title: Reaction of gadolinium chelates with ozone and hydroxyl radicals.
abstract: Gadolinium chelates are used in increasing amounts as contrast agents in magnetic resonance imaging, and their fate in wastewater treatment has recently become the focus of research. Oxidative processes, in particular the application of ozone, are currently discussed or even implemented for advanced wastewater treatment. However, reactions of the gadolinium chelates with ozone are not yet characterized. In this study, therefore, rate constants with ozone were determined for the three commonly used chelates Gd-DTPA, Gd-DTPA-BMA, and Gd-BT-DO3A, which were found to be 4.8 ± 0.88, 46 ± 2.5, and 24 ± 1.5 M(-1) s(-1), respectively. These low rate constants indicate that a direct reaction with ozone in wastewater is negligible. However, application of ozone in wastewater leads to substantial yields of (•)OH. Different methods have been applied and compared for determination of k((•)OH+Gd chelate). From rate constants determined by pulse radiolysis experiments (k((•)OH+Gd-DTPA) = 2.6 ± 0.2 × 10(9) M(-1) s(-1), k((•)OH+Gd-DTPA-BMA) = 1.9 ± 0.7 × 10(9) M(-1) s(-1), k((•)OH+Gd-BT-DO3A) = 4.3 ± 0.2 × 10(9) M(-1) s(-1)), it is concluded that a reaction in wastewater via (•)OH radicals is feasible. Toxicity has been tested for educt and product mixtures of both reactions. Cytotoxicity (MTT test) and genotoxicity (micronuclei assay) were not detectable.
authors.affiliation: IWW Water Centre , Moritzstraße 26, 45476 Mülheim an der Ruhr, Germany.
authors.forename: Maike
authors.initials: M
authors.lastname: Cyris
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Knolle
authors.forename: Jessica
authors.initials: J
authors.lastname: Richard
authors.forename: Elke
authors.initials: E
authors.lastname: Dopp
authors.forename: Clemens
authors.initials: C
authors.lastname: von Sonntag
authors.forename: Torsten C
authors.initials: TC
authors.lastname: Schmidt
mesh_terms: D000818:Animals; D016466:CHO Cells; D002614:Chelating Agents / Q000737:chemistry* / Q000633:toxicity; D003287:Contrast Media / Q000737:chemistry*; D003412:Cricetulus; D004492:Edetic Acid / Q000737:chemistry / Q000633:toxicity; D005682:Gadolinium / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry; D008279:Magnetic Resonance Imaging; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry / Q000633:toxicity; D004369:Pentetic Acid / Q000737:chemistry / Q000633:toxicity; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000633:toxicity
chemical_list: D002614:Chelating Agents; D003287:Contrast Media; D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical; D010126:Ozone; D004369:Pentetic Acid; D004492:Edetic Acid; D005682:Gadolinium