Cobalt(III) Oxidation of Organic Compounds and Its Application to a Determination of Chemical Oxygen Demand at Room Temperature

Abstract

Cobalt(III) oxidation of diverse organic compounds was studied in a batch system. An aqueous solution of an organic compound was mixed with a cobalt(III) solution (ca. 0.04mol dm-3), prepared through the electrolysis of a cobalt(II) solution in a strong acidic medium, with a volume ratio of 1:2. The oxidation of the organic compound was evaluated from the decrement in absorbance of the mixed solution at 610nm, the wavelength of absorption maximum of the cobalt(III) ions. The cobalt(III) ions were found to be strong enough to oxidatively decompose organic compounds at room temperature; the oxidation was rapid and almost complete in 10min. The chemical oxygen demand (COD) of sample solutions was calculated from the amount of cobalt(III) ions consumed for the oxidation. The obtained COD value for each sample was comparable to that determined by an official method based on permanganate oxidation. It is concluded that not only is the cobalt(III) oxidation practical for the treatment of organic compounds but it has possibilities as a novel method of COD determination, because it can be done rapidly in a simple operation with no requirement for heating.