The pH dependence of the oxidation state and coordination structure of Fe in mediator-assisted electrochemically reduced nontronite

Structural iron (Fe) in clay minerals is an important redox-active component, yet its redox behavior remains incompletely understood. This study investigates the pH dependence of the oxidation state and local coordination environment of structural Fe in nontronite. By combining mediator-assisted electrochemical analysis with 57 Fe Mössbauer spectroscopy, this study demonstrated that (i) structural Fe reduction was promoted at lower pH and (ii) the relative contributions of distinct Fe(II) coordination environments varied with pH.