【作者】 张强；

【导师】 王磊；

【作者基本信息】 西安建筑科技大学 ， 建筑与土木工程， 2022， 硕士

【摘要】 氟伐他汀是常用于治疗高胆固醇血症的他汀类药物。因传统污水处理技术很难将其彻底去除,而广泛存在于水环境中,对人类生命健康存在潜在的威胁。光催化技术是去除水环境中他汀类药物的有效途径。Bi₂WO₆是典型的铋系光催化剂,具备良好的可见光吸收性能。但是其导带位置较正,限制了以e^-还原O₂为核心产生·O₂^-的链式反应,进而影响多种类活性自由基产生。同时窄带隙结构引起光生电子、空穴快速复合导致光催化效率降低。本研究基于ZnIn₂S₄和Bi₂WO₆能带结构交错排列特征制备复合光催化剂,解决Bi₂WO₆多种类活性自由基产生受限和电子空穴快速复合问题。考察复合比例、水热反应时间、水热反应温度对复合光催化剂结构和性能的影响,获得最佳制备条件。研究复合催化剂投加量、污染物浓度、p H值、腐殖酸、阴阳离子和光源等条件对氟伐他汀去除效果的影响。通过活性自由基定性和定量分析、矿化度分析及降解路径和中间产物分析,揭示复合光催化剂性能提升机理。主要结论如下:（1）在水热反应时间720 min、水热反应160℃、ZnIn₂S₄复合量为30%时制备的ZIS@BW-30%复合光催化剂具有最佳光催化性能。其具有由Bi₂WO₆为外壳覆盖ZnIn₂S₄微球内核的核壳结构,比表面积为37.97 m²/g,带隙宽度为3.1e V,瞬态光电流最大,阻抗半径最小。在氙灯照射下,对氟伐他汀去除效率达到75.47%,相比单组分Znln₂S₄和Bi₂WO₆体系氟伐他汀去除率明显提高。（2）当ZlS@BW复合光催化剂投加量为0.2 g/L、氟伐他汀浓度为10 mg/L、溶液初始p H=9时,光催化降解效果最好,光照120 min后氟伐他汀去除率达到75.47%;阴阳离子均对降解氟伐他汀存在抑制作用,其抑制作用大小为:Mg²⁺>Ca²⁺>Na⁺>K⁺,CO₃^2->SO₄^2->HCO₃^->Cl^-;腐殖酸对氟伐他汀的去除影响显著,腐殖酸初始浓度达到1 mg/L时,氟伐他汀去除率降低20%,腐殖酸浓度达到10mg/L时,氟伐他汀去除率仅为29.49%;紫外灯照射下,氟伐他汀去除效果最好,去除率达到78.45%;ZlS@BW具有较高稳定性,四个批次循环降解实验中氟伐他汀去除率仅下降1.84%。（3）光催化反应过程中h⁺起关键氧化作用,·OH和·O₂^-起辅助作用。·O₂^-和·OH的浓度分别为1.36×10^-5mol/L和2.68×10^-7mol/L。ZlS@BW-30%复合光催化剂在光照下产生h⁺、·O₂^-和·OH等活性自由基,活性自由基协同攻击氟伐他汀长链化合物上的C-C键、C=C双键以及C-N键,使其生成短链有机化合物,然后这些有机化合物进一步被氧化分解生成H₂O和CO₂。ZlS@BW-30%复合光催化剂体系的矿化度达到44.19%,远远高于单组分催化体系的矿化度。ZlS@BW复合光催化剂相比于单组分ZnIn₂S₄和Bi₂WO₆性能提升的主要原因包括两点。一是在ZlS@BW复合光催化剂的Z-Scheme型异质结结构中ZnIn₂S₄价带的h⁺与Bi₂WO₆导带的e^-复合,有效延长ZnIn₂S₄导带上的e^-和Bi₂WO₆价带上h⁺的寿命,为其氧化含氧物质产生强氧化性活性自由基提供了机会。二是ZnIn₂S₄和Bi₂WO₆能带结构特征决定了ZlS@BW复合光催化剂可同步产生多种类活性自由基,h⁺、·O₂^-和·OH的协同氧化作用有利于提高复合光催化剂性能。更多还原

【Abstract】 Fuvastatin is one of the statins to treatment of hypercholesterolemia.Due to the difficulty of complete removal of fluvastatin by traditional wastewater treatment technology,it widely exists in the aqueous environment and poses potential threat to human life and health.Photocatalytic technology is an effective way to remove statins from water.Bi₂WO₆is a typical bismuth-based photocatalyst with excellent response performance of visible light.However,the conduction band of Bi₂WO₆is positive,which restricts the chain reaction to generate·O₂^-through reduction of O₂by electrons,and then affects the generation of multiple reactive radicals.Meanwhile,the narrow band gap structure causes rapid recombination of photogenerated electrons and holes,which leads the decrease of photocatalytic efficiency.In this study,the composite photocatalysts were prepared based on the staggered band alignment of ZnIn₂S₄and Bi₂WO₆to solve the problems of limited generation of multiple reactive radicals and rapid electron-hole recombination of Bi₂WO₆.The effects of compounding ratio,hydrothermal reaction time and hydrothermal reaction temperature on the structure and performance of the composite photocatalysts were investigated to obtain the optimal preparation conditions.The effects of catalyst dosage,pollutant concentration,p H,humic acid,ion and light source on the removal effect of fluvastatin were investigated using the composite catalysts prepared under the optimal conditions.The qualitative and quantitative analysis of active radicals in the composite photocatalyst system,mineralization analysis,degradation pathway and intermediate product analysis were used to reveal the enhancement mechanism of composite photocatalyst performance.The main conclusions are as follows.（1）The ZlS@BW-30%showed the best photocatalytic performance which was prepared at hydrothermal reaction time of 720 min,hydrothermal reaction of 160°C,and ZnIn₂S₄doping of 30%.The ZlS@BW-30%had a core-shell structure consisting of Bi₂WO₆microspheres as a shell covering a ZnIn₂S₄core,the specific surface area was37.97 m²/g,the band gap was 3.1 e V,and showed the maximum transient photocurrent,the smallest impedance radius.Under xenon lamp irradiation,the degradation efficiency of fluvastatin reached 75.47%,and the removal rate of fluvastatin was significantly improved compared with the single-component Znln₂S₄and Bi₂WO₆systems.（2）When the ZlS@BW-30%dosage was 0.2 g/L,the concentration of fluvastatin was10 mg/L and the initial p H=9 of the solution,the photocatalytic degradation effect was the best,and the removal rate of fluvastatin reached 75.47%after 120 min of light irradiation;The degradation of fluvastatin was inhibited in the presence of anions and cations,and the order of inhibitory effects were:Mg²⁺>Ca²⁺>Na⁺>K⁺.CO₃^2->SO₄^2->HCO₃^->Cl^-;the effect of humic acid on degradation of fluvastatin was significant,the removal rate of fluvastatin was reduced by 20%when the initial concentration of humic acid reached 1 mg/L,and only 29.49%was removed when the concentration of humic acid increased to 10 mg/L;the best degradation of fluvastatin was achieved under UV light irradiation,the removal rate reached 78.45%;ZlS@BW-30%possessed high stability,and the removal rate of fluvastatin only decreased by 1.84%in four batches of cyclic degradation experiments.（3）In the photocatalytic reaction,h⁺played key role in oxidation,while·OH and·O₂^-played secondary role.The concentration of·O₂^-and·OH was 1.36×10^-5mol/L and 2.68×10^-7mol/L,respectively.The ZlS@BW-30%composite photocatalyst generated reactive radicals such as h⁺,·O₂^-and·OH under light illumination.The C-C bond,C=C double bond and C-N bond on the long-chain compounds of fluvastatin were attacked under the synergistic oxidation of reactive radicals such as h⁺,·O₂^-and·OH to form short-chain organic compounds,which further oxidized and decomposed to form H₂O and CO₂.The mechanism for the photocatalytic performance enhancement of ZlS@BW included two points as follow.Firstly,the well-matched staggered band alignment of ZnIn₂S₄and Bi₂WO₆was utilized to form Z-scheme heterojunction.The h⁺in the valence band of ZnIn₂S₄was recombine with e^-in the conduction band of Bi₂WO₆to prolong the lifetime of e^-in the conduction band of ZnIn₂S₄and h⁺in the valence band of Bi₂WO₆,which provided more opportunities for generation of reactive radicals.Secondly,the synchronous generation of multiple ROS was achieved based the band structure of ZnIn₂S₄and Bi₂WO₆,the synergistic oxidation of h⁺,·O₂^-and·OH was contributed to improved the performance of the composite photocatalyst.更多还原