Photo-oxidation of iron(II) in water between pH 7.5 and 4.0
Photo-oxidation of [Fe(H2O)6]2+ proceeds at λ < 300 nm with formation of a solvated electron. At pH > 6.5, however, the photochemistry is dominated by the species [Fe(OH)]+(aq), which is photo-oxidised to FeIII even by filtered light of λ > 400 nm, without formation of solvated electrons. The compound γ-FeO(OH) is precipitated throughout the range, even in the presence of 0.56 mol dm–3 NaCl. The effect of pH on the mechanism is discussed, as are the implications for CO2 fixation.