Abstract: Metal ions are removed from solution by complexing with an immobilized polyethyleneimine, formed by first bonding a silane-propyl bridge to a substrate particle of silica or silicate, larger than 200 mesh. Then, polyethyleneimine is covalently bonded by a nitrogen to the bridge. Due to the spacing established by the bridge between the polyethyleneimine and substrate, the polyethyleneimine maintains high ion complexation capacity.

Abstract: A composition comprising a chelating compound which is a macrocyclic compound containing at least two coordinating centers in the ring, at least one of which is a neutral base moiety, and an organic acid containing at least one alkyl or alkenyl group containing 8 or more carbon atoms. The macrocyclic compound contains at least 10 ring atoms and especially at least 12 ring atoms. The neutral base moiety is typically a nitrogen moiety. Preferably there are at least four coordinating centers at least two of which are neutral base moities. The acid can be an alkyl or alkenyl substituted acid for example a long chain carboxylic acid. The composition can be used as an extractant system for the selective extraction of metals from an aqueous phase into an organic phase.