类水滑石化合物的制备及应用

水滑石类化合物是一类具有特殊层状结构的阴离子粘土材料,具有碱性、离子交换性以及"结构记忆效应",近年来备受人们的广泛关注。本文综述了HTLcs的制备方法及其在催化、离子交换、吸附、医药以及功能材料方面的应用。     

有机黏土矿物的研究进展及污水治理中的应用

环境中有机污染物、阴离子污染物以及重金属污染物的存在会对人类生命安全造成损害,因此受到研究者的重视。近年来,国内外研究人员使用不同材料对这些污染物进行吸附,其中有机黏土矿物因具有成本低、粒径小、比表面积大、阳离子交换容量高等优势备受瞩目。相比于未改性的黏土矿物,有机黏土矿物对有机污染物、阴离子污染物以及重金属污染物具有更高的吸附效率。文章主要综述了阳离子表面活性剂、阴离子表面活性剂、阳、阴离子表面活性剂、双子表面活性剂、非离子表面活性剂以及聚合物和硅烷偶联剂对黏土矿物的改性方法及改性机理,重点概述了有机黏土矿物在污水治理方面的应用,最后基于实际应用现状,对有机黏土矿物的发展与挑战进行了展望。     

水滑石类化合物的应用研究

水滑石类化合物（hydrotalcite-like compounds。简称HTLcs）是一类具有广阔应用前景的层柱状化合物．因其特殊的结构而具有特殊的性能,具有广泛的应用前景及研究范围。介绍了水滑石及类水滑石材料的合成方法以及作为催化剂、添加剂、吸附剂在有机合成反应等方面的应用．     

含吡啶基吸附材料的研究进展

介绍了含吡啶基吸附材料对金属离子、无机阴离子及有机污染物的吸附分离研究进展。吡啶环的氮原子具有较强的配位功能,能与多种金属离子形成络合物。这类吸附材料对金属离子显示出高的吸附容量和吸附选择性,其吸附金属离子后形成金属主体高分子,然后再利用金属离子与具有配位性能的无机阴离子、有机污染物通过路易斯酸-碱在水溶液中进行配体交换,从而达到吸附分离的目的。作为高分子交换配体(PLE),这类新型吸附材料将是今后发展的重点。     

介孔分子筛在废水处理中的应用

水中污染物严重危害人体健康,近年来发现介孔分子筛对废水中污染物有较好的吸附效果.概述了介孔分子筛在处理废水中无机污染物(金属阳离子和阴离子)和有机污染物的应用情况,阐述了影响其吸附的主要因素,并对应用前景进行分析.     

煅烧阴离子粘土对水污染物去除机理研究进展

煅烧阴离子粘土(LDO)因其比表面积大、改性空间大、具有结构记忆效应等特点而具有较好的吸附能力和光催化氧化的功能。本文主要研究了煅烧阴离子黏土的形成过程、特性及其对水污染物的去除机理研究进展。经煅烧处理后形成的LDO对水中的部分重金属离子、阴离子以及有机物等均具有较佳的吸附效果,吸附机理主要有阴离子插层、离子交换、静电引力、表面配位。在引入了具有光催化性能的阳离子或负载了二氧化钛后,LDO对水中有机物兼具吸附和持续的光催化作用。     

聚醚砜/类水滑石杂化超滤膜的制备及性能研究

有机无机杂化膜兼具有机膜、无机膜的优势,是水处理膜的研究热点之一。用氧化镁脱硫废渣制备类水滑石(HTLcs),并将其与聚醚砜(PES)共混,采用相转换法制备有机无机杂化超滤膜PES/HTLcs,考察了HTLcs对PES杂化膜结构及性能的影响。结果表明:HTLcs改善了膜的亲水性能,当HTLcs添加量为0.5%时,杂化膜具有最佳的纯水通量231.93 L/(m~2·h);杂化膜对牛血清蛋白(BSA)的截留率为85%,对聚乙二醇(PEG10K)的截留率在90%以上,均高于纯PES膜,且杂化膜具有更好、更稳定的抗污性能。     

PVDF/HTLcs超滤膜的制备及性能研究

用氧化镁脱硫废渣制备了类水滑石(HTLcs),将其与聚偏氟乙烯(PVDF)共混,采用相转换法制备HTLcs杂化PVDF超滤膜。考察了HTLcs对PVDF杂化膜表面形态、晶体结构、力学性能、热稳定性、渗透性能及抗污性能的影响。结果表明,杂化膜显示了更好的亲水性能和抗污性能,有较高的纯水通量和截留率,HTLcs的添加量为3%时,杂化膜得到最大的纯水通量243.67 L/(m~2·h),且具有较好的抗污性能,其恢复率最高达97.3%。     

Zr~(4+)掺杂对Mg/Al水滑石磷酸根吸附行为的影响

采用共沉淀法制备了系列不同Zr~(4+)含量的Mg/Al/Zr三元类水滑石材料,研究了其对废水中磷酸根离子的吸附性能。采用XRD、DRIFTS、氮气吸脱附等对材料的结构及织构性质进行了表征,并研究了溶液初始pH以及竞争阴离子对磷吸附量的影响。结果表明:掺杂Zr~(4+)能提高类水滑石层板正电荷密度以及增大层间距,有利于磷酸根阴离子的吸附;Mg/Al/Zr类水滑石对磷的吸附过程符合准二级动力学模型,吸附等温线符合Langmuir模型,当n(Zr~(4+))/(Al~(3+)+Zr~(4+))=0.3时,理论饱和吸附量最大,达到76.6 mg/g,比Mg/Al水滑石高出28.7%;酸性环境有利于磷酸根的吸附,而二价阴离子的竞争吸附作用会显著降低磷吸附效果。Mg/Al/Zr类水滑石对磷的吸附机理为静电吸引和阴离子交换协同作用。     

Zr4+掺杂对Mg/Al水滑石磷吸附行为的影响

采用共沉淀法制备了系列不同Zr4+含量的Mg/Al/Zr三元类水滑石材料，研究了其对废水中磷酸根离子的吸附性能。采用XRD、DRIFTS、氮气吸脱附实验等手段对材料的结构及织构性质进行了表征，并研究了溶液初始pH以及竞争阴离子对磷吸附量的影响。结果表明：掺杂Zr4+能提高类水滑石层板正电荷密度以及增大层间距，有利于磷酸根阴离子的吸附；Mg/Al/Zr类水滑石对磷的吸附过程符合准二级动力学模型，吸附等温线符合Langmuir模型，当n(Zr4+)/(Al3++Zr4+)为0.3时，理论饱和吸附量最大，达到76.6 mg/g，比Mg/Al水滑石高出28.7%；酸性环境有利于磷酸根的吸附，而二价阴离子的竞争吸附作用会显著降低磷吸附效果。Mg/Al/Zr类水滑石对磷的吸附机理为静电吸引和阴离子交换协同作用。     

类水滑石复合氧化物在烟道气脱SO2和NOx中的应用

简述了类水滑石复合氧化物的制备方法，并对类水滑石化合物为前驱体的复合氧化物作为环境友好催化材料在烟道气脱SO₂、NOx方面的研究进行了综述，指出应把研究重点放在类水滑石复合氧化物同时氧化吸附脱SO₂和NOx上     

Adsorption stages and interfacial orientations of cytidine sulphate at the mercury/electrolyte interface

The adsorption and interfacial orientations of cytidine sulphate were studied by out-of-phase ac voltammetry. The adsorption equilibrium and its attainment have been investigated as a function of various parameters such as pH, adsorption potential, adsorption time, temperature and the bulk concentration of cytidine sulphate. The time dependence of the electrode impedance indicates that the formation of a compact film controlled by nucleation/growth mechanism and the data were analysed according to the Avrami equation. Moreover, the role of the anions of the indifferent supporting electrolyte in the formation of the condensed film of the adsorbed molecules has been elucidated. The stacking interactions between adsorbed molecules are affected by the nature of the anions of the supporting electrolyte and are hindered by their specific adsorption. The adsorption parameters of cytidine sulphate has been computed at various pHs and for various anions in the supporting electrolyte.     

Preparation and Characteraction of New Magnetic Co–Al HTLc/Fe3O4 Solid Base

Novel magnetic hydrotalcite-like compounds (HTLcs) were synthesized through introducing magnetic substrates (Fe₃O₄) into the Co–Al HTLcs materials by hydrothermal method. The magnetic Co–Al HTLcs with different Fe₃O₄ contents were characterized in detail by XRD, FT-IR, SEM, TEM, DSC, and VSM techniques. It has been found that the magnetic substrates were incorporated with HTLcs successfully, although the addition of Fe₃O₄ might hinder the growth rate of the crystal nucleus. The morphology of the samples showed the relatively uniform hexagonal platelet-like sheets. The grain boundaries were well defined with narrow size distribution. Moreover, the Co–Al HTLcs doped with magnetic substrates presented the paramagnetic property.     

A comparison of the change from inhibiting to enhancing anions in the electrochemical oxidations of ethylene glycol and formaldehyde

Techniques dealing with inhibiting anions have previously been employed to measure their properties. The present approach is to change the behavior of inhibiting anions. Anions, which have long been considered to inhibit reactions, are shown to enhance some electrochemical reaction rates. Fluoroborate, nitrate, and (hydrogen) sulfate are separately shown to increase the current response of the electrochemical oxidation of formaldehyde. The reaction rate of the oxidation of ethylene glycol is increased but for a restrictive set of conditions. Experimental data, as well as theoretical considerations lead to the conclusion that adsorption of the added anions is the slow step of the process that increases the reaction rate. The differences in the response of ethylene glycol and formaldehyde follow well-documented changes of surface CO. These observations are consistent with general properties of the step in the part of the mechanism on the electrode surface that enhances the reaction rate.     

Untersuchung über die anionenadsorption mit hilfe markierter ionen

From previous work, the adsorption of anions is regarded as an essential factor for the different corrosion behaviour of metals in solutions containing different anions. Adsorption is measured by means of ³⁶Cl⁻, ⁸²Br⁻, ¹⁸ F⁻, ³⁶ClO₄⁻, ³⁵O₄²⁻, H³⁵S⁻ and ¹⁴CN⁻ on Pt, Ni and Fe in the form of sheets and evaporated films. Besides the determination of the adsorption after dipping into the solution, a method has been developed for the measurement of adsorption in contact with the solution and for the determination of its kinetics. The method can also be applied to O₂-free metal surfaces produced under vacuum. In this case, however, very rapid adsorption is observed, whereas normally saturation is reached only after many hours. It is concluded that, in general, exchange between oxygen on the metal and the anion takes place rather than simple adsorption.

The distribution of the anions adsorbed on the metal surface has been studied by autoradiography; adsorption takes place preferentially at the grain boundaries and increases when the crystal size decreases.

These results confirm the interpretation of passivation as a competition between various processes: metal dissolution, coverage by a passivating oxide film, and displacement of oxygen by anions.     

Effect of Rare Earth Doping on the Catalytic Activity of Copper‐Containing Hydrotalcites in Phenol Hydroxylation

The copper‐containing hydrotalcites (Cu‐HTLcs) are synthesized under microwave irradiation, the effect of rare earth elements (RE) on the synthesis of Cu‐HTLcs, wherein RE stands for rare earth elements, e.g., La, Y, Sm and Ce, is also investigated in the present work. The hydrotalcite structure of the synthesized samples is verified by XRD and FT‐IR. The results of their catalytic performances in phenol hydroxylation show that the doped rare earth elements can promote the catalytic activity of Cu‐HTLcs, exhibiting a good trend as follows: La>Y>Sm>Ce. XPS results show that the Cu⁺ species are produced after the interaction of La‐Cu‐HTLcs with H₂O₂. Combining with the catalytic test results, we propose a new mechanism about the generation of HO ^. radicals in phenol hydroxylation, it is assumed that HO‐Cu⁺‐OH species are first formed by the reduction of HO‐Cu²⁺‐OH located in hydrotalcites in the presence of H₂O₂, and then react with H₂O₂ to give rise to HO^. radicals.     

The removal of perchlorate using amine-functionalized mesoporous anion-exchange resins with different number of ligands

Perchlorate anion (ClO ₄ ^t- ) in water has become an environmental issue because it can impair proper functioning of the thyroid gland. For the removal of perchlorate anions from water, adsorption using anion-exchange resins has been generally used as the most suitable method. We have prepared mesoporous anion-exchange resins via simple functionalization of amine ligands with different numbers of functional groups, and used them for the removal of perchlorate anions from aqueous solutions. The physical and chemical properties of the prepared samples were measured using nitrogen adsorption-desorption measurement, elemental analyses, X-ray diffraction, and Fourier transform infrared spectroscopy. We also investigated equilibrium isotherms for the measurement of adsorption capacities and kinetic performances of the prepared samples. The prepared materials showed fast adsorption kinetic performances, and M-3N among the prepared materials exhibited high perchlorate adsorption capacity of 175.4mg/g compared with the results of the previous reports.     

Formation of tetramethylethylene radical cations after pentane adsorption on sulfated zirconia

Tetramethylethylene radical cations have been registered by ESR after pentane adsorption on sulfated zirconia. The radical cations proved to be not stable in the presence of oxygen, only molecular oxygen radical anions being registered. Tetramethylethylene formation and pentane disproportionation are shown to occur under illumination within the same spectral region proving that the former is formed as a by-product of pentane transformations.     

Photocatalytic degradation of chlorobenzene using solar and artificial UV radiation

In this work photocatalytic degradation of chlorobenzene has been studied using solar and artificial UV radiations. The effect of pH and the presence of different anions on the degradation of chlorobenzene has been studied for both cases. Chlorobenzene has been found to be a strongly adsorbing and hence rapidly degrading species when subjected to photocatalysis. The effect of pH in the range of 3–10 and the presence of different anions at a concentration of 0.1 mol dm^?3 on the adsorption was studied. Both pH and the presence of anions affect adsorption and the degradation but the overall effect is negligible (<5%). Copyright © 2004 Society of Chemical Industry