Determination of Metal-Chelate Complex Solubilities in Supercritical Carbon Dioxide

Abstract

With new interest in the processing of heavy metals by chelation incorporated with supercritical fluid extraction, an accurate metal-chelate complex solubility database has become increasingly important. To measure these solubilities, a dynamic measurement technique was developed to determine organometallic complex solubility as well as chelate agent or ligand solubility in supercritical carbon dioxide. This technique utilizes a mixed-solvent stream to eliminate potential clogging and pressure increases during expansion, problems inherent with most dynamic techniques used to measure solubilities in supercritical fluids. In addition, the technique may be readily used in conjunction with basically any analytical chemical method. After proving the accuracy of the new method by measuring phenanthrene solubility in supercritical carbon dioxide, solubility measurements of two commercially available chelate complexes, cupric acetylacetonate and diethyldithiocarbomate copper salt, were made at near ambient temperatures. A thermodynamic model was then incorporated to predict solubility in supercritical carbon dioxide at varying operational conditions. The model uses Peng−Robinson equation of state and van der Waals-1 mixing rules.

Solubility of β-diketonate complexes for cobalt(III) and chromium(III) in supercritical carbon dioxide

“…Cross et al [20] correlated the solubilities of copper(II) acetylacetonate (Cu(acac) 2 ) in scCO 2 using the Peng-Robinson equation of state, and the correlated results were in good agreement with the experimental data by fitting the critical temperature and pressure of Cu(acac) 2 as well as the binary interaction parameter, k ij , to the experimental data. Lagalante et al [16] used the regular solution theory of Hildebrand et al [21] to predict the solubilities of chromium(III) acetylacetonate (Cr(acac) 3 ).…”

Measurement of the solubility of metal complexes in supercritical carbon dioxide using a UV–vis spectrometer

“…Therefore, the critical properties must be estimated using a prediction method, such as the group contribution method, or they must be treated as adjustable parameters. Cross et al [8] correlated the solubility data of copper(II) acetylacetonate (Cu(acac) 2 ) in scCO 2 with a conventional mixing rule. The calculated results reproduced the experimental solubility data due to simultaneous determination of the critical temperature and pressure of Cu(acac) 2 , as well as the binary interaction parameter, k ij , by fitting the solubility data.…”

Study of effects of different parameters on supercritical fluid extraction of uranium from acidic solutions employing TBP as co-solvent

“…Several models have been proposed to predict and quantitatively explain solubility behavior of solutes in supercritical fluids. These models are based on Hildebrand solubility parameter or Peng-Robinson equation of state [16,17]. These models require a prior knowledge of thermodynamic properties of the solute.…”