Simultaneous oxidation of EDTA and reduction of metal ions in mixed Cu(II)/Fe(III)–EDTA system by TiO2 photocatalysis

Both the photooxidation of EDTA and the photoreduction of metal ions in metal–EDTA systems were investigated. EDTA oxidation by TiO2 photocatalysis occurred sequentially as Cu(II)–EDTA > Cu(II)/Fe(III)–EDTA > Fe(III)–EDTA. For Cu(II)–EDTA, EDTA was completely decomposed after only 60 min of irradiation. The rate of EDTA decomposition was directly correlated with the initial Cu(II) concentration in the case of a mixed Cu(II)/Fe(III)–EDTA system. The metal ions in a single metal–EDTA complex were removed following significant decomposition of EDTA. For a mixed Cu(II)/Fe(III)–EDTA system, however, no copper was removed whereas almost all of the iron was removed. The iron and copper species deposited on the TiO2 surface were identified via EPR and XPS as mixed FeO/Fe3O4 and Cu0/Cu2O, respectively.