ENVIRONMENTAL CHARACTERIZATION OF GOLD MINING TAILINGS TO PREVENT ACID MINE DRAINAGE AND CONTAMINATION – NOVA LIMA, MINAS GERAIS –BRAZIL

Abstract

Two different types of tailings from Au metallurgical treatment were studied for their acid mine drainage potential and elements mobility: flotation and leaching tailings from an already deactivated circuit, accumulated in the Cocuruto tailings dam circuit (old circuit); and roasted and leaching tailings form a current plant (current circuit), in Minas Gerais, Brazil. Detailed characterization of both types indicates the presence of fine grain size material with sulfides, but with different geochemical and mineralogical behavior. The samples from the current plant show high grades of Fe in the form of oxides, cyanide, and sulfates. On the other hand, samples from the old circuit are richer in Al, Ca, Mg, and Mn, present as silicates and carbonates. In these samples, there are also relics of preserved sulfides, such as pyrite and phyrrhotite. Concentrations of Zn, Cu, Au, and As are higher in the current circuit, while Cr and Hg stand out in the tailings from the old one. Although the obtained results show that in these cases the sulfide-wastes do not tend to generate acid mine drainage, leaching tests indicate the possibility of mobilization of toxic elements: As and Mn in the old circuit; Sb, As, Fe, Ni, and Se in the current circuit. Therefore, this work highlights the need for proper management and control even in alkaline drainage environments. Furthermore, the knowledge about the geochemistry and mineralogy as well as their evolution could support long-term decisions, such as safe disposal . In the present case, the Au grades and its occurrence also suggest the potential reuse as a sustainable strategy for the management of both types of tailings.