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.