Biodegradability of iopromide products after UV/H2O2 advanced oxidation

• Published in: Chemosphere (Oxford) Vol. 144; pp. 989 - 994
• Main Authors: Keen, Olya S., Love, Nancy G., Aga, Diana S., Linden, Karl G.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2016
• Subjects: Advanced oxidation; Biodegradability; Biodegradation; Biotransformation; Carbon; Degradation; Exposure; Hydrogen Peroxide - chemistry; Iohexol - analogs & derivatives; Iohexol - chemistry; Iohexol - isolation & purification; Iohexol - metabolism; Iopromide; Oxidation; Oxidation-Reduction; Photolysis; Quantum yield; Transformation products; Transformations; Ultraviolet Rays; Waste Water - chemistry; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - isolation & purification; Water Pollutants, Chemical - metabolism; Biodegradation; Transformation products; Iopromide; Advanced oxidation; Quantum yield
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2015.09.072

Iopromide is an X-ray and MRI contrast agent that is virtually non-biodegradable and persistent through typical wastewater treatment processes. This study determined whether molecular transformation of iopromide in a UV/H2O2 advanced oxidation process (AOP) can result in biodegradable products. The experiments used iopromide labeled with carbon-14 on the aromatic ring to trace degradation of iopromide through UV/H2O2 advanced oxidation and subsequent biodegradation. The biotransformation assay tracked the formation of radiolabeled 14CO2 which indicated full mineralization of the molecule. The results indicated that AOP formed biodegradable iopromide products. There was no 14C released from the pre-AOP samples, but up to 20% of all radiolabeled carbon transformed into 14CO2 over the course of 42 days of biodegradation after iopromide was exposed to advanced oxidation (compared to 10% transformation in inactivated post-AOP controls). In addition, the quantum yield of photolysis of iopromide was determined using low pressure (LP) and medium pressure (MP) mercury lamps as 0.069 ± 0.005 and 0.080 ± 0.007 respectively. The difference in the quantum yields for the two UV sources was not statistically significant at the 95% confidence interval (p = 0.08), which indicates the equivalency of using LP or MP UV sources for iopromide treatment. The reaction rate between iopromide and hydroxyl radicals was measured to be (2.5 ± 0.2) × 109 M−1 s−1. These results indicate that direct photolysis is a dominant degradation pathway in UV/H2O2 AOP treatment of iopromide. Other iodinated contrast media may also become biodegradable after exposure to UV or UV/H2O2. •Iopromide formed biodegradable products after UV/H2O2 treatment.•No appreciable mineralization (<1%) occurred during UV/H2O2 treatment.•Some of the products were biodegradable to full mineralization.•Most of the iopromide transformation in UV/H2O2 is from direct photolysis.