快速消解分光光度法测定高氯废水中低浓度化学需氧量

Determination of Low Chemical Oxygen Demand of Waste Water with High Chloride by Fast Digestion–Spectrophotometric Method

建立快速消解分光光度法检测高氯废水中低浓度化学需氧量(COD)的方法。通过提高催化液中硫酸银的浓度(46 g/L)充分络合氯离子,同时降低消解液中重铬酸钾的浓度至0.061 2 mol/L来抑制重铬酸钾与氯离子的反应,达到有效消除Cl~–干扰的目的。水样在165℃消解30 min,于600 nm波长检测吸光度,标准曲线法计算COD。实验结果表明,水样中COD质量浓度为20 mg/L时,2 000 mg/L的Cl~–不干扰COD的测定(相对误差小于10%),并且随着COD质量浓度的增加,Cl~–产生的干扰误差逐渐降低。对国家环境保护部标准样品进行了测定,COD测定值与标准值一致。样品加标回收率为97.0%~103.7%,测定结果的相对标准偏差为2.01%~6.33%(n=6)。该法快速,有毒试剂用量小,成本低,具有较高的准确度和良好的精密度,可以用于多数工业废水中COD的测定。

A fast digestion–spectrophotometric method for the determination of low chemical oxygen demand of waste water with high chloride was established. In order to suppress chloride interference,the concentration of Cr_2O_7^(2–) and catalyst were changed. As a digestion solution,low Cr_2O_7^(2–) about 0.061 2 mol/L was proved to be more better,meanwhile the concentration of Ag_2SO_4 about 46 g/L was increased for masking chloride. Samples were digested in glass tubes and heated at 165℃ for 30 min,then determined at λ=600 nm by spectrophotometry, COD was caculated by standard curve method. The experimental results showed that the mass concentration of COD in water samples of 20 mg/L,2 000 mg/L Cl– did not interfere with the determination of COD(relative error less than 10%). With the increase of COD mass concentration,the interference errors caused by Cl– was reduced gradually. The standard sample of the state environmental protection department was determined,the determination values of COD were consistent with the standard values. The recovery ranged from 97.0% to 103.7%,and the relative standard deviation of determination results was 2.01%–6.33%(n=6). The method is fast,low cost with small toxic reagent dosage,it can be used for COD determination of most of the industrial waste water with high accuracy and good precision.