EDTA leaching of Cu contaminated soil using electrochemical treatment of the washing solution

摘要

The feasibility of a two-phase method for remediation of Cu (364 ± 2 mgkg~(-1)) contaminated vineyard soil was evaluated. In the first phase we used ethylenediamine tetraacetae (EDTA) for Cu leaching, while in the second phase we used an electrochemical advanced oxidation process (EAOP) for the treatment and reuse of the washing solution for soil rinsing (removal of soil-retained, chelant-mobilized Cu complexes) in a closed loop. In the EAOP, a boron-doped diamond anode was used for the generation of hydroxyl radicals and oxidative decomposition of EDTA-metal complexes at a constant current density (40 mAcm ~(-2)). The released Cu was removed from the solution mostly as an electro-deposit on the cathode. Two consecutive additions of 10mmol kg~(-1) EDTA removed 26% of Cu from the soil, mostly from carbonate and oxide soil fractions (58% and 40% Cu reduction). The soil Cu oral availability (in vitro Physiologically Based Extraction Test) was reduced after remediation by 42% and 51% in the simulated stomach and intestinal phases. The discharge solution was clear, almost colorless, with pH 8.4 and 0.5 mg L~(-1) Cu and 0.07 mM EDTA. The novel method enables soil Cu availability stripping using small volumes of process waters, and no wastewater generation or other emissions into the environment.