The use of cyclonic ashes of fluidized bed burning of coal mine refuse for long-term immobilization of metals in soils

Abstract

Results from both laboratory scale simulation and field experiments using cyclonic ashes of fluidized bed bunting of coal mine refuse for immobilization of heavy metals in soils are described. The results show that this modified alumino-silicate had a long-lasting effect on bio-availability and leaching of metals from contaminated soils. A three step sorption mechanism is hypothesized: (1) an initial rapid first step representing adsorption onto highly accessible sites on the surface of the clays present in the ashes and on binding sites of the original soil components freed due to a "liming effect", followed by (2) a slower step of sorption which consists of coprecipitation with Al, Fe and Mn oxides and finally, on the longer term , (3) formation of metal silicates, crystal growth and diffusion into the mineral surface.