基于超声-ORP原理的快速COD检测法研究

Rapid COD detection method based on ultrasound assisted sample digestion and titration with ORP monitored

针对传统水质化学需氧量(COD)在线检测方法检测稳定性差、易受环境影响等缺陷,为提高水质COD在线检测效率和稳定性,本文提出一种超声波辅助消解(UASD)作用下基于氧化还原电位(ORP)的COD快速检测方法:UASD-ORP法。通过超声波辐照下空化气泡微射流的加强传质、表面自由基活化等特效作用消解待测水样,并结合监测溶液ORP确定滴定终点,保证COD检测的快速性、准确性、稳定性。实验表明,经UASD方法检测标准邻苯二甲酸氢钾(KHP)溶液的COD值同国标法测得的COD值非常接近,相对误差在-6.0%～-3.0%之间;对实际污水样品采用UASD-ORP法与标准方法测得COD值的准确度在-10.0%～-1.5%之间。UASD-ORP法完成COD检测周期在15～20 min,且测量重复性好,相对标准偏差RSD达到0.05%。实验表明该方法可行,推荐用于开发在线检测技术。

The detection results of COD and easily affected by the environment got from traditional detection method is widely inaccurate, unstable, In order to improve the efficiency and the stability of COD online detection results, a new method of COD detection method： UASD-ORP method based on ORP method which is assisted with the method of UASD method is proposed in this paper. It is based on the principle of ultrasonic chemistry and ORP method. Through the strengthening mass transfer of cavitation bubble＇s micro jet under the irradiation of ultrasonic, surface free radical activation and other effects to digest the water sample, combined with the macroscopic oxidation-reduction character of ORP monitoring solution, it contributed to the accuracy and stability of COD detection in the subsequent titration process. Experiments show that the measured COD value of the standard KHP solution by that method is very close to the value by the national standard method and the relative error is between in the -6.0% - -3.0%, the accuracy of the measured COD value by the mentioned method above and the value by the standard method in practical detection application of waste water samples is between -10.0% --, -1.5%. The process of COD detection in the use of UASD-ORP method is between 15-20 min and the repeatability is 0.05%.The experiments show that the method is significant, and can be used to develop COD online determination technology.