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Impact of humic acid on the photoreductive degradation of perfluorooctane sulfonate (PFOS) by UV/Iodide process

Sun, Zhuyu and Zhang, Chaojie and Chen, Pei and Zhou, Qi and Hoffmann, Michael R. (2017) Impact of humic acid on the photoreductive degradation of perfluorooctane sulfonate (PFOS) by UV/Iodide process. Water Research, 127 . pp. 50-58. ISSN 0043-1354. https://resolver.caltech.edu/CaltechAUTHORS:20171018-084528774

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Abstract

Iodide photolysis under UV illumination affords an effective method to produce hydrated electrons (e_(aq)–) in aqueous solution. Therefore, UV/Iodide photolysis can be utilized for the reductive degradation of many recalcitrant pollutants. However, the effect of naturally occurring organic matter (NOM) such as humic and fulvic acids (HA/FA), which may impact the efficiency of UV/Iodide photoreduction, is poorly understood. In this study, the UV photoreductive degradation of perfluorooctane sulfonate (PFOS) in the presence of I− and HA is studied. PFOS undergoes a relatively slow direct photoreduction in pure water, a moderate level of degradation via UV/Iodide, but a rapid degradation via UV/Iodide/HA photolysis. After 1.5 h of photolysis, 86.0% of the initial [PFOS] was degraded in the presence of both I− and HA with a corresponding defluorination ratio of 55.6%, whereas only 51.7% of PFOS was degraded with a defluorination ratio of 4.4% via UV/Iodide illumination in the absence of HA. The relative enhancement in the presence of HA in the photodegradation of PFOS can be attributed to several factors: a) HA enhances the effective generation of e_(aq)– due to the reduction of I2, HOI, IO_3− and I_3− back to I−; b) certain functional groups of HA (i.e., quinones) enhance the electron transfer efficiency as electron shuttles; c) a weakly-bonded association of I− and PFOS with HA increases the reaction probability; and d) absorption of UV photons by HA itself produces e_(aq)–. The degradation and defluorination efficiency of PFOS by UV/Iodide/HA process is dependent on pH and HA concentration. As pH increases from 7.0 to 10.0, the enhancement effect of HA improves significantly. The optimal HA concentration for the degradation of 0.03 mM PFOS is 1.0 mg L^(−1).


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.watres.2017.10.010DOIArticle
http://www.sciencedirect.com/science/article/pii/S0043135417308394?via%3DihubPublisherArticle
ORCID:
AuthorORCID
Zhang, Chaojie0000-0003-3108-8271
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 2017 Elsevier Ltd. Received 21 June 2017, Revised 3 October 2017, Accepted 5 October 2017, Available online 6 October 2017.
Subject Keywords:Perfluorooctane sulfonate (PFOS); Reductive defluorination; Hydrated electrons; UV/Iodide; Enhancement; Humic acid
Record Number:CaltechAUTHORS:20171018-084528774
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20171018-084528774
Official Citation:Zhuyu Sun, Chaojie Zhang, Pei Chen, Qi Zhou, Michael R. Hoffmann, Impact of humic acid on the photoreductive degradation of perfluorooctane sulfonate (PFOS) by UV/Iodide process, In Water Research, Volume 127, 2017, Pages 50-58, ISSN 0043-1354, https://doi.org/10.1016/j.watres.2017.10.010. (http://www.sciencedirect.com/science/article/pii/S0043135417308394)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82447
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:18 Oct 2017 23:26
Last Modified:09 Mar 2020 13:19

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