The adsorption behavior of divalent metal ions with β-diketone type chelating agents used in solvent extraction supported onto mesoporous silicate MCM-41 was investigated. It was found that most of the examined metal ions were adsorbed on MCM-41 as 1:2 complex with chelating agents. In addition, it was suggested that the adsorption ability of metal ions onto MCM-41 can be improved by controlling the hydrophobicity of the MCM-41 surface. Moreover, A cellulose fiber was modified with a multidentate ligand having nitrogen donor atoms, and the adsorption behavior of metal ions on the modified cellulose fiber was investigated. It was found that most of the studied metal ions including precious metal ions were adsorbed on the cellulose fiber modified with multidentate ligand.
This paper describes selective separation of cobalt and nickel ions from their mixed solution using the electrodialysis reversal (ED-R) process. In experiments using the conventional electrodialysis process, the fluxes of cobalt and nickel ions were almost identical under the conditions used. Conversely, when electrodialysis experiments were conducted in the presence of Ethylene Diamine Tetraacetic Acid (EDTA), cobalt ions preferentially permeated through a cation-exchange membrane and were well separated. Based on these results, cobalt and nickel ions were permeated into a compartment containing an EDTA aqueous solution by normal electrodialysis operation, and then ED-R was performed with the polarity reversed to separate the cobalt and nickel ions. The ED-R -operation facilitated to effectively separate the nickel and cobalt ions. We also attempted to recover the nickel ions and EDTA from their mixed solution using a precipitation method. The recovery rate of EDTA reached 80％, and the solution turned green at a lower pH of 0.4.