对光稳定性好利用率高的纳米ZnO复合材料成型机理和降解染料废水机理

Semiconductor photocatalytic technique has better application prospect in the deep treatment of organic dye wastewater, and the key problem is to synthesis photocatalyst with good response to visible light and high stability, utilization and activity of photodegradation. This research aims to obtain specific ordered structure zinc oxide composite (rGO-Metal/ZnO) with an enhanced dispersity and photocatalytic performance, which is performed via a simple polymer-assisted freeze-drying and supercritical-drying process based on the conformational entropy and group chemical characteristic of high-molecular polymer, and then, is doped by metallic ions and loaded by reduced graphene oxide. The inductive effect of polymer will be specifically and systematically studied on preparation mechanism and composite formation mechanism of this novel process, and the interaction mechanism of ZnO, the doped metal and rGO will be explained and the light utilization enhancement mechanism will be elucidated. The intermediate products and active groups will be detected by different characterization method in the dye wastewater photodegraded process, and the relationship between structure and photocatalytic activity will be explained; therefore, new mechanism model and kinetics equation of dyes photocatalytic degradation reaction will be derived and established, which will provide theoretical foundation and experimental data for the synthesis of composite photocatalyst and the application of semiconductor photocatalytic technique in organic dye wastewater deep treatment.

半导体光催化技术在有机染料废水深度处理领域具有较好应用前景，开发对可见光响应强、稳定性好、利用率高以及光催化活性优异的光催化剂至关重要。本研究旨在应用高分子聚合物的链构象和基团化学特性，协同冷冻干燥、超临界干燥等技术，经金属改性和还原氧化石墨烯（rGO）负载，制备特定有序结构的纳米氧化锌复合材料（rGO-Metal/ZnO），拟得到分散性好、光催化性能优的复合半导体光催化剂；系统考察聚合物在纳米氧化锌复合材料制备过程中的诱导效应，对聚合物辅助冻干法制备工艺机理和材料成型机理进行深入研究，阐明ZnO、掺杂金属及rGO三者之间的分子间相互作用机理，揭示光利用率增强机理；分析rGO-Metal/ZnO降解染料废水产生的中间产物和活性基团，阐释催化剂结构与性能之间的关系，构建光催化降解反应动力学模型和降解机理模型，为半导体光催化技术用于染料废水深度处理提供理论依据和数据支持。

染料废水含有毒、致癌、致畸、致突变成分，并且难降解，故对染料废水的深度治理一直备受青睐。半导体光催化技术由于能耗低、反应条件温和、操作简便、无二次污染等特点被广泛应用于污染物的降解领域的研究中。本文工作主要围绕聚合物辅助冻干法制备的纳米ZnO的改性，及其光降解染料废水的性能和降解机理的研究。具体研究内容及结论如下：（1）通过聚合物辅助冻干法一步合成法制备了负载贵金属Ag的纳米ZnO粉体。SEM和TEM观察到复合粉体具有较好的形貌特征和分散性。XRD证明绝大多数Ag负载在ZnO表面，有少量Ag存在于ZnO的晶胞内部。FT-IR和XPS也证明了Ag是以金属态的形式存在。光降解MB和MO实验中贵金属Ag的负载量优选为15%，MO和MB的初始染料浓度优选为10 mg·L-1，染料与催化剂的比值优选为1：30。（2）在Ag-ZnO光催化剂的基础上，通过水热还原法，将GO还原为片层rGO的同时，将rGO负载在Ag-ZnO的表面。SEM和TEM观察到Ag-ZnO-rGO三元复合材料中石墨烯较大的层状褶皱结构。Kubelka-Munk公式计算得到Ag-ZnO-rGO的禁带宽度最小，光吸收性能最优。以MO为模拟染料废水，在黑暗和紫外光条件下进行吸附和光催化反应，结果表明，Ag-ZnO-rGO复合材料结合了石墨烯和Ag两种材料的优点，既具有石墨烯的吸附性能又保持了较高的光反应活性。结合表征结果，对Ag-ZnO和Ag-ZnO-rGO的电子转移机制进行了进一步的阐释。（3）通过悬浮聚合和原位生长的方法成功地合成了一种新型复合材料UiO-66/PA。由于异相成核和稳定生长的控制，直径为400 nm的纳米UiO-66的直径减少了约90%，从而降低了转移阻力，有效地分离了光生载流子，暴露了更多的催化活性中心。在可见光照射下，在120 min内几乎完全降解RhB，重复实验表明该材料具有良好的稳定性。本文工作为ZnO材料在光降解染料废水上的工业应用打下坚实的基础。