Preparation and Proton Conductivity of Surfactant-Templated Mesoporous Silica Gels Impregnated with Protonic Acids

Surfactant-templated mesoporous silica gel that was impregnated with various protonic acids has been prepared, and we propose this material as a new type of proton conductor. The conductivity of the mesoporous silica gel that was impregnated with 5.0 M H₂SO₄ was ∼1 × 10⁻⁴ S/cm at room temperature in a dry nitrogen-gas atmosphere after drying in vacuo at room temperature; this value was four orders of magnitude greater than that of silica gel that was prepared via the conventional sol–gel method and impregnated with H₂SO₄. The amount of impregnated H₂SO₄ in the mesoporous silica gel was ∼2.5 times larger than that of impregnated H₂SO₄ in the conventional silica gel. The H₂O molecules in the mesoporous silica gel that was impregnated with H₂SO₄ remained in the pores of the gel, even after drying in vacuo at room temperature.     

Thin-Layer Chromatography of Metal Ions in Formic Acid Medium on Impregnated and Unimpregnated Silica Gel G: Semiquantitative Determination of Fe3+, Cd2+, Th4+, Al3+, Zn2+, UO2+ 2, VO2+, Ce4+, and Ni2+

Abstract

The adsorption behavior of metal ions in the formic acid-sodium formate system using unimpregnated as well as impregnated silica gel G as thin layers has been studied. A remarkable result of this study is the dramatic selectivity of impregnated silica gel G thin layers when compared to the corresponding unimpregnated silica gel G thin layers. This impregnation effect provides us with a new adsorbent phase which is sufficiently stable in the formic acid-sodium formate medium. Some important ternary separations have been achieved on silica gel G thin layers. Al³⁺, Ni²⁺, Fe³⁺, and Pb²⁺ have been qualitatively separated from mixtures of other ions. Cu²⁺ has been selectively separated on impregnated silica gel G thin layers. The semi-quantitative determination of nine metal ions on impregnated silica gel G layers has also been attempted.     

Effect of Preparation Method of Fe–based Fischer–Tropsch Catalyst on their Light Olefin Production

Fischer–Tropsch synthesis (FTS) for the production of light olefin from syngas was investigated on K–Fe–Cu–Al catalysts. The catalysts were prepared by different methods, such as K impregnated over co-precipitated Fe–Cu–Al, K impregnated over sol–gel (pechini) synthesized Fe–Cu–Al, Fe–Cu–K impregnated on alumina and K impregnated over co-precipitated Fe–Cu in a slurry phase of Al₂O₃. Among four catalysts, K impregnated over Fe–Cu–Al prepared by sol–gel method has shown the best activity. A favorable pore size distribution and pore volume, manifested in a facile reducibility of the iron oxide, is found to be responsible for high activity. The catalyst also exhibits high olefin selectivity compared with the others, due to the presence of moderate number of acid sites.     

Adsorption Studies of Heavy Metal Cations on Silica Flat Bed Induced with Microcrystalline Cellulose Gels: Quantitative Determination of Cobalt and Nickel by Optical Scanning Densitometry

Silica gel H impregnated with microcrystalline cellulose gel in alkaline medium was used as a stationary phase for the thin layer chromatography of heavy metal cations. A mixture of 10% aqueous potassium thiocyanate and triton X-100 in 1:1 v/v has been identified as the best combination of mobile phase for achieving selective separation of cobalt from nickel. The efficacy of the chromatographic system has been investigated by monitoring reproducibility of R_F values and spot compactness with respect to the change in sample concentration and matrix effect. The improved selectivity of impregnated silica gel H was expounded by SEM and FTIR studies. The typical surface modification as well as the chemical changes in impregnated silica gel H was attributed. Chromatograms of the cations were quantitatively evaluated by scanning densitometry in comparison with ICP elemental analysis. The proposed method is applied for the determination of cobalt and nickel cations in spiked samples of geological and industrial origin.     

PREDICTION OF BREAKTHROUGH CURVE OF METAL ION ON EXTRACTION CHROMATOGRAPHIC COLUMN

ABSTRACT

A mathematical model to predict the breakthrough curve of metal ion on an extraction chromatographic column was proposed. This model, which is the extension of that proposed in the previous paper (12), consists of the mass transfer equation of metal ion into a polymer gel impregnated with an extractant and the mass balance equation of chromatographic column. SDB (styrene-divinylbenzene copolymer) gels impregnated with CMP (dihexyl-N,N'-diethylcarbamoylmethylphosphonate), CMPO (octyl(phenyl)N,N'-diisobutylcarbamoylmethylphosphine oxide) and the equimolar mixture of CMP and CMPO were prepared. The column experiments for the extraction of Ce(III) from an aqueous solution containing nitrate ion were carried out. The predicted breakthrough curves of Ce(III) for the gels impregnated with CMP and the mixture of CMP and CMPO were in good agreement with the experimental ones. That for the gel impregnated with CMPO, however, overestimated the experimental data. This is due to adhesion among gel particles which is caused by the deliquescence of CMPO and not attributable to the mathematical model. These results suggest that the proposed model is applicable to the prediction of breakthrough curve and available as a design tool of extraction chromatographic column.     

磁性活性炭的制备与表征

探讨了负压浸渍法制备磁性活性炭的浸渍条件,浸渍溶液为油酸修饰的Fe3O4磁性凝胶均匀分散在正己烷溶剂中形成的磁性溶液. 通过对油酸修饰的磁性凝胶进行差热、热重和微热容分析确立了浸渍产物的热处理条件,考察了磁性溶液浓度、浸渍时间、浸渍温度对浸渍产物的影响,并采用X射线衍射对磁性活性炭的组份和结构进行了表征,采用磁强计测定了磁性活性炭的磁性能,用比表面、孔容测试技术比较了活性炭和磁性活性炭的比表面、孔体积和孔分布.     

Sol–gel synthesis of nano-sized silica in confined amorphous space of polypropylene: Impact of nano-level structures of silica on physical properties of resultant nanocomposites

Polypropylene (PP)/silica nanocomposites were prepared by the sol–gel reaction of silicon alkoxide that was impregnated in the confined amorphous nanospace of PP with the aid of supercritical carbon dioxide. This novel technique enabled us to prepare nanocomposites having a variety of silica morphology without altering the higher-order structures of PP, being ideal to study relationships between the silica morphology and mechanical properties of the nanocomposites. The synthesized silica particles were highly dispersed in PP with dimensions comparable to the amorphous thickness (<10 nm), while their mass fractal dimension acquired by small-angle X-ray scattering was dependent on the sol–gel conditions. We found that the Young's modulus as well as the storage modulus in melt viscoelastic measurements was negatively correlated with the mass fractal dimension of silica nanoparticles: A lower mass fractal dimension resulted in not only higher reinforcement but also percolation network formation at a lower silica loading.     

The Use of Impregnated Silica Gel Layers and Modified Celluloses in Thin-Layer Chromatographic Analysis of Inorganic Mixtures

Abstract

This review of literature covers salient features on the use of impregnated silica gel layers and modified cellulose layers as applied to the analysis of inorganic mixtures. One hundred and ten references have been cited from the literature published from 1963 to 1993. Although plain silica gel is commonly used for thin-layer chromatography of inorganics, silica gel impregnated layers play an important role for achieving particular separations of analytical importance and are more frequently used than plain adsorbents except for silica gel. Modified celluloses have received proper attention in the recent past, particularly for rare earths.     

DMF对二氧化硅薄膜性能的影响

以正硅酸乙酯、乙醇、盐酸和水为原料,引入N,N-二甲基甲酰胺(DMF),采用溶胶凝胶法和浸渍提拉技术在玻璃载片上进行涂膜,并研究了DMF的加入量对薄膜结构及性能的影响。结果表明,添加30%DMF的溶胶粘度有所降低,凝胶时间相应延长,但在干燥过程中能有效防止凝胶的开裂;添加体积分数30%DMF的二氧化硅膜具有良好的热稳定性,400℃以后没有明显的质量损失;薄膜平均孔半径约为7.08 nm,比表面积为53.168 m2.g-1,孔容积为0.188 320 cm3.g-1。     

复合吸附剂的基质选择与动态吸附性能测试

用不同类型的粗孔硅胶与氯化锂盐复合制备了一系列复合吸附剂。测量了它们的含盐量,并观察其腐蚀性。对纯硅胶与复合吸附剂的孔结构进行分析。测试了纯硅胶和复合吸附剂吸附水蒸气的性能等。实验证明,作为复合吸附剂的基质,不同类型的硅胶对复合的吸附剂影响很大。纯硅胶中,粗孔粒度为0.5～1.5 mm的硅胶吸附性能相对最好,但吸附量很小;复合吸附剂中,微球粗孔硅胶以及片状大孔硅胶虽然吸附量得到了大大的提高,但不易液解表面的氯化盐,将导致复合吸附剂膨胀结块影响传质通道,并腐蚀吸附床。大于2 mm的粗孔硅胶复合了氯化盐后,吸水产生毛细力将撑破硅胶骨架。因此,最适合复合吸附应用的硅胶基质为小颗粒耐水硅胶。在复合氯化盐后,吸水性能有了很大提高。同时,长时间循环吸附不会造成硅胶粉碎。     

Synthesis of Nanoparticulate Silica Composite Membranes by the Pressurized Sol–Gel Technique

A crack-free silica composite membrane has been synthesized from a nanoparticulate silica sol (particle diameter <10 nm) by a pressurized sol–gel coating technique developed in this study. The microporous silica layers with an estimated pore radius of 0.78 nm were deposited inside the pores (average pore size of 0.1 μm) of slip cast a-alumina support tubes. The microstructure of the coated layer was controlled by adjusting sol properties and pressurizing conditions. The room-temperature intrinsic permeability of N₂ through the silica membrane layer after heat treatment at 200°C is about 4.9 × 10⁻¹² mol·m/m²·s· Pa, and the mechanism of gas transport is Knudsen flow. The thermal stability of the silica composite membrane is excellent up to 500°C.     

Effect of sol size on nanofiltration performance of a sol-gel derived microporous zirconia membrane

This paper reports the effect of sol size on nanofiltration performances of sol–gel derived microporous zirconia membranes. Microstructure, pure water flux, molecular weight cut-off (MWCO) and salt retention of zirconia membranes derived from zirconia sols with different sizes were characterized. Thermal evolution, phase compo-sition, microstructure and chemical stability of unsupported zirconia membranes (powder) were determined by thermogravimetric and differential thermal analysis, X-ray diffraction, nitrogen adsorption–desorption and static solubility measurements. Results show that nanofiltration performance of zirconia membranes is highly depen-dent on sol size. The sol with an average size of 3.8 nm, which is smaller than the pore size of theγ-Al2O3 support (pore size:5–6 nm), forms a discontinuous zirconia separation layer because of excessive penetration of sol into the support. This zirconia membrane displays a MWCO value towards polyethylene glycol higher than 4000 Da. A smooth and defect-free zirconia membrane with a MWCO value of 1195 Da (pore size:1.75 nm) and relative high retention rates towards MgCl2 (76%) and CaCl2 (64%) was successfully fabricated by dip-coating the sol with an appropriate size of 8.6 nm. Zirconia sol with an average size of 12 nm exhibits colloidal nature and forms a zirconia membrane with a MWCO value of 2332 Da (pore size:2.47 nm). This promising microporous zirconia membrane presents sufficiently high chemical stability in a wide pH range of 1–12.     

Interaction Between an Acidic Extractant and an Octadecylamino Group Introduced into a Grafted Polymer Chain

Abstract

Poly‐glycidyl methacrylate (GMA) was appended onto a porous membrane of a hollow‐fiber form with an epoxy group density of 14 mol per kg of the starting porous membrane. Octadecylamine was added to the epoxy group of the polymer brush at a maximum molar conversion of the epoxy group into the octadecylamino group of 59%. An acidic extractant, bis(2,4,4,‐trimethylpentyl)phosphinic acid (Cyanex 272), was impregnated on the octadecylamino group by immersion of the octadecylamine‐added porous membrane in Cyanex 272/ethanol solution. The amount of impregnated extractant was 1.4 mol per kg of the GMA‐grafted porous membrane at a molar conversion of 59%. The phosphinic acid moiety of Cyanex 272 was attracted by the amino part of the octadecylamino group of the polymer brush to swell the entire volume of the porous membrane. This swelling compensated for the pore volume reduction caused by grafting the charged polymer brush to the pore surfaces of the porous membrane. The impregnated Cyanex 272 was repositioned on the charged polymer brush in response to the properties of surrounding liquids. The hydrophobic interaction enables the hydrophobic moiety of Cyanex 272 to associate with the octadecyl part of the octadecylamino group of the polymer brush to capture zinc ions. The binding efficiency of the Cyanex 272‐impregnated polymer brush for zinc ion was as high as 93%.     

肾综合征出血热灭活疫苗的纯化

目的为提高肾综合征出血热（ＨＦＰＳ）疫苗的免疫效果和减少副反应。方法用ＥＬＩＳＡ检测ＨＦＲＳ 病毒抗原的方法,比较疫苗原液通过不同孔径滤膜的浓缩效果;比较离子交换和凝胶过滤的纯化效果。结果用 孔径３０万相对分子质量滤膜浓缩时,过滤液中仍有部分病毒抗原检出,经１０万相对分子质量滤膜过滤后,过滤液 中检测不到病毒抗原;用 Ｓｅｐｈａｒｏｓｅ ４ＦＦ凝胶柱层析浓缩时,经波长 ２８０ ｎｍ检测到 ３个吸收峰,其中仅在第 １峰中检 测到病毒抗原,收集第１峰,几乎回收全部病毒抗原,去除杂蛋白约９０％左右。结论本纯化方法适合于ＨＦＲＳ疫 苗的规模化生产。     

Sol–gel preparation of titania multilayer membrane for photocatalytic applications

The main goal of the present study is to prepare a titania membrane with high permeability and photocatalytic activity for environmental applications. In this investigation a mesoporous titania multilayer membrane on alumina substrate is successfully fabricated via the sol–gel processing method. The prepared titania polymeric sol for the membrane top layer has an average particle size of 11.7 nm with a narrow distribution. The resulting TiO₂ multilayer membrane exhibits homogeneity with no cracks or pinholes, small pore size (4 nm), large specific surface area (83 m²/g), and small crystallite size (10.3 nm).The permeability and photocatalytic properties of the titania membrane were measured. The photoactivity of the titania membrane was examined to be 41.9% after 9 h UV irradiation based on methyl orange degradation. This measurement indicates high photocatalytic activity per unit mass of the catalyst. Through multilayer coating procedure, the photocatalytic activity of the membrane improved by 60% without sacrificing the membrane permeation. The prepared TiO₂ photocatalytic membrane has a great potential in developing high efficient water treatment and reuse systems due to its multifunctional capability such as decomposition of organic pollutants and physical separation of contaminants.     

Physicochemical characteristics of acrylic-acid polymer-impregnated cement pastes

Various Portland cement pastes were made using water cement ratios of 0·20, 0·25, 0·35 or 0·40 and then cured for 1, 3, 7, 28, 90 or 180 days. These pastes were impregnated with acrylic acid monomer under vacuum and the monomer-impregnated samples were then treated at two different temperatures, 40 or 60°C, for the polymerization process, using benzoyl peroxide as initiator. Several physicochemical studies were carried out on each cement paste; these studies include compressive strength tests, bulk density, compressive strength versus gel/space ratio relationships, polymer load, X-ray diffraction analysis and differential thermal analysis. Results have indicated that compressive strength improvement in acrylic acid-polymer impregnated cement pastes is mainly dependent on initial water/cement ratio, curing time and gel/space ratio. The results of X-ray diffraction analysis and differential thermal analysis indicated that the intrusion of polymer into the cement paste matrix does not affect the phase composition of the Portland cement hydration products.     

Experimental and Theoretical Studies of Actinide and Lanthanide Ion Transport Across Supported Liquid Membranes

In this work, we propose a new transport mechanism for metal ions relevant for used nuclear fuel separation processes by a supported liquid membrane (SLM). Two SLM extraction systems were investigated where the membrane was impregnated with either di-(2-ethylhexyl)phosphoric acid (HDEHP) or tributyl phosphate (TBP). A HDEHP impregnated membrane was used to extract neodymium (III), representative of a typical trivalent lanthanide. Cerium, which was oxidized by sodium bismuthate from trivalent to tetravalent state, was extracted by TBP. Oxidized cerium was used as a surrogate for oxidized americium to investigate the kinetics and possibility of americium and curium separation by membrane extraction. Both extraction systems were operated at varying nitric acid concentrations, and changes in the kinetics and extraction efficiency of metal ions were investigated. The proposed transport mechanism that was chosen for our studies was modified from the previous works by Danesi et al.^[1,2] and Cussler et al.^[3] The mechanism was selected due to the ability to accommodate and describe transport phenomena across a SLM when formation of extractant nano-channels in the membrane may exist. We were able to obtain acceptable fit of the models to our overall data trends although chemical and physical conditions must be well established and purity and homogeneity of the membrane are critical. A reverse transport of metal ions was observed when leaving the system for longer times which agrees with our model. The membrane was investigated for degradation and shown to be stable after contact with up to 7 M nitric acid for over 2000 minutes. Finally, we examined the possibility of partitioning americium from curium using a SLM impregnated by TBP. Separation of americium from curium was observed although not to a degree that was expected based on the Ce(IV) transport. Incomplete oxidation of Am(III) to Am(V) and reduction of Am(VI) on the membrane surface are possible causes for this observed discrepancy. Our model was, however, able to accurately predict Cm(III) transport through the membrane.     

Aerobic Oxidation of Benzyl Alcohol in a Continuous Catalytic Membrane Reactor

Topics in Catalysis - A catalytic membrane reactor with a Au–Pd catalyst, impregnated at the inner side of the membrane, was studied in the catalytic oxidation of benzyl alcohol in flow. The...     

Preparation of Highly Dispersive Platinum Catalysts Impregnated on Titania-Incorporated Silica Support

Highly dispersive silica-impregnated platinum catalysts were prepared by incorporating titania to the surface of silica support and by treating the impregnated platinum precursor with hydrogen peroxide. High dispersion of platinum on the titania-incorporated silica support was confirmed by XRD, TEM, EXAFS, and X-ray photoelectron spectroscopy (XPS) techniques. The platinum particles dispersed on silica ranged from 1 to 2 nm in size, although the loading amount of platinum was as high as 4 wt.%. The strong interaction between platinum and titania suppressed the migration and aggregation of the platinum particles on the surface, retaining a high dispersion of platinum. The platinum catalysts impregnated on the titania-incorporated silica showed higher catalytic activities in the combustion of methane than the platinum catalysts impregnated on the silica, while their catalytic activities were poor in the hydrogenation of nitrobenzene. Platinum dispersions and catalytic activities of the platinum catalysts on the silica support were discussed in relation to the strong interaction between platinum and titania.     

Development of an innovative mercury intrusion technique to examine defects plugging after CVD treatment of NF composite membranes

A novel method has been developed to reveal the possible existence of pore structure defects on the thin and ultra-thin separating layers of composite inorganic membranes. In this work the method is applied to sol–gel and CVD treated microporous membranes and involves a modified mercury porosimetry technique in which the only surface exposed for mercury intrusion is the one of the nanofiltration (NF) layer. The validity of the test method was verified by comparison with the outcome of gas phase permeability experiments. Defects of size above 5 nm are accurately and reliably detected. The size range from 3.6 nm to 5 nm, although “traceable” with normal mercury intrusion up to 60,000 psig, remains somewhat unexploited with the new technique. This is due to interferences induced by the elasticity properties (compression modulus and strength) of the material applied as a “plug” to membrane support. Continuity imperfections on the NF layer of a commercially available membrane were detected by application of the modified mercury intrusion technique. The area examined was about ∼7% of the total NF layer area exposed by the tube and the size of revealed defects was in the range between 20 nm and 100 nm. Furthermore sections of the defects bearing membrane were modified by chemical vapor deposition of SiO₂ to examine the possibility of mending the existing cracks. Significant reduction of the defects size has been observed with the novel mercury intrusion technique.