title: Recycling of complexometric extractants to remediate a soil contaminated with heavy metals.
abstract: Equilibrations were performed with complexing reagent(s) to mobilise Cd, Cu, Mn, Ni, Pb and Zn from a contaminated urban soil. The metal-laden aqueous extract was treated with zero-valent magnesium (Mg0) or bimetallic mixture (Pd0/Mg0 or Ag0/Mg0) to precipitate the heavy metals from solution while liberating the chelating reagent(s). Post precipitation, the pH of aqueous supernatant fraction was readjusted to approximately 5 and the solution was re-combined with the soil particulates to extract more heavy metal pollutants. A sparing quantity of EDTA (10 mmoles) mobilised 32-54% of the 5 mmoles of heavy-metals from the soil with three cycles but only 0.1% of the iron was removed. Three successive extractions with a mixture of complexing reagents (3 mmoles), 1:1 EDTA plus HEDC [bis-(2-hydroxyethyl)-dithiocarbamate], mobilised approximately 49% of the Pb, approximately 18% of the Zn and approximately 19% of the Mn burden but only 7% of the Cu, and 1% of the Fe from this soil. An appreciable fraction of the mobilised Pb and Cu and a portion of the Zn was cemented to the surfaces of the excess magnesium whereas virtually all of the Fe and Mn was removed from solution as insoluble hydroxides.
authors: Department of Food Science and Agricultural Chemistry, McGill University, Ste-Anne-de-Bellevue, Qué., Canada.
authors: Chia Chi
authors: CC
authors: Lee
authors: William D
authors: WD
authors: Marshall
mesh_terms: D001682:Biological Availability; D002614:Chelating Agents / Q000737:chemistry; D011232:Chemical Precipitation; D003247:Conservation of Natural Resources; D004492:Edetic Acid / Q000737:chemistry; D004787:Environmental Pollution / Q000517:prevention & control*; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000032:analysis* / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis*; D012995:Solubility
chemical_list: D002614:Chelating Agents; D019216:Metals, Heavy; D012989:Soil Pollutants; D004492:Edetic Acid