Keisuke Ohto

Separation of Cobalt and Nickel with Phenylphosphonic Acid Mono-4-tert-octylphenyl Ester by Liquid Surfactant Membranes

Abstract The separation of cobalt and nickel with liquid surfactant membranes (LSMs) was carried out in a stirred cell using a newly synthesized extractant. The effect of a surfactant on the kinetics of cobalt and nickel extraction was investigated to elucidate the role of a surfactant used in LSMs. The extraction equilibrium of these metals was also examined. Further, the interfacial tension between the organic and aqueous phases was measured to elucidate the adsorption equilibrium of a surfactant. It was found that the interfacial activity of the extractant is as high as that of a surfactant. In the extraction equilibrium study of these metals, extraction equilibrium constants were obtained for cobalt and nickel for the following equations: Co2+ + 2(HR)2=CoR2(HR)2 + 2H+ Ni2+ + 3(HR)2=NiR22(HR)2 + 2H+ The effects of the extractant and surfactant on the extraction rate of cobalt and nickel in LSMs were studied. The results were analyzed by a proposed model with an interfacial reaction, and rate constants ...

Rare Earth Metal Extraction by Liquid Surfactant Membranes Containing a Calixarene Carboxylate Derivative: Permeation Acceleration Effect of Sodium Ions

ABSTRACT Calixarene carboxylate derivatives were used as a mobile carrier for rare earth permeation in a liquid surfactant membrane (LSM) system. The effect of alkali metal ions on the extraction behavior of rare earth metals in both liquid-liquid extraction and LSM systems has been studied. The addition of sodium ions considerably enhanced the extraction ability of rare earth metals in the extraction equilibrium. Furthermore, the presence of alkali metal ions in the material solution affected the rate of rare earth permeation in LSMs. The most accelerative transport of rare earth metals by LSMs was achieved by the addition of sodium ions. This acceleration effect of sodium ions was predominant in a tetracarboxylate calixarene whose cavity size just fits the ionic diameter of sodium ions. The sodium-loaded calix[4]arene derivative showed good performance as an effective mobile carrier for rare earth metals in the presence of sodium ions.

Adsorption Behavior of Dithiocarbamate β-Chitosan Gels for Cadmium(II)

Adsorption gels were prepared by means of chemical modification of β-chitosan by immobilizing functional groups of dithiocarbamate to investigate its adsorption behavior for cadmium(II) such as effect of cross-linking, adsorption rate, pH dependency, loading capacity by batch-wise experimental work and mutual adsorptive separation of cadmium(II) from zinc(II) using a packed column. Thus prepared adsorption gel exhibited high selectivity towards cadmium(II) over zinc(II) and high loading capacity for cadmium(II) regardless of cross-linking. Satisfactory separation of cadmium(II) from zinc(II) was achieved using a packed column.