SUPERCRITICAL-FLUID EXTRACTION - METALS AS COMPLEXES

Metal species in solid and liquid materials can be extracted by superc ritical CO2-containing organic ligands. This SFE technique converts ch arged metal species into neutral metal complexes which become soluble in CO2. The efficiency of metal extraction using the in situ chelation -SFE method depends on a number of factors including (1) stability and solubility of ligand, (2) solubility of metal chelate, (3) water and pH, (4) temperature and pressure, (5) chemical form of metal species, and (6) matrix. Several different types of chelating agents including dithiocarbamates, beta-diketones, organophosphorus reagents and macroc yclic compounds have been tested for their ability to extract heavy me tals, lanthanides, and actinides from different sample matrices. With proper selection of ligands, separation of organic and inorganic metal species may be achieved using this SFE technique. Metal species extra cted by the SFE method probably represent the leachable metals present in solid matrices. (C) 1997 Elsevier Science B.V.