Design of a high efficiency electro-Fenton system with Fe0@Fe3O4/ACF composite cathode for lignin wastewater treatment

Lignin is a complex phenylpropanoid biopolymer conferring mechanical strength to plant cell walls. Biorefineries, along with pulp and paper industry, generate large quantities of lignin. Lignin valorization is an essential process for an advanced, sustainable, and economical biomass-based industry. In this study, for the first time nanostructured Fe0@Fe3O4 was loaded on active carbon fiber (ACF) as an oxygen diffusion cathode to be used in a heterogeneous electro-Fenton (E-Fenton) oxidation system. This novel Fe0@Fe3O4/ACF composite cathode was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), BET surface area analysis, transmission electron microscopy (TEM). On the degradation of lignin in water, this heterogeneous E-Fenton system with the Fe0@Fe3O4/ACF cathode showed much higher activity than other E-Fenton systems with commercial zero valent iron powders (Fe0) and Iron ions (Fe3+) under same condition. On the basis of experimental results, we proposed a possible pathway of lignin degradation in this heterogeneous Fe0@Fe3O4/ACF E-Fenton process. This heterogeneous E-Fenton system is very promising to remove organic pollutants in water.