Chlorine dioxide: how to make it?

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Chlorine dioxide: different methods - different purities

Because chlorine dioxide is difficult to transport, it is usually made on site (= in situ). It is generally formed as an aqueous solution or as a gas.

Unlike chlorine, chlorine dioxide does not form potentially carcinogenic trihalomethanes as by-products.

With chlorine dioxide, chlorite and chlorate can be formed as by-products, but the chlorate levels are still lower than with chlorine. At the doses used for disinfection in drinking water, these are present only in minimal concentrations and pose no danger to public health.

Chlorine dioxide can be generated in various ways. These different methods lead to different degrees of purity. The purer the chlorine dioxide formed, the fewer by-products ultimately end up in the water (for example when applying a disinfection based on a chlorine dioxide product).

In the preparation and handling of chlorine dioxide, diluted preparations are usually used and the release of gas is avoided.

Below are a number of methods that are applied in practice (= on a large scale):

Chlorine dioxide generated from sodium chlorate and hydrogen peroxide in the presence of a strong acid
Chlorine dioxide generated from sodium chlorite by electrolysis
Chlorine dioxide generated from sodium chlorite by acidification
Chlorine dioxide generated from sodium chlorite by oxidation

Conclusion:

Chlorine dioxide is usually made in situ.
Unlike chlorine, chlorine dioxide does not form dangerous trihalomethanes.
There are various ways to make chlorine dioxide, each with its own purity and stability.

Chlorine dioxide: how to make it?