Why Is CLO2 Very Different From Other Disinfectants?

What is Chlorine dioxide (ClO2)?

CIO2 is a yellow green gas from one atom of chlorine and two atoms of oxygen. CIO2 is very different in its chemical structure and behavior from Chlorine. It is 10 times more soluble in water than Chlorine It also has an odd number of valence electrons (19) therefore it is a paramagnetic radical according to Lewis theory on molecules with uneven number of electron.

How does CIO2 work to be Environmentally Friendly?

CIO2 oxidizes therefore produces harmful by-products.

Chlorine chlorinates organic compounds found in water which causes the formation of undesirable by products like:
(THMs) trihalomenthanes
(HAAs) haloacetic acids
CHCI3 chloroform

The above by products are harmful to humans, animals, aquatic lives and the environment.
CIO2 is also a resistant-free wide spectrum pathogens inactivator. The molecular minute size of CIO2 matters - CIO2 is only 0.124nm or 124 pm versus the smallest Norovirus about 27 to 38 nm.
Next, CIO2 Oxidation Potential in grabbing the most electrons from pathogens (5) versus (2) for other disinfectants to distinguish and kill a much wider range of pathogens.
CIO2 grabs the electrons from pathogens (oxidation) and breaks their molecular bonds , resulting in their deaths
Pathogens after losing 5 electrons will have no survival time and proteins to build resistance to CIO2.

By comparing the oxidation strength and oxidation capacity of different disinfectants, one can conclude that chlorine dioxide is effective at low concentrations. Chlorine dioxide is not as reactive as ozone or chlorine and it only reacts with sulphuric substances, amines and some other reactive organic substances. In comparison to chlorine and ozone, less chlorine dioxide is required to obtain an active residual disinfectant. It can also be used when a large amount of organic matter is present.

The oxidation strength describes how strongly an oxidizer reacts with an oxidable substance. Ozone has the highest oxidation strength and reacts with every substance that can be oxidized. Chlorine dioxide is weak, it has a lower potential than hypochlorous acid or hypobromous acid.


The oxidation capacity shows how many electrons are transferred at an oxidation or reduction reaction. The chlorine atom in chlorine dioxide has an oxidation number of +4. For this reason chlorine dioxide accepts 5 electrons when it is reduced to chloride. When we look at the molecular weight, chlorine dioxide contains 263 % ‘available chlorine’; this is more than 2,5 times the oxidation capacity of chlorine.

Table 2: the oxidation potentials of various oxidants.

oxidant oxidation strength oxidation capacity
ozone (O3) 2,07 2 e-
hydrogen peroxide (H2O2) 1,78 2 e-
hypochlorous acid (HOCl) 1,49 2 e-
hypobromous acid (HOBr) 1,33 2 e-
chlorine dioxide (ClO2) 0,95 5 e-

The following comparisons show what happens when chlorine dioxide reacts. First, chlorine dioxide takes up an electron and reduces to chlorite:

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