The application of exfoliated graphite electrode in the electrochemical degradation of p-nitrophenol in water

ABSTRACT

We report the application of exfoliated graphite (EG) as an electrode material in the electrochemical degradation of p-nitrophenol in water. Bulk electrolysis (degradation) of p-nitrophenol was carried out at a potential of 2.0 V (vs. Ag/AgCl) in the presence of 0.1 M Na₂SO₄ supporting electrolyte, while UV-Vis spectrophotometry was used to monitor the degradation efficiency. An initial p-nitrophenol load concentration of 0.2 mM for 3 h electrolysis time was studied under the optimized conditions of pH 7, and 10 mAcm⁻² current density. The electro-degradation reaction displayed a pseudo-first-order kinetic behavior with a rate constant (k_r) of 11×10⁻³ min⁻¹. The removal efficiency was found to be 91.5%. Chromatography coupled with time of flight mass spectrometry revealed p-benzoquinone as a major intermediate product. These results demonstrate the potential and viability of electrochemical technology as an alternative approach to water treatment using a low cost graphite electrode.

KEYWORDS:

• Degradation
• exfoliated graphite electrode
• electrochemical oxidation
• p-nitrophenol
• removal efficiency
• water

Acknowledgments

The authors would like to thank Mr Hlengilizwe Nyoni (Department of Applied Chemistry, University of Johannesburg) for the GCxGC-TOFMS analysis.

Funding

The authors acknowledge the financial support of Nanotechnology Innovation Centre, Mintek, South Africa; the Center for Nanomaterials Science Research, Department of Applied Chemistry, University of Johannesburg; the Faculty of Science, University of Johannesburg; and the National Research Foundation, South Africa.