基于离子选择电极法的密闭电石炉尾气中氰化氢的测定

Determination of HCN in closed carbide furnace tail gas by ion selective electrode

采用离子选择电极法测定密闭电石炉尾气中HCN的质量浓度,并与硝酸银容量法、异烟酸-吡唑啉酮分光光度法做对比。结果表明,3种方法均能满足密闭电石炉尾气中HCN的测定要求,相对标准偏差分别为2.26%、1.41%、1.94%,加标回收率分别为96.2%-100.4%、97.9%-101.5%、96.6%-101.3%。离子选择电极法检测范围与精密度均能满足尾气中氰化氢的测定要求,能用于尾气中HCN的日常监测;硝酸银容量法精确度相对其他两种方法较低,适合于精密度要求不高的场合;异烟酸-吡唑啉酮分光光度法精密度高,检测限低,但测定范围较窄,样品需稀释才能增加测定范围。

The paper is inclined to report our study on how to determine the HCN in closed carbide furnace tail gas by using the samples of the exhaust. In proceeding with our study, we have collected samples from a closed calcium carbide furnace in Yunnan under the well controlled condition. So far as we know, it would be possible for us to adopt three methods to achieve our research goal, which are： the ion selective electrode method, the silver nitrate titration method and the iso-nicotinic acid-pyrazdone photometric method. The said three methods are supposed to meet the demands to determine the HCN in the closed carbide furnace tail gas. The experiments we have done help us to find that the absorption liquid gained by using the ion selective electrode method was 10 g/L potassium nitrate and 4 g/L sodium hydrate, while the absorption liquid gained by using the silver nitrate titration method and the iso-nicotinic acid-pyrazdone photometric method could both be used to get the 10 g/L sodium hydrate. The relative standard deviations as the result of using the three methods are： 2.26%, 1.41% and 1.94%, with the recovery rates being 96.2%- 100.4%, 97.9% - 101.5%, and 96.6% - 101.3%, respeetively. Comparing the three methods, it can be found that the ion selective eleetrode method enjoys a wider measuring range （0.1 - 10 mg/L）, yet the concentration of CN- may keep a good linear relation with the response value （R2 = 0.99108）. However, the ion selective electrode method proves to be suitable for determining the HCN in the general exhaust. As to the silver nitrate titration method, it is highly limited in its range of detection （0.25 rag/L）, though it is possible to reduce the limit of the detection by decreasing the eoncentration of the silver nitrate standard solution. It is just for this reason that the method is suitable for the situation when high precision is not needed. And, in comparison with the other two methods, the isonicotinic acid-pyrazdone photometric method enjoys the highest precision and the minimally relative standard in deviation （RSD = 1.41 % ）, it is suitable for determining the HCN in exhaust. But the determining process of iso-nicotinic aeid-pyrazdone photometric method tends to be much more multitudinous, for the measure range was narrow （0.016 -0.25 mg/L） and the limit of detection was low, therefore, the eoncenteation of absorptive liquid should be diluted if the method were Used.