Redox-active minerals
are ubiquitous in the environment and are
involved in numerous electron transfer reactions that significantly
affect biogeochemical processes and cycles as well as pollutant dynamics.
As a consequence, research in different scientific disciplines is
devoted to elucidating the redox properties and reactivities of minerals.
This review focuses on the characterization of mineral redox properties
using electrochemical approaches from an applied (bio)geochemical
and environmental analytical chemistry perspective. Establishing redox
equilibria between the minerals and working electrodes is a major
challenge in electrochemical measurements, which we discuss in an
overview of traditional electrochemical techniques. These issues can
be overcome with mediated electrochemical analyses in which dissolved
redox mediators are used to increase the rate of electron transfer
and to facilitate redox equilibration between working electrodes and
minerals in both amperometric and potentiometric measurements. Using
experimental data on an iron-bearing clay mineral, we illustrate how
mediated electrochemical analyses can be employed to derive important
thermodynamic and kinetic data on electron transfer to and from structural
iron. We summarize anticipated methodological advancements that will
further contribute to advance an improved understanding of electron
transfer to and from minerals in environmentally relevant redox processes