Radiation induced degradation of ehtylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and dodecylbenzenesulfonic acid (DBS) in water

The photolysis (λ=254 nm) of aqueous EDTA, NTA and DBS in the presence of oxygen, ozone and TiO2 individually and in mixtures of them as well as by ozonation only was investigated. Very high EDTA degradation yields were obtained by the synergistic action of UV light (λ=254 nm) in the presence of ozone and TiO2. By adding of a 2.5 mg.ml-1 TiO2 suspension to an aqueous solution of 1x10-3 mol.dm-3 EDTA and passing through 1.9 mg.dm-3.min-3O3 a Giph (-EDTA) = 12.0 and at 29.3 mg.dm-3.min-1O3 a Giph = 25.2 was obtained. Comparative studies were performed with γ-irradiation under similar conditions. A somewhat higher yield of EDTA degradation, Gi(-EDTA) = 13.5 was observed upon γ-radiolysis of 1x10-3 mol.dm-3 EDTA in the presence of 1.9 mg.dm-3.min-1O3 and 2.5 mg.ml-1 TiO2. In both cases the EDTA degradation depended on the absorbed radiation dose (UV-light or γ-rays), on the O3-concentration, and on the amount of suspended TiO2. By increasing the O3 concentration also the degradation yield was strongly increased. Analysis of products resulting from photolysis and radiolytic of EDTA, NTA and DBS in the presence of oxygen, performed by the GC/MS-method are also reported. Pulse Radiolysis and chemical analysis of DBS in aqueous solution were performed and the results are presented. Economic considerations concerning the pollutant degradation by combined photochemical methods in comparison to ionizing radiation under similar conditions of EDTA, NTA and DBS have been made. (author)