【作者】 叶林静；

【导师】 关卫省；

【作者基本信息】 长安大学 ， 环境工程， 2014， 博士

【摘要】 随着人类健康及生活质量的大幅提高，药品及个人护理品（PPCPs）在日常生活中被广泛使用，环境对其负载量大，由于这类化学物质具有环境效应、遗传毒性效应和生理生态毒性，对这种新型污染物的处理技术正受到人们的密切关注，抗生素就是其中代表性化合物。目前，生物处理、物理吸附和光解作用等传统处理技术降解抗生素效率低且受水体环境限制，高级氧化技术利用高反应活性的羟基自由基可降解持久型生物难降解的有机物从而被广泛应用于污水处理过程。半导体光催化剂高级氧化过程是基于n型半导体在一定波长的光辐射下，半导体的能带中产生光生电子与空穴，与表面吸附的有机物发生氧化还原反应使其被降解去除。ZnO生产成本低，具有宽带隙可在紫外光照射下具有很强的光催化活性，但在实际应用中光催化剂存在太阳光利用率低、光生载流子重新复合降低催化活性和催化剂回收利用难等缺点。本论文通过改变ZnO的纳米结构，通过与不同功能材料复合影响其禁带宽度同时引入磁性性能，利用低温水热合成技术设计制备了四类ZnO基微纳米光催化材料；通过系统的测试方法对制备的四类光催化剂的晶相、形貌、元素组成、光学、磁性及重复利用性等特征进行研究；对四环素(TC)，土霉素(OTC)和强力霉素(DC)三种四环素类抗生素进行了光催化降解并探讨其降解动力学行为。本论文主要研究结果如下：1.硅基衬底水热法合成ZnO纳米材料及其光催化性能的研究（1）利用水热法以Si(100)作为基材，通过简易两步合成了中空六棱柱ZnO纳米材料，并利用多种表征手段对ZnO的结构、形貌、光学和磁学性质进行表征。结果表明，以硝酸锌为锌盐，KOH浓度为1.6M时得到了结构规整的高纯度中空六棱形ZnO纳米材料，单个中空六棱柱的长和高均为200nm，中空结构直径为100nm。这种中空ZnO样品显示了一定的铁磁性，其饱和磁化强度在5K和300K下分别为2.38×10-2emu/g和0.42×10-2emu/g。光催化性能测试表明，中空ZnO具有丰富的吸附位点，在暗反应吸附过程中吸附量大，纳米材料在UV辐射下对TC，OTC和DC具有很高的光催化降解效率，分别达到96.44%，77.83%和84.83%，且光催化反应符合一级反应动力学模型，反应速率常数为2.013×10-2min-1，1.272×10-2min-1和1.561×10-2min-1。（2）利用Si(111)作为基材，水热法两步合成了花状ZnO微纳米结构，利用多种表征手段对ZnO的晶相、形貌、光学和磁学性质进行分析。结果显示，当KOH浓度为1.5M时，100oC反应12h可制得包含多个花瓣和一个花簇中心的花状结构ZnO，其中花瓣大小为500nm，一个完整花朵尺寸为1μm。这种花状ZnO的铁磁性较高，饱和磁化强度为3.6×10-2emu/g。光催化性能测试表明，花状ZnO纳米材料在UV辐射下对TC，OTC和DC可分别达到96.47%，63.77%和91.15%的降解率，且光催化反应为一级动力学反应，反应速率常数为2.414×10-2min-1，1.03×10-2min-1和1.976×10-2min-1。2. Fe3O4复合ZnO制备磁性核壳结构光催化剂及其光催化性能的研究利用共沉淀及煅烧两步法合成了锥形核壳结构的磁性Fe3O4/ZnO纳米材料。对材料的组分、形貌、结构、光学及磁力性质进行表征发现，类似锥形的核壳Fe3O4/ZnO尺寸在100nm，以Fe3O4纳米簇为核，ZnO为壳；这种复合材料具有很强的铁磁性，Fe3O4/ZnO的饱和磁矩(Ms)为46.89emu/g，Fe3O4/ZnO光催化剂在外加磁场作用下能够实现有效的回收并显示了较高的再利用性。Fe3O4的复合使ZnO的带隙能有效降低至2.83eV；光催化性能测试表明，Fe3O4/ZnO光催化剂较纯ZnO显示了很高的可见光利用率，对TC、DC和OTC的降解率分别为81.02%,70.94%和63.67%，通过对光催化反应动力学分析发现Fe3O4/ZnO对四环素的降解符合一级动力学方程，反应速率大于纯ZnO和P25TiO2。另外对表面活性剂改性的磁性核Fe3O4的分散性，并对Fe3O4本身作为一种磁性载体的吸附行为进行分析。结果显示，改性后纳米Fe3O4结晶度及分散性明显提高，较尺寸为25nm的未改性Fe3O4，PVP和PEG–4000改性Fe3O4颗粒尺寸分别减小至20nm和10nm；同时改性产物均保持了较高的磁性。在吸附四环素(TC)过程中，静态吸附实验表明，PEG–4000改性Fe3O4吸附容量最高（47.62%），PVP改性Fe3O4的吸附能力（36.1%）优于未改性Fe3O4（13.45%）；PEG–4000改性Fe3O4吸附TC过程中，主要的吸附机制是氢键作用，Langmuir等温线模型更好地拟合了吸附平衡数据，其吸附动力学遵循孔内扩散模型，并以表面吸附为主，粒内扩散为辅。再生实验表明经过三次解析与重复利用实验后仍显示较高的吸附容量。3. CoFe2O4复合ZnO制备空心圆锥结构光催化剂及其光催化性能的研究利用Si(100)衬底辅助两步法水热合成了具有中空圆锥结构的磁性ZnO/CoFe2O4纳米材料。通过对材料的组分、形貌、比表面积、孔隙率、磁学和光学性质进行表征。结果表明，以择优刻蚀过程和磁性纳米颗粒的吸引效应共同作用制备了以中空圆锥形ZnO为骨架，CoFe2O4纳米粒子包覆在其表面，形成了长为200-300nm，圆锥底面直径为200nm的核壳结构。与ZnO的带隙能3.22eV相比，CoFe2O4的复合使得ZnO/CoFe2O4的带隙能降低至2.68eV。通过BET和BJH计算可知这种中空圆锥结构ZnO/CoFe2O4的高比表面积88.1593m2/g和孔体积0.18cm3/g使光催化剂具有更多反应位点。ZnO/CoFe2O4光催化剂在外加的磁场作用下能够实现有效回收，经过四个循环光催化反应，降解率几乎没有发生明显下降。ZnO/CoFe2O4光催化剂对TC、DC和OTC的降解率分别达到72.42%,66.18%和55.92%，比较光催化降解率及反应速率常数，ZnO/CoFe2O4的光催化活性明显高于P25TiO2。4. CdS-CoFe2O4复合ZnO磁性光催化剂的制备及其光催化性能的研究（1）利用水热法调节不同物料配比、反应时间合成了ZnO/CdS复合纳米材料。采用多种表征手段分析材料的组分、形貌和光学性质。结果表明，当锌源与镉源的物料摩尔比为25:1，反应时间10h可获得形貌最佳的ZnO/CdS复合物，即尺寸为1μm的多孔棒状ZnO骨架表面粘附了尺寸在几十纳米的CdS粒子。ZnO/CdS复合物的带隙能为2.87eV，在日光照射下反应120min，对TC、DC和OTC的光催化降解率分别达到81.65%,70.68%和54.61%，ZnO/CdS对四环素的降解符合一级动力学方程，且降解反应速率很快；在紫外光照射下，ZnO/CdS催化剂几乎可以完全降解这三种抗生素，证明了该复合物催化剂的高催化效率。（2）利用ZnO、CdS和CoFe2O4三组份前驱体溶液水热合成了磁性ZnO/CdS/CoFe2O4纳米材料。通过对材料的组分、形貌、磁学和光学性质进行表征，并对这种磁性复合物的光催化效率以及重复利用率进行测试。结果表明，圆柱形ZnO尺寸在500nm，其表面粘附了大量尺寸在100nm的块状CdS/CoFe2O4纳米粒子。三组份的复合使得ZnO/CdS/CoFe2O4的带隙能降低至2.07eV，同时该复合材料的饱和磁化强度为6.65emu/g。利用ZnO/CdS/CoFe2O4分别催化TC、DC和OTC三种抗生素，降解率分别达到82.96%，68.93%和58.53%，降解反应速率很快，符合一级动力学方程；重复使用四个循环，ZnO/CdS/CoFe2O4对TC的降解率仍保持65%以上。更多还原

【Abstract】 With the substantial improvements in human health and living quality, Pharmaceuticaland Personal Care Products (PPCPs) are widely used in daily life, and there are large load ofthe effluents discharged into the environment. Because the PPCPs like antibiotics haveenvironmental effects, genotoxic effects and toxicity of physiology and ecology, publicconcern has been aroused of the wastewater treatment technique on removing these emergingcontaminants for their possible threats to aquatic environment and human health. Currently,the traditional techniques including biological treatment, physical adsorption and photolysisdegradation have restricted by the water condition with disadvantages of low degradabilityand intricate procedure. Advanced oxidation processes make use of highly reactive hydroxylradical degrading the persistent and refractory biodegradation organic compound, which arewidely used in the sewage treatment process.Advanced Oxidation of semiconductor photocatalyst is typically based on n-typesemiconductor, the photogenerated electrons and holes generated from the energy band underirradiation at certain wavelength range, which lead to the degradation of pollutants absorbedon the surface of photocatalyst by the redox reaction. ZnO has a wide bandgap and lowproduction cost standing out of the semiconductor photocatalysts. However, the lowutilization of sunlight and electron–hole pair recombination reduced the the catalytic activityand recycling of ZnO. In this paper, four kind of ZnO-based magnetic photocatalysts designedby changing the ZnO nanostructures, hybrid the different band structure composite materialsand bring in the magnetic materials prepared by low-temperature hydrothermal method. Byarious of characterization, the crystalline phase, morphology, chemical composition, opticaland magnetic properties and the reusability were investigated. Meanwhile, their behaviours ofphotocatalytic degradation of three tetracyclines antibiotics were studied by the batchphotoreaction operations.The main conclusions included the following items:1. Hydrothermal synthesis of ZnO nanomaterials on silicon substrate and theirphotocatalytic properties (1) Hollow hexahedral ZnO nanocrystals were prepared by using a facile two-step ofhydrothermal procedure on a Si(100) substrate. The structure, morphology, photocatalytic andmagnetic properties of the products were examined. The results demonstrated that theuniformly sized ZnO of hexahedral structure is200nm and a hole with diameter of100nm,when the zinc source is Zinc nitrate and the concentration of KOH is1.6M. Hollow ZnOnanocrystals were proved having ferromagnetic property, the Ms is2.38×10-2emu/g at5Kand0.42×10-2emu/g at300K. Further investigation on the photocatalytic activity of theproducts showed the degradation of TC, OTC and DC is96.44%，77.83%and84.83%, whichcan be described by the frst order kinetic model, the rate constant is2.013×10-2min-1,1.272×10-2min-1and1.561×10-2min-1, respectively.(2) Flower-like ZnO micro and nano structures were prepared by using a facile two-stepof hydrothermal procedure on a Si(111) substrate. The structure, morphology, photocatalyticand magnetic properties of the products were examined. The results showed that flower-likestructure nanoparticles with the size of1μm can be obtained at100oC with1.5M KOH,which contains multiple petals with the diameter of500nm and a flower cluster center.Flower-like ZnO structures showed positive ferromagnetic property, the Ms is3.6×10-2emu/gtested at room temperature. Further investigation on the photocatalytic activity of the productsshowed the degradation of TC, OTC and DC under mercury lamp is96.47%,63.77%and91.15%, respectively, which can be described by the frst order kinetic model, and the rateconstant is2.414×10-2min-1,1.03×10-2min-1and1.976×10-2min-1, respectively.2. Preparation of ZnO/Fe3O4magnetic core-shell structure composite and theirphotocatalytic propertiesMagnetic Fe3O4/ZnO core-shell nanomaterials have been successfully prepared by usingtwo-step method with coprecipitation and annealing treatment. The material composition,morphology and magnetic properties were examined and verified. The results showed that thestrongly-magnetic materials have the diameter of100nm, the Fe3O4nanoparticles work as themagnetic core while ZnO is the photocatalytic shell, and the nanocomposites can be recycledunder magnetic field since the Ms is46.89emu/g. The recombination action of Fe3O4reducedthe bandgap energy to2.83eV, leading to high photocatalytic degradation on TC, DC andOTC, and the degradation rate is81.02%,70.94%,63.67%, respectively. The photocatalysis of Fe3O4/ZnO can be described by the frst order kinetic model, the low reaction rate requiredlong reaction process. Meanwhile, The nano-Fe3O4was modified by surfactants working asan magnetic adsorbent to remove TC from aqueous solutions. The nano-Fe3O4crystalline anddispersion was improved significantly by PEG-4000, the particle diameter of unmodifiedFe3O4, PVP-Fe3O4and PEG-4000-Fe3O4is25nm,20nm and10nm, respectively. The resultsof batch adsorption experiments suggested hydrogen bonds formation between hydroxylgroups played a leading role in removing TC, and PEG-4000-Fe3O4has the greatestabsorption capacity(47.62mg/g) comparing with PVP-Fe3O4(36.1mg/g) and Fe3O4(13.45mg/g), the equilibrium data was fitted to the Langmuir isotherm model better than theFreundlich model The kinetic property of modified Fe3O4was well described by theintraparticle diffusion model, dominated by surface adsorption and intraparticle diffusionacted as auxiliary adsorption.3. Hydrothermal synthesis of hollow cone-like ZnO/CoFe2O4heterostructures andtheir photocatalytic propertiesHeterostructures of hollow cone-like ZnO/CoFe2O4nanocomposites are successfullyfabricated by a two-step hydrothermal route with assistance of Si(100) substrate. The materialstructure, composition, morphology, specific surface area, the magnetic and optical propertieswere investigated. The findings illustrated that through preferential etching process and theattractive effects of magnetic nanoparticles, hollow cone-like nanocomposites were assembledby CoFe2O4coated on the ZnO bone-structure with diameter of200-300nm in length and200nm in hole. Band gap energy of the nanocomposites (2.68eV) is lower than that of pure ZnO(3.22eV). This special heterostructures brought novel surface area of88.1593m2/g and thetotal porosity of0.18cm3/g. The degradation on TC, DC and OTC of nanocomposites underxenon light reaches72.42%,66.18%and55.92%, and the photocatalysis can be described bythe frst order kinetic model.4. Preparation of CdS/ZnO and CdS/CoFe2O4/ZnO composite photocatalyst andtheir photocatalytic properties(1) ZnO/CdS nanocomposites were synthesized by hydrothermal method with optimumthe ratio of raw materials and reaction time. The structure, morphology and photocatalyticproperty of the products were examined. The results demonstrated that the ZnO/CdS of optimal morphology was obtained at zinc and cadmium molar ratio of25:1reacted for10h,there are several CdS nanoparticles adhere to the surface of porous ZnO rod skeleton. Theband gap energy of nanocomposites is about2.87eV, leading to the degradation on TC, DCand OTC under xenon light reached81.65%,70.68%and54.61%respectively. Moreover,ZnO/CdS catalyst almost completely removed three antibiotics under UV irradiation, provedhigh catalytic efficiency of the composite catalyst.(2) Using ZnO, CdS and CoFe2O4as precursor solution, ZnO/CdS/CoFe2O4nanocomposites were synthesized by hydrothermal method. The morphology, magnetic andoptical properties of nanomaterials were characterized, also the photocatalytic efficiency andreusability were tested. The results showed that the cylindrical ZnO with the size of500nmwas coated by a large number of block CdS/CoFe2O4nanoparticles with the diameter of100nm. The complex photocatalysts have a narrow bandgap of2.07eV because of themulti-componets, while the saturation magnetization of the composite material is6.65emu/g.TC, DC and OTC were photocatalyzed by ZnO/CdS/CoFe2O4under xenon light, anddegradation rate were82.96%,68.93%and58.53%, respectively. The degradation reactionrate worked in line with first-order kinetics. The TC degradability of ZnO/CdS/CoFe2O4remained above65%after repeated three cycles.更多还原