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Electro-oxidation by graphite anode for naphthenic acids degradation, biodegradability enhancement and toxicity reduction.

Authors
  • Abdalrhman, Abdallatif Satti1
  • Zhang, Yanyan2
  • Gamal El-Din, Mohamed3
  • 1 Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada. , (Canada)
  • 2 Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada; Department of Civil Engineering, New Mexico State University, Las Cruces, NM 88003, United States. , (Canada)
  • 3 Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada. Electronic address: [email protected] , (Canada)
Type
Published Article
Journal
The Science of the total environment
Publication Date
Jun 25, 2019
Volume
671
Pages
270–279
Identifiers
DOI: 10.1016/j.scitotenv.2019.03.262
PMID: 30928756
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Electro-oxidation (EO) by using graphite anode and at relatively low current densities was successfully applied for the degradation of commercial naphthenic acids (NAs) mixture in water samples. At current densities of 0.5, 2.5, and 5 mA/cm2, acid extractable fraction (AEF) was removed by 42.2%, 57.0% and 67.9%, respectively, while classical NAs were degraded by 76.9%, 77.6% and 82.4%, respectively. EO reactivity towards NAs increased with increasing the carbon number (n) and was higher for cyclic NAs compared to the acyclic component. Oxidized NAs containing O3 and O4 were also degraded effectively during EO. The biodegradability of organics in the NA mixture was clearly improved by 1.7, 2.5 and 2.7 folds when the samples were pre-treated with EO at current densities of 0.5, 2.5, and 5 mA/cm2, respectively. The aromatic fraction in the commercial NA mixture consisted mainly of single-ring aromatics and was degraded effectively by EO. Biodegradation alone was able to reduce the toxicity of the commercial NA mixture towards Vibrio fischeri; however, the combination of EO with biodegradation resulted in a complete removal of the toxicity, showing a synergistic effect of combining these two processes. Coupling EO with aerobic biodegradation can result in an effective and energy-efficient treatment option for NA-bearing waters such as oil sands process water (OSPW) and refinery effluents. Copyright © 2019 Elsevier B.V. All rights reserved.

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