超分子结构草甘膦插层水滑石的组装及结构研究

提出了一种新的绿色农药缓释剂模型——超分子结构草甘膦缓释剂.依据插层组装理论,以阴离子层状材料镁铝水滑石(MgAl-LDH)为插层主体,以除草剂草甘膦为插层客体,由共沉淀法一步组装得到超分子结构草甘膦插层镁铝水滑石(MgAl-LDH-gly).通过对MgAl-LDH-gly的结构、主客体相互作用及化学组成确认,建立了MgAl-LDH-gly的近似超分子结构模型,并对其缓慢释放草甘膦的可行性进行了分析.     

水滑石无机阴离子交换剂的合成与表征

采用水热法制成了镁铝碳酸盐型、镁铝硝酸盐型、镁铝盐酸盐型、镁铝羟基型等插层镁铝类水滑石,比较了层间含不同阴离子类水滑石的结构差异和高温热处理后的结构稳定性.通过离子交换方式以镁铝羟基型为基材插层组装无机阴离子基团MoO42-、WO42-、CO32-和NO3-制得不同的阴离子插层类水滑石.通过XRD、TEM、XPS和热分析方法对镁铝类水滑石和阴离子插层类水滑石进行了表征.     

超分子结构姜黄素插层镁铝水滑石的组装、结构及缓释性能

以镁铝水滑石为主体, 以中药提取物姜黄素为客体, 由共沉淀法、离子交换法和焙烧复原法三种不同方法组装得到超分子结构复合材料——姜黄素插层镁铝水滑石. 并用XRD, IR, HPLC等手段对该材料进行了表征. 结果表明, 共沉淀法和离子交换法成功组装得到两种不同结构的姜黄素插层产物, 使材料的层间距扩大为0.82～1.36 nm, 层间客体姜黄素阴离子是以平行或者单层垂直的定位方向排列于层间的. 考察了该材料在不同pH值的磷酸盐缓冲溶液中的缓释性能, 其缓释历程为客体阴离子与介质中 的离子交换过程. 该研究指出了阴离子层状材料——水滑石在中药释释剂领域的应用潜力.     

硫代硫酸根插层水滑石的层间限域反应

将无机阴离子硫代硫酸根(S2O23-)限域在锌铝水滑石(LDH)层间,并研究了其在水滑石层板限域空间内被铁氰根(Fe(CN)63-)氧化的反应过程.通过X射线衍射(XRD)和傅里叶变换红外(FTIR)光谱仪对反应的中间产物和最终产物进行的表征发现,氧化产物连四硫酸根(S4O62-)进入到溶液中,还原产物亚铁氰根(Fe(CN)64-)则保留在水滑石层间.进一步系统研究了该反应的动力学过程,考察了硫代硫酸根插层水滑石用量、铁氰化钾浓度和温度对反应的影响.结果表明该氧化还原反应符合球体内扩散模型.根据温度对反应速率影响,得出了该反应的表观活化能为24.6kJ.mol-1,比相同条件下溶液中反应活化能降低了约13.7kJ.mol-1.采用分子动力学(MD)模拟计算了水分子含量对硫代硫酸根插层水滑石层间距大小的影响.计算表明:在水溶液环境中,水滑石微反应器的尺寸在特定方向具有可调控性.根据实验表征和理论计算对该层间反应的机理进行了探讨.因此,该类层状材料可以作为一种新型纳米级微反应器应用于调控化学反应.     

层状水滑石对吡啶二甲酸异构阴离子的选择性插层行为

本文采用焙烧复原法研究了镁铝水滑石与吡啶二甲酸异构阴离子单体及其混合体的插层反应，实验发现镁铝水滑石对吡啶二甲酸异构阴离子存在着明显的选择性，有机酸异构体优先进入层间的顺序是：2,3-吡啶二甲酸>2,5-吡啶二甲酸>2,4-吡啶二甲酸>3,5-吡啶二甲酸>3,4-吡啶二甲酸>2,6-吡啶二甲酸。利用XRD、IR和TG测试技术对样品进行了表征，同时采用Gaussian-98软件包中ab initio 分子轨道法（HF/6-31G）计算了吡啶二甲酸异构阴离子的分子结构，理论结合实验探讨了阴离子在水滑石层间可能的空间构型，分析了其结构与插层行为的关系。研究表明镁铝水滑石层状材料插层过程中具有分子识别能力，可用于分离有机异构阴离子。     

2-羟基-4-甲氧基二苯甲酮-5-磺酸插层水滑石的制备及性能(英文)

以层状镁铝双金属氢氧化物(MgAlLayeredDoubleHydroxides,Mg-AlLDHs)为主体,以有机紫外光稳定剂2-羟基-4-甲氧基二苯甲酮-5-磺酸(BP)为客体,结合焙烧复原法和阴离子交换法合成了具有超分子结构有机-无机插层复合物(MgAl-BPLDHs),研究了层间阴离子、反应介质、pH值、反应时间等因素对于插层材料超分子结构的影响。用FTIR、XRD、TG-DTA、UV-Vis和粒度分析对其不同尺度的结构、热稳定性和紫外光稳定性等进行表征。结果表明,采用阴离子交换法难以进行插层反应;通过焙烧复原法可显著降低MgAl-LDHs层间CO2-离子,从而有利于BP阴离子交换进入MgAl-LDHs层间,在去离子水中,水温100℃,pH=7,反应时间为48h,BP过饱和的条件下合成得到最高插层率的MgAl-BP-LDHs;主体水滑石层板与客体以静电力和氢键相互作用,得到的超分子结构材料具有良好的热稳定及兼具优异的紫外屏蔽、吸收性能,是一种新型的有机-无机复合光热稳定剂。     

纳米晶镁铝水滑石的制备及其热分解机理

研究了无机阻燃剂镁铝水滑石纳米晶的制备及其热分解机理.采用常压下,一步反应的液相法制备镁铝水滑石试样，用XRD和TEM测试试样的相组成和形貌，针状镁铝水滑石纳米晶体的长度约80 nm.依据DSC和DTA-TG测试结果，发现镁铝水滑石纳米晶的热分解由两个阶段组成:第一个吸热峰出现在220 ℃左右，第二个吸热峰出现在380 ℃左右.研究了反应时间对所得镁铝水滑石试样的热分解性能的影响，发现延长反应时间，镁铝水滑石试样的第一次、第二次热分解的起始温度升高,第一次热分解的失重值增大，最后剩余氧化物的量增大，从而增强镁铝水滑石阻燃剂的阻燃性能.根据不同升温速率下获得的DSC测试数据，应用Achar微分法、Šatava-Šesták积分法和Ozawa积分法对镁铝水滑石纳米晶热分解的第二个阶段进行了动力学计算和分析，确定该段的热分解机理函数积分式为(1－α)－1－1.     

2-羟基-4-甲氧基二苯甲酮-5-磺酸插层水滑石的制备及性能

以层状镁铝双金属氢氧化物（MgAl Layered Double Hydroxides,Mg-Al LDHs）为主体,以有机紫外光稳定剂2-羟基-4-甲氧基二苯甲酮-5-磺酸（BP）为客体,结合焙烧复原法和阴离子交换法合成了具有超分子结构有机-无机插层复合物（MgAl-BP-LDHs）,研究了层间阴离子、反应介质、pH值、反应时间等因素对于插层材料超分子结构的影响。用FTIR、XRD、TG-DTA、UV-Vis和粒度分析对其不同尺度的结构、热稳定性和紫外光稳定性等进行表征。结果表明,采用阴离子交换法难以进行插层反应;通过焙烧复原法可显著降低MgAl-LDHs层间CO₂^-离子,从而有利于BP阴离子交换进入MgAl-LDHs层间,在去离子水中,水温100℃,pH=7,反应时间为48 h,BP过饱和的条件下合成得到最高插层率的MgAl-BP-LDHs;主体水滑石层板与客体以静电力和氢键相互作用,得到的超分子结构材料具有良好的热稳定及兼具优异的紫外屏蔽、吸收性能,是一种新型的有机-无机复合光热稳定剂。     

镁铝类水滑石对阳离子染料中性红的吸附及机理研究

研究了镁铝类水滑石对中性红的吸附及其作用机理,考察了时间、pH、温度、电解质浓度等因素对吸附作用的影响。结果表明,镁铝类水滑石对中性红的吸附动力学符合准二级动力学方程,热力学符合Langmuir吸附等温式。在实验范围内,吸附量随溶液pH的增大而增加,随温度的升高而降低,随电解质浓度的增加先增加后降低。吸附过程是放热、熵减小的自发过程。镁铝类水滑石对中性红的吸附缘于为类水滑石与中性红分子中π电子的较强静电吸引作用。     

基于主-客体相互作用的插层水滑石光敏特性研究

本文基于水滑石类插层材料(LDHs)特有的超分子结构及其功能可调控性,采用离子交换法成功合成了邻、间、对硝基苯甲酸阴离子(o-、m-、p-NBA-)插层的锌铝水滑石,并研究了插层产物的光敏性能。插层后这3种异构体化合物都在紫外光照射下表现出不同的光响应程度,即光敏作用:m-NBA-LDHo-NBA-LDH≈p-NBA-LDH。用PXRD、FTIR、UV/Vis和理论计算研究了光敏性能,并提出了可能的光敏机理,为其应用于新型感光材料提供了一定的理论基础。     

Silver nanoplates: a highly sensitive material toward inorganic anions

This paper demonstrates a simple sensing method to detect inorganic anions by silver nanoplates (edge length of approximately 70 nm and thickness of approximately 2 nm) in aqueous solution. By this method, the solution system containing silver nanoplates shows a high sensitivity on the order of 1 x 10(-6) M in detecting halides, phosphate, and thiocyanate ions in water at room temperature. The sensitivity could be identified by the shift in the surface plasmon resonance (SPR) band in UV-vis spectrum. The selectivity of such a sensing system toward various anions was also studied, and it was found that this sensing system could distinguish individual anions (e.g., Cl-, Br-, I-, H2PO4-, and SCN-) from other anions (e.g., F-, SO42-, CH3COO-, NO3-, and ClO4-) and inorganic cations (e.g., Zn2+, Cd2+, and Cu2+) under the given conditions. The sensing mechanism was also analyzed. It was proposed that the particle surface electron charging, which is mainly determined by the interaction tendency between silver atoms and various inorganic anions in water, is responsible for the shift in the SPR observed. The need for further studies was finally discussed, particularly for systems composed of mixed anions.     

Determination of inorganic cations and anions by ion-exchange chromatography with evaporative light-scattering detection

Evaporative light-scattering detection (ELSD) was investigated for the direct determination of alkali and alkaline-earth cations by cation-exchange chromatography. Successful single run analysis of Na+, K+, Mg2+ and Ca2+ was achieved in 11 min on the Hamilton PRP-X200 column using an aqueous solution of ammonium formate as mobile phase under a salt concentration step gradient mode (20 mM and 100 mM). Surprisingly the use of ELSD reveals a weak retention of inorganic anions (Cl-, NO3-, SO4(2-)) onto the polymeric cation exchanger, which enables the simultaneous determination of inorganic anions (C1- and NO3-) associated with the cations analysed (Na+ and K+).     

Analysis of trace inorganic anions in weak acid salts by single pump cycling‐column‐switching ion chromatography

The application of ion chromatography with the single pump cycling‐column‐switching technique was described for the analysis of trace inorganic anions in weak acid salts within a single run. Due to the hydrogen ions provided by an anion suppressor electrolyzing water, weak acid anions could be transformed into weak acids, existing as molecules, after passing through the suppressor. Therefore, an anion suppressor and ion‐exclusion column were adopted to achieve on‐line matrix elimination of weak acid anions with high concentration for the analysis of trace inorganic anions in weak acid salts. A series of standard solutions consisting of target anions of various concentrations from 0.005 to 10 mg/L were analyzed, with correlation coefficients r ≥ 0.9990. The limits of detection were in the range of 0.67 to 1.51 μg/L, based on the signal‐to‐noise ratio of 3 and a 25 μL injection volume. Relative standard deviations for retention time, peak area, and peak height were all less than 2.01%. A spiking study was performed with satisfactory recoveries between 90.3 and 104.4% for all anions. The chromatographic system was successfully applied to the analysis of trace inorganic anions in five weak acid salts.     

Electrophoretic mobility study on ion-ion interactions in an aqueous solution.

Ion-ion interactions between anions and their pairing ions in aqueous solutions were studied through the measurements of electrophoretic mobilities of analyte ions in capillary zone electrophoresis, where the electrophoretic method for the analysis of ion association reaction is shown to be more useful than the conductometric method widely used in the analysis of the reactions. The electrophoretic mobility of monovalent inorganic anions was almost identical even when the concentrations of alkali metal ions and quaternary ammonium ions in the migrating solution were varied up to 15 mM. On the other hand, the electrophoretic mobility of organic anions, such as monovalent and divalent anions, decreased with increasing concentrations of quaternary ammonium ions. Changes in the electrophoretic mobilities were analyzed by a non-linear least-squares method giving ion association constants. The results indicate that the proposed method is applicable to the analysis of such reactions to give the mobility change. The ion association constants obtained in an aqueous solution were related to the extraction constants of the ion associates, and the contributions of the association process and the distribution process were clarified.     

Interaction of inorganic anions with iron-mineral adsorbents in aqueous media — A review

A number of inorganic anions (e.g., nitrate, fluoride, bromate, phosphate, and perchlorate) have been reported in alarming concentrations in numerous drinking water sources around the world. Their presence even in very low concentrations may cause serious environmental and health related problems. Due to the presence and significance of iron minerals in the natural aquatic environment and increasing application of iron in water treatment, the knowledge of the structure of iron and iron minerals and their interactions with aquatic pollutants, especially inorganic anions in water are of great importance. Iron minerals have been known since long as potential adsorbents for the removal of inorganic anions from aqueous phase. The chemistry of iron and iron minerals reactions in water is complex. The adsorption ability of iron and iron minerals towards inorganic anions is influenced by several factors such as, surface characteristics of the adsorbent (surface area, density, pore volume, porosity, pore size distribution, pH_pzc, purity), pH of the solution, and ionic strength. Furthermore, the physico-chemical properties of inorganic anions (pore size, ionic radius, bulk diffusion coefficient) also significantly influence the adsorption process. The aim of this paper is to provide an overview of the properties of iron and iron minerals and their reactivity with some important inorganic anionic contaminants present in water. It also summarizes the usage of iron and iron minerals in water treatment technology.     

Novel imidazolium stationary phase for high-performance liquid chromatography

A new imidazolium anion-exchange phase immobilized on silica is synthesized. HPLC separations of common inorganic anions (IO3-, Cl-, NO2-, Br-, NO3-, I-, SCN-) have been performed using a HPLC column (200 mm x 4.6 mm I.D.) packed with this stationary phase, with a phosphate buffer solution as the mobile phase and UV detection at 200 nm. The effects of pH and concentration of eluent on the separation of anions have been studied. Chromatographic parameters are calculated and the results show that the new stationary phase is of significant potential for the analysis of these anions. Successful separations of some ordinary organic anions have also been achieved with the said stationary phase. Meaningfully, organic and inorganic anions can be determined simultaneously and satisfactorily with several neutral compounds using the column. The separation of some organic compounds including hydroxybenzenes, bases and amines by this stationary phase with only water as the eluent has been investigated.     

Comparison of liquid chromatographic behaviors on N-methylimidazolium functionalized ZrO(2)/SiO(2)-4 and N-methylimidazolium functionalized SiO(2) stationary phases

A new stationary phase N-methylimidazolium functionalized ZrO(2)/SiO(2)-4 (Zr/SilprMim) has been prepared. The chromatographic property of this stationary phase is investigated by ion chromatography (IC) with inorganic and organic anions, and normal phase HPLC with basic compounds and hydroxybenzenes. The effects of pH and the strength of Lewis base of eluent on separation of anions are studied. This new stationary phase is also compared with a N-methylimidazolium functionalized SiO(2) stationary phase (SilprMim). The results show that this new stationary phase can be used in analysis of inorganic anions with great prospects. At the same time, successful separations of some organic anions can be obtained by using phosphate buffer solution as mobile phase. This new stationary phase also has a distinct advantage in the separation of basic compounds in normal phase. But due to the presence of Lewis acid sites on the surface of ZrO(2)/SiO(2)-4, Lewis bases such as hydroxybenzenes adsorb very strongly on this new stationary phase, and Lewis acid sites can be masked or modified by the eluent that contain Lewis base groups.     

Simultaneous separation of 17 anions by capillary electrophoresis with the addition of an organic solvent

Seventeen inorganic and organic anions, that normally are insufficiently separated via ion chromatography, were completely separated by the addition of an organic solvent to a solution of BGE combined with an adjustment of the apparent pH via CE in combination with indirect UV absorbance detection. Methanol, ethanol, and acetonitrile were examined for their utility in manipulating the selective separation of anions. Methanol and acetonitrile were better modifiers than ethanol at enhancing the resolution of anions comigrating in an aqueous solution of BGE. Methanol was selected as the modifier that provided the largest separation window that could achieve a complete separation of the target analytes. Via the use of methanol, manipulation of the selectivity between inorganic anions and that between inorganic and organic anions was enhanced, but the separation between organic anions remained difficult when only methanol was used. By varying the apparent pH of the BGE in the presence of 10% v/v methanol, however, the separation selectivity between organic anions was substantially improved. Eventually, 7 inorganic and 10 organic anions were simultaneously separated using BGE at a pH of 6.3 in the presence of 10% v/v methanol.