Gold processing residue from Jacobina Basin: chemical and physical properties

Abstract

Gold processing residues or tailings are found in several areas in the Itapicuru River region (Bahia, Brazil), and previous studies indicated significant heavy metals content in the river sediments. The present work focused on an artisanal gold processing residue found in a site from this region. Samples were taken from the processing residue heaps and used to perform a physical and chemical characterization study using X-ray diffraction, scanning electron microscopy, neutron activation, X-ray fluorescence, induced coupled plasma-mass spectrometry, among others analytical methods. The results indicate that the material is composed mainly by quartz and goethite. The average size of the processing residue particles is about 150 microns, and the density is close to that of quartz. The main elementary constituents are silicon, iron, aluminum, magnesium, and potassium. Among the trace elements, it can be highlighted: sodium, titanium, chromium, zirconium, calcium, sulfur, manganese, copper, mercury, and gold. A remarkable feature of these gold processing residue is that the gold and mercury are both concentrated in the fine and coarse particles. The processing residue gold content is of about 1.8 mg/kg and the mercury content is of about 10 mg/kg. The gold content of this residue has the same order of magnitude of gold ores treated by a cyanidation plant in this region.