Remediation of metal polluted hotspot areas through enhanced soil washing--evaluation of leaching methods.
Soil washing offers a permanent remediation alternative for metal polluted sites. In addition, the washed out metals can be recovered from the leachate and re-introduced into the social material cycle instead of landfilled. In this paper, soil, bark and bark-ash washing was tested on four different metal polluted soil and bark samples from hotspots at former industrial sites. Six different leaching agents; HCl, NH4Cl, lactic acid, EDDS and two acidic process waters from solid waste incineration, were tested, discussed and evaluated. For the soil washing processes, the final pH in the leachate strongly influences the metal leachability. The results show that a pH < 2 is needed to achieve a high leaching yield, while <50 w% of most metals were leached when the pH was higher than 2 or below 10. The acidic process waste waters were generally the most efficient at leaching metals from all the samples studied, and as much as 90-100 w% of the Cu was released from some samples. Initial experiments show that from one of these un-purified leachates, Cu metal (>99% purity) could be recovered. After a single leaching step, the metal contents of the soil residues still exceed the maximum limits according to the Swedish guidelines. An additional washing step is needed to reduce the contents of easy soluble metal compounds in the soil residues. The overall results from this study show that soil and bark-ash washing followed by metal recovery is a promising on-site permanent alternative to remediate metal polluted soils and to utilize non-used metal resources.
['Fedje|Karin Karlfeldt|KK|', 'Yillin|Li|L|', 'Strömvall|Ann-Margret|AM|']
D000643:Ammonium Chloride D005591:Chemical Fractionation D002857:Chromium D003300:Copper D004787:Environmental Pollution D052918:Environmental Restoration and Remediation D005029:Ethylenediamines D006863:Hydrogen-Ion Concentration D019344:Lactic Acid D008670:Metals D012989:Soil Pollutants D013386:Succinates D013548:Sweden
Metals Leaching Soil washing Cu Sequential extraction Soil remediation