THE SORPTION BEHAVIOR AND SEPARATION OF SOME METAL THIOCYANATE COMPLEXES ON POLYETHER-BASED POLYURETHANE FOAM

The preliminary screening tests on the preconcentration of lanthanum(I II), aluminium(III), molybdenum(VI), gallium(III) and tungsten(VI) thi ocyanate complexes in aqueous media by unloaded foam indicated a reaso nable percentage of metal ions were retained on the foam. The influenc e of various parameters affecting the retention of these complex speci es from the aqueous media by the foam were critically studied and the possible mechanisms of the sorption of the compounds were suggested. H owever, owing to the complex chemical nature of the polyether-polyuret hane foam, several mechanisms may be involved simultaneously. Attempts for the quantitative retention and recovery of the tested complexes b y the foam columns were also made and satisfactory results were obtain ed. The height equivalent to theoretical plates (HETP) of the foam col umns were calculated from the chromatograms and break through capacity curve and were found in the range 1.8-2.3 mm at flow rates up to 15 c m3/min. The proposed foam column method has been successfully used for the separation of a series of complex mixtures of the tested metal th iocyanate complexes in aqueous media. The membrane properties of the f oam sorbents offer unique advantages over conventional bulk type granu lar sorbents in rapid, versatile effective separations and preconcentr ations of different complexes from fluid samples.