Skip to main content
U.S. flag

An official website of the United States government

Comparative evaluation of short-term leach tests for heavy metal release from mineral processing waste

January 1, 2006

Evaluation of metal leaching using a single leach test such as the Toxicity Characteristic Leaching Procedure (TCLP) is often questionable. The pH, redox potential (Eh), particle size and contact time are critical variables in controlling metal stability, not accounted for in the TCLP. This paper compares the leaching behavior of metals in mineral processing waste via short-term extraction tests such as TCLP, Field Leach Test (FLT) used by USGS and deionized water extraction tests. Variation in the extracted amounts was attributed to the use of different particle sizes, extraction fluid and contact time. In the controlled pH experiments, maximum metal extraction was obtained at acidic pH for cationic heavy metals such as Cu, Pb and Zn, while desorption of Se from the waste resulted in high extract concentrations in the alkaline region. Precipitation of iron, caused by a pH increase, probably resulted in co-precipitation and immobilization of Cu, Pb and Zn in the alkaline pH region. A sequential extraction procedure was performed on the original waste and the solid residue from the Eh-pH experiments to determine the chemical speciation and distribution of the heavy metals. In the as-received waste, Cu existed predominantly in water soluble or sulfidic phases, with no binding to carbonates or iron oxides. Similar characteristics were observed for Pb and Zn, while Se existed mostly associated with iron oxides or sulfides. Adsorption/co-precipitation of Cu, Se and Pb on precipitated iron hydroxides was observed in the experimental solid residues, resulting in metal immobilization above pH 7.

Publication Year 2006
Title Comparative evaluation of short-term leach tests for heavy metal release from mineral processing waste
DOI 10.1016/j.scitotenv.2005.10.021
Authors S. R. Al-Abed, P. L. Hageman, G. Jegadeesan, N. Madhavan, D. Allen
Publication Type Article
Publication Subtype Journal Article
Series Title Science of the Total Environment
Index ID 70028406
Record Source USGS Publications Warehouse