Performace Of Multichannel Monolithic-porous-carbon Cathode In Degradation Of Organic Pollutants

In recent years,electrochemical technology has received increasing attention in wastewater treatment,especially in the degradation of refractory Persistent Organic Pollutants.The most widely used electrochemical devices are flat-plate mixed devices and carbon membrane flow-through devices.However,the mass transfer process of the former is limited while the electrode thickness of the latter is only millimeter-scale,and carbon nanomaterials are easily leaching from the electrode surface into solution,which is difficult to scale up and applied to practical water treatment.In order to overcome the above problems,a monolithic porous carbon?MPC?electrode was prepared by carbonizing wood with natural vertical channels;A flow-through electrochemical device with a MPC cathode was then constructed.Wastewater treatment performance and mechanism of organic pollutants degradation were subsequently analyzed as follows:MPC electrode was prepared by carbonization and KOH activation process.MPC involved the vertical channel arrays of 1-10?m and 50?m,could shortenthe diffusion distance of pollutants and accelerat mass transfer.The channel walls had abundant micropores and mesopores.Also,MPC had a specific surface area of 468 m²·g^-1 and provided more active sites for the reaction.X-ray photoelectron spectroscopy and infrared show that MPC had abundant oxygen-containing functional groups on the surface.A flow-through electrochemical reactor was constructed by using MPC as the cathode.Phenol,sulfamethoxazole and atrazine were used as the target pollutants to investigate the degradation performance of the flow-through reactor.The optimal operating conditions were20 mg·L^-1,100 s,1 mA and pH 7.The removal efficiency of phenol and TOC could reach90%and 85%,respectively,with a residence time of 100 s.For the other two pollutants,the residual concentration of effluent were reduced to 1-5 mg·L^-1 at the residence time of 100-300s.Additionally,MPC had excellence stability and repeatability.In order to investigate the mechanism of pollutants degradation,double-cell reactor was used to analyze the contribution of cathode and anode for the pollutants degradation,and the reactive oxygen species in the system were detected by UV-visible spectrophotometry and electron paramagnetic resonance spectroscopy.The results show that the pollutant was mainly degraded in the cathode,and there were H₂O₂ and·OH in the system.The reactive oxygen species were also detected in the cathode cell by a double-cell reactor,and the·OH was identified as the main reactive oxygen species responsible for pollutant degradation,which is produced by the three-electron reduction of oxygen in the cathode.In addition,degradation of pollutants in the system was a combination of electro-assistant adsorption and electrochemistry,and the best degradation effect of pollutants was at 1 mA?1.5-1.9 V?.Above all,a flow-through electrochemical reactor with a MPC cathode can realize the rapid degradation of various organic pollutants,which lays a foundation for the industrial application of the flow-through electrochemical reactor.