Redox reactivity of iron nano-minerals for natural production of radical species

Heterogeneous Fenton-like reactions using airborne O2 as sole oxidant are gaining a fast-growing interest to eliminate organic contaminant in soils and groundwaters. At BM23 beamline, we will quantify the redox states of iron using Fe K-edge XANES spectroscopy in reactive Fe(II)-nanominerals previously subjected to reduction/oxidation experiments mimicking redox fluctuations at natural redox boundaries (water-table in soils and floodplains). We will also determine the evolution of the local structure around iron after redox cycling steps, using Fe K-edge EXAFS spectroscopy. Redox and structural information gained on the reactive Fe mineral substrates will be directly compared with the amount of radical species measured by EPR-spin trapping (see Figure) and to degradation rates of priority pollutants (HAP, pesticides) measured by ECOSYS/INRAE in similar redox cycling experiments. This study is supported by ANR project DEPOLECO (2022–2025) and is a main part of two PhDs.