Photoredox Reactions at the Surface of Iron(III) (Hydr)Oxides

FeOx-TiO2 Film with Different Microstructures Leading to Femtosecond Transients with Different Properties: Biological Implications under Visible Light

“…Binary-oxides semiconductors due to their optical absorption and semiconductor behavior have been widely used for environmental decontamination purposes like FeOx-TiO 2 . These binary oxides play an important role in pollutant and bacterial abatement involving redox processes 3 4 . The mineral deposits of ilmenite (FeTiO 3 ) leach out Fe/Fe-ions and to a lesser degree Ti important in natural cleaning cycles.…”

“…The mineral deposits of ilmenite (FeTiO 3 ) leach out Fe/Fe-ions and to a lesser degree Ti important in natural cleaning cycles. After interacting with organic matter in water bodies, the Ti and Fe-species/ions re-crystallize again on the original matrix after catalyzing the abatement of pollutants in the ppb to the micromolar range 3 4 .…”

Influence of pH on the Kinetics and Mechanism of Photoreductive Dissolution of Amorphous Iron Oxyhydroxide in the Presence of Natural Organic Matter: Implications to Iron Bioavailability in Surface Waters

“…In order to explain the pH dependence of the LMCT-mediated reduction of AFO-bound Fe­(III), it is important to understand the mechanism of LMCT-induced reduction of Fe­(III) present in AFO. The results of earlier studies of the photoreductive dissolution of various iron oxides under acidic conditions − suggested that the direct reduction of AFO-bound Fe­(III) occurs when surface-located Fe­(III)­L complexes undergo reduction via LMCT, followed by the detachment of Fe­(II) formed from the surface (eqs and ). In this mechanism, the pH dependence of iron oxide reduction was mainly attributed to the influence of pH on the adsorption of ligand onto the surface. …”

“…Iron is a critical micronutrient and plays a pivotal role in shaping the ecosystem structure and function in coastal and open ocean environments. , As such, the processes that convert iron from the refractory to labile (bioavailable) form are critical to the functioning of aquatic environments, particularly those high-nutrient low-carbon regions where iron bioavailability is now recognized to control primary productivity. − The most refractory forms of iron present in natural waters are typically iron­(III) oxides and oxyhydroxides. , Two main processes are recognized to transform the nonlabile iron­(III) oxides and oxyhydroxides to labile form under circumneutral pH conditions, namely, ligand-promoted dissolution as a result of iron binding by organic moieties [including natural organic matter (NOM) and/or microbially produced siderophores] − and/or reductive dissolution on interaction with reduced organic moieties and/or light. − Of these, photoreductive dissolution of iron oxides is believed to be a particularly important pathway for the formation of labile iron species in surface waters. ,,,− …”

“…In addition to controlling Fe availability, the dissolution of iron oxides and oxyhydroxides will also impact the fate of other contaminants (such as heavy metals and/or organic pollutants) that are adsorbed to the iron oxide surface. 30 We would also like to highlight that even though the photoreductive dissolution of iron oxides has been extensively studied in the past, [11][12][13][14][15][16][17][18][19]31 most of the work undertaken has been performed either at low pH (where dissolution rates are high) and/or using crystalline iron oxides (such as lepidocrocite, goethite, or hematite). In natural waters, fresh AFO formed as a result of oxidation of ferrous iron that may enter via fluxes from anoxic bottom sediments or groundwater seepage and/or phototransformation of crystalline iron oxides 16 is expected to play a much more prominent role in controlling Fe bioavailability than the crystalline phases.…”