The effect of use of Ni/Fe and mZVI on phenol removal with the heterogenous fenton process and in-situ generation of H 2 O 2

To degrade phenol with the heterogeneous Fenton-like process and to compare the results, micro-scale zero-valent iron particles (mZVI) and nickel-coated iron bimetallic particles (Ni/Fe) were used. Oxygen was given to the system and converted to H₂O₂ and •OH radicals. The changes in the properties of mZVI and Ni/Fe particles after the reaction were determined by scanning electron microscope (SEM), X-ray energy-dispersive spectrometer (EDX), Brunauer-Emmett-Teller (BET), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) before and after the reaction. For phenol removal with an initial phenol concentration of 25 mg/L, initial pH of 3 and air flow rate of 150 L/h, 3 g/L dosage and 360 min reaction time for mZVI, 1.5 g/L dosage and 240 min for Ni/Fe reaction time were sufficient. Under these conditions, 76% and 98% phenol removal and 39% and 47% total organic carbon (TOC) removal were obtained for mZVI and Ni/Fe, while 189 and 85 mg/L H₂O₂ were produced, respectively. While SO4-2 and PO4-3 caused a slight increase in phenol removal efficiency in the mZVI system, these ionic species and Cl^- and NO3- caused a decrease in the efficiency in the Ni/Fe system. The possible degradation pathway for phenol was suggested by high performance liquid chromatography (HPLC) analysis and hydroquinone, pyrocatechol, maleic acid, benzoquinone and acetic acid were the main intermediates. According to the cost analysis, when using mZVI to treat 1 m³ 25 mg/L phenolic wastewater, the cost was $228.15, which was 1.45 times higher than the cost for Ni/Fe.