石墨烯/g-C3N4复合阳极光电催化氧化银氰络合物与同步还原回收银的机制研究

The resourceful treatment of metal-complexes in waste water is the research hotspot in environmental area. In this project, simultaneous photo-electrocatalytic (PEC) oxidation of cyanides and electro-reduction recovery of silver toward the silver cyanides waste water from the electroplating industries will be studied. The graphene/g-C3N4 composite film electrode with high catalytic performance and good stability will be prepared. The excellent electron transfer ability of graphene could enhance the photo generated electron-hole separation efficiency of the g-C3N4. The preparation process of the graphene/g-C3N4 film will be optimized; the modification mechanism of graphene toward g-C3N4 will be analyzed; and the structure-activity relationship will be established. The as-prepared graphene/g-C3N4 film will be used as photoanode in a PEC reactor containing silver cyanides waste water. The silver cyanides will be degraded via photo-electrocatalytic oxidation, while the released silver ions will be simultaneously recovered via electro-deposition in cathode; The main influence on the degradation and recovery process will be analyzed, and the corresponding mechanism will be proposed. The decomplexation process of silver cyanides, oxidation process of cyanides and recovery of silver process will be studied; The photo-electrochemical adjustment and water condition adjustment will be proposed to acquire the high-efficiently degradation of silver cyanides and recovery of silver process simultaneously. This project will provide technique and theoretical support for the resourceful treatment toward silver cyanide complexes, and the research on the graphitic carbon nitride electrode will enrich the acknowledge on the photo-electrochemical purification of water.

废水中重金属络合物的资源化处理是当前研究的热点和难点之一。本项目针对电镀工业中产生的含银氰络合物废水，开展光电催化氧化银氰络合物并同步电还原回收银的研究。首先研制高效稳定的石墨烯/g-C3N4复合薄膜电极，利用石墨烯优良的电子传导能力提高g-C3N4薄膜的光生电子-空穴分离效率，优化石墨烯/g-C3N4薄膜电极的制备条件，明晰石墨烯与g-C3N4的结合形式，阐明薄膜电极的结构与性能之间的构效关系。以所制复合电极为光阳极，利用光电催化氧化方法降解银氰络合物；同时利用阴极的电还原作用对释放出来的银离子进行电沉积回收；详细分析其主要影响因素与影响机制；深入探究光电催化氧化银氰络合物的破络合过程、氰根的氧化途径以及银的电沉积回收微观过程；掌握高效氧化络合物与回收银的光电化学与水质调控方法。本项目研究可为银氰络合物的资源化处理提供技术支持，有关氮化碳电极的研究也将丰富对光电化学净水的认识。

重金属络合物的资源化处理是当今环境领域的研究热点和难点之一。该项目主要围绕光电化学水处理技术，开展了材料制备、体系构建、污染物去除机制分析的研究，实现了光电催化氧化银氰络合物并同步还原回收银。在材料设计方面，采用高温液相生长法，以静电纺丝SiO2纤维膜为基底，利用氮化碳前驱体中的-NH2与苝酸二酐（PTCDA）中的O=C-O-C=O在N2气氛保护下进行酰胺化反应，原位制备了苝酰亚胺（PTCDI，简称PI）修饰的聚合物氮化碳纤维膜（PI-g-C3N4纤维膜），制备纤维膜具有良好的可见光响应性能，在过硫酸盐条件下可以有效氧化水中有机污染物。在光电催化体系构建方面，以水热法制备的氧化钛纳米管（TiO2 NRs）电极为光阳极，钛片为阴极构建了光电催化体系，用于处理含银氰络合物废水。与单独电催化（EC）和光催化（PC）相比，光电催化（PEC）能更有效的使银氰络合物破络合，氧化氰根并同步回收银。在PEC体系中，1.0 V偏压（vs SCE）条件下，总氰的去除率为76.58%，银的回收率为84.48%。进一步构建了以BiVO4为光阳极、以Cu2O/CuO为光阴极的光催化燃料电池（PFC）体系。将PFC体系用于降解苯酚并同时回收银，PFC体系中银离子可显著提高苯酚的氧化效率，同时银完全回收。此外，构建了集氧化与沉淀一体的光电催化反应体系，该体系以TiO2/Ni-Sb-SnO2（TNA/NSS）双功能电极为光阳极，以活性炭纤维（ACF）为阴极，外加Fe2+，用于处理H2PO2−废水，实现了以磷酸铁（FePO4）形式回收磷。项目详细分析了光电催化过程的主要影响因素与影响机制；深入探究了光电催化氧化银氰络合物的破络合过程、氰根的氧化途径以及银的电沉积回收微观过程。本项目研究可为银氰络合物的资源化处理、有机-无机复合污染废水以及实际化学镀镍废水的处理提供理论依据和技术支持。