Degradation of organic pollutants by a Co₃O ₄-graphite composite electrode in an electro-Fenton-like system

A novel composite electrode was constructed by pressing together Co₃O₄ and graphite and it was used as the cathode in an electro-Fenton-like (EFL) system. The poor electron transport characteristic of Co₃O₄ was overcome by incorporating graphite. In situ electro-catalytic generation of hydroxyl radicals (·OH) occurred at high current efficiencies from pH 2–10, extending the traditional Fenton reaction pH range. Cyclic voltammetry and AC impedance spectrometry were used to characterize the composite electrode. The ability of the EFL system to degrade organic compounds was investigated using sulforhodamine B (SRB) and 2,4-dichlorophenol (2,4-DCP) as probes. Decoloration of SRB (1.0×10⁻⁵ mol/L) was complete (100%) in 150 min and SRB was effectively degraded from pH 2–10. The decomposition of SRB was studied using Fourier transform infrared spectroscopy (FT-IR) and total organic carbon (TOC) analysis and results indicated that the final degradation products were carbon dioxide, carboxylic acids and amines. The EFL system also decomposed 2,4-DCP and the degradation was 98.6% in 240 min. Electro-catalytic degradation of SRB occurs by a ·OH mechanism. After 5 times reused, the degradation rate of SRB did not significantly slow down. The electrode shows excellent potential for use in advanced oxidation processes (AOPs) used to treat persistent organic pollutants (POPs) in wastewater.