Chlorine dioxide (ClO2) is a highly effective, eco-friendly disinfectant and microbiocide that carries US EPA, FDA and
UK Government approvals for many of its uses. It is a selective oxidant that eliminates both planktonic and sessile
bacteria, disinfects surfaces, and rapidly destroys biofilms.
Chlorine Dioxide is a small, volatile and very strong molecule consisting of 1 Chlorine atom and 2 oxygen atoms. It is
a chemical compound with the formula ClO2. It has a molecular weight of 67.45 and exists as a gas at normal
temperatures and pressures. Chlorine dioxide exists as a free radical in dilute solutions.
Chlorine dioxide is a strong bactericide and virucide at concentrations as low as 0.1 ppm. It will eliminate both planktonic and sessile bacteria; disinfect surfaces; and rapidly destroy problematic biofilm. With minimal contact time, it is highly effective against many pathogenic organisms including bacterial spores, Legionella, Tuberculosis, MRSA, VRE, Listeria, Salmonella, amoebal cysts, Giardia cysts, E. coli, and Cryptosporidium. Importantly, chlorine dioxide also destroys biofilm so bacterial re-growth is significantly impeded.
Chlorine Dioxide is an oxidizing biocide and not a metabolic toxin. This means that chlorine dioxide kills microorganisms
by disruption of the transport of nutrients across the cell wall, not by disruption of a metabolic process.
•It has a molecular weight of 67.45.
• It is a gas at normal temperatures and pressures.
• It has a melting point of -59 oC.
• It has a boiling point of 11 oC.
• It is yellowish/green and has an odour similar to that of Chlorine.
• It is denser than air and is water soluble at standard temperatures and pressures (up to 2500ppm).
• It is explosive in air at concentrations (> 10%).
• It is prohibited from road and sea transport in its “free” form, and is normally generated at the point of application
using two precursor chemicals.
• It will decompose in the presence of UV, high temperatures, and high alkalinity(>pH12).
Chlorine dioxide (ClO2) was discovered in 1814 by Sir Humphrey Davy. He produced the gas by reacting sulphuric acid with potassium chlorate.
Chlorine dioxide was first produced in 1814 by reacting sulphuric acid with potassium chlorate.
Today, most methods involve using either a chlorate (ClO3-), or chlorite (ClO2-) salt, with an acid,
sometimes in the presence of a Chlorine Donor.
Methods for chlorine dioxide production:
5NaClO2 + 4HCl → 4ClO2 + 5NaCl + 2H2O
2NaClO2 + HOCl → 2ClO2 + 5NaCl + NaOH
2NaClO3 + H2O2 + H2SO4 → 2ClO2 + 2Na2SO4
2NaClO2 + Cl2 → 2ClO2 + 2NaCl
5NaClO2 + 4NaHSO4 → 4ClO2 + NaCl + 4Na2SO4 + 2H2O
2NaClO2 + Na2SO8 → 2ClO2 + 2Na2SO4
Chlorine dioxide is not the same as chlorine. While chlorine dioxide has “chlorine” in its name, its chemistry is
very different from that of chlorine. Although both chlorine dioxide and chlorine are oxidising agents (or electron
receivers), chlorine dioxide is significantly more effective as a biocide and disinfectant than chlorine. This is
because chlorine molecules have the capacity to accept only two electrons, whilst chlorine dioxide has
the capacity to accept five.
Chlorine dioxide penetrates the bacteria cell wall and reacts with vital amino acids in the cytoplasm of
the cell to kill the organism. The byproduct of this reaction is chlorite. Of importance is that toxicological
studies have shown that ClO2’s disinfection by-product, chlorite, poses no significant adverse risk to
Fifty years of worker experience has demonstrated that chlorine dioxide is a safe compound when handled properly.
World-wide, nearly 4.5 million pounds per day of chlorine dioxide are used in the production of pulp and paper. However,
as with any and all disinfectant chemicals, if handled improperly, or consumed internally or absorbed or subjected to
prolonged exposure, ClO2 can be toxic. However, it is also this toxicity that makes ClO2 a good water disinfectant agent.
Chlorine dioxide is far more environmentally friendly than other oxidising biocides and disinfectants including chlorine and
bromine. Substituting chlorine dioxide for chlorine eliminates the formation of toxic halogenated disinfection by-products
including trihalomethanes (THMs) and other chlorinated compounds that are harmful to the environment. In fact chlorine
dioxide actually helps to remove substances that can form trihalomethanes. The disinfection is by oxidation as chlorine
dioxide does not have either addition or substitution reactions associated with its chemistry.
Chlorine dioxide is a strong bactericide and virucide at concentrations as low as 0.1 ppm. It will eliminate both planktonic
and sessile bacteria; and rapidly remove problematic biofilm. With minimal contact time, it is highly effective against
many pathogenic organisms including:
• Bacterial spores
• Legionella (Legionnaires’ disease)
• Giardia cysts
• Taste and odour
• THM/HMM formation
• Planktonic and sessile organisms
Chlorine dioxide is a water-soluble gas, it does not ionize to form weak acids (as chlorine and bromine do) in aqueous
solutions. This allows chlorine dioxide to be effective over a wide pH range (4 – 10). For example, the pH dependent
speciation of chlorine produces hypochlorite ion and hypochlorous acid (HOCl). Hypochlorite is only 1/30 to 1/200
as effective as HOCl. Chlorine dioxide being a neutral species with rapid disinfection kinetics is 100% available for
disinfection in hard or soft water.
NO. Stablized Chlorine Dioxide is NOT Chlorine Dioxide!!!
Though “stablized chlorine dioxide” is in the product name, it is not chlorine dioxide. There are only trace amounts of chlorine dioxide (ClO2) in the stabilized chlorine dioxide compound.
The correct description of product is “stabilized chlorite” which is a salt-based product. They are prepared by buffering sodium chlorite with carbonate or phosphate and hydrogen peroxide. This stablizes the chlorite, not chlorine dioxide. When generating useful concentrations of chlorine dioxide in a stabilized chlorite product, either chlorine or a strong acid must be introduced. Even though stabilized chlorite is an oxidizing agent, but does not have the same oxidizing properties. The oxidizing action of chlorite is much lower, and is far less useful..
Chlorine Dioxide (ClO2) is a extremely powerful bactericide and virucide at very low concentrations. It will eliminate bacteria and destroy biofilm. With very short contact times, chlorine dioxide is extremely effective against many pathogens including but not limited to:
• Taste and Odors
• THM & MHM formations
• Bacterial Spores
Chlorine Dioxide uses a very unique kill mechanism. Nearly all disinfectants destroy bugs by corroding their cell walls. Chlorine dioxide is neither ionic nor carries a hydration sphere, and diffuses as a gas into an intact cell, disrupting cell content. DNA is very sensitive to any radical reaction, which is exactly what chlorine dioxide does once it is in the cell wall. This mechanism is unique in the world of disinfectants, and it is because of this mechanism chlorine dioxide does not care whether it is a superbug or not – it simply kills it, despite antibiotic resistance that particular bug may have. That’s the beauty of the chlorine dioxide molecule, no resistance now, or in the future. Chlorine dioxide will at some point start to be seen as a solution for some of the antibiotic resistant organisms we are running into for the same reasons.