The flotation of sphalerite mine tailings as a remediation method

Sphalerite tailings are the most important type of waste in the mining district of Sardinia. This situation justifies the interest in the applicability of flotation as a remediation technique by which declassify the tailings (reducing the concentration of heavy metals). The flotation of mine tailings represents a novelty if aimed at environmental remediation. Instead, it is a widespread industrial practice for recovering secondary raw materials. In this case, the scientific aspects are rarely explored: this situation explains the limited number of cases examined, the review of which, however, represents a necessary premise for the research undertaken. Furthermore, the availability of industrial case demonstrates reprocessing is not only a technically possible process but also of economic interest. After an overview of the environmental problem in abandoned mining areas, the paper recalls the fundamental elements useful for developing a comparison between the main operating methods adopted in the flotation of Pb and Zn sulphides, both as primary ores (high and low Zn content) and as tailings. The case history also includes the treatment of Zn oxidized compounds. The comparison demonstrates that the treatment of sphalerite tailings can follow the same approach as that of low-grade primary ores, but with evident economic advantages, and allows achieving those, far greater, of the multiple environmental effects.