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Kinetics and model development of iohexol degradation during UV/H 2 O 2 and UV/S 2 O 8 2- oxidation.
- Source :
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Chemosphere [Chemosphere] 2019 Aug; Vol. 229, pp. 602-610. Date of Electronic Publication: 2019 May 03. - Publication Year :
- 2019
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Abstract
- The degradation rates and kinetics of one commonly used iodinated contrast medium, iohexol, were investigated and compared during ultraviolet (UV) photolysis, UV/H <subscript>2</subscript> O <subscript>2</subscript> and UV/S <subscript>2</subscript> O <subscript>8</subscript> <superscript>2-</superscript> advanced oxidation processes (AOPs). Results indicate that the iohexol degradation rate increased in the order of UV/H <subscript>2</subscript> O <subscript>2</subscript> < UV irradiation < UV/S <subscript>2</subscript> O <subscript>8</subscript> <superscript>2-</superscript> and followed pseudo-first-order kinetics. Increasing persulfate concentration significantly increased iohexol degradation rate, whereas increasing H <subscript>2</subscript> O <subscript>2</subscript> concentration caused reverse effect. Radical scavenging test results show that UV photolysis, OH and radicals all contributed to iohexol degradation during UV/S <subscript>2</subscript> O <subscript>8</subscript> <superscript>2-</superscript> , but OH was the main contributor during UV/H <subscript>2</subscript> O <subscript>2</subscript> and was consumed by excess H <subscript>2</subscript> O <subscript>2</subscript> . The kinetic models of iohexol degradation by both AOPs were developed, and the reaction rate constants with OH and were calculated as 5.73 (±0.02) × 10 <superscript>8</superscript> and 3.91 (±0.01) × 10 <superscript>10</superscript> M <superscript>-1</superscript> s <superscript>-1</superscript> , respectively. Iohexol degradation rate remained stable at pH 5-9 during UV irradiation and UV/H <subscript>2</subscript> O <subscript>2</subscript> , but gradually decreased at pH 5-7 and remained stable at pH 7-9 during UV/S <subscript>2</subscript> O <subscript>8</subscript> <superscript>2-</superscript> . The presence of anions displayed inhibitory effects on iohexol degradation during UV/S <subscript>2</subscript> O <subscript>8</subscript> <superscript>2-</superscript> in the order of Cl <superscript>-</superscript> >HCO <subscript>3</subscript> <superscript>-</superscript> ≫ SO <subscript>4</subscript> <superscript>2-</superscript> . UV/S <subscript>2</subscript> O <subscript>8</subscript> <superscript>2-</superscript> AOP exhibited high degradation efficiency and stability on the basis of UV irradiation, which can be applied as a promising degradation method for iohexol. UV/S <subscript>2</subscript> O <subscript>8</subscript> <superscript>2-</superscript> AOP can effectively mineralize iohexol to CO <subscript>2</subscript> but promoted the generation of toxic iodoform (CHI <subscript>3</subscript> ), and the subsequent chlorination had the potential to reduce the content of disinfection by-products; therefore, further evaluation of possible environmental hazards is warranted.<br /> (Copyright © 2019 Elsevier Ltd. All rights reserved.)
Details
- Language :
- English
- ISSN :
- 1879-1298
- Volume :
- 229
- Database :
- MEDLINE
- Journal :
- Chemosphere
- Publication Type :
- Academic Journal
- Accession number :
- 31100631
- Full Text :
- https://doi.org/10.1016/j.chemosphere.2019.05.012