Health & Environmental Research Online (HERO)


Print Feedback Export to File
4878008 
Journal Article 
Aggregation behavior of cobalt(II), and nickel(II) and copper(II) bis(2-ethylhexyl) phosphate complexes in n-heptane 
Yu, ZJ; Ibrahim, TH; Neuman, RD 
1998 
1 
Solvent Extraction and Ion Exchange
ISSN: 0736-6299 
Marcel Dekker Inc 
New York 
16 
6 
1437-1463 
English 
WOS:000076582900007 
The solution behavior of divalent transition metal-bis(2-ethylhexyl) phosphate (M(DEHP)(2), M = cobalt, nickel or copper) complexes in n-heptane have been investigated by vapor pressure osmometry, viscometry and dynamic light scattering. Co(DEHP)(2) complexes tend to form large macromolecular species with a mean aggregation number N-agg as large as 225, and the size of the macromolecular species decreases with increasing Co(DEHP)(2) concentration. In contrast, Cu(DEHP)(2) complexes tend to form small macromolecular species N-agg = 4-8 which increase in size with increasing Cu(DEHP)(2) concentration. On the other hand, Ni(DEHP)(2) complexes land Ni(DEHP)(2). 2H(2)O complexes when the molar ratio of H2O to Ni(DEHP)(2) is 2) form small macromolecular species N-agg = 5.2, while large polydisperse macromolecular species are able to form with a mean apparent hydrodynamic radius as large as 15 nm at both high complex concentration and high water content. The macromolecular species formed by Ni(DEHP)(2). 2H(2)O complexes can solubilize large amounts of water tone order of magnitude more than that of Co(DEHP)(2) or Cu(DEHP)(2) complexes). The remarkable differences in aggregation and water solubilization behavior among the three M(DEHP)(2) systems are discussed. It is proposed that the macromolecular species in all three M(DEHP)(2) systems are quasi-one-dimensional association microstructures, i.e., rodlike reversed micelles, rather than polymers as believed by many authors in the literature. 
Metal; Solvent extraction; Agglomeration; Cobalt compounds; Composition effects; Copper compounds; Heptane; Light scattering; Macromolecules; Micelles; Molecular structure; Nickel compounds; Solubility; Viscosity measurement; Polydispersity; Transition metal-bis ethylhexyl phosphate; Organometallics; metal; Solvent extraction