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Extraction of palladium(II) with through-hole type microcapsules containing trioctylamine

Kiyoyama S., Shiomori K., Yoshida M.

Ars Separatoria Acta

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2009/2010

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No. 7

49-60

EN

Large-diameter and through-hole type microcapsule with entrapped trioctylamine (TOA) as an extractant were prepared by (W/O/W) emulsification and in-situ polymerization method. The morphologies of the microcapsules, their encapsulation efficiencies for TOA, and their forward and back extraction properties for palladium(II) were investigated. The microcapsules ranged in size from 210-420 ěm. The encapsulation efficiency of TOA was approximately 100% for all the microcapsules, which indicates minimal loss of TOA during preparation of the microcapsules. Through-hole type microcapsules were obtained when inner aqueous phase contained a high concentration of sodium chloride, and at a moderate agitation speed in the first emulsification. With the through-hole type microcapsules the extraction equilibrium approached one, and the extraction rate was very high compared to other preparation conditions and (O/W) type microcapsules.

2

Preparation of effective and fast extraction media for palladium (II) using microcapsules

Minamihata K., Kiyoyama S., Shiomori K., Yoshida M., Hatate Y.

Ars Separatoria Acta

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2007

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No. 5

55-67

EN

Microcapsules containing tri-n-octylamine as an extractant with the diameter of less than 25µm were prepared by using SPG membrane emulsification and insitu polymerization method. The morphologies of microcapsules, the encapsulation efficiencies of tri-n-octylamine, the extraction properties of palladium (II) from hydrochloric acid solution and the back extraction properties of palladium (II) from microcapsules were investigated. The average diameter of obtained microcapsules was about half of the pore diameter of SPG membrane. The encapsulation efficiency of tri-n-octylamine was approximately 100% for all the microcapsules prepared in this study. Therefore, it can be said that there was practically no loss of tri-n-octylamine during the preparation of microcapsules. All microcapsules prepared in this study reached forward extraction equilibrium within 5 minutes and the forward extraction ratio reached nearly 1. The back extraction of palladium (II) from microcapsules was carried out using 0.1M-hydrochloric acid solution containing a prescribed amount of thiourea. The back extraction occurred promptly and the back extraction ratio was high enough to elute all palladium (II) out from the microcapsules. Furthermore, by repeating forward and back extraction experiments, the durability of microcapsules was examined. From the result, it can be said that tri-n-octylamine was encapsulated rigidly and there was no leakage during extraction and back extraction experiment. Thus it seemed that the microcapsules were capable to be used in a repeated operation.

3

Extraction equilibria of hypophosphorous, phosphorous and phosphoric acids by toluene solution of tri-n-octylamine

Sana T., Shiomori K., Kawano Y.

Ars Separatoria Acta

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2003

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No. 2

125-138

EN

The extraction equilibria of hypophosphorous, phosphorous and phosphoric acids with tri-n-octylamine as an extractant in toluene were measured at 303K. Under these conditions, undissociated acid (A’) reacts with the amine (B) to form various complexes in toluene. The complexes formed and equilibrium constants were estimated by a graphical analysis method. The complexes formed in these systems were found to be A’nB type species for hypophosphorous acid, A’nBm type species for phosphorous acid, (A'B)n type species for phosphoric acid, respectively. The experimental results could be explained by reaction models and equilibrium constants for each acid.

4

Extraction rate of nickel in aqueous ammonium sulfate solution with 5-dodecylsalicylaldoxime in kerosene

Sana T., Fujii R., Shiomori K., Kawano Y., Nagayoshi K.

Ars Separatoria Acta

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2002

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No. 1

35-44

EN

In order to clarify the adsorption equilibrium for the species of the extractant and the extraction complex, the interfacial tensions between the aqueous and the organic solutions were investigated, using equilibrated kerosene solution in the presence of 5-dodecylsalicylaldoxime (LIX® 860-IC) and aqueous solution in the presence and absence of nickel ion. The interfacial tensions decreased with increasing in the concentration of LIX® 860-IC. Experimental results of the interfacial tension were analyzed by Gibb’s adsorption isotherm. The adsorption equilibrium constant and the interfacial area for the extractant and the extraction complex were determined. The extraction rate of nickel from the aqueous ammonium sulfate solution with LIX® 860-IC in kerosene was investigated using a Lewis-type transfer cell. The concentration effects of extractant, nickel, and hydrogen ion on the extraction rate were examined. The extraction rate increased with increasing in the concentrations of nickel and the extractant, and approached to constant values depending on the extractant concentration at a high concentration of nickel. The rate increased with decreasing in the concentration of hydrogen ion, and approached to constant values depending on the extractant concentration. These results were analysed based on an interfacial reaction model in which the reaction proceeds between an extractant species adsorbed at the interface and nickel ion in the aqueous solution. The extraction rate is interpreted based on the rate equation in which the interfacial reaction between a 1:1 nickel chelate complex species adsorbed at the interface and the extractant in the organic solution is the rate-determining step. The reaction rate constants and equilibrium constants were determined.

5

Back-extraction mechanism of lysozyme from reverse micelles in sodium bis 2-ethylhexyl sulfosuccinate and long chain alkyl amine mixed systems

Shiomori K., Honbu T., Sana T., Kawano Y., Kuboi R.

Ars Separatoria Acta

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2002

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No. 1

45-54

EN

Extraction and back-extraction of lysozyme are investigated using a mixed micellar system of sodium bis(2-ethylhexyl) sulfosuccinate and long chain alkyl amines. Either di-n-octylamine or di-2-ethylhexylamine is used as the amine added. In these systems, reverse micelles is not formed at acidic pH range. Lysozyme extracted at pH which is slightly lower than the isoelectric point of lysozyme is successfully back-extracted by destruction of the micelles at acidic pH range. By increasing the amine concentration, the pH values, at which the back-extraction of lysozyme began, are raised, and the activity of the back-extracted lysozyme decreases. Linear relationship between the concentration of the amine added in the system and that of lysozyme back-extracted exists .