The asbestos mine “Stragari” (Kragujevac municipality, central Serbia) operated for approximately four decades, exploiting chrysotile asbestos and generating several million tons of tailings composed primarily of finely crushed serpentinite rock. These tailings are rich in magnesium (≈25 wt.%); yet, efficient magnesium recovery is hindered by the high acid consumption associated with serpentinite mineral dissolution. The objective of this study was to optimize the extraction of magnesium as magnesium chloride hexahydrate (MgCl2×6H2O) from asbestos mine tailings using hydrochloric acid as the leaching agent. The effects of key process parameters (including thermal activation—roasting, hydrochloric acid concentration, leaching temperature, and leaching duration) were systematically investigated. Experiments in this study were conducted using concentrations of HCl 0.5, 1, 1.5 and 2 M, temperatures of 60, 70 and 80 °C and durations of 60 and 180 min, with constant stirring speed (350 rpm) and 20% initial pulp density. The resulting pregnant leach solution was purified by controlled neutralization with Mg(OH)2 followed by evaporation to obtain MgCl2×6H2O. A preliminary techno-economic assessment indicates that the proposed process is economically feasible and provides a foundation for future scale-up studies. The results demonstrate that balancing acid consumption with magnesium recovery, rather than pursuing maximum extraction efficiency, can enable profitable industrial-scale production of a value-added magnesium compound while contributing to asbestos tailings remediation.
Stanković et al. (Thu,) studied this question.
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