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What is Chlorine Dioxide?

Chlorine dioxide is an extremely effective, eco-friendly micro-biocide that carries US EPA, FDA and UK Government approvals for many uses. It is a selective oxidant that eliminates both planktonic (floating organisms), infectious bacteria, odor causing bacteria, disinfects surfaces, and rapidly destroys biofilm. The chemical formula for chlorine dioxide is ClO2, it has a molecular weight of 67.45 and exists as a gas at normal temperatures and pressures. Its molecule is small, very strong but volatile comprising one chlorine atom and two oxygen atoms.

​​Read on as you are certain to learn just how effective Chlorine Dioxide can be as an innovative solution to bacterial and microbial management. All of our products are prepared for both residential and commercial applications such as Air Treatment, Food & Beverage, High School & College, Hospitality, Medical, Senior Living.  

With expertise across many industries, our company is positioned to help solve nearly any challenge. Contact us to discuss your opportunity, and thank you for taking the time to visit our site.

Chlorine Dioxide through the years

1983 - The EPA recommends chlorine dioxide as a solution to trihalomethanes (THMs). When chlorine is used to disinfect water and make it potable (chlorination), THMs are produced as a by-product. THMs have been linked to cancer (i.e., they are carcinogenic). Chlorine dioxide does not produce THMs.

1988 - The EPA registers chlorine dioxide in the gaseous form (produced from sodium chlorite) for use in sterilization. Indicated uses include sterilizing manufacturing and laboratory equipment, environmental surfaces, and rooms.

1990 -Use of chlorine dioxide as a disinfectant, sanitizer and sterilizer grows across many industries and countries. Some of the industries are the beverage industry, fruit and vegetable processing plants, pulp and paper industries, and industrial waste treatment sites. These industries are spread across the United States, the United Kingdom and Europe.

2001 -Chlorine dioxide is one of the decontamination agents used by the United States government against the Anthrax attacks of 2001. The Anthrax attacks are a frightful example of bioterrorism. The spores of a bacterium Bacillus anthracis are used, which can cause the life-threatening disease ‘anthrax’ in victims. The choice of chlorine dioxide is due to its established sporicidal and sterilizing properties.

2005 -Chlorine dioxide is used to eradicate mold and mildew from homes flooded by Hurricane Katrina in New Orleans, Louisiana. Chlorine dioxide penetrates biofilm to effectively eradicate them.

Discover greenO2 Chlorine Dioxide Powders

Our A and B component system is an innovative product used to generate pure Chlorine Dioxide onsite. No byproducts such as chlorite and chlorates puts greenO2 chlorine dioxide at the front of most disinfection and sanitation applications where other disinfection products fail. greenO2 products are very effective and can kill a wide range of bacteria, viruses, fungus, molds and other microbes, including odor causing bacteria such as urine and feces.

The Chemistry behind Chlorine Dioxide

Historical reference

Nearly 200 years ago Sir Humphrey Day invented chlorine dioxide. The gas was obtained by way of a chemical reaction of sulphuric acid and potassium chlorate.  Chemists later found that CIO2 and CI2 (Chlorine) have ‘some’ properties in common, but are also remarkably different. CIO2 is a yellowish-green gas with a chlorine smell, which in its concentrated form is irritating to the eyes, nose and throat. However, both materials are completely different when it comes to their physical and chemical properties, regardless of the fact that they both have a chlorine atom in their molecular structure.

Differences in Water Between Chlorine Dioxide and Chlorine

The single biggest difference between CLO2 (Chlorine Dioxide) and CL2 (Chlorine) is the way they behave in water. Chlorine dioxide is 10 x more soluble in water than chlorine. Chlorine dioxide also does not hydrolise in a solution. This means that it behaves like a “true” dissolved gas and maintains its oxidation and biocide capabilities within wide pH range from 4 to 10. Chlorine on the other hand disassociates in water and forms hypochlorine acid and bichlorine acid. Hypochlorine acid then becomes the primary biocide, but in case of a higher pH is transformed into the hypochlorination. This hypochlorination has as a biocide only 1/20 to 1/300 of the strength of hypochlorine acid itself. Therefore, chlorine is only an effective biocide in case of controlled pH (+- 7,4 – 7,6). The high solubility of chlorine dioxide not only occurs in water, but also in many organic substances such as; oils, solvents, etc. And keep in mind that it is as efficient at pH 4 as with pH 10.

Molecular properties / Oxidation

Chlorine dioxide is a very small, volatile and very strong molecule that disinfects by means of oxidation and not by means of substitution like chlorine. The following statement is VERY IMPORTANT when defining differences between the two compounds. The oxidation strength of chlorine dioxide is lower than the oxidation strength of chlorine, but the oxidation capacity is greater than 2X times higher. Oxidation strength describes how strong an oxidant reacts with oxidizable material. The stronger the oxidation strength, the higher the amount of oxidizable materials with which the reaction takes place. Chlorine dioxide by comparison, is much weaker, so the benefit to the end user means far less reaction to materials it is being used with. It has a lower oxidation potential than ozone, chlorine gas and hypo chlorine acid. HOWEVER: the oxidation capacity depends on the number of electrons that are being exchanged during an oxidation-reduction reaction. Higher oxidation capacity = more effective biocidal effectiveness, or in other words, higher bacterial kill rates in shorter contact times.

The chlorine atom in chlorine dioxide has an oxidation level +4. Because of this chlorine dioxide can take on five electrons during the process of reduction to chloride. When we compare to chlorine, chlorine dioxide disposes of 263 % “available chlorine”. This is 2.5 times the oxidation capacity of chlorine. Because of this lower oxidation strength chlorine dioxide is far more selective than chlorine. Chlorine dioxide does not chlorinate, to create a chlorine compound.

IMPORTANT: Chlorine is a stronger oxidant which WILL REACT with a larger number of chemicals, including ammonium. These properties REDUCE the effectiveness of chlorine as biocide. Because chlorine dioxide has a higher oxidation capacity than ozone or chlorine, less chlorine dioxide is required for a residual concentration in the case of disinfection.

Oxidation Capacity Continued

We now know that chlorine dioxide has an oxidation capacity 2x as strong as that of chlorine, and the oxidation strength on the other hand remains lower. It is because of this lower oxidation strength that chlorine dioxide is more selective than chlorine and will not lose its capacity as an excellent biocide. In contrast, because chlorine is a strong oxidizer it reacts with more chemicals, which breaks down its potential to be an effective biocide.

​​Properties of Chlorine Dioxide

Thanks to the specific physical and chemical properties of chlorine dioxide, it is ideal for controlling microbiological contamination wherever it may occur; Fluid Decontamination, Surface Decontamination, Spatial Decontamination. Chlorine dioxide already has a rich history as an efficient biocide as well as a fluid or surface disinfectant. It also has very broad scope applications in areas such as; Drinking-Water Disinfection, Waste Water treatment, Agriculture and Horticulture, Cooling tower and Cooling water systems.

Chlorine dioxide behaves as a “true” gas in water, and other solutions. This can be compared to how CO2 behaves when it is dissolved in a can of soda. Chlorine Dioxide keeps its original chemical structure and properties in a solution. This is a very important quality not only for efficiency, but also for safety when used. This means that chlorine dioxide stays equally efficient in a liquid solution as it does in its gaseous form. Chlorine by contrast is an acid gas which dissociates in a hypo chlorine acid and a bi chlorine acid. From a safer perspective chlorine dioxide does not chlorinate any organic material. There are also no trihalomethanes, or other possible carcinogenic compounds generated as there are in the case of chlorine. Chlorine dioxide can be kept safely in solution after generation until it is used.

Bio film

Chlorine dioxide is strongly soluble in water and in different organic substances. This strong solubility allows chlorine dioxide to blast its way through some substances that protect particular micro organisms. This is not the case of many other biocides such as chlorine/bleach. A very good example of this is the fact that many bacteria in water, particularly those with sporulating properties, are protected by a poly saccharide film, otherwise known as BIOFILM. Many other biocides including chlorine cannot penetrate such films because of its ionic properties in water.

How Chlorine Dioxide Penetrates Biofilm

Chlorine dioxide penetrates these protective layers and kills the underlying harmful micro organisms. This quality of chlorine dioxide make it an ideal choice to eliminate BIO FILM, especially in drinking-water pipes and cooling towers. This special trait of chlorine dioxide also makes it an obvious means as a disinfectant for the removal of many different pathogenic organisms (Legionella). Chlorine dioxide also does not have any corrosive effects, is not pH or temperature dependent, and is insensitive to the hardness of water. In addition, in the case of user concentrations, and in contrast to many chlorine products, it does not cause any influence on taste or smell of the water. When used in cooling towers as a water disinfectant, chlorine dioxide has additional advantages because the efficiency is increased and the energy consumption is being reduced by the removal of biofilm. In addition, chlorine dioxide can also be used in the oil industry where it penetrates hydrocarbon layers and thus can oxidize contamination and bacteria that are protected by these above-mentioned structures.

Less harmful side effects

Aside from its biocidal effectiveness, there are enormous time, cost, and health benefits of using chlorine dioxide. When used in treatment, chlorine dioxide does not need any special post treatment, nor does it have to be wiped/washed down from surfaces in cases of surface decontamination. Because of its very ‘active’ nature, Chlorine dioxide is degradable in a very natural way. For example, a small concentration of 750 ppm chlorine dioxide will disappear completely, without any post treatment, within a couple of hours. And will not leave any harmful, or visible residue on the treated surfaces. In the case of every chlorine dioxide molecule, it will degrade into simple, non irritating sodium salt. It is a combination of these positive properties that compelled the USEPA to use chlorine dioxide in government buildings to treat for anthrax in 2001.

CIO2 an effective biocide

The characteristic property of CIO2 to react through oxidation and not via substitution, turns this product into an excellent alternative for chlorine, especially when it comes to drinking-water disinfection. There is no forming of possible carcinogen halogenized by-products in the case of CIO2. CIO2 will neither form significant amounts of aldehydes, ketons, keton acids, etc. with organic components in water, which is the case with OZONE. (O3). The reaction of CIO2 with micro-organisms or other organic materials takes place in two steps. During the first phase of the reaction the CIO2 molecule takes on one electron and the chlorietion (CIO2-akes on 4 more electrons and we get chloride (Cl-). The elimination mechanism of CIO2 is still not completely clear. Although it is sure that CIO2 kills microbes by penetrating the cell wall and prevents the essential protein formation. CIO2 is also more effective against viruses than chlorine and ozone. CIO2 is effective too against protozoa, growing profusely in the water, like e.g. Giardia, Lambia and Crytosporidium. They cause the respective giardiasis and cryptosporidiosis.