title: Reductive and oxidative degradation of iopamidol, iodinated X-ray contrast media, by Fe(III)-oxalate under UV and visible light treatment.
abstract: Iopamidol, widely employed as iodinated X-ray contrast media (ICM), is readily degraded in a Fe(III)-oxalate photochemical system under UV (350 nm) and visible light (450 nm) irradiation. The degradation is nicely modeled by pseudo first order kinetics. The rates of hydroxyl radical (OH) production for Fe(III)-oxalate/H2O2/UV (350 nm) and Fe(III)-oxalate/H2O2/visible (450 nm) systems were 1.19 ± 0.12 and 0.30 ± 0.01 μM/min, respectively. The steady-state concentration of hydroxyl radical (OH) for the Fe(III)-oxalate/H2O2/UV (350 nm) conditions was 10.88 ± 1.13 × 10(-14) M and 2.7 ± 0.1 × 10(-14) M for the Fe(III)-oxalate/H2O2/visible (450 nm). The rate of superoxide anion radical (O2(-)) production under Fe(III)-oxalate/H2O2/UV (350 nm) was 0.19 ± 0.02 μM/min with a steady-state concentration of 5.43 ± 0.473 × 10(-10) M. Detailed product studies using liquid chromatography coupled to Q-TOF/MS demonstrate both reduction (multiple dehalogenations) and oxidation (aromatic ring and side chains) contribute to the degradation pathways. The reduction processes appear to be initiated by the carbon dioxide anion radical (CO2(-)) while oxidation processes are consistent with OH initiated reaction pathways. Unlike most advanced oxidation processes the Fe(III)-oxalate/H2O2/photochemical system can initiate to both reductive and oxidative degradation processes. The observed reductive dehalogenation is an attractive remediation strategy for halogenated organic compounds as the process can dramatically reduce the formation of the problematic disinfection by-products often associated with oxidative treatment processes.
authors.affiliation: Department of Chemistry and Biochemistry, Florida International University, Miami, FL 3319, USA.
authors.forename: Cen
authors.initials: C
authors.lastname: Zhao
authors.affiliation: Department of Chemistry and Biochemistry, International Forensic Research Institute (IFRI), Florida International University, Miami, FL 33199, USA.
authors.forename: Luis E
authors.initials: LE
authors.lastname: Arroyo-Mora
authors.affiliation: Department of Chemistry and Biochemistry, International Forensic Research Institute (IFRI), Florida International University, Miami, FL 33199, USA.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: DeCaprio
authors.affiliation: Department of Environmental and Occupational Health, School of Rural Public Health, Texas A&M University, Texas 77843, USA.
authors.forename: Virender K
authors.initials: VK
authors.lastname: Sharma
authors.affiliation: Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, USA.
authors.forename: Dionysios D
authors.initials: DD
authors.lastname: Dionysiou
authors.affiliation: Department of Chemistry and Biochemistry, Florida International University, Miami, FL 3319, USA. Electronic address: osheak@fiu.edu.
authors.forename: Kevin E
authors.initials: KE
authors.lastname: O'Shea
mesh_terms: D002853:Chromatography, Liquid; D003287:Contrast Media / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D017665:Hydroxyl Radical / Q000737:chemistry; D007479:Iopamidol / Q000737:chemistry*; D007700:Kinetics; D008027:Light; D013058:Mass Spectrometry; D019815:Oxalic Acid / Q000737:chemistry*; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D013481:Superoxides / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D003287:Contrast Media; D013481:Superoxides; D017665:Hydroxyl Radical; D019815:Oxalic Acid; D007479:Iopamidol
keywords: Fenton and photo-Fenton; Hydroxyl radical; Superoxide anion radical; X-ray contrast media