Electrochemical Evidences for Promoted Interfacial Reactions: The Role of Fe(II) Adsorbed onto [gamma]-Al^sub 2^O^sub 3^ and TiO^sub 2^ in Reductive Transformation of 2-Nitrophenol

This study was aimed at elucidating the role of adsorbed Fe(II) on minerals in the reductive transformation of 2-nitrophenol (2-NP) by using electrochemical methods. The studies of Fe(II) adsorption and 2-NP reduction kinetics showed that the identity of minerals such as ...-... and ... and the solution pH were crucial factors to determine the Fe(II) adsorption behavior and to influence the rate constant (k) of 2-NP reduction. Furthermore, two electrochemical methods, cyclic voltammetry (CV) and electrochemical impedance spectrometry (EIS), were applied to characterize the Fe(II) reactivity with both the mineral-coated and mineral-free electrodes. The electrochemical evidence confirmed that the peak oxidation potential (E...) of complex Fe(II) can be significantly affected by the solution pH; the enhanced reductive transformation of 2-NP can be related to the reduced E... of surface-complex Fe(II) and the reduced charge transfer resistance (R...) of the Fe(III)/Fe(II) couple. All these relationships were studied quantitatively. At pH 6.7, the measured E... and R... decreased in the order .../GC < ...-.../GC < GC (E..., 0.140 < 0.190 < 0.242 V; R..., 0.30 < 0.41 < 0.78 kW), while the 2-NP reduction on different minerals were in the order ... > ...-... > nonmineral (k x 10..., 7.91 > 0.64 > 0.077 min...). (ProQuest: ... denotes formulae/symbols omitted.)