Abstract:

Interference occurs in the process of COD determination,if there is residual persulfate in the water sample to be tested. The interference effect caused by K₂S₂O₈ on COD determination has been investigated,the causes of interference analyzed, and the measure to eliminate the corresponding interference proposed. The research results show that the residual K₂S₂O₈ has certain reducibility, so as to make the COD testing value be higher than actual value. The relationship between its concentration and COD is obviously linear. The contribution of COD change value by l mg of K₂S₂O₈ is about 0.029 79 mg. In COD standard solution system, ΔCOD₁ which is the difference value between COD measured value and raw water actual COD and linear equation calculated ΔCOD₂ which is contribution value of COD by K₂S₂O₈ is 0.88%-1.99% of raw water actual COD. In bio-chemically treated landfill leachate system, the difference value between ΔCOD₁ and ΔCOD₂ is 1.23%-7.18% of raw water actual COD. The linear equation can reflect the COD state of actual water sample better, and is thus able to eliminate the interference caused by the residual K₂S₂O₈ in COD determination.

Key words: COD, K₂S₂O₈, interference elimination

摘要：

待测水样中若残留过硫酸盐会对COD的测定产生干扰。考察了K₂S₂O₈对COD测定的干扰情况，分析干扰原因，并提出相应的消除干扰措施。研究表明，残留的K₂S₂O₈具有一定的还原性从而使COD测定值高于实际值，其浓度与COD之间呈现显著的线性关系，1 mg K₂S₂O₈对COD变化值的贡献约为0.029 79 mg。在COD标准溶液体系中，ΔCOD₁（COD测定值与原水实际COD的差值）和线性方程计算的ΔCOD₂（K₂S₂O₈对COD的贡献值）的差值为原水实际COD的0.88%~1.99%；在经生化处理后的垃圾渗滤液体系中，ΔCOD₁与ΔCOD₂的差值为原水实际COD的1.23%~7.18%。该线性方程较好地反映了实际水样的COD，借此可消除残留K₂S₂O₈对COD测定的干扰。

关键词: COD, 过硫酸钾, 干扰消除

CLC Number: 

• X832