Highly selective solvent extraction of Zn(II) and Cr(III) with trioctylmethylammonium chloride ionic liquid

Abstract

This study investigates the recovery of Zn(II) and Cr(III) from aqueous solutions based on solvent extraction with trioctylmethylammonium chloride [TOMA+][Cl‐], commercialy named Aliquat 336. Single metal solutions and binary mixtures of both metals were considered. The effect of relevant operating conditions such as pH, contact time, initial concentration, O/A phase volumetric ratio, and temperature were evaluated. Additionally, loading capacity and stripping studies were performed. Results showed that [TOMA+][Cl−] is an effective extracting agent for Zn(II), reaching maximum removal capacity at pH 1.8 and demonstrating fast extraction kinetics. Extraction efficiencies above 99% were achieved at 0.5, 0.75, and 1.00 O/A volumetric phase ratios for 0.1 g/L initial Zn(II) concentration. At 1 g/L and 10 g/L concentration, for the same O/A ratios, approximately 88% of the initial Zn(II) was extracted. In contrast, it was found that negligible amounts of Cr(III) were transferred to the [TOMA+][Cl−] phase at the 1‐5 pH range. Selectivity studies showed that Zn(II) removal is boosted in the presence of Cr(III), although no Cr(III) is extracted. [TOMA+][Cl−] exhibited a high Zn(II) storage capacity, since after 25 loading cycles with 1 g/L, the loading capacity reached approximately 13.5 g/L, and after five loading cycles with 5 g/L, the capacity reached 19.4 g/L. Stripping tests revealed that NaOH is an efficient agent for the removal of Zn(II) from the ionic liquids, reaching 98.5% removal after two cycles, whereas HNO3 is not a suitable agent, reaching less than 40% removal after three cycles. [TOMA+][Cl−] revealed high potential for separating Zn(II) from Cr(III).

Solvent Extraction of Metal Ions from Synthetic Copper Leaching Solution Using R4NCy

“…Alves-Lima et al extracted selectively Zn(II) over Cr(III) using Aliquat 336. In the best conditions, the reaches recover about 99% of Zn(II) [34]. Regel-Rosocka et al reported zinc and iron extraction using Cyphos IL 101 and Cyphos IL 104.…”

“…These ILs have attracted the attention of metal recovery because of their low volatility, thermal stability, good extraction for metal, and chemical stability [26][27][28]. The use of Aliquat 336, or ILs based on this commercial reagent, demonstrates fast extraction kinetics for zinc, cobalt, nickel, and rare earth, among others [29][30][31][32][33][34]. On the other hand, the Cyphos ILs family was used in several systems reported in the literature.…”