Comparative studies of photo- and radiation-induced degradation of aqueous EDTA.: Synergistic effects of oxygen, ozone and TiO2 (acronym: CoPhoRaDe/EDTA)

The photolysis (lambda = 254 nm) of aqueous EDTA 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 (lambda = 254 nm) in the presence of ozone and TiO2, By adding of a 1.5 mg ml(-1) TiO2 suspension to an aqueous solution of 1 x 10(-3) mol dm(-3) EDTA and passing through 1.9 mg dm(-3) min(-1) O-3 a G(1)(ph) (-EDTA) = 12.0 and at 29.3 mg dm(-3) min(-1) O-3 a G(1)(ph) = 25.2 was obtained. Comparative studies were performed with gamma-irradiation under similar conditions. A somewhat higher yield of EDTA degradation, G(i)(-EDTA) = 13.5 was observed upon gamma-radiolysis of 1 x 10(-3) mol dm(-3) EDTA in the presence of 1.9 mg dm(-3) min(-1) O-3 anti 1.5 mg ml(-1) TiO2. In both cases the EDTA degradation depended on the absorbed radiation dose (UV-light or gamma-rays). on the O-3-concentration, and on the amount of suspended TiO2. By increasing the O-3 concentration also the degradation yield was strongly increased. Analysis of products resulting from photolysis and radiolytic of EDTA in the presence of oxygen, performed by the GC/MS-method are also reported. Economic considerations concerning the pollutant degradation by combined photochemical methods in comparison to ionising radiation under similar conditions have been made, (C) 1999 Elsevier Science Ltd. All rights reserved.