Abstract:

To understand the effect of salt on the performance and mechanism of electrocatalytic degradation, the performance test of electrocatalytic oxidation of an industrial wastewater was carried out. The effect of salt on the electrocatalytic oxidation was analyzed by investigating the COD (chemical oxygen demand) removal efficiency under different salt contents (0.1%—2.0%), current densities (5—20mA/cm²), plate spacing (0.5—1.5cm) and pH (4—10). The production of active species in different salt-containing systems was analyzed by electron paramagnetic resonance (EPR/ESR) technique. In addition, the service life of the electrode was evaluated by a rapid test method. The results showed that the maximum COD removal efficiency of the electrocatalytic system without salt and with the addition of NaCl and Na₂SO₄ were 58.4%, 84.7% and 63.3%, respectively, and the corresponding current efficiencies were 15.4%, 19.6% and 16.7%. A quadruple peak intensity of 1∶2∶2∶1 was found in the original electrocatalytic system, which was consistent with the characteristic peak of \bullet \mathrm{O}\mathrm{H}. The characteristic peaks of \bullet \mathrm{O}\mathrm{H}、¹O₂和·{\mathrm{O}}_{\mathrm{2}}^{-} were found in the electrocatalytic system with Na₂SO₄, while similar characteristic peak of chlorine-containing free radicals were additionally found in the electrocatalytic system with NaCl. Under the enhanced test conditions, the electrode lifetime was 11460s. NaCl was beneficial to increasing the maximum COD removal rate with high current efficiency and enriching the types of active species.

Key words: electrochemistry, salinity, oxidation, performance, radical, wastewater

摘要：

为研究盐分对电催化降解性能与机理的影响，选取了某项目生产废水为对象，开展了电催化氧化处理废水性能试验。通过考察不同盐质量分数（0.1%~2.0%）、电流密度（5~20mA/cm²）、极板间距（0.5~1.5cm）和pH（4~10）条件下化学需氧量（chemical oxygen demand，COD）的去除效能，分析盐分对电催化氧化处理废水性能的影响，并利用电子顺磁共振波谱仪解析不同含盐体系活性物种的产生情况。此外，采用快速测试法评估了电极的使用寿命。试验结果表明，原水电催化体系、加NaCl电催化体系和加Na₂SO₄电催化体系的COD最大去除率分别为58.4%、84.7%和63.3%，相应的电流效率依次为15.4%、19.6%和16.7%。原水电催化体系存在峰值强度为 1∶2∶2∶1的四重峰，与∙OH的特征峰吻合，加Na₂SO₄电催化体系存在∙OH、¹O₂和·{\mathrm{O}}_{\mathrm{2}}^{-}的特征峰，而加NaCl电催化体系除了上述3种活性物种，还发现含氯自由基的相似特征峰。在强化试验条件下，电极使用时间为11460s。NaCl有利于提高电催化氧化体系COD的最大去除率和电流效率，丰富活性物种种类。

关键词: 电化学, 盐分, 氧化, 性能, 自由基, 废水