DETERMINATION OF METAL-CHELATE COMPLEX SOLUBILITIES IN SUPERCRITICAL CARBON-DIOXIDE

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