After using and selling mixed bed resins for some five or more years now we often get asked the questions: What is Mixed Bed Resin, otherwise known as Ion Exchange resin, how does it work and what do you use it for. We will answer these questions and more in this article. But first let’s consider what Mixed Bed resin is.
Mixed bed resin is comprised of small plastic beads that are either positively charged called cations or negatively charged called anions. These plastic beads purify water by removing almost all of the dissolved minerals. The resulting water can be used to clean windows and cars without spotting.
That is the short answer but there is more so please read on as it can be used for many more different reasons.
In this article we will consider:
- How Does Mixed Bed Resin Work?
- How Long Does Mixed Bed Resin Last?
- Does Resin Deteriorate
- What is The Difference Between Cation and Anion Resin?
- What are Mixed Bed Resins Used For?
- What is Ion Exchange Resin and How Does it Work?
After doing much research and having used the mixed bed resin in business for many years we can assure you that it is very helpful and a great time saver and money saver if used in the correct way.
How Does Mixed Bed Resin Work?
Mixed Bed Resin works by deionizing water, which is achieved by removing the ions or minerals from water. These ions are electrically charged having a positive or negative charge. The ion exchange resin is used to exchange the cations and anions with hydroxl and hydrogen to leave pure water.
This process is important for the applications that use water as a rinse or ingredient where the ions are considered impurities and therefore need to be removed.
In municipal or tap water there are many cations such as Calcium and Magnesium along with many anions such as Chlorides and Sulphates.
Below is a table of most of the ions found in tap water that mixed bed resin or ion exchange resin will remove.
|Removed by Cation Resins||Removed by Anion Resins|
These small plastic beads contain chemical properties that are charged, with either a positive or a negative charge.
The cation resin bead has a negative charge and so attracts positive ions such as Calcium and Magnesium. There are two basic types of cations. They are strong acid cation and weak acid cation. For producing pure water or deionized water you need strong acid cation.
The anion resin bead has a positive charge and so attracts negative ions such as Silica and Chlorides. There are two types of anion resins. They are strong base anion and weak base anion.
In Mixed Bed Resin, the beads used are a mixture of strong base anions and strong acid cations. This combination will remove most minerals or ions in water making it pure.
How Long Does Mixed Bed Resin Last?
Mixed Bed Resin can last indefinitely if stored correctly in vacuum-sealed bags and away from UV light which promotes oxidation. However generally 2 years from manufacturing is the guaranteed lifespan of an unopened vacuum-sealed bag that is stored away from sunlight and below 40 degrees Celsius.
If you have an opened bag of resin, then you can still maintain its effectiveness by storing the resin in an airtight bag, or better a food saver bag that you can vacuum seal ensuring that it is kept in a place out of direct sunlight with a temperature below 40 degrees Celsius.
However, in saying this, I keep my opened bags of mixed bed resin in my van as I buy the 25litre bags and only use about 10 litres at a time. I see no noticeable decline in performance. My van has tinted windows so that keeps most of the UV light out and I place the opened bag into a box. The temperatures in my van stays below 40 degrees Celsius as its not so hot where I live.
I have heard some unopened Mixed Bed Resin bags having being stored for 10 years and when analysed still performed as good as fresh new resin. I personally had a bag of mixed bed resin that was at least a year old and was open and had dried out. I decided to go ahead use it to see if it was still going to work and it still gave me the same reading of Total Dissolved Solids (TDS) as fresh resin.
As long as you store your resin out of direct sunlight, below 40 degrees Celsius and keep the bag as sealed as much as possible and away from exposure to air as much as you can, then it should last pretty much indefinitely.
The main concern, and this is more of a concern than the shelf life, is the regeneration process of your resin before you bought it. As long as it has been regenerated as strong acid cation and strong base anion resin then that’s more important for performance than how long it has been stored. This will give you the desired 0 TDS reading for ultra-purification and spot free rinsing.
I had the experience of buying a tonne of Mixed Bed Resin from a supplier in China assuming that it would be strong acid cation and strong base anion only to find that it hadn’t been regenerated properly and so rather than being strong it was weak. This led to a TDS (Total Dissolved Solids) reading of 10 or more rather than 0. Fortunately, I was able to use a higher-grade resin to polish down the lower grade resin and still achieve a 0 TDS reading.
I now use a resin from a company in India which produces a very high grade long lasting resin that produces the desired 0 ppm TDS readings.
You may also be wondering how long your mixed bed resin will last while using it, before you need to discard and replace with fresh resin.
There are so many factors to take into consideration when answering this question. What is the TDS (Total Dissolved Solids) reading of the water that you want to purify? Is it above 100ppm (Parts Per Million)? Your resin will become depleted fairly quickly if the water you are purifying is above 100ppm.
To test the PPM of your water you use a TDS meter, which can be bought from Amazon very cheaply. They work by testing the conductivity of the water, since the solids or ions in the water allow a current to be measured between the TDS meters sensors. A reading of 1 ppm indicates that there is 1 mg of dissolved solids per kilogram of water. Ideally for rinsing you would like to have a reading of 0 ppm.
The other factor you need to take into consideration is how often you are using the resin. The more you use the resin the quicker it will deplete. If I use my mixed bed resin only for an hour once a week to wash my car it will obviously last me a lot longer than using it for an hour every day to wash my car.
The best way to know how long your resin will last is from your own personal experience. I sell our resin to a Car Sale Yard who washes down on average 30 cars twice a week. His tank is a 20-litre tank and the resin lasts 6 weeks. Obviously, a bigger tank means that he doesn’t have to change his resin as often as someone with a smaller 5-litre tank. The TDS reading of the untreated water is 70 ppm so it’s not such a strain on the mixed bed resin to bring it down to 0 ppm.
I use a 10-litre tank for window cleaning and usually change the resin once every two to three months. I use it probably a couple of times a week on average for maybe a couple hours.
However, if you really want to know the lifespan of your resin then use a flow meter. It’s a small device that you can buy from your hardware store that keeps a count of how many gallons of water have passed through it.
You place it onto the tap before your tank of resin before using your mixed bed resin each time. When your resin is exhausted you can see how many gallons it was able to clean. All things being equal, that is as long as you measured your tap water TDS reading before use and as long as it roughly stayed consistent each time you used the resin.
I used to check my resin lifespan this way but found it easier just to use a handheld TDS meter and every so often check the reading of the water exiting from my tank. As long as the TDS reading is below 10 ppm, that’s good enough for me to clean windows with a spot-free finish. Some tanks have an inline TDS meter which is built into the tank allowing you to continually monitor the effectiveness of your resin.
Some resins you can buy now even have the ability to change colour as they are depleted so you can ‘see’ when you need to replace the resin in your tank.
Does Mixed Bed Resin Deteriorate?
Mixed Bed Resin will deteriorate if stored in temperatures above 40 degrees Celsius and if exposed to UV light such as direct sunlight. It will also deteriorate over time as it is used to purify water due to the exchange of ions.
As mentioned earlier, it is best to keep your resin in air tight bags in a dark cool place to ensure maximum lifespan of your resin and its effectiveness at purifying water.
Some mixed bed resin suppliers can supply you with resin in 5-litre vacuum-sealed bags so you only need to open one bag at a time as you need it. Whereas with the larger 25-litre bags you may only use a few litres at a time and so have the problem of ensuring the remaining resin is as airtight as possible while unused.
The advantage of a 25-litre bag of resin however is the cost. The larger 25-litre bags are more cost-effective per litre than the 5-litre bags.
What is The Difference Between Cation and Anion Resin?
The difference between cation resin and anion resin is that anion resin is positively charged while cation resin is negatively charged.
This means that the negatively charged ions such as silica and chlorides are attracted to the positively charged anion resin. And the positively charged ions such as Magnesium and Iron are attracted to the negatively charged cation resin. This is how the dissolved solids or ‘impurities’ are removed from water to make it ‘pure’.
What are Mixed Bed Resins Used For?
Mixed bed resins are used for purifying water by removing ions or dissolved solids in the water. This process makes the water useful for rinsing, such as in window cleaning and microelectronics cleaning, and as an ingredient such as in pharmaceuticals.
The main reason I use mixed bed resin is to rinse windows after mopping them with a detergent. The resulting finish is a clean streak-free, spot-free shine without the need for a squeegee. It saves me a lot of time and money to use the resin in a 5 litre or 10-litre tank specialized tank. This system is called a water fed system.
If I didn’t use the resin and just rinsed the windows with normal tap water, they would dry spotted. The spotting is due to the dissolved solids in the water being left behind after the water evaporates off the glass. If left unchecked this spotting will etch into the glass leaving unsightly stains that become very hard to remove. You need special abrasive material and a lot of scrubbing to remove the water stains as can be seen with many glass shower units.
Another common reason to use mixed bed resin is for cleaning cars. It reduces the time needed to clean a car as you don’t need to wipe it down once it is rinsed off. The water will again dry spot free and leave a very clean shiny finish.
There are many other applications for the pure water resulting from mixed bed resin such as pharmaceutical and industrial uses.
What is Ion Exchange Resin and How Does it Work?
Ion Exchange Resin is comprised of a bed of cation and anion resins which are negatively and positively charged respectively to purify water by removing ions or salts. To accomplish this, an exchange occurs by trapping ions in the resin beads and releasing other ions.
It is just another name for mixed bed resin which explains the process that occurs. This process is an exchange of ions by the mixed bed resin medium to purify water.
It works exactly the same as mixed bed resin as described earlier above in this article.
Ion exchange resin is generally an insoluble supportive structure usually in the shape of very small (typically 0.25 mm – 0.5 mm radius) microbeads, usually a yellow or white colour, and made from an organic chemical compound substrate.
These tiny micro beads are very typically permeable, providing a very large area of surface both inside and on them.
The collecting and trapping of those ions will occur along with the subsequent release of other ions, and so this process is actually called ion exchange.
It gets better….
Ion-exchange resin beads are widely used in many different purification, decontamination and separation processes.
Commonly these include water purification and water softening.
Want to know the best part?
These resin beads are great for window cleaners and car washing. They take out all of the minerals in the water leaving pure water for that spotless and streak free finish.