COD测定废液中Ag2S04的回收循环利用研究

目的研究COD测定废液中Ag2SO4的回收和利用，实现资源的循环利用，提高利用效率，节约实验成本，减少环境污染。方法以COD测定废液为研究对象，将Ag2SO4通过NaCl转化为AgCl沉淀，再用Zn粒在酸性介质中进行还原，使AgCl转化为银粉；所得银粉在少量HN03存在的条件下，用浓H2S04氧化，将其转化为Ag2SO4，重新用于COD测定实验。结果通过一系列实验研究表明，有70％的银可以得到回收，所得Ag2SO4再次用于COD测定实验，标准样品的COD测定误差在许可范围之内；实际污水中COD的测定实验结果表明，Ag2SO4循环使用的测定误差平均为7．4％。结论实验证明回收的Ag2SO4可以作为COD测定实验的催化剂循环使用，可操作性良好，在节约实验成本的基础上，对于环境保护、减少污染物排放量方面有显著效果。但是COD测定结果的偏差较大，重现性有待进一步改进提高。

Study on the recycling of Ag2SO4 from the waste water of COD determination

Objective-To study the recycling of AgzSO4 from the waste liquid of COD determina tion in order to realize the recycling of resources, improve utilization efficiency, save the experimental cost of COD determination and reduce the pollution discharge into environment. Methods-The waste liquid of determinating COD is as the research object, the AgzSO, reacts with NaC1 to form AgC1 pre cipitation, which is reduced with zinc in acid medium to form Ag power, which is oxidized in concen trated sulfuric acid and a small amount of HNO3 to form Ag2SO, which is reused for the COD meas urement experiment. Results-A series of experimental studies show that 70% of silver can be recy cled, the Ag2SO4 obtained with chemical method can be used again for COD determination experiments as a catalyst, the margin of error in COD determination of standard samples is in the accepted range; the actual result of the COD determination in wastewater experiment show that the average error of the COD determination is 7.4 % when the Ag2SO4 is used again. Conclusion-A number of experimen tal studies show that the recycled Ag~SO, can be used again in the COD determination as a catalyst and it has good maneuverability. Besides saving the experimental cost, the reutilization of the waste water of COD determination is beneficial to environmental protection and remarkable for reducing pollutant discharge. However, the deviation degree of COD determination results is larger and the reproduc ibility of experimental results needs further improvement.