Effects of Surfactants on the Degradation of Diclofenac by Manganese Oxide

Wen-Hui Kuan, Yu-Jung Liu and Ching-Yao Hu
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Wen-Hui Kuan: Department of Environmental and Safety Engineering, Ming Chi University of Technology, Taishan, New Taipei City 24301, Taiwan
Yu-Jung Liu: Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Rd., Taipei 10617, Taiwan
Ching-Yao Hu: School of Public Health, Taipei Medical University, 250 Wu-Xing Street, Taipei 11031, Taiwan

IJERPH, 2020, vol. 17, issue 12, 1-12

Abstract: Amine-containing pharmaceuticals are the most often detected pharmaceuticals in wastewater and ambient aquatic environments. They can usually be degraded by manganese oxide (MnO 2 ), which is a common natural oxidant in soils. Surfactants often coexist with pharmaceuticals in wastewater. Some amine-containing pharmaceuticals, such as diclofenac (DIC), are acidic and are thus ionic compounds in neutral conditions. These compounds, therefore, have similar properties to surfactants. Surfactants, thus, may influence the adsorption and degradation processes of DIC by MnO 2 . The effect of the type of surfactant on the degradation of DIC by MnO 2 was investigated in this study with the addition of two common biodegradable surfactants (cetyltrimethyl-ammonium bromide (CTAB) and sodium dodecylsulfate (SDS)). The results indicated that the cationic surfactant (CTAB) significantly increased the degradation rate in neutral and alkaline conditions. On the other hand, the anionic surfactant (SDS) slightly increased the DIC removal rate in an acidic condition but significantly decreased the removal in neutral and alkaline conditions. Coexisting cationic surfactants not only influenced the kinetics but also altered the transformation mechanism of DIC by MnO 2 . Decarboxylation is the main transformation mechanism of DIC in the presence of CTAB, while both decarboxylation and hydroxylation are the main transformation mechanisms in the absence of CTAB.

Keywords: manganese dioxide; diclofenac; anionic surfactant; cationic surfactant (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2020
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