| Summary: | 碩士 === 國立中央大學 === 機械工程研究所 === 88 === Silver recycling from silver-containing waste has been studied in this work to prepare powder for manufacturing the silver electrode used in batteries. Experimented parameters such as reaction temperature,reactant concentration,and surfactant concentration were varied to find out an optimum condition to produce silver powder in a capacity 0.6kg/h.
The results demionstrated that : (1)the production rate of silver powder increases with increasing the reaction temperature; (2)the capacity increases with increasing the concentration of Ag(NH3)2+;(3)the yield of silver powder can be enhanced by decreasing the concentration of surfactant ; (4)it is better to mix the reactant at lower temperatures than at room temperature to assure the operation of the mixer ; (5)the waste liquid can be re-use 3 cycles , disposed with KMnO4 to follow the emission regulation ; (6)the purity of the silver powders produced from this process is 99.9%.
It was also found that the experimented parameters influence the powder properties. The average particle size of silver powders increase with increasing the reaction temperature and Ag(NH3)2+ concentration , however,the powder densities(apparent density and tap density)are unaffected. Addition of surfactant such as caprylic acid and ethanoltriamine decreases the powder densities.In the presence of caprylic acid, the average particle size of the silver powders produced decreases with increasing the reaction temperature, thus increasing the specific surface area of the powder.
The heat-treated silver powders(at temperature>350℃)are more suitable for use in electrode application because the shrinkage can almost be neglected in the process of electrode preparation. The discharge efficiencies for the silver electrode made of all the silver powders are higher than 70%, thus they are satisfactary in bettery application.
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