高氯离子、低COD废水中COD的测定

Analysis of COD in wastewater with high chloridion and low COD

建立了适用于高氯离子、低COD废水中COD的重铬酸钾测定方法。分别采用甘油、二氯丙醇、β,β′-二氯异丙醚和氯化钙配制模拟高氯废水,考察了氧化剂重铬酸钾溶液浓度、掩蔽剂加入量(以m(HgSO_4)∶m(Cl^-)表示)对测定效果的影响。实验结果表明:以低浓度(0.05 mol/L)重铬酸钾溶液为氧化剂时,测定数据波动范围小,相对误差也低(-1.4%^+0.4%);对于高氯低COD废水的COD测定,当COD大于100 mg/L时按m(HgSO_4)∶m(Cl^-)=10∶1加入硫酸汞掩蔽剂,当COD小于100 mg/L时按m(HgSO_4)∶m(Cl^-)=20∶1加入硫酸汞掩蔽剂,并采用浓度为0.05 mol/L的重铬酸钾溶液作为氧化剂,能较好地消除氯离子对COD测定的干扰,相对误差在5%以内;将优化后的测定条件应用于实际环氧氯丙烷生产废水COD的测定,重现性良好,当m(HgSO_4)∶m(Cl-)分别为10∶1和20∶1时,相对误差分别为+3.3%和+2.9%,COD平均回收率分别为103.4%和102.9%。

The potassium dichromate method for analysis of COD in wastewater with high chloridion and low COD was established. The factors affecting the determination effect were studied using the simulated high chloridion wastewater containing calcium chloride with glycerinum,dichloropropanol and β,β ′-nemamort,respectively. The experimental results showed that：Small data fluctuation range and low relative error （-1.4% to ＋0.4%） could be achieved using the low concentration （0.05 mol/L） potassium dichromate solution as oxidant;For analysis of COD in wastewater with high chloridion and low COD,when the mercury sulfate masking agent was added according to m（HgSO4）∶m（Cl-）=10∶1 for more than 100 mg/L of COD and m（HgSO4）∶m（Cl-）= 10∶1 for less than 100 mg/L of COD,and the potassium dichromate solution with 0.05 mol/L of concentration was used as oxidant,the interference of chloridion on COD determination could be eliminated,the relative error was within 5%;Good reproducibility is proved by using the method for determination of COD in the actual epichlorohydrin production wastewater,when m（HgSO4）∶m（Cl-） was 10∶1 and 20∶1,the relative error was ＋3.3% and ＋2.9%,while the average recovery rates was 103.4% and 102.9%,respectively.