Phytoremediation of Pb contaminated soil with polymer-coated EDTA

EDTA-assisted phytoextraction of lead (Pb) has been developed, but concerns have arisen due to the possibility of leaching of both Pb and EDTA to ground water caused by uncontrolled release. We developed five types of controlled-release EDTA (polymer-coated EDTA) by coating the EDTA with a polyolefin polymer. A test of the release rate showed that the duration for the release of 75% of total EDTA ranged from 3 to 210 days. A pot experiment was conducted to compare the effect of these polymer-coated EDTA and non-coated EDTA on the concentrations of Pb and EDTA in soil solution, and Pb accumulation in sorghum (Sorghum bicolor L. cv. EARLY SUMAC) in a Pb-contaminated soil. One of the polymer-coated EDTAs, C-EDTA-4, with a release period of 80 days proved to be the best in decreasing Pb and EDTA concentrations in soil solution, and increasing Pb accumulation in sorghum shoots compared to the direct application of EDTA. Our results suggest that polymer-coated EDTA has a potential for phytoextraction of Pb with a reduced environmental risk.