Metal Ion Extraction with Bipyridine Derivatives as Chelating Ligands in Supercritical Carbon Dioxide

Abstract

Three fluorinated bipyridine ligands have been designed and synthesized as chelating agents for the extraction of metal ions in supercritical CO 2 (sc-CO 2 ). The ligand solubilities in sc-CO 2 were investigated at different temperatures and pressures, and the measured data have been correlated using a semiempirical model. The calculated results showed satisfactory agreement with the experimental data. Based on these data, metal ion extraction with the three compounds as chelating agents in sc-CO 2 was performed from spiked filter paper, whereby ligand 1 showed the highest extraction efficiency, especially for Ni 2+ and Cu 2+ . The extraction constants, K ex , of the three chelating ligands were seen to increase with increasing extraction efficiency for the same metal ion in the same extraction system.

Metal Ions Extraction from Solid Matrix in Supercritical Carbon Dioxide with DMBP as Chelating Ligand

“…In our previous papers, two series of bipyridine derivatives had been used to extract metal ions from solid matrix to sc-CO 2 , and the results exhibited that all of them were highly efficient for the extraction of all the eight metal ions [8,12]. In present work, although the extraction efficiencies were not good comparing our former reported work, the selectivity for Co 2þ ion is very promising and interesting.…”

“…According to literatures [8,12,28], the kinetics of solvent extraction of cationic ions is complex since it involves mass transfer coupled with a chemical reaction in a heterogeneous system. Based on the measurements and our experience with these systems, the reaction of DMBP with metal ions in the solid phase can be represented as follows:…”

“…Recently, supercritical fluid extraction (SFE) has been evaluated in areas such as soil contamination, environmental analysis, nuclear waste clean up, and so on [1][2][3][4]. Carbon dioxide, the most commonly used solvent in SFE, is nontoxic, nonflammable, nonpolluting, and relatively inexpensive [5][6][7][8]. Moreover, it has moderate critical constants (T c ¼ 304.15 K, P c ¼ 7.39 Â 10 6 MPa), variable density, higher diffusion coefficient, lower viscosity, and reduced environment impact [9].…”

Solubilities and partial molar volumes of N,N′-dibutyl-oxalamide, N,N′-dihexyl-oxalamide, N,N′-dioctyl-oxalamide in supercritical carbon dioxide

“…However, solubility data under high and low temperature in scCO 2 are less frequently reported [12][13][14][15]. Furthermore, CO 2 is a nonpolar molecule with a low dielectric constant, which prevents it from dissolving hydrophilic compounds with high polarity, metal ions and high-molecular-mass compounds [16][17][18][19][20][21][22][23][24][25][26][27][28]. One solution suggested to enhance the solubility is to introduce some CO 2 -philic compounds into the scCO 2 system.…”

“…However, fluorides are quite expensive and toxic, and silicone-functioned amphiphiles require relatively high pressure to generate a single-phase solution in scCO 2 . Thus, design and synthesis of new non-fluorous CO 2 -philic compounds has become an interesting challenge [18][19][20].…”