BATCH LEACHING STUDIES OF RUNDLE OIL-SHALE

The leaching of Fe, Mn, Al, Zn, Cd, Pb, Ni, Cu, As, and Se from samples of raw and retorted Kerosene Creek seam oil shale and Telegraph Creek seam claystone from the Rundle oil shale deposit, Australia, was studied over the pH range 2 to 9.5. Low pH values were used to simulate the effects of possible acidification that might occur by oxidation of pyrite contained in the solids. The variation in leachate composition with pH highlighted the shortcomings of any batch test that seeks to categorize the behavior of a waste material solely on the basis of extraction at a single pH value. In this context, the results provided by the Resource Conservation and Recovery Act (RCRA) toxicity and American Society for Testing and Materials (ASTM) leach tests were compared. The RCRA test would not have identified As as being a potential problem in leachate from the retorted shale because, at pH 5, this element (in the form of arsenate) is strongly adsorbed to the shale matrix. The natural pH of a slurry of this waste is, however, greater than 9. Under these conditions, As is the trace element present in the highest concentrations in the leachate.