【作者】 郭敬维；

【导师】 尹秋响； 那平；

【作者基本信息】 天津大学 ， 化学工程， 2013， 博士

【摘要】 “十二五”规划以来，水体重金属污染的防治技术，尤其是水体中重金属的深度去除技术已经成为重点研究内容之一。本论文以水体中重金属砷和铬的高效去除为研究目标，制备了纳米二氧化钛材料和三维二氧化钛纳米材料，采用SEM、TEM、XPS及N2吸附-脱附等手段对材料进行表征，并对水体中As(III)的吸附-氧化过程、Cr(VI)的吸附-还原性能和机制进行了研究。工作内容如下：1）以钛酸丁酯为前躯体制备了二氧化钛纳米材料，定性探讨了纳米TiO2颗粒粒径、比表面积和表面羟基含量对As(III)的吸附和催化氧化过程的影响，结果表明金红石相二氧化钛具有催化氧化能力，表面羟基为其发挥作用的功能基团。2）采用无模板法进行三维金红石相TiO2纳米材料构建，探讨了反应时间、温度、前驱体浓度、干燥温度以及搅拌方式对三维TiO2纳米结构和形貌形成的影响；采用SEM、TEM以及XPS分析手段对材料的微观结构和组分进行了分析，表明TiO2球为微米级别，具有核-壳结构，其中壳结构是由结晶度高的金红石相刺状结构构成，核结构是由低结晶度金红石相和无定形TiO2纳米颗粒构成。无模板法制备的TiO2具有大量的微孔结构，表面羟基密度约为18.9OH/nm2，产率可达97.8%。对TiO2三维纳米结构的形成机制分析表明，材料生长前期受生长由动力学和结晶动力学控制，后期存在奥斯特瓦尔德效应作用。3）针对水体中As(III)和As(Ⅴ)、Cr(VI)和Cr(Ⅲ)的吸附过程，开展了动力学和热力学实验，考察了溶液pH值，共存离子对吸附容量的影响，结合三维TiO2的微观结构阐明了重金属的吸附机制。结果表明材料的结构和组成促进了砷和Cr(VI)的化学吸附过程；在pH=2-10的范围内，pH值对TiO2除砷性能的影响较小，As(III)和As(Ⅴ)的吸附容量都保持在24和17mg g-1以上，吸附过程与配合物形成过程中H+和OH-的释放相关；材料对砷的吸附容量可达60mg g-1以上，5min内可完成至少80%的吸附过程，并可将砷浓度降低到检测限以下（0.02μgL-1）。随着pH值的升高，材料对Cr(VI)的吸附容量由28mg g-1（pH=2.1）降低到6mg g-1(pH=10.3)，对Cr(Ⅲ)几乎不吸附，吸附容量<1.5mg g-1。4）在UV/TiO2系统中，采用XPS分析手段探究了As(III)的吸附与氧化、Cr(VI)的吸附与还原行为。紫外光可提高TiO2的表面羟基功能基团密度，形成亚稳态吸附位点，具有高反应活性和低热力学稳定性。因此，紫外光可促进As(Ⅴ)的吸附速率，不能提高其吸附容量；紫外光促进了As(III)由双齿配位向单齿配位转化，晶体缺陷处的-H2O/-OH在催化氧化过程中起直接作用；另外，金红石相TiO2可应用到Cr(VI)的还原应用中。更多还原

【Abstract】 Prevention and remediation technology of heavy metal pollution, especially thedepth removal technology of heavy metal in water has become one of the key researchcontents. In this paper, in order to remove arsenic and chromium in water, nanometertitanium dioxide materials and three-dimensional rutile phase titanium dioxidematerials were prepared. The characterization of these materials was performed bySEM, TEM, XPS and N2adsorption-desorption methods. As(III) adsorption-oxidation process, Cr(VI) adsorption-reducing property and mechanism in water werestudied. The work was as follows:Titanium dioxide nanoparticles were prepared from tetrabutyl titanate adopted asprecursor.The anatase phase and rutile phase crystals with different particle size wereobtained by sintering method. The effects of TiO2particle size, specific surface areaand the surface hydroxyl content for As(III) adsorption and catalytic oxidation werestudied. The results showed that the rutile phase titanium dioxide had catalyticoxidation ability and the surface hydroxyl was the functional group for adsorption.Three-dimensional rutile TiO2nanostructures were prepared using template-freemethod. The effects of reaction time, temperature, precursor concentration, dryingtemperature and stirring methods on the structure and morphology ofthree-dimensional TiO2structure were discussed. The microstructure and compositionof the materials were performed by SEM, TEM and XPS. The results showed that thediameter of TiO2spheres was in micron level with a core-shell structure. The shellstructure was composed of spiny rutile phase structure with a high degree ofcrystalline; the core structure was composed of rutile with low crystallinity andamorphous TiO2nanoparticles. Using this method, the yield of TiO2wasapproximately97.8%and the surface hydroxyl density was approximately18.9OH/nm2. The formation mechanism of TiO2three-dimensional nanostructures wasfurther studied, which was controlled by particle growth kinetics and crystallizationgrowth kinetics in prophase and by the Ostwald effect in anaphase.In view of the adsorption process of As(III), As(Ⅴ), Cr (VI) and Cr(Ⅲ) in water,thermodynamic and kinetic experiments were carried out. Effect of PH values,coexisting ions and the structure of TiO2on the adsorption behavior was analysed indepth. Experiment results showed that its structure and composition were in favour of the adsorption of arsenic and Cr(VI), the impact of pH value was related to the releaseof H+and OH-in the compound formation process. In the range of pH=2-10, As(III)and As(Ⅴ) adsorption capacity was above17and24mg g-1; The adsorption capacityof As(Ⅴ) was60mg g-1.The adsorption process achieved at least80%within5minand the residual arsenic concentration decreased under detection limit. With theincreasing of pH, the adsorption capacity of Cr(VI) decreased from28mg g-1(pH=2.1)to6mg g-1(pH=10.3) and the adsorption capacity of Cr(Ⅲ) was less than1.5mg g-1.In UV/TiO2system, the As(III) and Cr(VI) adsorption-reduction process werediscussed. Ultraviolet light enhance hydroxyl functional group density of TiO2, butthese hydroxyl was unsteady adsorption sites with high reactivity and lowthermodynamics stability. Ultraviolet light cannot improve the adsorption capacity ofAs(Ⅴ) but the adsorption rate.-H2O/-OH in crystal defects played a direct role incatalytic oxidation process; rutile TiO2could be applied to Cr(VI) reductionapplication.更多还原