Abstract
The development of a cost effective CO2-based hydrometallurgical process was realized through examining the extraction performance of a nearcritical carbon dioxide/CO2-soluble alkylamine extraction system over a large range of temperatures, pressures, and compositions, as well as through characterizing the phase behavior of the highly CO2-soluble alkylamines. A most important discovery of this research is that Fluorolink exhibits a higher CO2 solubility than other fluorinated alkylamines examined in past efforts. Development of these novel polymeric chelating agents is of great utility since these CO2-philic materials show high solubilities of 15 wt% at 860 psi and 25 °C. In addition to its high thermodynamic affinity for carbon dioxide, Fluorolink was chosen as the model complexing agent because of its ability to target the zinc metal ions of interest and form stable metal complexes. The chelating power of the complexing agent is validated by the large formation constant for the zinc metal complex of 1.0×1013 and the quantitative zinc extraction efficiency of 99% attained using a hexane/Fluorolink extractant system. It is because of the material’s high CO2 solubility as well as its chelating power that the complexing agent was capable of extracting zinc in quantitative amounts from aqueous solutions containing high metal loadings of 5,000 ppm while operating at relatively low system pressures of 1,500 psi and below. This analysis validated the extraction mechanism via examination of reagent partitioning behavior, existence of zinc in carbon dioxide, stoichiometry of complexation process, and identification of the anion responsible for charge neutralization.
Published Version
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