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- Ålund, Marie, et al.
(författare)
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Leaching of metals from contaminated soil with polyhydroxicarboxylic acids of natural origin
- 2009
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Konferensbidrag (refereegranskat)abstract
- The effect of addition of complexing agents, generated from natural products, on the release and redistribution of metals from contaminated soil has been studied. Water soluble humic substances (fulvic acids, FA) generated by leaching of high-molecular weight humic matter (peat) at high pH, and isosaccharinic acid (ISA), generated by degradation of wood (saw-dust) at high pH was used and compared with some synthetic complexing agents representing naturally occurring products: Citric acid (CA), ethylenediamine disuccinic acid (EDDS) and methylglycine diacetic acid (MGDA).Four contaminated soils with elevated levels of particularly As, Cr, Cu, Ni and Pb at maximum levels of 1.5, 1.2, 1.7, 0.14 and 3.8 g/kg, respectively (two from shooting-ranges, one from a steel-works site and one from a wood impregnation site) were leached with alkaline solutions (pH 12) containing peat degradation products (1.2 g/l TOC; some 90 % FAs) and wood degradation products (0.7 g/l TOC, some 50-60 % ISA), as well as solutions of CA, EDDS and MGDA (0.25 mM, pH 6-8). Metal releases were analysed after various leaching times: 24 h, 1 week, 5 weeks. Results are related to the total content of metals in the soil (XRF-analysis), total leachable fractions (sequential leaching according to Tessier) and leaching with nitric acid (pH 3).A release of some 10 % of the lead inventory and up to 50 % of the copper in one of the soils could be achieved in the FA and ISA leaching systems, while the synthesised agents EDDS and MGDA led to releases of some 60-90 %. The effects of FA and ISA were generally significantly lower than those of the other complexing agents for As, Cr, and Ni, but significantly higher for V (present at the level 40 mg/kg). Thus, a significant enhancement of the release of particularly copper and lead from the contaminated soils by leaching with alkaline (pH 12) leachates of wood and/or peat appears to be feasible.
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