改性钛基PbO2电极的制备及其对COD的快速检测

通过制备Ti/α/β-PbO₂、Ti/Ag/β-PbO₂这两种含有不同中间层的钛基二氧化铅电极来探究电催化氧化技术快速测定葡萄糖模拟废水中有机物(COD)含量的可行性。为了评估两种电极的各项性能,首先采用扫描电镜(SEM)、X射线衍射(XRD)对电极进行形貌表征,其次进行电化学性能测试包括线性伏安曲线(LSV)、塔菲尔曲线(Tafel)、循环伏安曲线(CV)以及交流阻抗测量分析。结果表明,Ti/α/β-PbO₂电极表面晶体结构更加均匀,晶粒尺寸偏小,具有更大的电活性表面积。Ti/α/β-PbO₂电极的析氧电位为1.77 V,为·OH的产生提供良好条件。在Tafel、CV测试中,Ti/α/β-PbO₂电极的交换电流密度i₀及比电容C_p分别为0.0995 A·cm^-1、0.004098 F·cm^-1均高于Ti/Ag/β-PbO₂电极,说明Ti/α/β-PbO₂电极的耐腐蚀性以及释放电子的能力优异。最终选用Ti/α/β-PbO₂电极为工作电极。Ti/α/β-PbO₂电极检测COD的最佳条件为：氧化电位1.30 V、电解时间150 s、电解液浓度0.03 mol·L^-1 硝酸钠(NaNO₃)。电化学法与比色消解法测定COD的相关系数可达0.9909,同时具有良好的重现性与相关性,COD的检测范围为0 mg·L^-1 ~ 500 mg·L^-1。在误差允许的范围内可以替代标准的重铬酸钾法,为实现COD的在线快速检测提供参考价值。

Preparation of Modified Titanium Based PbO2 Electrode and Its Rapid Detection of COD

In the traditional Ti/β-PbO₂ electrode, the crystal lattice difference between β-PbO₂ and Ti matrix is large, and the prepared electrode is easy to fall off and has a short service life. It needs to be modified in actual use. Based on the advantages of α-PbO₂ material and Ag material in terms of adhesion and conductivity, respectively, the above two materials are selected as the intermediate layer of Ti/β-PbO₂ electrode to improve electrode performance. In this paper, by preparing Ti/α/β-PbO₂ and Ti/Ag/β-PbO₂ electrodes with different intermediate layers, the superiority and feasibility of electrocatalytic oxidation technology for rapid determination of organic matter (COD) content in simulated glucose wastewater were investigated. Firstly, the properties of the two electrodes were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) to characterize the surface morphology and crystal structure of the electrodes, respectively. The electrode surfaces of Ti/α/β-PbO₂ and Ti/Ag/β-PbO₂ had no other granular crystal bare leakage, and their crystal arrangement was relatively compact. Compared with Ti/Ag/β-PbO₂, the crystal structure of Ti/α/β-PbO₂ electrode surface was more uniform and the grain size was smaller. Secondly, a series of electrochemical performance tests were carried out on the two electrodes by employing linear scanning voltammetry (LSV), Tafel curve analysis, cyclic voltammetry (CV) and AC impedance spectroscopy. The results show that the crystal structure of Ti/α/β-PbO₂ electrode surface was more uniform, and the grain size was smaller, and the electroactive surface area was larger. The oxygen evolution potential of Ti/α/β-PbO₂ electrode was 1.77 V, which provides a good condition for the formation of ·OH. In Tafel and CV tests, the exchange current density i0 and the specific capacitance CP of Ti/α/β-PbO₂ electrode were 0.0995 A·cm^-1 and 0.004098 F·cm^-1, respectively, which are higher than those of Ti/Ag/β-PbO₂ electrode, indicating that Ti/α/β-PbO₂ electrode has excellent corrosion resistance and electron releasing ability, Finally, the Ti/α/β-PbO₂ electrode was selected as a working electrode. The results show that the optimum conditions for the determination of COD by Ti/α/β-PbO₂ electrode were as follows: the oxidation potential 1.30 V, electrolysis time 150 s, electrolyte concentration 0.03 mol·L^-1 sodium nitrate (NaNO₃). The correlation coefficient of COD measured by electrochemical method and colorimetric digestion method reached 0.9909, and it had good reproductivity and correlation. The detection range of COD was 0 mg·L^-1 ~ 500 mg·L^-1, which can replace the standard potassium dichromate method within the error allowable range, and provide reference value for the realization of rapid online COD detection. In follow-up studies, actual water samples such as surface water or sewage plant effluent will be compared with the colorimetric digestion method, and attention will be paid to the sensitivity of the electrode after multiple cycles of use.