Research On The Promotion Mechanism Of Formaldehyde Degradation By Electro-Fenton System Based On Reaction Region Control

Formaldehyde as a typical pollutant in the indoor environment,has always attracted much attention.Activated carbon is often used to adsorb formaldehyde,but the adsorption amount is limited.Electro-Fenton technology has received widespread attention because of its strong degradation ability and low secondary pollution.However,the traditional electro-Fenton system has the problem of mismatch between pollutant concentration and free radical concentration distribution.In this paper,the concept of reaction region control is proposed,that is,formaldehyde and active substances are adsorbed near the cathode of activated carbon in the electro-Fenton system,forming a local high concentration of formaldehyde and free radical reaction region,increasing the probability of molecular collision,and realizing the efficient degradation of formaldehyde by the system.In this paper,activated carbon was modified by nitrogen doping,and the effects of different modified activated carbon cathodes on the adsorption and2e-ORR selectivity of formaldehyde and H₂O₂were studied.The adsorption energy of nitrogen-doped actived carbon on formaldehyde and H₂O₂,the energy barrier for activating H₂O₂to generate·OH,and the energy barrier for the reaction of·OH with formaldehyde were calculated through quantum chemical simulation.Finally,nitrogen-doped actived carbon is used as the cathode of the electro-Fenton,which realizes the reaction region control and promotes the degradation effect of the electro-Fenton system on formaldehyde.The adsorption energies of different nitrogen-doped carbon bases on formaldehyde and H₂O₂were calculated.Among them,pyrrolic nitrogen and graphite nitrogen can enhance the hydrogen bond interaction and Van der Waals force respectively to improve the adsorption capacity of the carbon-based surface to formaldehyde,while pyridinic nitrogen can enhance the hydrogen bond interaction and promote the adsorption of H₂O₂on the carbon-based surface.For models containing pyrrolic nitrogen and graphite nitrogen,the energy barrier is lower than the original carbon base surface,indicating that these two nitrogen-doped forms are conducive to the activation of H₂O₂to·OH.Simulation studies of·OH oxidation of formaldehyde have shown that pyridinic nitrogen and pyrrolic nitrogen both promote the reaction between·OH and formaldehyde.The degradation efficiency of the system to formaldehyde was explored by using modified activated carbon as an electro-Fenton cathode.The experimental results confirmed that the activated carbon cathode has the best nitrogen doping ratio.Under this modified condition,the cathode has the best H₂O₂and formaldehyde adsorption properties.The 2e-ORR selectivity of the modified cathode was significantly improved,and the removal rate of formaldehyde increased from 47.27%to 70.19%,indicating that the reaction region control is an effective method to strengthen formaldehyde degradation.Finally,this method is used in a simulated room containing formaldehyde to achieve effective degradation of formaldehyde.In this paper,the adsorption properties of different nitrogen-doped actived carbon cathodes to formaldehyde and H₂O₂are explored,the adsorption mechanism is clarified,and the energy barrier of different nitrogen-doped forms of cathodes to activate H₂O₂to·OH to degrade formaldehyde is analyzed.Using it as the cathode of the electro-Fenton system,the reaction region control is realized,and the effect on formaldehyde degradation is significantly improved.The results of this research can provide theoretical guidance for the development of efficient clean treatment technology for formaldehyde in the air.