Rhenium extraction from pressure oxidative leaching solution of molybdenite concentrate using hydrophobic deep eutectic solvents

Abstract

This research is one of the early studies to evaluate the capability of hydrophobic deep eutectic solvents (DESs) as an eco-friendly solvent for precious and strategic metal extraction, rhenium (Re). In this study, the selective transfer of Re from aqueous solution and pressure oxidative leaching solution of molybdenite concentrate was investigated by mixing fatty acid (Decanoic acid) and quaternary ammonium salt (Aliquat 336). To evaluate the extraction potential of hydrophobic-DES in the ratio of Decanoic acid (Deca):Aliquat 336 = 2:1, FTIR, 1H NMR, thermal gravimetric analysis was used. For finding an optimum condition for Re separation, various extraction conditions were initially investigated in synthetic aqueous solution. In this area, the maximum extraction percentage was obtained at a concentration of Re = 100 mg/L, ratio of organic to aqueous phase (O:A) = 1 to 25, contact time = 10min, pH = −0.5, and temperature = 25°C. In the stripping step, the recovery of >90% Re at selected O:A = 5:1 showed that significant reduction of water consumption. After that, the complex situation for selective Re extraction from molybdenite leaching solutions with different cations and anions was studied. For increasing the extraction and separation factor of Re in comparison to the other ionic specious (e.g., Cu, Fe, Mo and S), the neutralization process was also applied. To understand the extraction mechanism for Re, anion exchange constant (KOE) and ion pair constant (KIP) were determined. In this area, the ion pair formation was chosen as the main reaction mechanism; however, anion exchange reaction was not negligible role in Re extraction. Toxicity study on hydrophobic-DES was investigated by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. The obtained results according to IC50 and viability of cells culture represented the low toxicity of hydrophobic-DES.