超声强化金刚石膜电极电化学降解效率的机制

从电化学氧化的传质过程、吸附与脱附、电极反应3个步骤,考察了超声强化金刚石膜电极(BDD)电化学降解效率的机制.超声对上述3个步骤都有显著影响.超声增强了污染物的传质过程,苯酚和邻苯二甲酸的传质系数分别由5.4×10-6m/s和6.7×10-6m/s增大至2.0×10-5m/s,提高了270%和199%.污染物在BDD电极表面的电化学吸附特性决定了超声对吸附与脱附过程的作用.苯酚的吸附量大,但中间产物难于脱附,超声虽然使得吸附量由6.49×10-10mol/cm2减小至1.39x10-10mol/cm2,但促进了产物的脱附,产生了正效应,有利于直接氧化,氧化峰电流提高了32%;邻苯二甲酸的吸附能力弱,超声使得吸附量由1.25×10-11mol/cm2进一步减小至3.11×10-12mol/cm2,产生了负效应,导致直接氧化消失.超声可以显著提高BDD电极的降解效率,而且对苯酚降解的促进作用更为明显.苯酚的平均电化学氧化能量利用率提高了287%,高于邻苯二甲酸的224%,这主要是因为超声可以同时强化苯酚的直接氧化和间接氧化,但对于邻苯二甲酸,间接氧化得到了加强,却不发生直接氧化.

Mechanism of Enhancement on Boron-doped Diamond Electrode Electrochemical Degradation Efficiency by Ultrasound

Mass transport process, adsorption and desorption, and electrochemical reaction were analyzed to investigate the mechanism of enhancement on boron-doped diamond (BDD) electrode electrochemical degradation efficiency by ultrasound (US). US has considerable influences on the above steps of electrochemical oxidation. Mass transport coefficients of Ph and PA reach 2.010^-5 m/s with US, from 5.410^-6 m/s and 6.710^-6 m/s in EC process, increasing by 270% and 199%, respectively. The effect of US on adsorption and desorption has relationship with electrochemical adsorption properties of pollutants on BDD electrode surface. The adsorption amount of Ph decreases from 6.4910^-10 mol/cm² to 1.3910^-10 mol/cm², with the desorption of polymer intermediates promoted, so US makes positive effect with benefit to direct oxidation and oxidation peak current increases by 32%. For PA, the adsorption amount decreases from 1.2510^-11 mol/cm² to 3.1110^-12 mol/cm² with US, and no direct oxidation happens in US-EC process. US can improve degradation efficiency of BDD electrode and the enhancement on Ph degradation is more effective. Average electrochemical oxidation energy efficiency (AEE) of Ph increases by 287%, more than 224% of PA. This is because both direct and indirect oxidation for Ph can be enhanced by US, while for PA, direct oxidation almost disappears.