Synthesis and characterization of amide-Functionalized analogues of glycine-betaine based ionic liquids and an exemplified use for the separation of copper(II) and cobalt(II)

ABSTRACT

Novel series of amide functionalized analogues of glycine-betaine-based ionic liquids (AGB-ILs), namely, [N,N,N-tri(n-butyl)(2-aminoalkyl-2-oxoethyl)]ammonium (alkyl = n-butyl, and n-octyl) associated with tetrafluoroborate (BF₄⁻), hexafluorophosphate (PF₆⁻), bis(trifluorosulfonyl)imide (Tf₂N⁻), dicyanamide (Dca⁻), 4-chlorosalicylate (ClSal⁻) and saccharinate (Sac⁻) anions have been synthesized and fully characterized by spectroscopic methods (IR, ¹H and ¹³C NMR) and elemental analysis. The alkyl chain length of the organic cation and the chemical nature of inorganic or organic anion on physicochemical properties such as melting point, glass transition and decomposition temperatures, and viscosity have been described. To determine the sensitivity of Dca ligand to pH, the effect of the pH on the extraction properties of aqueous Cu²⁺ and Co²⁺ ions has been investigated in the pH range 1 to 5.

KEYWORDS:

• Ionic liquids
• glycine-betaine
• liquid-liquid extraction
• copper
• cobalt

Acknowledgments

The authors are grateful to the “Region Grand Est” and the FEDER for a Grant to P. D. Diabate and L. Boulafrouh, and for its financial support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author contributions

Conceptualization, Laurent Dupont and Aminou Mohamadou; Data curation, Pape Diaba Diabate and Lamia Boulafrouh; Funding acquisition, Laurent Dupont and Aminou Mohamadou; Investigation, Pape Diaba Diabate and Lamia Boulafrouh; Methodology, Laurent Dupont and Aminou Mohamadou; Supervision, Stéphanie Boudesocque, Laurent Dupont and Aminou Mohamadou; Writing – original draft, Pape Diaba Diabate and Stéphanie Boudesocque; Writing – review & editing, Stéphanie Boudesocque, Laurent Dupont and Aminou Mohamadou.

Statement of novelty

• According to the author’s knowledge no work is dedicated to the amino-functionalized analogues of glycine-betaine ionic liquids (AGB-ILs) and their application in the extraction of Pb(II), Cu(II) and Co(II).

• As far as the authors are aware, there is no work carry on the hydrolysis of the ester functionalized cation of the ILs in a strongly acidic medium whereas the amino-functionalized cations do not undergo hydrolysis.

• To improve the rate extraction of Pb(II) ion, it is preferred that the coordinating anion of the IL possesses oxygen atoms than nitrogen.

• Therefore, the extraction mechanism of the Cu(II) and Co(II) ions depends the hydrophobicity of the organic cation as well as the metal salt anion.

Additional information

Funding

This work was developed within the scope of the project 16/PRC/126, financed by national funds through the “Region Grand Est” under Grant [D201600637] and the FEDER under the Grant Number [D201600639].