Comparisons of metal leachability for various wastes by extraction and leaching methods

The objective of this research was to evaluate three extraction tests, i.e. , toxicity characteristic leaching procedures (TCLP), extraction procedure (EP), and American Society for Testing and Materials (ASTM) methods, for th eir ability to extract metals in chemical sludge and incineration bottom as h, in terms of the precision of analytical results. Typical chemical sludge s, including the electroplating and dye-stuff sludges, the municipal solid waste incineration bottom ash, the leather debris, and the steel-mill botto m residue containing Cd, Cr, Cu, Pb, and Zn were prepared for the lysimetry test (dynamic testing) to compare with the extraction results. Results sho w that for bottom residue and dye-stuff sludge, the concentration of metal leached was almost the same between the lysimetry leaching and the TCLP tes ts. The metal concentration followed the order: TCLP approximate to EP > AS TM. TCLP and EP exhibited almost the same relative standard deviation (RSD) value. Therefore, the results of the TCLP tests for bottom residue and dye -stuff sludge, which have a low metal content and alkalinity, can be used t o estimate the metal concentration leached by typical acid rain in Taiwan; whereas the ASTM extraction test may be a better indicator of the lysimetry test. (C) 2001 Elsevier Science Ltd. All rights reserved.