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本文研究了Pt、Pd、Au、Rh及Ir在盐酸介质中用铜置换的动力学.通过体系电位的测定,了解到贵金属置换率与体系电位的关系,并与计算所得的结果一致.研究了置换速度与温度、酸度及搅拌速度的关系.其结果为:温度对Au、Ir的反应速度无明显影响,而对Pt、Pd及Rh影响较大,大于60℃时能加快其反应速度,并在60℃均有转折.酸度对Ir的置换无影响,酸度增加能使Au的置换速度减慢,酸度在1.75~2.14 M对Pt、Pd及Rh均有较好的效果.当温度大于60℃时,置换速率常数对数值与搅拌速度成直线关系增加.实验证明:铜置换贵金属为一级反应,即log Co/Ct与反应时间成直线关系.置换反应速度大小顺序为:Au>Pd>Pt>Rh>Ir.Ir在各实验条件下均不被置换.通过显微镜观察及X-射线结构分析,研究了晶核生成速度及晶粒生长速度与温度、时间的关系.讨论了该过程的反应机理.
In this paper, the kinetics of the substitution of Pt, Pd, Au, Rh and Ir for copper in hydrochloric acid medium was studied. The relationship between the exchange rate of noble metal and the potential of the system was obtained by measuring the potential of the system and was consistent with the calculated results. The results showed that the temperature had no significant effect on the reaction rate of Au and Ir, but had a significant effect on Pt, Pd and Rh, and the reaction rate could be accelerated if the reaction temperature was above 60 ℃ All have transitions at 60 ° C. The acidity has no effect on the Ir substitution, the increase of acidity can slow down the Au substitution rate, and the acidity of 1.75 ~ 2.14 M has a good effect on Pt, Pd and Rh.When the temperature is higher than 60 ℃ , The logarithm of displacement rate constant increases linearly with the stirring rate.The experimental results show that the copper substitution is a first order reaction, ie, the log Co / Ct has a linear relationship with the reaction time.The order of the displacement reaction rates is Au> Pd> Pt > Rh> Ir.Ir was not substituted under all experimental conditions.The relationship between nucleation rate and grain growth rate and temperature and time was studied by microscopic observation and X-ray structure analysis.The reaction of the reaction mechanism.