Design, Synthesis, and Evaluation of Novel, Highly CO2-Soluble Chelating Agents for Removal of Metals

The environmentally benign nature of CO 2 and the ever-increasing regulations on the use of conventional solvents present CO 2 as a solvent of choice for extraction processes for remediation of contaminated media, as a substitute for CFCs in precision cleaning processes, etc. However, because of the low solubility of metal ions and conventional metal chelating agents, there has been only limited progress in use of CO 2 as a solvent in the extraction of metals. Consequently, we have embarked on the molecular design and synthesis of several novel, highly CO 2 -soluble chelating agents. This paper describes the synthesis and evaluation of these chelating agents that exhibit solubilities in excess of 100 mmol/L of CO 2 at room temperature and pressures of 1100−2000 psi and extract as much as 98% of metals such as mercury, lead, arsenic, chromium, and iron from various matrices in laboratory-scale extractions that use pure CO 2 as the solvent.