An integrated value chain to iron-containing mine tailings capitalization by a combined process of magnetic separation, microwave digestion and microemulsion – assisted extraction

Abstract

The recovery of metals from tailing ponds or dumps is a priority as they remained stored on large areas around the mining operations and represent an aggressive pollution source of natural water bodies. The paper objective is to develop a combined process for iron-containing mine tailings capitalization associates the benefits of magnetic separation to reduce the iron content, microwave digestion for metals forms solubilization from solid matrix and microemulsion for their extraction, concentration, and recycling from the digested sample. The magnetic separation of ferromagnetic fraction, with over 50 % iron, leads to an improved extraction efficiency. The optimum digestion procedure uses aqua regia, hydrogen peroxide (30 % H2O2) and microwaves. The microemulsion extraction using Brij 30 (polyoxyethylene (4) lauryl ether) as surfactant, ethyl acetate:butyl acetate (1:1, v/v) as oil phase and acidic metal solutions as aqueous phase, and also NaSCN (0.1 M) as carrier agent, performed at room temperature and atmospheric pressure, reveals that excellent recovery performance for iron (98.3 %), lead (98.5 %), zinc (93.0 %) can be obtained. In addition, copper (63.0 %) is recovered quite efficiently. The maximum microemulsion loading capacity in terms of mass of total metal ions/L was 351 mg/L and was achieved by two successive extractions. It has been demonstrated that by two successive extractions, the loading capacity is mainly represented by iron content. The results obtained demonstrate that the three combined procedures involving magnetic separation, microwave digestion and microemulsion assisted extraction ccontributes to the reduction of mine waste deposits and, consequently, the environmental pollution with heavy metals.