Kinetic investigations of quinoline oxidation by ferrate(VI)

ABSTRACT

Quinoline is considered as one of the most toxic and carcinogenic compounds and is commonly found in industrial wastewaters, which require treatment before being discharged. Removal of quinoline by the use of an environmentally friendly oxidant, potassium ferrate(VI) (K₂FeO₄), was assessed by studying the kinetics of the oxidation of quinoline by ferrate(VI) (Fe(VI)) as a function of pH (8.53–10.53) and temperature (21–36°C) in this work. The reaction of quinoline with Fe(VI) was found to be first order in Fe(VI), half order in quinoline, and 1.5 order overall. The observed rate constant at 28°C decreased non-linearly from 0.5334 to 0.2365 M^–0.5 min⁻¹ with an increase in pH from 8.53 to 10.03. Considering the equilibria of Fe(VI) and quinoline, the reaction between quinoline and Fe(VI) contained two parallel reactions under the given pH conditions. The individual rate constants of these two reactions were determined. The results indicate that the protonated species of Fe(VI) reacts more quickly with quinoline than the deprotonated form of Fe(VI). The reaction activation energy Ea was obtained to be 51.44 kJ·mol⁻¹, and it was slightly lower than that of conventional chemical reaction. It reveals that the oxidation of quinoline by Fe(VI) is feasible in the routine water treatment.

KEYWORDS:

• Ferrate(VI)
• quinoline
• oxidation
• kinetics
• water treatment

Acknowledgments

The authors wish to thank Dr Hongru Li and Prof. Qian Gou for useful comments on the paper. This paper benefitted from the three anonymous reviewers.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was funded by Natural Science Foundation Project of CQ CSTC [grant number 2011BB7087] and was supported by a grant from the Fundamental Research Funds for the Central Universities [grant number CQDXWL-2012-039].