title: Degradation of iopromide by combined UV irradiation and peroxydisulfate.
abstract: The aqueous degradation of iopromide, an iodinated X-ray contrast media (ICM) compound, by the combination of UV(254) irradiation and potassium peroxydisulfate (K(2)S(2)O(8)) has been studied in laboratory scale experiments. The influence of various parameters on the performance of the treatment process has been considered, namely the UV irradiation light intensity, the initial concentrations of iopromide and peroxydisulfate, and the initial solution pH. Iopromide degradation increased with UV light intensity and peroxydisulfate concentration, but decreased with initial pH. Under specific conditions complete removal of iopromide was achieved within 30 min, and near-complete mineralisation (loss of solution TOC) within 80 min. Degradation was believed to be caused by a combination of direct photolysis, sulphate radical attack, and, to a minor degree, direct oxidation by peroxydisulfate. Approximate values for the reaction rate constants have been determined and found to be equal to 1-2x10(4) M(-1) s(-1) for sulfate radicals, and 1-2 M(-2) s(-1) for S(2)O(8)(2-). Overall compound degradation was observed to follow first-order kinetics where the rate constant decreased with initial solution pH. During the reaction, the solution pH decreased as a consequence of sulfate radical scavenging.
authors.affiliation: Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
authors.forename: Ting W
authors.initials: TW
authors.lastname: Chan
authors.forename: Nigel J D
authors.initials: NJ
authors.lastname: Graham
authors.forename: Wei
authors.initials: W
authors.lastname: Chu
mesh_terms: D003287:Contrast Media; D016166:Free Radical Scavengers; D006863:Hydrogen-Ion Concentration; D007472:Iohexol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects; D007700:Kinetics; D017744:Medical Waste Disposal / Q000379:methods*; D016877:Oxidants / Q000737:chemistry; D010545:Peroxides / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D003287:Contrast Media; D016166:Free Radical Scavengers; D017744:Medical Waste Disposal; D016877:Oxidants; D010545:Peroxides; D013431:Sulfates; D007472:Iohexol; C038192:iopromide