Ozonation rate of water-soluble chelates and related compounds.

概要

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Metal-EDTA complexes and related compounds were oxidized by ozone, and the destruction rates of chelates were obtained over a wide range of pH values. The degradation of EDTA was initiated by the electrophilic attack of ozone on the nitrogen lone pair. Therefore, the reactivity of EDTA chelates was strongly affected by the conditional stability constant, K, which was related to the availability of the nitrogen lone pair. In the range of K < about 1 × 104, the formation of the coordinate bond was not sufficiently strong, and the degradation rate of the EDTA chelates was nearly equal to that of free EDTA. In the range of K > 105, however, the degradation rate of the EDTA chelates decreased with an increase in the stability constant. The removal rate of metals from EDTA, NTA and IDA complexes decreased with an increase in the number of coordination sites per ligand. Approximately two molecules of ozone were needed to destruct one coordination site of each ligand.
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