Keen Olya S, Love Nancy G, Aga Diana S, Linden Karl G
Department of Civil, Environmental and Architectural Engineering, University of Colorado, UCB 428, Boulder, CO 80309, USA; Department of Civil and Environmental Engineering, University of North Carolina, 9201 University City Blvd, Charlotte, NC 28223, USA.
Civil and Environmental Engineering Department, University of Michigan, Ann Arbor, MI 48109, USA.
Chemosphere. 2016 Feb;144:989-94. doi: 10.1016/j.chemosphere.2015.09.072. Epub 2015 Oct 2.
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 (14)CO2 which indicated full mineralization of the molecule. The results indicated that AOP formed biodegradable iopromide products. There was no (14)C released from the pre-AOP samples, but up to 20% of all radiolabeled carbon transformed into (14)CO2 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) × 10(9) 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.
碘普罗胺是一种X射线和MRI造影剂，几乎不可生物降解，并且在典型的废水处理过程中具有持久性。本研究确定了碘普罗胺在UV/H2O2高级氧化过程（AOP）中的分子转化是否会产生可生物降解的产物。实验使用在芳环上标记有碳-14的碘普罗胺来追踪碘普罗胺通过UV/H2O2高级氧化及随后的生物降解过程中的降解情况。生物转化试验追踪了放射性标记的(14)CO2的形成，这表明分子完全矿化。结果表明，AOP形成了可生物降解的碘普罗胺产物。在AOP处理前的样品中没有(14)C释放，但在碘普罗胺经过高级氧化后进行42天生物降解的过程中，高达20%的所有放射性标记碳转化为(14)CO2（相比之下，AOP处理后灭活对照中的转化为10%）。此外，使用低压（LP）和中压（MP）汞灯测定碘普罗胺的光解量子产率分别为0.069±0.005和0.080±0.007。两种紫外光源的量子产率差异在95%置信区间内无统计学意义（p = 0.08），这表明使用LP或MP紫外光源处理碘普罗胺具有等效性。测得碘普罗胺与羟基自由基之间的反应速率为(2.5±0.2)×10(9) M(-1) s(-1)。这些结果表明，直接光解是UV/H2O2 AOP处理碘普罗胺的主要降解途径。其他碘化造影剂在暴露于紫外线或UV/H2O2后也可能变得可生物降解。
