Investigation On The Construction And Electrocatalytic Degradation Phenol Performance And Mechanism Of Mesh Titanium Based DSA Electrode

The performance improvement of electrocatalytic oxidation system is a research hotspot of electrochemical water treatment technology.The catalytic activity,stability and mass transfer performance of electrode system are the most important characteristics,which are closely correlated with the electrode structure and composition.Dimensionally Stable Anode(Dimensionally Stable Anode,DSA)has gained wide attention because of its superior stability,and as one type of DSA,Ti/SnO2-Sb becomes the research hotspot due to its better electrocatalytic activity.In this paper,the performance and mechanism of electrochemical degradation of pollutants by mesh titanium(Ti)based electrode were studied.The effects and mechanism of mesh titanium substrate on the performance of Ti/SnO₂-Sb electrode,the influence of mesh titanium nanotube(TiO₂-NTs)substrate on the stability and catalytic performance of Ti/TiO₂-NTs/SnO₂-Sb electrode,and the influence of mesh cathode on mass transfer and transformation process of pollutants were systematically studied.The promotion-mechanism of phenol degradation by the electrocatalytic system composed of mesh Ti/TiO₂-NTs/SnO₂-Sb anode and mesh cathode was investigated.In this paper,the mesh Ti was chosen as the substrate to fabricate Ti/SnO₂-Sb electrode instead of the traditional planar Ti,and the characteristic and advantage of mesh anode was analyzed in detail.Compared with the planar Ti based metal anodes(P-Ti/SnO₂-Sb),the M-Ti/SnO2-Sb electrode prepared on titanium mesh had fewer surface cracks,denser surface,lower surface charge transfer resistance(9.49?)and larger active surface area(74.88?).These characteristics promoted the generation of more?OH on M-Ti/SnO2-Sb surface.COMSOL simulation result showed that the mesh substrate structure enhanced the disturbance of fluid near the electrode,resulting in the increase of mass transfer coefficient,which was 1.67times of that of P-Ti/SnO₂-Sb.When the current density was 10 m A/cm²,the TOC removal rate and mineralization current efficiency(MCE)of M-Ti/SnO2-Sb were21.6%and 9.95%higher than those of P-Ti/SnO₂-Sb,and the service lifetime of electrode was 1.89 times longer than that of P-Ti/SnO₂-Sb.In order to further improve the electrocatalytic performance of the mesh titanium metal anode,titanium dioxide nanotube arrays(M-TiO₂-NTs)were synthesized on the surface of the mesh Ti substrate by anodic oxidation method.The effect of the M-TiO₂-NTs substrate on the electrocatalytic performance and stability of Ti/SnO2-Sb(M-Ti/TiO2-NTs/SnO2-Sb)were studied,and the result was compared with those of M-Ti/SnO2-Sb without anodizing and titanium dioxide nanotube arrays oxidized on planar Ti/Tin dioxide(P-Ti/TiO2-NTs/SnO2-Sb).The results showed that SnO₂ can enter into the inner part of M-TiO₂-NTs and the tube clusters formed by M-TiO₂-NTs after adding M-TiO₂-NTs interlayer,which improved the specific surface area of M-Ti/TiO2-NTs/SnO2-Sb(4.03 cm²/cm²)and catalyst loading(6.98±0.03 g/m²).Meanwhile,the stability of the electrode was greatly improved,and the accelerated service lifetime of M-Ti/TiO2-NTs/SnO2-Sb was 105 h.In addition,M-Ti/TiO2-NTs/SnO2-Sb electrode can degrade phenol effectively,and the TOC removal rate can reach 98.2%after 100min of electrocatalytic degradation.In order to further improve the conversion efficiency of pollutants,the effects of planar cathode and mesh cathode on pollutant removal were compared,and the efficiency of electrocatalytic system under various influent velocities was analyzed.The results showed that the conversion efficiency of pollutants was effectively improved by using the mesh cathode.During the intermittent static flow experiment,the pseudo first order kinetic constant of phenol degradation by the mesh cathode system was 26.3%higher than that of the planar cathode system.When the influent flow rate increased to 0.062 m/s,the k value of phenol degradation in the mesh cathode system increased by 30.1%compared with that at static condition.Computational fluid dynamics(CFD)simulation results showed that the mesh cathode can increase the flow rate on the anode surface and inside the reactor effectively,thus improving the mass transfer performance and pollutant degradation in the electrocatalytic system.The mass transfer coefficient(k_m)of the system was proportional to the influent flow rate,when the influent flow rate was 0.032 m/s,the k_m of the planar cathode and the mesh cathode electrocatalytic system were 3.65?10^-5 m/s and 6.14?10^-5 m/s,respectively.The km of the mesh cathode electrocatalytic system was 40-55%higher than that of the flat cathode.In addition,the CFD simulation results were in accordance with the experimental results,which showed that the model used in this paper can reflect the fluid flow in the system accurately.The electrocatalytic reactor was constructed by using mesh Ti/TiO₂-NTs/SnO₂-Sb anode and mesh cathode as electrode materials,and the mechanism of pollutant degradation was discussed.The active surface area and oxygen evolution overpotential(1.87 V vs.Ag/Ag Cl)of M-Ti/TiO₂-NTs/SnO₂-Sb anode were improved by the radial extension of TiO₂-NTs on the mesh Ti substrate,which further enhanced the production of·OH,and the adsorbed oxygen concentration on anode surface was 28.3%.The mass transfer coefficient of the mesh cathode system was 1.25?10^-4m/s,which was 1.40 times higher than that of planar cathode(8.92?10^-5m/s),so as to improve the utilization efficiency of·OH.The results showed that the larger active surface area and three-dimensional structure with radial growth of M-Ti/TiO₂-NTs/SnO₂-Sb anode provide the basis for the mass production of·OH,and the use of mesh cathode accelerated the transfer rate between organic matter and·OH,the utilization efficiency of·OH,strengthening the mass transfer process in the system.As a result,the ability of electrocatalytic degradation of pollutants in the reactor was finally improved jointly.