Nanofiltration of Acid Mine Drainage in an Abandoned Mercury Mining Area

In Asturias (north of Spain), mercury mining has been identified as a potential source of trace elements such as As, Sb, Pb, and Hg. In particular, at Los Rueldos mine site, some of these contaminants are dissolved in acidic mine drainage (AMD). Here we treated this leachate by means of nanofiltration to remove some of its pollutants. In order to improve our understanding of the geochemical factors involved in nanofiltration, we analyzed sediment geochemistry and the origin of acidic waters. In coherence with the observation of similar behaviors of As, Fe, and Al in the nanofiltration tests, a clear geochemical association between As, Sb, S, and Fe both in sediments and in the occurrence of AMD was detected. The FILMTEC (TM) NF-2540 membrane used in this study proved to be highly suitable for the treatment and concentration of the metallic and semimetallic contaminants in the acidic water, even at low pH and moderate pressures.