垃圾渗滤液是一种高氯高氮难降解有机废水，生化处理（BCT）耦合膜工艺是渗滤液处理的主流技术。然而，BCT单元出水中难降解有机物和氨氮（NH₄⁺-N）残留浓度高，加剧膜污染，降低膜工艺处理效能。光电化学（PEC）系统具有高效、低耗降解有机污染物等优势。但是由于光催化电极中均质半导体内部光生电子-空穴对复合率高，导致异质界面电子注入量低；且电荷跨固液界面转移损耗能量高，限制了PEC系统性能的提升。本文通过钒酸铋（BiVO₄）晶面的电荷预分离，异质结结构和光生电子传输路径的优化，固液界面电阻的降低，完成光阳极材料结构的改性；并与气体扩散阴极相耦合，在低电压配置下优化载流子传输效率，实现对PEC系统中电荷的多级强化分离、定向迁移和高效利用；驱动高浓度氯离子（Cl^-）高效转化为活性氯，实现对渗滤液BCT出水中难降解有机物和NH₄⁺-N的同步高效去除。所取得的主要创新成果如下：

    （1）制备了可见光驱动的碘酸银/钒酸铋（AgIO₃/BiVO₄）光催化材料，实现了光生电子-空穴对的两级分离。首先，通过调控光生电子和空穴在BiVO₄不同晶面上的空间分布，实现光生电子和空穴分别在{010}和{110}晶面上的聚集，完成电荷在均质半导体内部的预分离，提高异质界面的光生电子传输量。然后利用Ⅱ型异质结结构，促进光生电子从BiVO₄{010}晶面向AgIO₃的定向迁移，实现光生电子-空穴对的两级分离。研究结果表明，当AgIO₃和BiVO₄的摩尔配比为40%时，禁带宽度为2.28 eV，光电转化效率提升了5.5%。在可见光驱动下，对卡马西平（CBZ）降解率达到97.86%（60 min），显示出对有机污染物优异的降解效果。然而AgIO₃/BiVO₄循环稳定性差、粉末催化材料分离回收效率低，因此筛选WO₃为AgIO₃的稳定、高效的替代材料。

     （2）设计并制备了具有高效电子传输结构的氧化钨/钒酸铋-硼酸钴盐（FTO/WO₃/BiVO₄-CoB_i）光阳极，实现光生电子的多级强化分离，提升PEC系统性能。通过耦合材料结构改性的光阳极与工艺参数优化的PEC系统，驱动Cl^-向活性氯物种的转化，实现有机污染物与NH₄⁺-N同步高效去除。光阳极首先通过定向晶面生长的十面体BiVO₄阵列和WO₃/BiVO₄异质结，实现两级电荷分离；然后CoB_i传输层降低固/液界面电荷转移电阻，提升了光生空穴向溶液中氧化还原当量物质的转化；最后，在低电压驱动下实现光生电子的快速定向迁移，最终实现多级强化电荷分离。在该系统中，空穴和•OH主导有机污染物降解，同时活性氯（Cl•和•ClO为主、Cl₂、HClO）主导NH₄⁺-N脱除。当被处理模拟废水中CBZ、NH₄⁺-N和Cl^-浓度分别为5 mg/L、50 mg/L和0.2 mol/L时，单室PEC系统在可见光强100 mW/cm²和电压2.0 V vs. Ag/AgCl的条件下，CBZ降解率达到99.99%（40 min），NH₄⁺-N脱除率为75.40%（120 min），同时NH₄⁺-N向N₂的定向转化率达到89.62%。活性氯是NH₄⁺-N脱除的必要条件，通过对氮的逐级氧化有效抑制了因过度氧化产生的硝态氮（NO₃^--N）。

     （3）制备了具有原位类Fenton性能的石墨毡/乙炔黑/磷化铜（AB/GF/AB/Cu_xP）气体扩散阴极，提高了PEC系统的阴极电子利用效率。与FTO/WO₃/BiVO₄-CoB_i光阳极匹配，构建双室PEC系统，强化了系统有机物降解同步脱氮能力。以含有CBZ、腐殖酸（225~235 mg/L TOC）和NH₄⁺-N（50 mg/L）的高Cl^-模拟废水为处理对象，系统运行180 min，阳极TOC去除率为42.00%，NH₄⁺-N脱除率达到92.00%以上；改性后阴极对CBZ的去除率提升了26.12%，对TOC的去除率从铂片、石墨毡、石墨毡/乙炔黑为阴极时的9.64%~11.29%增加至24.15%，NH₄⁺-N氧化率达到42.50%。提出了双室PEC系统的强化催化机理，阴极形成了原位类Fenton反应，产生具有强氧化还原能力的阳阴极反应活性区。

     （4）论证了多级电荷分离PEC系统对渗滤液BCT出水的有机物降解同步脱氮能力。分别以仅含高NH₄⁺-N以及同时含有NH₄⁺-N、NO₃^--N和亚硝氮的两种渗滤液BCT单元出水为处理对象，系统均表现出良好的NH₄⁺-N向N₂的定向转化控制（85.45%~96.10%）和脱氮效果（脱氮速率9.19~10.48 mg/(L·h)）；同时渗滤液化学需氧量明显降低（去除速率37.1~54.0 mg/(L·h)），腐殖酸类和富里酸类有机质被有效降解。该系统抑制了宽范围pH和共存物质（包括多种重金属离子、无机盐离子和有机质组分）对光阳极耦合气体扩散阴极处理效能的负面影响，拓展了PEC系统处理复杂水质条件污废水的适用范围。核算了系统的电极制备成本和处理运行成本，证实了系统具备较好的经济性。

       综上所述，本研究通过设计具有电荷预分离性能和低固液界面电阻的光阳极，耦合改性的气体扩散阴极和工艺参数优化的PEC系统，促进了电荷的多级分离、定向迁移和高效利用过程。驱动了渗滤液BCT出水中高浓度Cl^-转化为强氧化性活性氯，实现高效的有机污染物降解和NH₄⁺-N同步脱除，拓展了PEC系统处理高Cl^-高NH₄⁺-N难降解有机污废水的适用范围。

     Landfill leachate is a kind of organic wastewater with high chlorine and nitrogen. The coupled membrane and biochemical treatment (BCT) is the main technology of leachate treatment. However, the residual concentration of refractory organic matter and ammonia nitrogen (NH₄⁺-N) in BCT unit effluent is high, which aggravates the membrane pollution and reduces the membrane processing efficiency. Photoelectrochemical (PEC) system has the advantages of high efficiency and low consumption in the degradation of organic pollutants. However, due to the high recombination rate of photogenerated electron-hole pairs in the homogeneous semiconductor, the amount of electron injection at the heterogeneous interface is low. Moreover, the energy comsumption of charge transfer across the solid-liquid interface is high, which limits the improvement of PEC system performance. In this paper, the photoanode material structure was modified by charge pre-separation of bismuth vanadate (BiVO₄) crystal surface, optimization of heterojunction structure and photogenerated electron transport path, and reduction of solid-liquid interface resistance. Coupled with the gas diffusion cathode, the carrier transmission efficiency was optimized under low voltage configuration to realize multistage enhanced separation, directional migration and efficient utilization of charges in PEC system. The high efficiency transformation of high concentration chloride ions (Cl^-) into active chlorine species was driven to achieve the simultaneous efficient removal of refractory organic matter and NH₄⁺-N in leachate BCT effluent. The main achievements of innovation are as follows:

      (1) A visible-light-driven silver iodate/bismuth vanadate (AgIO₃/BiVO₄) photocatalyst was prepared to achieve two-stage separation of photogenerated electron-hole pairs. Firstly, by regulating the spatial distribution of photogenerated electrons and holes on different crystal planes of BiVO₄, the aggregation of photogenerated electrons and holes on the crystal planes of {010} and {110} was realized, which completed the charge pre-separation within a homogeneous semiconductor and improved the transfer amount of photogenerated electrons at the heterogeneous interface. Then, type Ⅱ heterojunction structure was used to promote the directional migration of photogenerated electrons from BiVO₄ {010} crystal plane to AgIO₃, realizing the two-stage separation of photogenerated electron-hole pairs. The results showed that when the molar ratio of AgIO₃ to BiVO₄ was 40%, the band gap was 2.28eV, and the photoelectric conversion efficiency was improved by 5.5%. Driven by visible light, the degradation rate of carbamazepine (CBZ) reached 97.86% (60 min), showing excellent degradation effect on organic pollutants. However, the cycle stability of AgIO₃ was poor and the separation and recovery efficiency of powder catalytic materials was low. Therefore, WO₃ was determined as a stable and efficient alternative material for AgIO₃.

       (2) A tungsten oxide/bismuth vanadate-cobalt borate (FTO/WO₃/BiVO₄-CoB_i) photoanode with efficient electron transport structure was designed and prepared to realize multistage enhanced separation of photogenerated electrons and improve the performance of PEC system. Through coupled photoanode with improved material structure and PEC system with optimized process parameters, the transformation of Cl^- to active chlorine species was driven to achieve efficient degradation of organic pollutants and the removal of NH₄⁺-N. Firstly, the photoanode realized two-stage charge separation through the directional crystal decahedral BiVO₄ array and WO₃/BiVO₄ heterojunction. Then the CoBi layer reduced the charge transfer resistance at the solid/liquid interface and improved the conversion of photo-generated holes to redox equivalents in solution. Finally, under the drive of low voltage, the rapid directional migration of photogenerated electrons and the multistage enhanced charge separation were realized. In this system, the degradation of organic pollutants was dominated by holes and •OH, while the removal of NH₄⁺-N was dominated by active chlorine (mainly Cl• and •ClO, Cl₂ and HClO). When the simulated wastewater containing 5 mg/L CBZ, 50 mg/L NH₄⁺-N and 0.2 mol/L Cl^- was treated in the single-chamber PEC system under 100 mW/cm² visible light intensity and 2.0 V vs. Ag/AgCl potential, the degradation rate of CBZ reached 99.99% (40 min), the removal rate of NH₄⁺-N was 75.40% (120 min), and the conversion rate of NH₄⁺-N to N₂ reached 89.62%. Active chlorine was a necessary condition for the removal of NH₄⁺-N, which effectively inhibited the nitrate nitrogen (NO₃^--N) produced by excessive oxidation through the stepwise oxidation of N.

     (3) The gas diffusion cathode of graphite felt/acetylene black/copper phosphide (AB/GF/AB/Cu_xP) with in situ Fenton-like performance was prepared, which improved the cathode electron utilization efficiency of PEC system. The two-compartment PEC system was constructed by matching FTO/WO₃/BiVO₄-CoB_i photoanode and AB/GF/AB/Cu_xP cathode, which enhanced the ability of simultaneous nitrogen removal and organic degradation. The high Cl^- simulated wastewater containing CBZ, humic acid (225~235 mg/L TOC) and NH₄⁺-N (50 mg/L) was taken as the target water. After 180 min of system operation, TOC removal rate was 42.00% and NH₄⁺-N removal rate was more than 92.00%. After modification, the CBZ removal rate of the cathode increased by 26.12%, the TOC removal rate increased from 9.64%~11.29% of platinum sheet, graphite felt, graphite felt/acetylene black as the cathode to 24.15%, and the NH₄⁺-N oxidation rate reached 42.50%. The enhanced catalytic mechanism of two-compartment PEC system was proposed. In situ Fenton-like reaction was formed at the cathode, and a positive cathode reactive zone with strong redox ability was produced.

     (4) The ability of multistage charge separation PEC system for organic matter degradation and simultaneous nitrogen removal in leachate BCT effluent was demonstrated. The effluent from two BCT units of leachate containing only high NH₄⁺-N and containing NH₄⁺-N, NO₃^--N and nitrite nitrogen were respectively taken as the treatment objects. All the systems showed good directional conversion of NH₄⁺-N to N₂ (85.45%~96.10%) and denitrification efficiency (denitrification rate 9.19~10.48 mg/(L·h)). At the same time, COD of the leachate decreased significantly (removal rate 37.1~54.0 mg/(L·h)), and organic matter of humic acid and fuluric acid were effectively degraded. The system could suppress the negative effects of pH and co-existing substances (including a variety of heavy metal ions, inorganic salts ions and organic components) on the treatment of landfill leachate by the photoanode coupled gas diffusion cathode system, and expand the application scope of PEC system to treat wastewater under complex water quality conditions. The electrode preparation cost and processing cost of the system were calculated, and it is proved that the system has good economy.

     In conclusion, this study promoted the multistage separation, directional migration and efficient utilization of charge by designing a photoanode with charge pre-separation performance and low solid-liquid interface resistance, coupled with a modified gas diffusion cathode and an optimized PEC system with process parameters. It drived the conversion of high concentration Cl^- into strong oxidizing active chlorine in leachate BCT effluent, realized the high efficient degradation of organic pollutants and the removal of NH₄⁺-N, and expanded the scope of application of PEC system in the treatment of high Cl^-, high NH₄⁺-N and refractory organic wastewater.