FAQ - Preparation of Chlorine Dioxide

This page was copied with acknowledgement from www.clo2.com/factsheet/preparation.htm
Send any comments to the maintainer Roger Caffin

ClO2 made from Sodium Chlorite:

Acidification of Chlorite
5 ClO2- + 4 H+ --> 4 ClO2 + 2 H2O + Cl-

Oxidation of Chlorite by Chlorine
2 NaClO2 + C12 --> 2 NaCl + 2 C1O2

Oxidation of Chlorite by Persulfate
2 NaClO2 + Na2S2O8 --> 2 C1O2 + 2 Na2SO4

Action of Acetic Anhydride on Chlorite
4NaClO2 + (CH3CO)2O --> 2ClO2 + NaClO3 + NaCl + 2 CH3CO2Na

From Sodium Hypochlorite and Sodium Chlorite
NaOCl + 2 NaClO2 + 2 HCl --> 2 ClO2 + 3 NaCl + H2O

Electrochemical oxidation of chlorite
ClO2- --> ClO2 + e-

Dry chlorine/chlorite (laboratory method)
NaClO2 + 1/2 Cl2 --> ClO2 + NaCl (solid)

ClO2 made from Sodium Chlorate:

Reduction of Chlorates by Acidification in the Presence of Oxalic Acid
2 HClO3 + H2C2O4 --> 2 ClO2 + 2 CO2 + 2 2O

Reduction of Chlorates by Sulfur dioxide (Mathieson Process)
2 NaClO3 + H2SO4 + SO2 --> 2 ClO2 + 2 NaHSO4

ERCO R-2® and ERCO R-3® Processes
NaClO3 + NaCl + H2SO4 --> ClO2 + 1/2 Cl2 + Na2SO4 + H2O

ERCO R-5® Process
NaClO3 + 2HCl --> ClO2 + 1/2 Cl2 + NaCl + H2O

ERCO R-8® and ERCO R-10® Processes
3 NaClO3 + 2 H2SO4 + 0.85 CH3OH --> 3 ClO2 + Na3H(SO4)2 + H2O + 0.05 CH3OH + 0.6 CHOOH + 0.2 CO2

ERCO R-11® Process
NaClO3 + 1/2 H2O2 + H2SO4 --> ClO2 + NaHSO4 + H2O + 1/2 O2

As to how it works, the following quote comes from elsewhere on the same web site:

In aqueous solution, the reaction:

ClO2 + e- <--> ClO2-

has a standard redox potential, E0 = + 0.954 V at 25° C, which accounts for the strong oxidizing power of chlorine dioxide. In natural biochemical systems, sulphur-containing amino-acids such as cystine, methionine, and tyrosine react readily with chlorine dioxide. Other amino-acids, including leucine, valine, glycine, glutamic acid, and aspartic acid react less rapidly.

Those of you who follow the biological world will realise that the amino acids mentioned are basic to life. The high redox potential will deal with the lesser ranks such as viruses.

At this stage I do not know what 'Erco' is, although it seems to be a brand name associated with the company cited at the top. Never mind.