SEPARATION AND PRECONCENTRATION OF TRACE-ELEMENTS AND THEIR PHYSICOCHEMICAL FORMS IN AQUEOUS-MEDIA USING INERT SOLID MEMBRANES

A survey is given over various methods for separation and enrichment o f trace elements and their speciation in aquatic media using membrane filtration. The methods are mainly used for three purposes: (1) studie s of size distribution patterns for trace elements in order to estimat e the association of the elements with suspended particles and soluble compounds of different nature, (2) preseparations of interfering cons tituents of solutions to be analysed in continuous flow instruments, ( 3) separation and preconcentration of inorganic ions in membrane filtr ation cells with and without chemical reagents. The capabilities and l imitations inherenent in the methods are critically discussed. The mos t interesting results have been obtained for size fractionation techni ques and for membrane separations in the presence of separating reagen ts. These and especially other membrane methods require further resear ch to identify more clearly their respective advantages and limitation s.