水解聚合铝溶液中Al30形态的研究*

水解聚合铝形态一直是分析、催化、土壤、地球化学、新材料、环境科学和生物毒理学等众多领域研究的前沿和热点。Keggin 结构的Al₃₀ 形态是迄今为止发现的电荷最高的水解铝聚合阳离子,具有独特的分子结构和纳米分子尺寸,它对催化化学、新型功能材料、高效絮凝剂的开发以及铝的水解聚合转化规律研究具有重要意义。本文主要论述了Al₃₀形态的形成、形态分析方法、结构模型以及形成机理等方面的最新研究进展,并对水解聚合铝溶液的研究发展趋势进行了展望。     

水解聚合铝溶液中Al30形态的研究

水解聚合铝形态一直是分析、催化、土壤、地球化学、新材料、环境科学和生物毒理学等众多领域研究的前沿和热点。Keggin 结构的Al₃₀ 形态是迄今为止发现的电荷最高的水解铝聚合阳离子,具有独特的分子结构和纳米分子尺寸,它对催化化学、新型功能材料、高效絮凝剂的开发以及铝的水解聚合转化规律研究具有重要意义。本文主要论述了Al₃₀形态的形成、形态分析方法、结构模型以及形成机理等方面的最新研究进展,并对水解聚合铝溶液的研究发展趋势进行了展望。     

羟基聚合铝形体结构的X射线衍射和核磁共振表征研究进展

探讨水解聚合铝的形态分布以及铝的水解聚合转化规律一直是环境化学、催化材料化学和铝的生态毒理效应研究的前沿热点课题。本文综述了国内外X射线衍射和核磁共振波谱技术在羟基聚合铝形体结构表征方面的研究进展,对方法的各自特点进行了全面比较,并就未来研究动向做了展望。     

羟基聚合铝晶体研究进展

羟基聚合铝的研究在环境化学中具有重要作用。自然条件下存在的无机单核铝本身具有毒性,而多核铝是比单核铝更毒的铝形态,它们很容易进入人体和植物产生毒害作用。因此,水解聚合铝形态研究一直是环境化学、地球化学和材料催化等众多研究领域的前沿热点课题。本文综述了在新环境材料开发中羟基聚合铝晶体研究的进展,对已获得表征的典型羟基聚合铝的结构特点进行了对比与评述,讨论了不同羟基聚合铝晶体的科学意义和应用价值。     

铝盐水解聚合及其形态转化过程的电位滴定曲线研究

通过对中等滴碱速度下强制铝盐水解聚合过程中的电位滴定曲线分析,提出了临界点的概念。临界点是铝盐水解聚合电位滴定曲线的特征点,它与实验条件有关,临界点的变化反映了实验条件对铝盐水解聚合过程和羟基铝形态转化的影响．按照OH与Al摩尔比的大小,利用铝盐水解聚合电位滴定曲线的3个临界特征点,可以将铝的形态变化定量地划分为4个区：即水解单核铝区（包括Al^3 和单核铝Ala);低／中聚合铝区(主要包括Al2～Al12形态);高聚合铝区(主要包括AL13～AL54形态)和溶胶／凝胶区(Ale即Al(OH)3形态);溶胶／凝胶溶解区主要形态为Al(OH)4^-),从而为研究铝的水解聚合过程提供了定量基础。同时考察了铝浓度、温度、卤素离子、硅酸根、有机酸根等多种凶素对铝溶液碱滴定pH～n曲线及其划分铝形态临界点的影响,探讨了这些凶素对铝盐水解聚合过程及其形态转化的影响规律,为研究各种凶素对铝的水解聚合过程的影响提供了一种新思路。     

环境中羟基聚合铝型体的形成和形态转化规律

本文综述了近十年来可溶态铝在水体、土壤溶液及水和土壤矿物界面上的水解、聚合、絮凝和沉积行为及其形态转化过程和机理的研究进展，系统地总结并评价了目前已经报道过的各种羟基聚合铝型体及其形成条件、测试方法、热力学稳定常数以及可能结构等，分析了各种因素如粘土矿物的种类、OH^-／Al摩尔比、各种有机和无机配体离子以及实验条件等对羟基聚合铝形态变化的影响规律。引用文献50篇。     

水解聚合铝阳离子Al13和Al30的27Al核磁共振定量研究

采用不同磁场强度的NMR谱仪和不同测试温度,对水解聚合铝溶液中Keggin结构的聚合铝阳离子形态的定量分析方法进行了研究。检测结果表明,高场27A l NMR分析技术不仅能精确定量地检测出水解聚合铝溶液中具有Keggin结构的[A lO4A l12(OH)24(H2O)12]7 (简称A l13)聚合阳离子,而且还能定量地检测出[(A lO4)2A l28(OH)56(H2O)26]18 (简称A l30)聚合阳离子。提高测试温度,有利于降低A l30共振峰的线宽,增强其分辨率。在70℃测试温度下,采用高场27A lNMR分别对8种中、高浓度(0.1~2.0 mol/L)水解聚合铝溶液中的A l13和A l30形态分布进行了定量研究,证实了A l30形态是高浓度水解聚合铝溶液中的一种优势聚合形态。     

环境水体中聚合铝形态的分析测试技术研究进展

酸性环境中,沉积物释放和土壤淋失的可溶态铝大量进入环境水体,并在水体中以及水和颗粒物界面上发生聚合、絮凝、沉降以及络舍、吸附和电中和等物理化学反应,严重影响着其它元素的生物地球化学循环和其它污染物的迁移和归趋,具有重要的生态和生物效应。而Al^3 及其羟基水解聚合物的形态分析是研究环境和生物体系中铝的毒性、生物有效性和传输机理以及天然水体的自净机理的关键。由于直接有效测定上的困难,对天然水体中是否存在铝水解聚合型体这一观点并未达成共识,其结论也存在一些争议甚至相悖的情况。本文综述了近二十年来环境水体中聚合铝形态测试技术研究的新进展。引用文献60篇。     

通过Boltzmann拟合方程定量计算Al(Ⅲ)盐强制水解聚合溶液中的羟基多核铝型体

在表征聚合铝的3种传统测试方法中,只有酸碱电位滴定法至今还没有用于定量计算羟基多核铝。本文依据Al(Ⅲ)盐强制水解聚合过程的电位滴定实验结果,利用铝盐水解聚合电位滴定曲线的三个临界特征点,同时利用Origin软件自备的Boltzmann方程对滴定曲线拟合,可以很方便地计算出铝盐强制水解聚合溶液中聚合铝的含量。模式计算结果与Al-Ferron逐时络合比色法的测试结果线性符合较好,为研究Al(Ⅲ)盐水解聚合过程及其聚合铝形态的定量测定尝试了一种新的方法。     

不同结构烷基铝催化异戊二烯齐聚与聚合行为研究

烷基铝(AlR₃)作为Ziegler-Natta催化剂体系的助催化剂组分,起到烷基化、还原主金属化合物、参与活性中心形成与演变、链转移剂等重要作用.然而烷基铝自身对二烯烃单体也具有催化作用.本工作采用不同结构烷基铝如三乙基铝(Al Et3)、三异丁基铝(Al(i-Bu)₃)、氢化二异丁基铝(AlH(i-Bu)2)、一氯二乙基铝(AlEt₂Cl)、二氯一乙基铝(AlEtCl₂),研究了烷基铝的种类和浓度对异戊二烯催化行为的影响.采用核磁共振氢谱(1H NMR)、凝胶渗透色谱(GPC)、气相色谱-质谱联用(GC-MS)等对产物的微观结构(顺式-1,4-和反式-1,4-含量)和分子量及分布等进行了表征,探讨了不同结构烷基铝的催化行为.发现烷基铝不仅可以催化异戊二烯齐聚,与微量水作用后还可以引发异戊二烯阳离子聚合,得到顺反混合结构的线性聚合物.烷基铝浓度对其催化行为有较大影响.当n(Al)/n(M)=1050×10^-5时, AlEtCl2的催化活性显著提高,产物主要为线性聚合物;而其他...     

Hydrolytic polycondensation of alkoxysilanes and modification of polymerization reactions

Polymers having oxide network chains are produced by hydrolytic polycondensation of metal alkoxides and alkoxysilanes. Molecular morphology and molecular size distribution of these inorganic polymers are strongly affected by certain nonchemical parameters. Included among these parameters is the molecular separation of interacting species during the polymerization. There is strong evidence that the molecular size expansion occurs by two distinct processes: initially by a gradual “growth” process, and later by “recombination” of high-molecular weight species. The later process often leads to a bi-modal molecular size distribution. The concentration of water-rich siloxane solutions leads to significant molecular size expansion by further oxide network formation. No similar polymer size growth occurs during the concentration of alcohol based solutions. This difference in the polymeric activities can be related to the difference in the terminal bond under the two different conditions.     

土壤和水体中可溶性铝硅酸盐的形成及其环境意义

阐述了土壤环境中铝的释放，水解，单体和多聚体羟基铝，铝硅酸盐复合离子ｐｒｏｔｏ－ｉｍｏｇｏｌｉｔｅ的形成和影响因素及其生态效应。     

Al(30): A Giant Aluminum Polycation

Simple hydrothermal treatment of the well-known aluminum polycation varepsilon-Al(13) produces the novel Al(30) structure (see picture), the largest polycation yet observed. Its characterization, by X-ray diffraction and NMR spectroscopy, also solved previously unassigned signals in (27)Al NMR spectra of other Al - O species.     

无机晶须材料的合成与应用

本文综述了无机晶须材料的合成与应用研究现状.近年来我国在这一研究领域取得了很大发展,以"硼酸铝晶须产业化"项目为代表的无机晶须材料的工业化生产,无疑将对我国高技术新材料的发展起极大的促进作用.本文还对几种典型的无机晶须材料--SiC晶须、Al18B4O33晶须、K2Ti6O13晶须、CaCO3晶须、Mg2B2O5晶须、莫来石晶须的合成与应用研究现状作了概述,并就其研究前景作了展望.     

Interfacially formed organized planar inorganic, polymeric and composite nanostructures

This paper discusses synthetic strategies for fabrication of new organized planar inorganic, polymeric, composite and bio-inorganic nanostructures by methods based on chemical reactions and physical interactions at the gas-liquid interface, Langmuir monolayer technique, interfacial ligand exchange and substitution reactions, self-assembling and self-organization processes, DNA templating and scaffolding. Stable reproducible planar assemblies of ligand-stabilized molecular nanoclusters containing definite number of atoms have been formed on solid substrate surfaces via preparation and deposition of mixed Langmuir monolayers composed by nanocluster and surfactant molecules. A novel approach to synthesis of inorganic nanoparticles and to formation of self-organized planar inorganic nanostructures has been introduced. In that approach, nanoparticles and nanostructures are fabricated via decomposition of insoluble metal-organic precursor compounds in a layer at the gas-liquid interface. The ultimately thin and anisotropic dynamic monomolecular reaction system was realized in that approach with quasi-two-dimensional growth and organization of nanoparticles and nanostructures in the plain of Langmuir monolayer. Photochemical and redox reactions were used to initiate processes of interfacial nucleation and growth of inorganic phase. It has been demonstrated that morphology of resulting inorganic nanostructures can be controlled efficiently by variations of growth conditions via changes in state and composition of interfacial planar reaction media, and by variations of composition of adjacent bulk phases. Planar arrays and chains of iron oxide and ultrasmall noble metal (Au and Pd) nanoparticles, nanowires and new organized planar disk, ring, net-like, labyrinth and very high-surface area nanostructures were obtained by methods based on that approach. Highly organized monomolecular polymeric films on solid substrates were obtained via deposition of Langmuir monolayer formed by water-insoluble amphiphilic polycation molecules. Corresponding nanoscale-ordered planar polymeric nanocomposite films with incorporated ligand-stabilized molecular metallic nanoclusters and interfacially grown nanoparticles were fabricated successfully. Novel planar DNA complexes with amphiphilic polycation monolayer were formed at the gas-aqueous phase interface and then deposited on solid substrates. Toroidal and new net-like conformations were discovered in those complexes. Nanoscale supramolecular organization of the complexes was dependent on cationic amphiphile monolayer state during the DNA binding. These monolayer and multilayer DNA/amphiphilic polycation complex Langmuir-Blodgett films were used as templates and nanoreactors for generation of inorganic nanostructures via metal cation binding with DNA and following inorganic phase growth reactions. As a result, ultrathin polymeric nanocomposite films with integrated DNA building blocks and organized inorganic semiconductor (CdS) and iron oxide quasi-linear nanostructures were formed. It has been demonstrated that interaction of deposited planar DNA/amphiphilic polycation complexes with bulk phase colloid inorganic cationic ligands (CdSe nano-rods) can result in formation of new highly organized hybrid bio-inorganic nanostructures via interfacial ligand exchange and self-organization processes. The methods developed can be useful for investigation of fundamental mechanisms of nanoscale structural organization and transformation processes in various inorganic and molecular systems including bio-molecular and bio-inorganic nanostructures. Also, those methods are relatively simple, environmentally safe and thus could prove to be efficient practical instruments of molecular nanotechnology with potential of design and cost-effective fabrication of new controlled-morphology organized planar inorganic and composite nanostructured materials. Possible applications of obtained nanostructures and future developments are also discussed.     

Effect of pH on the aluminum salts hydrolysis during coagulation process: formation and decomposition of polymeric aluminum species

Effect of pH on the aluminum chloride hydrolysis at low concentration was investigated in detail by electrospray ionization (ESI) mass spectrometry. In particular, formation and decomposition processes of polymeric aluminum species were discussed. When coagulant AlCl(3) was diluted to normal coagulant dose (1.5 x 10(-4) mol/L), hydrolysis occurred immediately. Monomeric and dimeric aluminum species were the main products at pH 4.0. With pH increasing, hydrolysis and polymerization processes were accelerated. Monomeric and dimeric aluminum species hydrolyzed and polymerized into small polymeric aluminum species (Al(3)-Al(5) species) at pH 4.8. Through aggregation and self-assembly, the small polymeric aluminum species polymerized into median polymeric species (Al(6)-Al(10) species) at pH 5.0. In the same way, small and median polymeric aluminum species further aggregated into large polymeric species (Al(11)-Al(21) species). When pH was up to 5.8, metastable median and large polymers species decomposed into small aluminum species, then further disaggregated into dimeric species. With pH increased to 6.4, majority of aluminum species formed to Al(OH)(3) amorphous flocs. Accordingly, coagulant hydrolysis mechanism from polymerization toward decomposition was proposed. Furthermore, formation and decomposition of polymeric aluminum species in AlCl(3) solution followed the "Core-links" model, while those of Keggin-Al(13) species in polyaluminum solution was based on the "Cage-like" model.     

热重-差示扫描量热法研究金属铝盐与载体的相互作用

通过浸渍法将相同负载量的不同类型的金属铝盐负载在介孔分子筛HMS内外表面,用热重-差示扫描量热(TG-DSC)法研究了金属铝盐热性质的变化。将负载型金属铝盐干燥、焙烧,得到负载型催化剂Al2O3/HMS样品,用X射线衍射(XRD)、N2吸附-脱附等手段对样品进行了介孔结构表征,并初步考察了催化剂上烷基化反应的活性。实验结果表明:负载金属盐的起始分解温度均高于金属盐,证明了金属盐与载体之间有相互作用。Al2O3/HMS催化剂在对苯二酚烷基化反应中表现出不同的催化活性。这种催化活性的高低与催化剂比表面积、孔容的大小没有相应的顺变关系,与负载金属盐与载体的相互作用有关,相互作用越弱,催化剂在烷基化反应中表现出的催化活性越高。