Sustainable reprocessing of Pb–Zn mine tailings through froth flotation for resource recovery and environmental remediation in abandoned mining regions

Abstract

The abandoned Touissit-Bou Beker mining district has accumulated tens of millions of tons of tailings, stored without environmental safeguards. Due to the limited ore processing method, the tailings exhibit a significant zinc (2 wt%) and lead (0.3 wt%) content, mainly buried in carbonate minerals. These tailings pose environmental concerns but also offer economic opportunities. This study investigated the feasibility of decontaminating these tailings using froth flotation to produce a clean mineral byproduct. Composite samples were collected via reverse circulation (RC) drilling, and flotation conditions were optimized. Quantitative mineralogy and environmental behavior were assessed using quantitative evaluation of materials by scanning electron microscope (QEMSCAN®) and toxicity characteristic leaching procedure (TCLP), respectively. Under optimal conditions — potassium amyl xanthate (KAX) 350 g/t, CuSO₄ 1,250 g/t, Na₂S 1,250 g/t, sodium hexametaphosphate (SH) 1,750 g/t, and pH 11—Zn and Pb recoveries reached up to 94 % and 71 %, respectively. Residual Pb–Zn remained partially locked within the non-sulfide gangue minerals or present as slime particles. TCLP results indicate minimal risk, suggesting reprocessing mine tailings in abandoned mine sites in Morocco could offer economic and environmental benefits. The current study is expected to serve as a reference for decision-makers when evaluating sustainable management options for mine tailings.