塩化ロジウム酸水溶液のヒドラジン還元処理

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An aqueous H3RhCl6 solution was treated by N2H4 reduction for the purpose of producing fine Rh powder. The reaction behaviors were investigated at temperatures below 80 under the blowing of N2 to agitate the sample solution. The Rh compound precipitated from the addition of an NaOH solution to alkalize the H3RhCl6 solution. This compound showed some sharp X-ray diffraction lines, but they could not be identified. The precipitation ratio was measured by ICP analysis for Rh concentration of the filtrate. The ratio for precipitation time of 15 minutes was considered to be the equilibrium value because the ratio did not change after 15 minutes. It was clarified from the relation between the equilibrium ratio and the concentration of added NaOH solution that all of the Rh in the solution was precipitated in the case of a concentration above 0.5 mol/l. The values of the precipitation ratio were hardly affected by precipitation temperatures between 20 and 80°C. After the treatment completed precipitation of Rh in the solution, an N2H4 solution was added to the solution and reduced the compound to metal Rh. It was shown by SEM observation and measurement of the particle size distribution of the filtrated solid that distinction between the Rh compound and metal Rh was very difficult in terms of shape and size. The particles had the diameter of 0.05 ∼ 0.1μm and partly aggregated. The reduction ratio was measured from the analysis of the Rh compound in a filtrated solid because the compound was easy to dissolve in acid. However, metal Rh was difficult to dissolve by such an aqua regia. The reduction curves were obtained from reduction behavior with the reduction time in the temperature range of 60 ∼ 80°C. The initial reaction rate was obtained from the initial straight line of the reaction curve. The temperature dependency of the rate gave 96 kJ/mol as the activation energy of the reduction. Consequently, it was considered that the reduction was rate-determined by the chemical reaction.
社団法人資源・素材学会の論文
1999-07-25

塩化ロジウム酸水溶液のヒドラジン還元処理

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