多孔型g-C3N4/Ti-MOFs异质结对畜禽养殖废水中抗生素的可见光催化降解行为及机理研究

The antibiotic pollution in wastewater and natural water environment is becoming more and more serious. Photocatalysis is an important and environmental-friendly method to restore the antibiotic-polluted water. In this technology, photocatalyst is one of the key factors that affect the treatment efficiency, however, the relationship between photocatalyst structure and photocatalytic activity and the degradation mechanisms of antibiotic are not clear. Here, the present project is planned to prepare porous graphite carbon nitride/titanium-metal organic frameworks(g-C3N4/Ti-MOFs) photocatalyst with interface coupling heterostructure via an easily controlled route. Various methods including high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflection spectroscopy, steady-state and transient absorption spectra, and time-resolved fluorescence spectroscopy will be applied to characterize the structure, component and property of heterostructured photocatalyst and clarify the adjustive rule. Further, we aim to explore comprehensively the photocatalyst properties for the removal of antibiotic in livestock wastewater, involving in adsorption behavior, photocatalytic activity and stability. The molecular simulation will be carried out to calculate the molecular orbital, energy, thermodynamics and bonding parameters. Then, the transfer and capture of photogenerated carriers and the interaction among medium, free radicals and antibiotic will be analyzed. The degradation intermediates and transient processes will also be investigated. It is expected that these results provide the microcosmic insight about the antibiotic degradation mechanism on the surface of photocatalyst or in aqueous solution. In a word, this study will provide the theory basis and practicable method for antibiotic polluted-water/wastewater treatment.

废水和自然水体中抗生素污染日益严重。光催化是解决废水和自然水体中抗生素污染的一种环境友好型重要方法。光催化剂是影响抗生素去除的关键因素，但其结构特性与光催化降解能力之间的构效关系以及降解抗生素的内在机理尚未明确。项目拟优化与控制合成类石墨型氮化碳/钛金属有机骨架界面耦合异质结多孔材料，利用高分辨透射电子显微镜、X射线光电子能谱、紫外-可见漫反射光谱、稳态和瞬态吸收光谱、时间分辨荧光光谱等技术，表征与明确材料的结构、组成、性质与调控机制。探究光催化剂对畜禽养殖废水中抗生素的吸附分配、可见光催化降解的影响特性及其稳定性。模拟与计算抗生素和中间产物的分子轨道、能量、热力学性质与成键等参数，追踪降解中间产物与瞬态过程，结合光生载流子与活性自由基作用方式，实现从微观上洞悉抗生素在光催化剂表面及介质中降解与反应机理。项目有望为处理含抗生素的废水及自然水体提供理论依据与实践方法。

我国多地江河湖泊水体中受到不同程度的抗生素污染，在畜禽养殖业发达的区域，抗生素污染尤为严重。光催化技术具有能耗低、操作简便、反应条件温和、氧化能力强且无二次污染等特点，在解决废水中抗生素污染问题具有独特的优势。本项目通过控制合成了类石墨型氮化碳、钛金属有机骨架及其耦合异质结多孔材料，明确了材料的结构、组成、性质与调控机制。探究了光催化剂对畜禽养殖废水中抗生素的吸附分配、可见光催化降解的影响特性及其稳定性。模拟与计算了抗生素分子的分子轨道与能量，追踪与分析了降解中间产物，结合光生载流子与活性物种作用方式，从微观上探究了抗生素在光催化剂表面及介质中降解与反应机理。研究结果表明：基于氮化碳与钛金属有机骨架材料的光催化技术能有效去除畜禽养殖污水中的抗生素如盐酸四环素、盐酸金霉素等，对处理自来水、水库水、河水、反渗透浓缩液和制药废水中的抗生素，同样有效；对于污水中低浓度抗生素，该光催化剂对其去除率可接近100%；畜禽养殖废水中的高浓度NOx-N和NH3-N是造成盐酸金霉素降解效率下降的主要原因，而湘江水中的天然有机物是抑制盐酸金霉素降解的主要因素；抗生素的催化降解过程的活性物种主要涉及h+、•O2-和•OH；抗生素分子如盐酸盐四环素中的C-C=O或C-N-C片段成为活性物种最初的攻击点，然后通过失去含氮甲基官能团、羟基化、脱烷基化作用、脱水作用与开环反应，最终将其矿化成二氧化碳、水、无机物及无毒的小分子有机物；提出的异质结构筑方法对合成去除污水中抗生素的光催化材料具有普适性与有效性。本项目为解决畜禽养殖废水中的抗生素问题提供了合适的技术与光催化材料和合成方法，实现了从微观上洞悉抗生素在表界面与水中降解与反应的机理；为去除污水中抗生素提供了理论依据与实践方法。