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Two‐step persulfate and Fenton oxidation of naphthenic acids in water
Author(s) -
Xu Xiyan,
Pliego Gema,
Zazo Juan A,
Liu Shuming,
Casas Jose A,
Rodriguez Juan J
Publication year - 2018
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.5569
Subject(s) - persulfate , mineralization (soil science) , chemistry , naphthenic acid , reagent , aqueous solution , biodegradation , nuclear chemistry , inorganic chemistry , organic chemistry , catalysis , corrosion , nitrogen
BACKGROUD In the current study, two‐step persulfate and Fenton oxidation has been investigated for the mineralization of naphthenic acids at 80 °C and initial pH ≈ 8. This pH evolves during the persulfate oxidation step towards the optimum for Fenton oxidation (≈ 3). The effects of persulfate and H 2 O 2 doses, iron concentration, duration of the persulfate oxidation step and operating temperature have been assessed. RESULTS The combined treatment allowed up to ≈ 80% mineralization of cyclohexanoic acid using fairly low relative amounts of reagents (20 and 30% of the stoichiometric for persulfate and H 2 O 2 , respectively). For mineralization of cyclohexanoic acid, 115 and 87 kJ mol ‐1 were obtained as representative values of the apparent activation energy for the persulfate and Fenton oxidation steps, respectively. The system was also successfully tested with other naphthenic acids, including cyclohexanebutyric acid, 2‐naphthoic acid and 1,2,3,4‐tetrahydro‐2‐naphthoic acid. Treatment of the naphthenic acids tested by this system gave rise to easily biodegradable effluents consisting mainly of short‐chain organic acids. The biodegradability was confirmed by the BOD 5 /COD ratio and respirometric tests. CONCLUSION The results show the potential application of this approach as a promising cost‐effective solution for the treatment of naphthenic acids‐bearing aqueous wastes. This approach has significant advantage compared with the single thermally‐activated persulfate or Fenton oxidation, since it allows a high mineralization at reduced reagent cost upon replacing part of the persulfate by less expensive H 2 O 2 . © 2018 Society of Chemical Industry