Preparation of Fenton-like coating catalyst on Q235 carbon steel by plasma electrolytic oxidation in silicate electrolyte

Plasma electrolytic oxidation (PEO) on Q235 carbon steel has been applied in the silicate electrolyte. The ceramic coatings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and scanning electron microscopy (SEM). The effects of ceramic coating preparation conditions on the surface morphology, composition, thickness and phenol degradation by Fenton-like reaction were investigated. The results indicated that the ceramic coating with porous structure was comprised of amorphous phases SiO₂ and Fe₃O₄. The average pore diameter and thickness of the ceramic coating increased slightly with the increase of reaction time and current density of PEO. In addition, the ceramic coatings were mainly composed of Si, Fe, Na, P, and O according to the EDS analysis. The phenol degradation experiments indicated that the removal efficiency was reduced with the increase of reaction time, but increased at 30 min. On the contrary, the degradation rate was first enlarged, and then decreased with the increase of current density. The 96% removal efficiency of phenol was achieved after 120 min degradation at the condition of 35 mg/L phenol, 6.0 mmol/L H₂O₂, pH 4.0 and T = 303 K while 6 cm² ceramic coating was used as Fenton-like catalyst which was prepared under 12 A/cm² and 10 min. The total leached Fe was below the EU directives (< 2 mg/L). The leached Fe originated not only from the substrate, but also from ceramic coating. The unique advantages over the nanoparticle and excellent stability endowed it with desirable and promising application in the wastewater treatment.