【作者】 李娜；

【导师】 常志东；

【作者基本信息】 北京科技大学 ， 化学， 2020， 博士

【摘要】 由于微/纳米结构材料的性质独特,使其一直备受科学家们的关注和研究。目前,研究的难点和方向主要集中于对材料的组成、尺寸、维度和晶体结构的调控,使材料的微观结构和性质相关联,最终实现特定功能材料的可控设计和合成。由于低共熔溶剂(DES)具有类似离子液体的物理化学性质,使其能够作为前驱物合成微/纳米结构材料。本文的主要工作是设计合成金属水合物基DES,并基于DES合成微/纳米结构的吸附材料,从晶体的生长行为及其材料的微观结构之间的关系为理论基础,采用溶剂热法为主要的合成手段,合成了系列微/纳米结构材料,并对材料的吸附性能和吸附机制进行了研究。本文的主要研究工作如下:(1)室温下,首次合成了 MgCl2·6H2O/尿素(Urea)型DES,利用该DES制备了微米级立方形貌的无水MgCO3单晶,分析了产物的成核与生长过程。通过对影响晶体生长的因素的分析,发现外加溶剂水和DES中组分的含量会对碳酸镁结构和形貌产生影响,此外,立方体的尺寸可由反应温度进行调控。证明了 MgCl2·6H2O/Urea型DES具有为无水MgCO3晶体的生长提供金属盐、沉淀剂、液体环境和结构导向剂等多重作用。(2)以MgCl2·6H2O/Urea型DES合成的无水MgCO3为前驱物热解合成了立方微/纳米结构的MgO吸附材料。MgO对刚果红(CR)、苋菜红(AR)和靛蓝胭脂红(IC)等阴离子染料具有很强的吸附能力,对吸附动力学、吸附等温线、吸附热力学及吸附机制等进行了探讨。MgO均一的微米级尺寸结构使其更易于与水分离,甚至可以自然沉降,在废水处理中具有广阔的应用前景。(3)设计合成了 AlCl3·6H2O/PEG 200(摩尔比为1:3)型DES,基于MgCl2·6H2O/Urea 和 AlCl3·6H2O/PEG 200 合成了三维(3D)微/纳米结构的Cl-插层MgAl层状双氢氧化物(LDH)。产物对甲基橙(MO)、CR和IC等阴离子染料具有相当高的吸附能力(1051.87 mg·g-1、889.76 mg·g-1和512.55 mg g-1),明显高于文献中报道的大多数LDH,分析了 LDH的吸附机制。简而言之,用DES制备LDH是一种有效策略,可实现Cl-嵌入层间并减少CO32-污染,从而使阴离子染料的吸附迅速而高效。(4)室温下,首次合成了 SrCl2·6H2O/Urea(摩尔比为1:3)型DES,以此为反应溶剂,得到了结晶性良好的微/纳米结构的SrCO3十二面体,向SrCl2·6H2O/Urea 型 DES 中添加一定量的 AlCl3·6H2O/PEG 200 型 DES,得到了锶铝复合物。探讨了 SrCO3及锶铝复合物与CR染料作用的差异,实验表明锶铝复合物的吸附效果强于SrCO3,两种锶化合物经四次循环吸附后吸附能力依旧80%以上,SrCO3及锶铝复合物的应用拓展了吸附剂的种类。更多还原

【Abstract】 Due to the unique nature of micro/nano structured materials,it has always attracted the attention and research of scientists.At present,the difficulty and direction of research mainly focus on the regulation of the composition,size,dimension and crystal structure of the material,correlating the microstructure and properties of the material,and finally achieving the controllable design and synthesis of specific functional materials.Due to the physicochemical properties of deep eutectic solvent(DES)similar to ionic liquids,it can be used as a precursor to synthesize micro/nanostructured materials.In this work,the micro/nano structured adsorbents were synthesized with DES based on metal hydrate salts.Based on the relationship between the growth behavior of crystals and the micro structure of the materials,a series of micro/nano-structural materials were synthesized by the solvothermal method.In addition,the adsorption properties and mechanism of the materials were studied.The main works of this paper are as follows:(1)A novel DES containing MgCl2·6H2O and urea was synthesized for the first time at room temperature by grinding.The uniformly dispersed anhydrous MgCO3 single crystal with microcubic morphology was first synthesized through a facile solvothermal method using the DES(MgCl2·6H2O/Urea).Furtherly,the nucleation and growth of anhydrous MgCO3 were investigated.Based on the analysis of the factors affecting crystal growth,it was found the structure and morphology of anhydrous MgCO3 were affected by additional water and the components of DES.Besides,the size of the micro-cubes can be adjusted by the reaction temperature.In a word,the prepared anhydrous MgCO3 had good crystallinity and uniform morphology,which indicated the multiple effects of DES including metal resource,precipitant,solvent,and structure directing agent.(2)The micro/nanostructured MgO with the cubic morphology was synthesized by the pyrolysis of anhydrous MgCO3 which synthesized by the DES(MgCl2·6H2O/Urea).As evaluated as adsorbent,the strong adsorption capacity of the MgO micro-cubes towards anionic dyes of Congo red(CR),Amaranth(AR)and Indigo carmine(IC)was proved.The adsorption kinetics,adsorption isotherm,adsorption thermodynamics and adsorption mechanism were discussed.Particularly,their uniformly distributed micrometer-scale structures make them easier to separate from water,or even natural sedimentation,exhibiting wider application prospect in wastewater treatment.(3)The DES of AlCl3·6H2O/PEG 200(molar ratio 1:3)was synthesized and further characterized.The Cl-intercalated MgAl layered double hydroxide(LDH)with three-dimensional(3D)hierarchical structure was synthesized via one-step solvothermal method based on DES including MgCl2·6H2O/Urea and AlCl3·6H2O/PEG 200.The as-prepared Mg2Al-Cl LDH acquired high uptake capacities(1051.87,889.76 and 512.55 mg·g-1)for anionic dyes of Methyl orange(MO),CR and IC at 25℃ much higher than most reported LDHs in literatures.The adsorption mechanism was discussed.In a word,the LDH was prepared with DES is a directive and effective strategy to achieve the admirable Cl-intercalation and reduction of the CO32-contamination,which makes the adsorption rapidly and high-effectively for anionic dyes.(4)The DES containing SrCl2·6H2O and urea(molar ratio 1:3)was synthesized for the first time at room temperature.Using it as the reaction solvent,the SrCO3 with good crystallinity was obtained,exhibiting the micro/nano structure with dodecahedron morphology.In addition,the SrCO3 complex doped aluminum compound was also synthesized by the mixture of AlCl3·6H2O/PEG 200 and SrCl2·6H2O/Urea.It was found that the adsorption capacity of the SrCO3 complex doped aluminum compound was improved compared to the pure SrCO3 sample by the analysis of the interaction difference between CR and two samples.In addition,the adsorption capacity of the two samples was still more than 80%after four cycles.In a word,the application of SrCO3 and its complex expanded the variety of adsorbents.更多还原