Liquid-Gas Interface of Iron Aqueous Solutions and FentonReagents

Fenton chemistry, involving the reaction between Fe2+and hydrogen peroxide,is well-known due to its applications in the mineralization of extremely stable molecules.Different mechanisms, influenced by the reaction conditions and the solvation sphere of ironions, influence the fate of such reactions. Despite the huge amount of effort spent investigatingsuch processes, a complete understanding is still lacking. This work combines photoelectronspectroscopy and theoretical calculations to investigate the solvation and reactivity of Fe2+andFe3+ions in aqueous solutions. The reaction with hydrogen peroxide, both in homogeneousFenton reagents and at the liquid-vapor interface, illustrates that both ions are homogeneouslydistributed in solutions and exhibit an asymmetric octahedral coordination to water in the caseof Fe2+. No indications of differences in the reaction mechanism between the liquid-vaporinterface and the bulk of the solutions have been found, suggesting that Fe3+and hydroxylradicals are the only intermediates.