Insight into the Fe-Ni/biochar composite supported three-dimensional electro-Fenton removal of electronic industry wastewater

Abstract

For the efficient removal of the bio-refractory organic pollutants in the electronic industry wastewater, the Ni-Fe (oxides) modified three-dimension (3D) particle electrode was applied in electro-Fenton system (3D/EF), where iron ions were released from anode and deposited onto algal biochar (ABC) to prepare composite catalyst during reaction process. Firstly, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis were applied to confirm successful fabrication of the 3D particle electrode materials. Secondly, COD removal efficiency could reach about 80%, which was about 20% higher than that in 2D/EF system, under the optimized conditions as 2.0 g/L of Ni-ABC particle electrodes, initial pH of 3, 100 mL/min of aeration intensity and 20 mA/cm² of applied current density. Thirdly, characterized using three-dimensional fluorescence spectroscopy and GC-MS analysis, it seemed that most of the macromolecular substances could be degraded, whereas mono-2-ethylhexyl phthalate (MEHP) was identified as the most abundant and representative compound. Finally, possible degradation pathway of MEHP in 3D/EF system was proposed including dealkylation, cleavage of C-O bond, and demethylation. Therefore, this study provides a new strategy in designing EF system employing bimetal doped biochar composite for an efficient elimination of organic pollutants within electronic industry wastewater.

Keywords: Degradative pathway; Electronic industry wastewater; MEHP; Ni–Fe/biochar composite; Particle electrode; Three-dimensional electro-Fenton.