Abstract

MENDEZ-ORTIZ, Blanca Adriana; CARRILLO-CHAVEZ, Alejandro; MONROY-FERNANDEZ, Marcos Gustavo  and  LEVRESSE, Gilles. Influence of pH and alkalinity in the sorption of As and heavy metals by Fe oxi-hydroxides in skarn-type Pb-Zn-Ag tailings. Rev. mex. cienc. geol [online]. 2012, vol.29, n.3, pp.639-648. ISSN 2007-2902.

Processes of heavy metals and arsenic sorption onto Fe oxyhydroxides derived from leachates of Pb-Zn-Ag skarn-type mineralization, were investigated through humidity cell experiments and hydrogeo-chemical modeling. Humidity cell tests and leaching column experiments were conducted to determine the influence of pH and the concentration of dissolved metals and arsenic in the leacheates. The leachates had pH values near neutrality (pH = 7) and a relatively low concentration of toxic metals in solution, despite the evident dissolution of sulfide minerals. The oxidation ofpyrrhotite and the acid-consuming dissolution reaction of calcite catalyze the precipitation of ferryhidrite (Fe oxyhydroxide), which acts as adsorbing surfaces for metals and metalloids in solution (As, Cu, Pb and Zn). The sorption by ferryhydrite in ore deposits of this type represents one of the controlling mechanisms of the concentrations of As and heavy metals under pH conditions between 6 and 8 (near neutrality).

Keywords : hydrogeochemical modelling; mine tailings; acid mine drainage; environmental geochemistry.