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The sorption capacity of selected heavy metals (Cd, Pb, Cu, Cr) to five Estonian soils was evaluated using spiked subsoil samples in laboratory experiments. The experimental sorption data fitted well to the linear Freundlich isotherm. The sorption of metals in subsoil depended on the soil type, e.g., mineral composition. The results indicate that the content of quartz and carbonates is important in affecting the metal sorption capacity of subsoil. On the basis of our data the possibility of penetration in depth and accumulation of mobile metals was evaluated. It was concluded that increase in dissolved Cd and accumulation of other metals in the subsoil of Podzol is expected. The accumulation of Pb could be the main process for soils with a high amount of dolomite.

Oil shale ash (OSA) from the circulating fluidized bed (CFB) boiler was granulated and used as a sorbent for the removal of phenols from shale oil wastewater. The method for preparation of the sorbent involved washing of the ash, mixing with clay, gelling the mixture with sodium alginate solution, solidifying the granules in barium chloride solution, drying and calcination of the granules and modifying with a surfactant -- hexadecyltrimethylammonium bromide (CTAB). The sorbent was characterized by specific surface area (BETN2), X-ray diffraction (XRD) and 29Si Magic Angle Spinning- Nuclear Magnetic Resonance (MAS-NMR) analysis. Batch adsorption experiments were conducted to determine the phenol adsorption isotherm at 20 °C and removal of water-soluble phenols from phenolic shale oil processing wastewater. Removal of phenols from wastewater was found to be 50--65% under given conditions. [ABSTRACT FROM AUTHOR]

To estimate the environmental properties of oil shale ash-based mortars the leaching of harmful components was studied. The leachates were highly alkaline. The predominant ions were Ca2+, K+, Na+, SO4 2-. The leachable content of soluble components in PF ash mortars was higher in comparison with that in CFB ash mortars. Results indicated that over curing time the fraction of readily soluble inorganic components decreased and the mobility of potentially hazardous Cd and Zn did not increase. Addition of bypass dust could affect the content of leachable ions. Results give new knowledge about the environmental properties of oil shale ash-based materials, including backfilling composites for underground mining technology. [ABSTRACT FROM AUTHOR]

A field study of the leaching of trace elements from the upper soil layer of a spent shale deposit was carried out. The study was conducted by installing a set of samplers in both active and closed parts of the deposit. Leachates were analyzed for pH, conductivity and concentrations of elements by ICP-MS. The results indicated release of metals from both parts of the deposit. Among the elements Mo, Zn, Ni, Cu, Cr and V were most mobile. The highest concentrations of Mo (104 μg/l), Zn (80 μg/l) and Ni (76 μg/l) were found in leachates from the active part of the deposit. [ABSTRACT FROM AUTHOR]