制革废水中化学需氧量测定方法研究

Determination Method of Chemical Oxygen Demand in Tannery Wastewater

针对国家标准测定化学需氧量(COD)的方法存在的操作繁琐、用时长、二次污染严重等问题,提出快速消解-分光光度法(简称快速消解法)对制革废水中化学需氧量进行分析,并对方法可行性进行验证。试验结果表明,在硫酸银加入量为0.04 g;硫酸加入量为4 mL;重铬酸钾用量为1 mL;适合的消解温度为165℃;最佳消解时间为10 min的条件下,COD浓度与吸光度值相关度R^(2)超过0.99;对不同浓度污水测试结果相对标准偏差(RSD)范围为0.68%~2.97%,相对标准偏差控制在3%内。测试结果与国家标准方法对比,测定的相对标准偏差范围为0.43%~2.89%,均小于3%;相对误差范围为-1.47%~1.26%,均小于2%,表现出良好的准确性。对于COD值小于50 mg/L的样品,可以通过快速消解法对未知水样进行分析,对测定值小于50 mg/L的结果进行修正,修正后结果与国家标准测试结果一致,同时可简化测试过程,提升检测效率。

In view of the problems of complicated operation,long time and serious secondary pollution in the determination of chemical oxygen demand(COD)in the national standard,a rapid digestion-spectrophotometry(rapid digestion method for short)was proposed to analyze the chemical oxygen demand in tannery wastewater,and the feasibility of the method was verified.The test results show that the amount of silver sulfate added is 0.04 g.The amount of sulfuric acid added is 4 mL.The dosage of potassium dichromate is 1 mL.The suitable digestion temperature is 165℃.When the optimal digestion time is 10 min,the correlation between COD concentration and absorbance value R^(2)exceeds 0.99.The relative standard deviation(RSD)of the test results of sewage with different concentrations is 0.68%~2.97%,and the RSD is controlled within 3%.Compared with the national standard method,the measured relative standard deviation range is 0.43%~2.89%,both less than 3%;The relative error range is-1.47%~1.26%,which is less than 2%,showing good accuracy.For samples with COD value less than 50 mg/L,unknown water samples can be analyzed by rapid digestion method,and the results with measured value less than 50 mg/L can be corrected.The corrected results are consistent with the national standard test results,so as to simplify the test process and improve the work efficiency.