Promoted oxidation of diclofenac with ferrate (Fe(VI)): Role of ABTS as the electron shuttle

Huiyu Dong; Zhimin Qiang; Junfeng Lian; Jiuhui Qu

doi:10.1016/j.jhazmat.2017.04.056

Promoted oxidation of diclofenac with ferrate (Fe(VI)): Role of ABTS as the electron shuttle

J Hazard Mater. 2017 Aug 15:336:65-70. doi: 10.1016/j.jhazmat.2017.04.056. Epub 2017 Apr 25.

Authors

Huiyu Dong¹, Zhimin Qiang², Junfeng Lian³, Jiuhui Qu¹

Affiliations

¹ Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences,18 Shuang-qing Road, Beijing 100085, China.
² Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences,18 Shuang-qing Road, Beijing 100085, China. Electronic address: qiangz@rcees.ac.cn.
³ School of Architectural, Surveying and Mapping Engineering, Jiangxi University of Science and Technology,86 Hong-qi Road, Ganzhou 341000, China.

PMID: 28472710
DOI: 10.1016/j.jhazmat.2017.04.056

Abstract

Reaction of Fe(VI) with 2,2'-azino-bis-(3-ethylbenzothiazoline -6-sulfonate) (ABTS) is widely adopted to determine aqueous ferrate (Fe(VI)) concentration based on ABTS⁺ formation. Interestingly, this study found that the addition of ABTS could accelerate the oxidation of diclofenac (DCF) by Fe(VI) significantly. Observed first-order rate constant of DCF in the presence of 30μM ABTS was found to be 36.2 folds of that without ABTS, with values of 3.08 and 0.085min^-1, respectively. It was partly attributed to the formation of ABTS⁺. The apparent second-order rate constant (k_app) for the oxidation of ABTS by Fe(VI) at pH7.0 was determined to be 1.1×10⁶M^-1s^-1, which was 3-5 orders of magnitude higher than those for the reactions of ABTS⁺ with DCF (k_app,ABTS⁺_-DCF=2.8×10³M^-1s^-1) and Fe(VI) with DCF (k_{app,Fe(VI)-DCF}=17.7M^-1s^-1). Both the k_{app,Fe(VI)-ABTS} and k_{app,Fe(VI)-DCF} decreased obviously with increasing pH, while the k_app,ABTS⁺_-DCF exhibited little pH dependency. By acting as the electron shuttle, ABTS could enhance the removal efficiency of DCF over wide pH and natural organic matter concentration ranges. This study provides new insights to reconsider the role of organic matter during Fe(VI) oxidation and highlights the potential for increasing the reactivity of Fe(VI).

Keywords: ABTS; Diclofenac; Electron shuttle; Ferrate.