Edafología. Volumen 5. Diciembre 1998. pag 59-70
PROCESOS DE INMOVILIZACIÓN DE ELEMENTOS TRAZA EN AGUAS ACIDAS DE MINA
C. Monterroso y F. Macías
Dpto. Edafología y Química Agrícola, Facultad de Biología, Universidad de Santiago, 15706 Santiago
Abstract
Acid mine waters may precipitate Fe-rich minerals which have importance in regulating heavy metals solubility. In this study the scavenging potential of the precipitates collected from a coal mine in Galicia (NW Spain) was evaluated. Analyses of 26 samples of precipitates and associated solutions showed that schwertmannite or jarosite are formed from waters with pH<4 and high sulfate content (>2000 mg L-1), and goethite was the dominant phase at pH>4. In addition, soluble sulfates were commonly formed during dry periods. Distribution coefficients for Mn, Co, Cu, Zn, Ni, and Cd showed a preferental accumulation of these elements in the soluble-sulfate phase. Schwertmannite adsorbed small amounts of these cationic metals due to the very low pH of the solution and goethite only adsorbed significant amounts of Zn. Lead appeared to be strongly associated with jarosite phase; very low concentration of Pb was found in the solution. Chromium is a relatively immobile metal because was adsorbed on schwertmannite precipitates.
Key words: acid sulfate waters, adsorption, heavy metals, pyrite oxidation