三价铬氧化方法比较研究

Comparative study on methods for trivalent chromium oxidation

三价铬氧化为六价铬、六价铬与二苯碳酰二肼显色是测定水溶液中三价铬含量最常用的方法,该方法的关键是既要方便快捷地将三价铬完全转化为六价铬,同时还要避免氧化剂与显色剂反应干扰测定。通过实验比较了几种文献中报道的三价铬氧化方法,并进行了优化研究。实验结果表明,高锰酸钾、过硫酸铵和过氧化氢都是适宜的三价铬氧化剂,而高氯酸和溴效果不好。综合准确、简便、安全等因素,推荐过硫酸铵和过氧化氢作为首选氧化剂。

Oxidation of Cr（Ⅲ） to Cr（Ⅵ） is the most common method to determine trace Cr（Ⅲ） in water by diphenylcarbohydrazide spectrophotometric method.The key of this method is not only the convenience and expedition of the totally conversion of Cr（Ⅲ） to Cr（Ⅵ）,but also avoids the disturbance of the reaction between the oxidizing agent and chromogenic agent.The methods reported in literature were compared with experiments and some procedures were optimized.Results showed that KMnO_4,（NH_4）_2S_2O_8,and H_2O_2 were all good candidates to oxidize Cr（Ⅲ） for spectrophotometric measurement.On contrary,perchloric acid and bromine got unsatisfactory effect.From the viewpoints of accuracy,convenience and safety,persulfate and hydrogen peroxide are the best oxidants for trace Cr（Ⅲ） determination in water by spectrophotometry.