Analytical Sciences

Decomposition of Free Chlorine with Tertiary Ammonium

Hajime KATANO,* Kohei UEMATSU,* Hirosuke TATSUMI,** and Toshihide TSUKATANI***

*Department of Bioscience, Fukui Prefectural University, Eiheiji, Fukui 910-1195, Japan
**International Young Researchers Empowerment Center, Shinshu University, Matsumoto, Nagano 390-8621, Japan
***Research and Development Division, Nicca Chemical, Co. Ltd., Bunkyo, Fukui 910-8670, Japan

The reaction of free chlorine with tertiary ammonium or amine compounds in aqueous solution was studied by the amperometry at a rotating Pt-disk electrode. The amperometric method can be applied to follow the concentration of free chlorine (c_Cl) even in the presence of chloramine species. By addition of mono- and dibutylammonium to the solution containing free chlorine, the step-like decrease in c_Cl was observed, indicating the rapid formation of the stable chloramine species. By addition of tributylammonium, the c_Cl was decreased exponentially to nearly zero even if the free chlorine was present initially in excess. The c_Cl-t curves can be explained by tributylammonium-species-catalyzed decomposition of free chlorine to chloride ion. The catalytic decomposition was observed also with the tertiary-ammonium-based anion-exchange resins. Furthermore, the anion-exchange resins exhibited the decomposition of not only free chlorine but also chloramines in water.

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