Mineral Processing for Environmental Management

Tailings rich in heavy metals (Pb, Zn) from former mining activity exposed to the air, oxidation and climatic conditions without any prior precautions are a source of environmental contamination. Jebel Ressas tailings (Northern Tunisia) is an important and a challenging case. These tailings require special attention due to their fine texture and their heterogeneous composition. Froth flotation process has been conducted in order to minimize the environmental impacts of Pb–Zn tailings. Removal of heavy metals (lead and zinc) from mine waste of Jebel Ressas carried out through froth flotation process is a new approach applied for the first time in Tunisia. Representative samples of tailings were collected from surface, sides and base of the dumps. All the samples were undertaken to the laboratory, dried until constant weight. Then all were mixed, weighed and quartered through a riffle sampler. Model analysis was performed using XRD diffraction, metallographic microscopy and SEM/EDS, liberation mesh (d80) and chemical analysis to identify minerals. Bench-Scale Flotation tests were conducted in laboratory Denver stainless steel cell after mechanical preparation. All reagents (collector, activator and depressant) were analytical high grade. Tailing minerals were: galena, sphalerite, cerussite, smithsonite, hemimorphite, hydrozincite and willemite, in a matrix of quartz, calcite, dolomite, gypsum and clays. Chemical analysis of the raw materials indicated a total Pb of 2.25% and a total Zn of 2.41%. Flotation process led to a final treated product having low grade of heavy metals with Pb content of 800 ppm (0.08% Pb) and Zn content of 500 ppm (0.05% Zn). Selective flotation has been extensively used to separate galena and sphalerite based on hydrophobic surface properties. Zinc oxide minerals flotation had occurred with correspondent flowsheet. Thus, environmental management starts from scientific research at laboratory level to large-scale application.