重铬酸钾法测定炼油废水COD的适用性分析

为了分析0.250 mol/L与0.025 mol/L重铬酸钾法测定炼油催化剂行业高氯废水COD的适用性，进行了比对实验。结果表明：两者测定结果相差60.5～76.8 mg/L；高浓度重铬酸钾法精密性较好， RSD%≤4.8%，准确度较高，与氯气校正法测定结果基本吻合，相对误差≤6%；低浓度的重铬酸钾法精密性相对较差， RSD%≥8.1%，与氯气校正法测定结果相对误差大于40%，准确度低。在控制稀释水样Cl-浓度500～800 mg/L范围时，采用重铬酸钾法测定COD，适宜于高浓度的方法。

Applicability Analysis of Potassium Dichromate Method to COD Determination in Refinery Wastewater

The suitability of COD determination by the potassium dichromate method in high chlorine content of dilution refinery wastewater sample was compared between using high （ 0.250 mol/L） and low （ 0.025 mol/L） concentrations. The differences between two concentrations of the determination results varied from 60.5 mg/L to 76.8 mg/L. The accuracy of result detected by high concentration potassium dichromate method （ RSD%≤4.8%） was close to what from chlorine rectification method （ARD≤6%）. The accuracy of low concentration potassium dichromate method was lower （RSD%≥8.1%）, with ARD above 40%compared to chlorine rectification method. When the chlorine ion content in dilution wastewater sample was controlled from 500 mg/L to 800 mg/L, the results were in good accuracy using high （ 0.250 mol/L） concentration potassium dichromate method.