Biodegradation of Ethylenediamine-Based Complexing Agents

Results are presented from a study in which the degradability of ethylenediamine derivatives with different kinds and number of substituents was examined, including methyl, ethyl, hydroxyethyl, carboxymethyl, and acetyl substituents. EDTA, ethylenediamine-N,N'-diacetic acid, N-(2-hydroxyethyl)ethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, and propylenediaminetetraacetic acid were used. An initial concentration of the complexing agents of approximately 100 mg/l was used in the experiments. The susceptibility of the compounds to biodegradation increased in the following order: acetyl, methyl, ethyl, hydroxyethyl, and carboxymethyl. Decomposition of the ethylenediamine derivatives appeared to proceed either via an oxidative cleavage of the chain between the nitrogen atoms or via an oxidative cleavage of the bond between the N atom and the carboxymethyl group.