Photodegradation of organic pollutants in aqueous solutions caused by Fe(OH)_aq2+ photolysis: Evidence of OH radical formation

Abstract

Photochemistry of Fe(III) hydroxocomplexes has a great interest because of possibility of hydroxyl radical formation at the primary photochemical step. This mechanism is based mainly on the analysis of the final products of photochemical reactions between light-excited Fe(III) complexes and organic compounds. However, realization of an alternative mechanism of photolysis, based on the intermolecular electron transfer from organic molecules located in the second coordination sphere to the light-excited complex could take place. To distinguish these mechanisms, the experiments on the nanosecond laser flash photolysis of Fe(OH)aq2+ in water solutions (pH 3) with organic additives; namely nitrobenzene, N,N-dimethylformamide, and phenol have been performed. And the formation of the organic radicals Ph(•OH)NO2, HCON(CH2•)(CH3), and Ph(OH)2•, was observed, respectively. The rate constants of the formation and decay of the radicals coincide with those found in literature. The results support the formation of the hydroxyl radical upon the photolysis of Fe(OH)aq2+.

Phototransformation of nitrobenzene in the Songhua River: Kinetics and photoproduct analysis

“…It is clear that all of the four photoproducts increased with the irradiation time, with o-NP as the main photodegradation product. The result is in accordance with the results of previous researchers (Pozdnyakov et al 2004;Loebl et al, 1949;Eberhardt and Yoshida, 1973;Fendler and Gasowski, 1968). Eberhardt and Yoshida (1973) have explained the observed isomer distribution using the SCF-MO theory.…”

The Comparison of Photocatalytic Degradation and Decolorization Processes of Dyeing Effluents

“…The photocatalytic process can be carried out under heterogeneous, for example, TiO 2 [11,12] (2) and/or homogeneous conditions, for example, Fe 3+ salts [13,14] as follows:…”

Photolysis of sulfosalicylic acid in aqueous solutions over a wide pH range

“…These acids can form complexes with many transient metals (including Fe(III)) whose photochemistry can contribute substantially to the balance of organic compounds in water [2][3][4][5][6][7][8][9]. It is worth noting that aromatic acids have their own strong absorption bands in the UV range and can be subjected to photochemical transformation under solar radiation in a free noncoordinated state.…”