Simulated solar photocatalytic processes for the simultaneous removal of EDDS, Cu(II), Fe(III) and Zn(II) in synthetic and real contaminated soil washing solutions

Metal contamination of natural soil is a global problem. In many cases the contamination is due to anthropogenic activities, and, sometimes, it comes from illegal waste disposal due to uncontrolled industrial development. One of the ways of solving metal soil contamination is by soil washing using a chelating biodegradable agent (EDDS). However, the resulting liquid wastes that contain the extracted metals and chelating agents have to be submitted to further treatments for a complete detoxification before being discharged into the environment. The simultaneous removal of EDDS and three metals (Cu, Fe and Zn) from both synthetic waters (home prepared) and real contaminated soil washing mixtures at neutral pH has been investigated, a lab-scale, considering four artificial solar driven photocatalytic technologies (TiO2/hν/N2, TiO2/hν/air, Fe(III)-EDDS/hν/air and Fe(III)-EDDS/hν/H2O2/air). The soils were sampled in the Province of Naples (South of Italy) in a zone infamously known for its high incidence of cancer mortality. The results indicate that both the type and the sequence of photocatalytic technologies that need to be apply should be chosen prudently considering both the nature and the content of the soil washing solutions.