| Electrochemical oxidation technology has unique advantages such as green,efficient,flexible and controllable,and has gradually become a research hotspot in the field of water treatment in recent years.Among electrochemical oxidation anode materials,boron doped diamond（BDD）electrodes are favored by researchers for their extremely strong electrochemical oxidation activity,low energy consumption for pollutants removal,excellent stability and safety.Despite the huge application potential,there are still some major hurdles to overcome in taking BDD electrochemical oxidation technology from the laboratory to practical application.The first is the screening of BDD electrode substrates to guarantee the high catalytic activity and stability of BDD electrodes.The next step is to design a three-dimensional structure of BDD electrode with abundant active sites and high mass transfer capacity to achieve the synergistic enhancement of"large active area+high mass transfer rate".In addition,efficient electrochemical water treatment also requires the combination of anode oxidation and cathodic reduction,and through the synergistic integration of electrolyte and electrode materials in the electrochemical system to fill shortcomings and enhance effectiveness.In response to the above problems,to further improve the effectiveness of water treatment and to promote the practical application of electrochemical water treatment technology,this thesis addresses the following aspects:（1）Taking the screening of BDD electrode substrate as an entry point,the effect of substrate effect on the structure of BDD electrode and its water treatment performance and mechanism was investigated.Substrates were found to regulate both the electrochemical activity and the stability of the electrodes.The oxidation rates of tetracycline on Ti/BDD and Si/BDD are comparable（faster than Nb/BDD and Ta/BDD）,however,Si/BDD requires more power consumption due to its poor electrical conductivity and Ti/BDD has the least power consumption.In order to scale up and use BDD electrodes at a more industrial level,it is necessary to focus on the design and development of Ti/BDD in view of its superior electrochemical oxidation efficiency,mechanical stability and economics.（2）Developing stable and efficient microporous BDD electrodes by designing porous structures on the material surface.Combining the intrinsic properties of porous Ti and BDD,microporous BDD electrodes with different pore diameter（10,30,50,100 and 150μm）structures were synthesized to reveal the relationship between pore diameter structure and BDD electrode performance.Compared with the flat BDD,the electroactive area of the microporous BDD increased from 1.91 cm2 cm-2to 5.75 cm2 cm-2,the electron transfer resistance decreased from 2.53Ωto0.5Ω,and the mass transfer coefficient increased from 2.84×10-5 m s-1 to4.58×10-5 m s-1,which increased the number of active sites and achieved the synergistic effect of electron transfer and liquid-phase mass transfer.The electrochemical oxidation efficiency of the BDD electrode was significantly enhanced.（3）To further improve the electron transfer and liquid-phase mass transfer processes,a new convection-diffusion-enhanced penetration BDD（3D-BDD）electrode was designed and prepared by three-dimensional conformation.It is prepared by designing a 3D-Ti substrate with periodic through-hole structure by metal 3D printing technology,and then depositing BDD film on the surface of the substrate.The electroactive area of 3D-BDD was found to increase from 2.04 cm2 cm-2 of 2D-BDD to 22.08cm2 cm-2,and the electron transfer rate on the surface of 3D-BDD was faster.Combined with CFD simulations and ESR tests,it was confirmed that the unique 3D configuration of 3D-BDD electrode can generate more active·OH and SO4·-for organic pollutants decomposition while achieving convective diffusion to enhance mass transfer.（4）The coupling technology based on BDD electrochemical oxidation was developed through the combination of electrolyte and electrodes.The feasibility of EO-PS technology for treating real cyanide-containing organic wastewater was investigated by further enhancing water treatment efficiency through BDD electrochemical oxidation-persulfate（EO-PS）dual-coupling technology,and the effects of operating parameters on the simultaneous degradation effect,kinetics and energy consumption of organic compounds and cyanide in wastewater were elucidated.It was found that reducing the current density,lowering the p H,increasing the temperature or concentrating the wastewater can reduce the energy consumption per pollutant removed.The surface morphology,composition and oxygen precipitation potential of the BDD electrode did not change significantly before and after the treatment of cyanide-containing organic wastewater（running time over 720 h）,and it has excellent stability.（5）A novel BDD electrochemical oxidation-persulfate-electro-Fenton（EO-PS-EF）tri-coupling technique was constructed,and its synergistic effects and mechanism were revealed.The pseudo-first-order reaction kinetic constant for the degradation of tetracycline in the EO-PS-EF tri-coupling system is 2.54×10-3 s-1,which is 10 times higher than that of the single EO system and 3-4 times higher than that of the binary system（EO-PS or EO-EF）.In addition,the influence of key operating parameters on the water treatment performance of the coupling system was explored.Direct evidence of·OH and SO4·-co-generation was provided by ESR tests,and possible oxidation mechanisms and degradation pathways were suggested.After 100 replicate tests,the tetracycline removal could still reach 100%within 30 min,demonstrating its long-term stability. |
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