A study on the desulfurization of sulfidic mine tailings for the production of a sulfurpoor residue

The mining industry generates large amounts of tailings every year. The most common destination for the tailings is deposition in tailings storage facilities (TSFs), which can have normous dimensions. The management and storage of such large volumes of material pose many challenges in terms of dam stability and immobilization of hazardous contaminants that represent
human-health and environmental risks, particularly for sulfide-containing materials. In addition, considerable amounts of precious and base metals can be lost in the tailings. Due to the economic value and growing industrial demand for precious and base metals, tailings may therefore be potential sources of secondary raw materials. This contribution investigates the flotation of pyrite-rich tailings, containing residual chalcopyrite, galena, and sphalerite, and high amounts of ultrafine particles. Flotation was used to recover the sulfide minerals and generate tailings with low sulfur content. The Cu-Pb-Zn-rich product could go to further treatment (e.g. (bio)hydrometallurgy) to recover the metals, while the low sulfur fraction could be used in the civil construction industry. Automated mineralogy (MLA) was used to provide quantitative mineralogical and textural data. Bench-scale experiments were performed by combining classic flotation and floc flotation (flotation of flocs of targeted minerals). Flotation of the material as received, as well as after classification into two fractions was performed. The samples as received and the coarser fraction (+37 µm) underwent classic flotation, while the finer fraction (-37 µm) was processed either by using the classic or the floc flotation approach. The flotation of the coarser particles provided higher sulfide recoveries, higher combined Cu-Pb-Zn grades in the concentrate (3.66 %), cleaner residues (1.6 % S), faster flotation rates, and a reduced reagent consumption. Likewise, the results from the fine particle flotation allowed lower S content in the residues (3.4 % S) as compared to the flotation of the original material. The results of the use of floc flotation for the finer fraction show an increase in the mass pull with a slight increase in the recovery of sulfides. Overall the development of a route to process the tailings proved to be promising and the use of a two-route approach indicates advantages as compared to a single route.