Heavy Metals Removal From Mine Wastes By the Development of a Novel Remediation Process

The management of heavy metal-contamined mining wastes is one of the critical global challenges for the present and future generations. In the mediterranean context, Jebel Ressas (JR) tailings (Northern Tunisia) present a serious pollution risk due to their high concentration of heavy metals, in particular lead (Pb) and zinc (Zn), with an heterogeneous mixture of sulphide and oxidized minerals. To address this issue, a modified-froth flotation method was developed and optimized for the specific characteristics of JR tailings to enhance heavy metals recovery. Representative samples of JR mine waste were collected and fully characterized using various techniques. Mineralogical analysis identified the presence of galena, sphalerite, cerussite, smithsonite, hemimorphite, hydrozincite and willemite. Chemical analysis of raw materials indicated a total Pb and Zn contents of 2.25% and 2.41%, respectively. After optimization of grinding time and determination of the mesh release, the froth flotation process, involving two steps, was applied. The floatability of both sulphide and oxidized minerals was significantly improved. A final treated product with substantially reduced heavy metals concentrations (0.08% Pb and 0.05% Zn) was obtained. The separation of sulfide minerals was achieved by xanthate collector under alkaline pH, while the flotation of oxidized minerals was facilitated by a combination of sulphidization, anionic collector and primary alkylamine-type cationic collector under alkaline pH.