Synergien bei der Extraktion von Palladium- und Rhodiumchelaten mit überkritischem Kohlendioxid

The influence of chelate structure and the addition of synergists on the extraction efficiency of acetylacetonates, 8-hydroxychinolinates and dialkyldithiocarbamates (DTC) of palladium and rhodium with supercritical carbon dioxide (scCO 2 ) were studied. Tributylphosphin additions to solutions of palladiumchelates in scCO 2 increased extraction yields significantly. The
solubilities of acetylacetonates and diisobutyldithiocarbamates of palladium and rhodium in scCO 2 were measured between 150 and 400 bar at 80 °C. Metal-DTC substituted with C 4 - or C 5 - alkylrests showed maximum solubilities in scCO 2 .
Optimised methods for preparation of homologous DTC are presented. The unknown
structure of Pd(II)-bis(N,N-dipentyldithiocarbamate) was solved by x-ray diffraction measurements. All chelates have been characterized with new HPLC methods and capacity factors have been determined. Ligand exchange reactions between homologous Pd-DTC in solution were discovered by HPLC separations and a correlation between structure and retention time was found. To quantify metals in chelat solutions new AAS applications in methanolic solutions have been validated.
The influence of tributylphosphine on palladium chelates was followed by UV-VISspectroscopy.
Several isosbestic points and wavelength shifts in the absorption spectra were
observed. The kinetics of the slow reaction of palladium(II)acetylacetonate with some primary amines were studied.
To recover platinum group elements out of acid solutions an in situ chelation-SFE process with DTC-ligands was elaborated. An enrichment of Pd in the extract and the separation of Rh and Pt was achieved when the process was applied to a natural ore sample.