光触媒, オゾンあるいは過酸化水素によるCN^-イオン含有水溶液の分解

Abstract

Decomposition reactions of aqueous CN- ions by TiO2 photocatalyst, ozone and/or hydrogen peroxide were investigated. The principal findings obtained are as follows:1) The presence of dissolved oxygen was necessary to decompose aqueous CN- ions photocatalytically. CN- was oxidized to CNO- with TiO2 catalyst, and then to CO32- and NO3-. Oxidation reaction of CNO- to CO32- and NO3- was far slower compared to that of CN- to CNO-. Photocatalytic oxidation reaction of CNO- at pHs 7 and 10 proceeded distinctly faster compared to that at pH 12. 2) Although ozone oxidation of CN- took the same paths as photocatalytic reactions, but it was faster than that of photocatalytic routes. Combined use of photocatalyst and ozone for the decomposition of CN- was more efficient.3) Decomposition product of CN- with hydrogen peroxide was found as CNO- and N2. Joint use of hydrogen peroxide and photocatalyst promoted reaction of CN- to N2.