[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 2.0×10~(-5)(m/s) with US,from(5.4×)10~(-6)(m/s) and 6.7×10~(-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 6.49×10~(-10)(mol/cm~2) to 1.39×10~(-10)(mol/cm~2),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 1.25×10~(-11)(mol/cm~2) to 3.11×10~(-12)(mol/cm~2) 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.