AliCy as Extractant to Remove Iron from Copper-Free Extreme AMD for Further Extraction of Zinc

A previous work showed that copper can be specifically extracted from acid mine drainage (AMD) classified as high-acid and extreme-metals (pH 1.19, ~63 g/L Fe, ~6.5 g/L Al, ~5.3 g/L Cu, ~1.9 g/L Zn and ~0.1 g/L Mn), using 30% (v/v) Acorga M5640 in Shell GTL (a kerosene like solvent) as extractant. Yet, to further extract zinc, another strategic metal in this water, using 0.9M D2EHPA or a mixture of 0.72 M D2EHPA plus 0.18M Cyanex 272 in kerosene as extractants, difficulties were observed due to iron co-extraction. Thus, an alternative solvent extraction strategy based on the use of the self-prepared ionic liquid AliCy 0.3M in kerosene was tested. The results revealed potential selectivity since 35% of iron was removed, while the removal of other metals was < 5%. Afterwards, higher concentrations of AliCy (0.6, and 1.2M) at different aqueous to organic ratios (A:O = 1:1, 1:2, 1:3 and 1:4) were tested on copper-free extreme AMD (after copper recovery with Acorga M5640), and the best compromise between iron extraction efficiency and selectivity was observed for 0.6M at A:O = 1:4 and also for 1.2M at A:O = 1:2 (75 to 80% removal or iron and 5 to 10% of zinc in both cases).