| Research Abstract |
1. To elucidate the mechanism of solvent extraction of palladium with didodecylmonothiophosphoric Acid, the extraction was carried out in a highly stirred tank or in a stirred transfer cell. Loading test of palladium with the extractant and measurement of interfacial tension of the extractant were also conducted. Concentration dependencies of the extraction rate were examined, from which an interfacial reaction model where four kinds of chloro-palladium complexes participate in the extraction reaction was presented. As the result of analyzing the extraction rate based on the model, the interfacial reaction rate constants between each chloro-palladium complex and the extractant adsorbed at the interface were obtained.
2. Trans-effect of thiocyanate ion on the extraction rate in the above-mentioned system was discussed. An addition of thiocyanate ion enhanced the extraction rate by 600 times. The experimental results were analyzed by considering the interfacial reactions between three kin
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ds of chloro-thiocyano-palladium complexes and the extractant adsorbed at the interface.
3. To examine alkyl-chain length of the extractant on the extraction rate, the extraction rate of palladium with dioctylmonothiophosphoric acid was measured. The interfacial reaction rate constants obtained from analyzing the extraction rate based on the same mechanism as mentioned above were somewhat greater than those of didodecylmonothiophosphoric acid.
4. Extraction of palladium with liquid surfactant membrane was carried out. First stripping equilibrium of dioctylmonothiophosphoric acid - palladium complex was measured by using thiourea as the stripping agent, and the stripping equilibrium constant was obtained. Then the stripping rate of palladium was measured in the stirred transfer cell, and the concentration dependencies of the rate were examined. Lastly the extraction of palladium with liquid surfactant membrane was conducted, from which it was found that a permeation mechanism of palladium through the liquid membrane was difficult to be clarified. Further study on this point will be necessary. Less
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