Alternating polarization of Fe modified carbon fiber materials. towards the development of single-electrode electro-Fenton batch reactors

Carbon felt electrodes (CF) were modified with different amounts of Fe0 (C|Fe) using a potentiostatic electro-deposition technique. The materials were characterized in terms of morphology, electrical properties and chemical composition using Scanning Electron Microscopy, Cyclic Voltammetry and Chemical Titration experiments. The Fe modified CF substrates under study were then polarized in an alternating fashion between two potential values to promote the electro-Fenton production of •OH radicals. While polarization at the most positive potential value (-0.7 V vs Ag|AgCl) resulted in the electrochemically produced Fenton mixture (H2O2 and Fe(II) from O2 reduction and Fe0 oxidation, respectively), polarization at the most negative potential value (-1.1 V vs Ag|AgCl) favored the deposition of Fe° from Fe cation species in solution. Experiments using two opposite charged dyes and different frequencies for the alternating polarization stimulus (16 mHz-166 Hz) in non-stirred solutions, allowed to detect not only the presence of the electrogenerated Fenton mixture in the vicinity of the electrode-solution interphase, but also the effect of the alternating polarization frequency on the amount of Fe(II) available for •OH radical production. These results demonstrate that under the proper polarization conditions, the C|Fe composite materials are characterized by anodic and cathodic zones that can be simultaneously used to produce the two components of the Fenton mixture in the substrate-solution interphase. It is suggested that this type of materials could constitute the basis of single electrode electro-Fenton (EF) batch reactors. [Display omitted]