DEGRADATION PATHWAY OF THE PHOTOCHEMICAL OXIDATION OF ETHYLENEDIAMINETETRAACETATE (EDTA) IN THE UV H2O2-PROCESS/

The degradation pathway for the oxidation of EDTA in the UV/H2O2-proce ss was investigated. In absence of iron ions, the mineralization of ED TA is dominated by the reaction of the HO-radicals generated by the ph otolysis of H2O2. The organic degradation products iminodiacetate (IMD A), glycinate, oxamate, glyoxylate, oxalate and formate, and the inorg anic degradation products carbon dioxide, ammonia, nitrate, nitrite, a nd cyanate were found. In the presence of iron ions, photolytic decarb oxylation processes inside the complex get an important role during de gradation, and the organic degradation products ethylenediaminetriacet ate (ED3A), ethylenediaminediacetate (EDDA), ethylenediaminemonoacetat e (EDMA) were also found. By combining product studies with balances o f carbon and nitrogen, the degradation pathway in the UV/H2O2-process could be elucidated. The degradation of EDTA was fast (k(deg) = 0.012 s(-1)), and no toxic degradation products were identified. Therefore, the process is well suited for the elimination of EDTA in water treatm ent.