Advanced oxidation for treatment of aqueous extracts from EDTA extraction of Pb and Zn contaminated soil

摘要

The feasibility of using advanced oxidation processes (AOPs): ozone, ozone/sonification, and ozone/ultraviolet (UV) irradiation in treatment to remove heavy metals and ethylenediamine tetraacetate (EDTA) from aqueous extracts, obtained after soil extraction with EDTA, was examined. Extraction of soil contaminated with 1,243 mg kg(-1) Pb and 1, 190 mg kg(-1) Zn with 40 mmol kg(-1) EDTA removed 41.8 +/- 0.9 and 7.2 +/- .0.2% of Pb and Zn. Of the AOPs tested, only the use of ozone/UV enabled the decomposition of EDTA-heavy metals complexes in aqueous soil extracts, and recovery of released Pb and Zn by sorption on a commercial sorbent Slovakite. After treatment, the concentration of Pb, Zn, and EDTA in the extracts was fairly low (2.87 +/- 1.15 mg L-1, 7.58 +/- 2.12 mg L-1, and 0.012 +/- 0.002 mmol L-1, respectively), and could presumably be reduced even further with a continuation of treatment. The treated extract was used for subsequent soil rinsing, which removed an additional 12.7 +/- 1.6 and 2.7 +/- 0.1% of soil Pb and Zn. The results of our study indicate that the use of ozone/UV is a feasible option for treatment of aqueous soil extracts from EDTA extraction. Treated extracts could be safely discharged or reused to lower requirements for process water.