Simultaneous extraction and recovery of gold(I) from alkaline solutions using an environmentally benign polymer inclusion membrane with ionic liquid as the carrier

Abstract

In this study, a polymer inclusion membrane (PIM) was used for the extraction and recovery of gold(I) from alkaline cyanide solutions in a prompt, concise manner. Compared with traditional solvent extraction technology, PIM is especially suitable for the separation of low concentration gold(I). A PIM containing [A336][SCN] as the carrier, polyvinylidene difluoride as a polymer matrix, and 2-nitrophenyl n-octyl ether as the plasticizer was prepared using solvent volatilization and characterized by several techniques. In addition, effects of several experimental factors on the extraction and recovery efficiencies were studied; the experimental factors included the concentration of the extractant, the stirring rate, the species of the polymer matrix, the initial gold concentration in the feed solution, and the KSCN concentration in the strip solution. Results revealed that the membrane composition and in particular, the carrier concentration, significantly affect the extraction of gold(I). The extraction mechanism involved an anion exchange reaction between the carrier [A336][SCN] embedded in the matrix polymer and the gold cyanide complex in the feed phase, followed by diffusion through the PIM, and Au(CN)2− is eventually recovered in the stripping phase. More than 98.2% of gold in the feed phase was transported through the PIM into the stripping solution, which contains 3.0 mol/L KSCN with a permeability coefficient of 1.02 × 10−5 m/s under optimal conditions. Furthermore, the membrane lifetime was also evaluated using a continuous mode, and excellent stability was achieved for at least 9 days of continuous operation. These promising results demonstrate that the PIM technology has good prospects for the extraction and recovery of gold from alkaline solutions.