Separation of Palladium from Alkaline Cyanide Solutions through Microemulsion Extraction Using Imidazolium Ionic Liquids

Abstract

In this paper, three imidazolium-based ionic liquids, viz., 1-butyl-3-undecyl imidazolium bromide ([BUIm]Br), 1-butyl-3-octyl imidazolium bromide ([BOIm]Br), and 1-butyl-3-hexadecyl imidazolium bromide ([BCIm]Br), were synthesized. Three novel microemulsions systems were constructed and then were used to recover Pd (II) from cyanide media. Key extraction parameters such as the concentration of ionic liquids (ILs), equilibration time, phase ratio (RA/O), and pH were evaluated. The [BUIm]Br/n-heptane/n-pentanol/sodium chloride microemulsion system exhibited a higher extraction percentage of Pd (II) than the [BOIm]Br/n-heptane/n-pentanol/sodium chloride and [BCIm]Br/n-heptane/n-pentanol/sodium chloride microemulsion systems. Under the optimal conditions (equilibrium time of 10 min and pH 10), the extraction percentages of these metals were all higher than 98.5% when using the [BUIm]Br/n-heptane/n-pentanol/sodium chloride microemulsion system. Pd(CN)42− was separated through a two-step stripping procedure, in which Fe (III) and Co (III) were first separated using KCl solution, then Pd(CN)42− was stripped using KSCN solution (separation factors of Pd from Fe and Co exceeded 103). After five extraction–recovery experiments, the recovery of Pd (II) through the microemulsion system remained over 90%. The Pd (II) extraction mechanism of the ionic liquid [BUIm]Br was determined to occur via anion exchange, as shown by spectral analysis (UV, FTIR), Job’s method, and DFT calculations. The proposed process has potential applications for the comprehensive treatment of cyanide metallurgical wastewater.

Alternative Extraction Systems for Precious Metals Recovery: Aqueous Biphasic Systems, Ionic Liquids, Deep Eutectic Solvents

“…Deng et al proposed a microemulsion extraction technique for palladium recovery from alkaline cyanide solutions using imidazolium ILs [43]. 1-butyl-3-undecyl imidazolium bromide ([BUIm]Br) was used as an extractant in a mixture of n-pentanol and n-heptane.…”

Efficient Metal Extraction from Dilute Solutions: A Review of Novel Selective Separation Methods and Their Applications

“…These methods have aimed to attain high selectivity and extraction efficiency levels while addressing the economic and technical challenges associated with conventional approaches for dilute solutions. Novel approaches, such as using air bubbles in SX [44][45][46], employing ionic liquids (IL) [47][48][49], and immobilized ligands [50][51][52], have shown promise in this regard.…”

“…In a recent study, palladium extraction from cyanide media was investigated using microemulsion systems incorporating imidazolium-based ionic liquids ([BUIm]Br, [BOIm]Br, and [BCIm]Br) in combination with n-heptane, n-pentanol, and sodium chloride [49]. The system containing [BUIm]Br ionic liquid demonstrated a higher metal extraction.…”