TY - JOUR

T1 - Highly selective solvent extraction of Zn( II ) and Cr( III ) with trioctylmethylammonium chloride ionic liquid

AU - Alves‐Lima, Décio F.

AU - Rodrigues, Carmina F.

AU - Pinheiro, Carolina T.

AU - Gando‐Ferreira, Licínio M.

AU - Quina, Margarida J.

AU - Ferreira, Abel G.

PY - 2022/1/31

Y1 - 2022/1/31

N2 - 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).

AB - 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).

KW - General Chemical Engineering

U2 - 10.1002/cjce.24051

DO - 10.1002/cjce.24051

M3 - Journal article

VL - 100

SP - 131

EP - 142

JO - The Canadian Journal of Chemical Engineering (Wiley InterScience Publishers)

JF - The Canadian Journal of Chemical Engineering (Wiley InterScience Publishers)

IS - 1

ER -