Removal of EDDS and copper from waters by TiO2 photocatalysis under simulated UV-solar conditions

The TiO2 photocatalytic oxidation of the N,N'-ethylenediamine-disuccinic acid and Cu(II) ions photoreduction were investigated in acidic solutions. The experimental results indicated a conversion of 100% for both EEDS and Cu(II) species whereas the mineralization degree was quite small (24%). The influence of several experimental variables, like purging gas, counter ion nature, pH, TiO2 type, photocatalyst load, initial concentration of cupric ions, radiation source (natural or artificial), was investigated. For almost equimolar feed ratios of reactants, EDDS was not totally removed whereas Cu(II) species were completely reduced. An analysis of the data collected indicated a Cu(II)/EDDS molar consumption ratio close to two. The presence of oxygen decreased the photoreduction process of Cu(II) species, whereas the initial concentration of Cu(II) ions and the counter ion (excepted for the chloride ions) did not affect the photocatalytic process. Ecotoxicity tests (Pseudokirchneriella subcapitata and Lemna minor) on treated samples indicated a marked decrease of the ecotoxicity for very prolonged reaction times. (C) 2014 Elsevier B.V. All rights reserved.