensure your water is clean, clear, and practically purified of any TDS.
Hard Water - As with any filter, hard water can reduce the life of DI resin. Softening the water prior to the DI cartridge, such as by a RO system, can extend the life of your DI filter.
Water Temperature - Water that is too hot can cause thermal degradation, lessening the resin life and reducing the effectiveness of the ion exchange process. Make sure to keep water temperatures within the recommended ranges for your DI Cartridge. The recommended temperature rating for the SP-ID200QC is 40℉ to 100℉ (4℃ to 38℃).
Application Size - If you are using a DI solution that is too small for your application, the resin will exhaust very quickly. Make sure the cartridge, system, or other filtration solution has an adequate amount of the correct type of resin to suit your application’s deionization needs.
Deionization is a highly effective, cost-effective solution to achieve nearly chemically purified water for ultra-pure water needs. It can be tailored to suit a variety of different applications depending upon the grade of resin and the charged ions applied to the media. For a high quality, general purpose DI filter, check out the SpiroPure SP-ID200QC Ready-to-Use Mixed-Bed Indicator Resin Deionization Filter Cartridge.
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