密闭消解-电位滴定法检测废水中的化学需氧量

Determination of chemical oxygen demand in waste water by closed digestion-potentiometric titration

在检测工业废水和生活污水中的化学需氧量(COD)时,采用密闭消解-电位滴定法(简称方法1,利用自制的密闭消解/滴定一体瓶及消解器)替代开口回流消解-指示剂滴定法(HJ 828-2017,简称方法2),解决了后者消解时间(120 min)长,氯离子干扰严重的问题。结果表明:采用方法1,消解时间较方法2缩短了近4/5,硫酸汞用量仅为后者的一半;以方法2测定结果为基准,2种方法的相对误差为-3.25%~4.26%,方法1可以满足生产检测要求;方法1测定实际废水的COD质量浓度相对标准偏差为0.31%~3.33%,精密度优于方法2。

The closed digestion-potentiometric titration(method 1,with self-made digestion/titration bottle and digester)was used instead of open reflux digestion-indicator titration(HJ 828-2017,method 2),which could resolve the problems of the latter such as long digestion time(120 min)and serious interference of chloride ion when measuring chemical oxygen demand(COD)in industrial waste water and domestic sewage.The results showed that using method 1,the digestion time was nearly 4/5 shorter than that of method 2,the consumption of mercury sulfate content was half than that of the latter.With method 2 as the reference,the relative error of the two methods was-3.25%-4.26%,method 1 could meet the requirements of production testing.The relative standard deviation of COD mass concentration of waste water was 0.31%-3.33%by method 1 and the precision was better than method 2.