Removal of copper, iron and zinc from soil washing effluents containing ethylenediaminedisuccinic acid as chelating agent through sunlight driven nano-Tio2-based photocatalytic processes

The aim of the present study is the application of integrated solar nano-TiO2 based photocatalytic processes for the removal of copper, iron, zinc and (S, S)-ethylenediamine-N, N'-disuccinic acid (EDDS), used as chelating agent, from soil washing effluents produced by the remediation of samples of potentially polluted soils taken in the "Land of Fires" (Italy). Removal efficiencies of 93.5% (copper), 99.6% (iron), 99.4% (zinc), 97.2% (EDDS) and 80.7% (TOC) were reached through sunlight driven photocatalytic treatments carried out in parabolic trough collectors located in Naples (Italy). The removal degrees were achieved for an incident UVA solar energy per unit volume (Qj, n) of 580 kJ L-1, estimated by taking into account both the effective irradiated surface area of the photoreactor (9.79 × 10-2 m2) and the local solar irradiances collected during the experiments. The combined nano-TiO2-photocatalytic processes applied were shown to sufficiently decontaminate the soil washing effluents to permit the recycling in the soil washing treatment or discharging to public sewers. The study suggests that the two-step solar photocatalytic process investigated can be really adopted as a useful solution for the decontamination of soil washing streams from some heavy metals and chelating organic agents.