Metal sequestering by a poly(ethylenimine)-sephadex G-25 conjugate containing 2,2 '-dihydroxyazobenzene

2,2'-Dihydroxyazobenzene (DHAB) was attached to poly(ethylenimine) (PEI) to obtain DHAB-PEI. Spectral titration revealed that uranyl, Fe(III), Cu(II), and Zn(II) ion form 1 : 1-type complexes with DHAB attached to PEI. Format ion constants for the metal complexes formed by the DHAB moieties of DHAB-P EI were measured by using various competing ligands. The results indicated that the concentrations of uranyl, Fe(III), and Cu(II) ions can be reduced to 10(-16)-10(-23) M at pH 8 with DHAB-PEI when the concentration of the DH AB moiety is 1 residue M. By using cyanuric chloride as the coupling reagen t, DHAB-PEI was immobilized on Sephadex G-25 resin to obtain DHAB-PEI-Seph. Binding of uranyl, Fe(III), Cu(II), and Zn(II) ion by DHAB-PEI-Seph was ch aracterized by using competing ligands. A new method has been developed for characterization of metal sequestering ability of a chelating resin. Forma tion constants and metal-binding capacity of two sets of binding sites on t he resin were estimated for each metal ion. DHAB-PEI-Seph was applied to re covery of metals such as uranium, Fe, Cu, Zn, Pb, V, Mn, and W from seawate r. The uranium recovery from seawater by DHAB-PEI-Seph does not meet the cr iterion for economical feasibility partly due to interference by Fe and Zn ions. The seawater used in the experiment was contaminated by Fe and Zn and , therefore, the efficiency of uranium extraction from seawater with DHAB-P EI-Seph could be improved if the experiment is carried out in a cleaner sea .