Affinity Extraction into CO2. 2. Extraction of Heavy Metals into CO2 from Low-pH Aqueous Solutions

This is the authors' abstract. We don't add key points for this paper.

Because it is an environmentally benign solvent, CO 2 is increasingly being evaluated as a medium with which to perform liquid−liquid extraction from water (unlike conventional organic solvents, no contamination of the aqueous phase results). A number of researchers have explored the design of highly CO 2 -soluble chelating agents to allow extraction of metal ions, yet the low pH of water in contact with CO 2 (2.8−3.0) can lead to poor extraction efficiencies with many common chelating agents. In this paper, we describe the generation of a CO 2 -soluble analogue to ammonium pyrrolidinedithiocarbamate, an agent which has been shown to effectively extract a variety of metal ions at pH's as low as 1.0. We have found that the CO 2 -soluble analogue can extract high fractions of copper, nickel, and cadmium, although, like conventional APDC, extraction of chromium was less successful.