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Pore Volume (pore + volume)
Kinds of Pore Volume Selected AbstractsUltra-deep desulfurization adsorbents for hydrotreated diesel with magnetic mesoporous aluminosilicatesAICHE JOURNAL, Issue 5 2010Wangliang Li Abstract Magnetic mesoporous aluminosilicates (MMAS) were synthesized by hydrothermal method and applied as ultra-deep desulfurization adsorbents for hydrotreated diesel. The size of oleic-coated magnetic Fe3O4 nanoparticles prepared by coprecipitation method was about 20 nm. MMAS shows better desulfurization properties for removal of sulfur compounds than NaY and MCM-41. The amount of Fe3O4 nanoparticles has significant effects on specific surface area/pore volume and acidic properties, thus, can affect the desulfurization properties of MMAS. Desulfurization properties of MMAS can be improved with the increase of temperature from 30,70°C and decrease the oil to adsorbent ratio. With the increase of Fe3O4 content, adsorption capacity first increased and then decreased. The sulfur adsorption of MMAS was due to the synergetic effect of strong molecular affinity of the magnetite to the sulfur compound and large surface area/pore volume of the mesoporous aluminosilicates. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] A Microporous Metal,Organic Framework with Immobilized ,OH Functional Groups within the Pore Surfaces for Selective Gas SorptionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2010Zhenxia Chen Abstract A new two-dimensional microporous metal,organic framework Cu(BDC-OH)(H2O)·0.5DEF [abbreviation: Cu(BDC-OH); H2BDC-OH = 2-hydroxybenzene-1,4-dicarboxylic acid; DEF = diethylformamide] with functional OH groups on the pore surfaces was solvothermally synthesized and structurally characterized. The activated Cu(BDC-OH) exhibits a moderate Langmuir surface of 584 m2,g,1, a pore volume of 0.214 cm3,g,1, and C2H2/CH4 and CO2/CH4 selectivity of 6.7 and 9.3, respectively, at 296 K, thereby highlighting the promise for its application in gas separation. [source] Base-Induced Formation of Two Magnesium Metal-Organic Framework Compounds with a Bifunctional Tetratopic LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2008Pascal D. C. Dietzel Abstract Two coordination polymers constructed from magnesium and the tetratopic organic linker 2,5-dihydroxyterephthalic acid are reported, denominated CPO-26-Mg and CPO-27-Mg. The organic component carries two different types of protic functional groups. The degree of deprotonation of the organic component can be regulated by the amount of sodium hydroxide employed in the synthesis, thus determining which of the compounds forms. In CPO-26-Mg, only the carboxylic acid groups of the linker are deprotonated and take part in the construction of the three-dimensional framework. The structure is non-porous, and its topology is based on the PtS net. In CPO-27-Mg, both the carboxylic acid and the hydroxy groups are deprotonated and involved in the construction of a microporous three-dimensional framework which is based on a honeycomb motif containing large solvent-filled channels. The metal atoms are arranged in chiral chains along the intersection of the honeycomb and contain one water molecule in their coordination sphere, which allows for the creation of coordinatively unsaturated metal sites upon dehydration. CPO-27-Mg is a potentially useful lightweight adsorbent with a pore volume of 60,% of the total volume of the structure and an apparent Langmuir surface area of up to 1030 m2,g,1. Its thermal stability was investigated by thermogravimetry and variable-temperature powder X-ray diffraction, which shows framework degradation to commence at 160 °C in air, at 235 °C under nitrogen, and at 430 °C in a dynamic vacuum. Thermogravimetric dehydration and re-hydration experiments at miscellaneous temperatures indicate that it is possible to obtain open metal sites in CPO-27-Mg, but the water is more tightly bound in this material than in the previously reported isostructural nickel compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Incorporation of a (Cyclopentadienyl)molybdenum Oxo Complex in MCM-41 and Its Use as a Catalyst for Olefin EpoxidationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2004Marta Abrantes Abstract The tricarbonyl complex [(,5 -C5H4 -COOMe)Mo(CO)3Cl] was prepared from the reaction of sodium (methoxycarbonyl)cyclopentadienide, (C5H4 -CO2Me)Na, with (Bu4N)[Mo(CO)5I]. Heating the ester with 3-(triethoxysilyl)propylamine gave the amide derivative {[,5 -C5H4 -CONH-C3H6Si(OEt)3]Mo(CO)3Cl}. The functionalised tricarbonyl complex was immobilised in the ordered mesoporous silica MCM-41 with a loading of 13 wt.-% Mo (1.4 mmol·g,1) by carrying out a grafting reaction in dichloromethane. Powder X-ray diffraction and nitrogen adsorption,desorption analysis indicated that the structural integrity of the support was preserved during the grafting and that the channels remained accessible, despite significant reductions in surface area, pore volume and pore size. The success of the coupling reaction was confirmed by 29Si and 13C (CP) MAS NMR spectroscopy. A supported dioxo complex of the type [(,5 -C5H4R)MoO2Cl] was subsequently prepared by oxidative decarbonylation of the tethered tricarbonyl complex using tert -butyl hydroperoxide (TBHP). The oxidised material is an active catalyst for the liquid phase epoxidation of cyclooctene with TBHP as the oxygen source. Similar catalytic results were obtained using the tethered tricarbonyl complex directly as a pre-catalyst since fast oxidative decarbonylation occurs under the reaction conditions used. For both systems, the desired epoxide was the only product and the initial activities were about 13 mol·molMo,1·h,1. The solid catalysts were recycled several times. Some activity was lost between the first and second runs but thereafter tended to stabilise. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] The inherent ,safety-net' of an Acrisol: measuring and modelling retarded leaching of mineral nitrogenEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2002D. Suprayogo Summary The inherent features of Acrisols with their increasing clay content with depth are conducive to reducing nutrient losses by nutrient adsorption on the matrix soil surfaces. Ammonium (NH4+) and nitrate (NO3,) adsorption by a Plinthic Acrisol from Lampung, Indonesia was studied in column experiments. The peak of the H218O breakthrough occurred at 1 pore volume, whereas the median pore volumes for NH4+ and NO3, ranged from 6.4 to 6.9 and 1.1 to 1.6, respectively. The adsorption coefficients (Ka in cm3 g,1) measured were 1.81, 1.51, 1.64 and 1.47 for NH4+ and 0.03, 0.09, 0.10 and 0.17 for NO3,, respectively, in the 0,0.2, 0.2,0.4, 0.4,0.6 and 0.6,0.8 m soil depth layers. The NH4+ and NO3, adsorption coefficients derived from this study were put in to the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model to evaluate their effect on leaching in the context of several cropping systems in the humid tropics. The resulting simulations indicate that the inherent ,safety-net' (retardation mechanism) of a shallow (0.8,1 m) Plinthic Acrisol can reduce the leaching of mineral N by between 5 and 33% (or up to 2.1 g m,2), mainly due to the NH4+ retardation factor, and that the effectiveness in reducing N leaching increases with increasing depth. However, the inherent ,safety-net' is useful only if deep-rooted plants can recover the N subsequently. [source] Hierarchical ZnS-In2S3 -CuS Nanospheres with Nanoporous Structure: Facile Synthesis, Growth Mechanism, and Excellent Photocatalytic ActivityADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Yingxuan Li Abstract Without using any templates or surfactants, hierarchical ZnS-In2S3 -CuS nanospheres with nanoporous structure are successfully synthesized via a simple and convenient process. The nanospheres are aggregations of densely packed nanoparticles and nanorods. Different to the oriented attachment (OA) mechanism reported in the literature, the formation of these nanorods is believed to follow a lateral OA mechanism (nanoparticles attach along the direction perpendicular to the crystallographic axes with lateral planes as the juncture) based on the experimental data. This process could be a general phenomenon and would provide a new insight into the OA mechanism. A detailed time-resolved TEM kinetic study of the formation of the complex structure is shown. The dipole mechanism and electric field-induced growth are found to be responsible for the final architecture. Photocatalytic activities for water splitting are investigated under visible-light irradiation (, > 400 nm) and an especially high photocatalytic activity (apparent yield of 22.6% at 420 nm) is achieved by unloaded ZnIn0.25Cu0.02S1.395 prepared at 180 °C for 18 h because of their high crystallinity, large pore volume, and the presence of nanorods with special microstructures. [source] Designed Multifunctional Nanocomposites for Biomedical ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Humphrey H. P. Yiu Abstract The assembly of multifunctional nanocomposite materials is demonstrated by exploiting the molecular sieving property of SBA-16 nanoporous silica and using it as a template material. The cages of the pore networks are used to host iron oxide magnetic nanoparticles, leaving a pore volume of 0.29,cm3,g,1 accessible for drug storage. This iron oxide,silica nanocomposite is then functionalized with amine groups. Finally the outside of the particle is decorated with antibodies. Since the size of many protein molecules, including that of antibodies, is too large to enter the pore system of SBA-16, the amine groups inside the pores are preserved for drug binding. This is proven using a fluorescent protein, fluorescein-isothiocyanate-labeled bovine serum albumin (FITC-BSA), with the unreacted amine groups inside the pores dyed with rhodamine B isothiocyanate (RITC). The resulting nanocomposite material offers a dual-targeting drug delivery mechanism, i.e., magnetic and antibody-targeting, while the functionalization approach is extendable to other applications, e.g., fluorescence,magnetic dual-imaging diagnosis. [source] Interactions between fauna and sediment control the breakdown of plant matter in river sedimentsFRESHWATER BIOLOGY, Issue 4 2010SIMON NAVEL Summary 1. A substantial portion of particulate organic matter (POM) is stored in the sediment of rivers and streams. Leaf litter breakdown as an ecosystem process mediated by microorganisms and invertebrates is well documented in surface waters. In contrast, this process and especially the implication for invertebrates in subsurface environments remain poorly studied. 2. In the hyporheic zone, sediment grain size distribution exerts a strong influence on hydrodynamics and habitability for invertebrates. We expected that the influence of shredders on organic matter breakdown in river sediments would be influenced strongly by the physical structure of the interstitial habitat. 3. To test this hypothesis, the influence of gammarids (shredders commonly encountered in the hyporheos) on degradation of buried leaf litter was measured in experimental systems (slow filtration columns). We manipulated the structure of the sedimentary habitat by addition of sand to a gravel-based sediment column to reproduce three conditions of accessible pore volume. Ten gammarids were introduced in columns together with litter bags containing alder leaves at a depth of 8 cm in sediment. Leaves were collected after 28 days to determine leaf mass loss and associated microbial activity (fungal biomass, bacterial abundance and glucosidase, xylosidase and aminopeptidase activities). 4. As predicted, the consumption of buried leaf litter by shredders was strongly influenced by the sediment structure. Effective porosity of 35% and 25% allowed the access to buried leaf litter for gammarids, whereas a lower porosity (12%) did not. As a consequence, leaf litter breakdown rates in columns with 35% and 25% effective porosity were twice as high as in the 12% condition. Microbial activity was poorly stimulated by gammarids, suggesting a low microbial contribution to leaf mass loss and a direct effect of gammarids through feeding activity. 5. Our results show that breakdown of POM in subsurface waters depends on the accessibility of food patches to shredders. [source] An approach to combined rock physics and seismic modelling of fluid substitution effectsGEOPHYSICAL PROSPECTING, Issue 2 2002Tor Arne Johansen ABSTRACT The aim of seismic reservoir monitoring is to map the spatial and temporal distributions and contact interfaces of various hydrocarbon fluids and water within a reservoir rock. During the production of hydrocarbons, the fluids produced are generally displaced by an injection fluid. We discuss possible seismic effects which may occur when the pore volume contains two or more fluids. In particular, we investigate the effect of immiscible pore fluids, i.e. when the pore fluids occupy different parts of the pore volume. The modelling of seismic velocities is performed using a differential effective-medium theory in which the various pore fluids are allowed to occupy the pore space in different ways. The P-wave velocity is seen to depend strongly on the bulk modulus of the pore fluids in the most compliant (low aspect ratio) pores. Various scenarios of the microscopic fluid distribution across a gas,oil contact (GOC) zone have been designed, and the corresponding seismic properties modelled. Such GOC transition zones generally give diffuse reflection regions instead of the typical distinct GOC interface. Hence, such transition zones generally should be modelled by finite-difference or finite-element techniques. We have combined rock physics modelling and seismic modelling to simulate the seismic responses of some gas,oil zones, applying various fluid-distribution models. The seismic responses may vary both in the reflection time, amplitude and phase characteristics. Our results indicate that when performing a reservoir monitoring experiment, erroneous conclusions about a GOC movement may be drawn if the microscopic fluid-distribution effects are neglected. [source] Multiple Functionalization of Mesoporous Silica in One-Pot: Direct Synthesis of Aluminum-Containing Plugged SBA-15 from Aqueous Nitrate Solutions,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2008Y. Wu Abstract Aluminum-containing plugged mesoporous silica has been successfully prepared in an aqueous solution that contains triblock copolymer templates, nitrates, and silica sources but without using mineral acid. The acidity of the solution can be finely tuned from pH 1.4 to 2.8 according to the amount of the introduced aluminum species which ranged from an Al/Si molar ratio of 0.25/1 to 4.0/1. The aluminum nitrate additive in the starting mixture, along with the weak acidity produced by the nitrates, contributes to the formation of plugged hexagonal structures and the introduction of different amounts of aluminum species into the mesostructure. Characterization by X-ray diffraction, transmission electron microscopy, and N2 sorption measurements show that the Al-containing plugged silicas possess well-ordered hexagonal mesostructures with high surface areas (700,860 m2,g,1), large pore volume (0.77,1.05 cm3,g,1) and, more importantly, combined micropores and/or small mesopores in the cylindrical channels. Inductively coupled plasma,atomic emission spectrometry results show that 0.7,3.0 wt,% aluminum can be introduced into the final samples. 27Al MAS NMR results display that about 43,60% aluminum species are incorporated into the skeleton of the Al-containing silicas and the amount of the framework aluminum increases as the initial added nitrates rises. Scanning electron microscopy images reveal that the directly synthesized Al-containing plugged silica has a similar morphology to that of traditional SBA-15. Furthermore, the Al-containing plugged samples have excellent performances in the adsorption and the catalytic decomposition of isopropyl alcohol and nitrosamine. Finally, the direct synthesis method is used to produce plugged mesoporous silicas that contain other metals such as chromium and copper, and the resultant samples also show good catalytic activities. [source] Microporous Metal,Organic Frameworks with High Gas Sorption and Separation Capacity,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2007Y. Lee Abstract The design, synthesis, and structural characterization of two microporous metal,organic framework structures, [M(bdc)(ted)0.5]·2,DMF·0.2,H2O (M,=,Zn (1), Cu (2); H2bdc,=,1,4-benzenedicarboxylic acid; ted,=,triethylenediamine; DMF: N,N -dimethylformamide) is reported. The pore characteristics and gas sorption properties of these compounds are investigated at cryogenic temperatures, room temperature, and higher temperatures by experimentally measuring argon, hydrogen, and selected hydrocarbon adsorption/desorption isotherms. These studies show that both compounds are highly porous with a pore volume of 0.65 (1) and 0.52,cm3,g,,1 (2). The amount of the hydrogen uptake, 2.1,wt,% (1) and 1.8,wt,% (2) at 77,K (1,atm; 1,atm,=,101,325,Pa), places them among the group of metal,organic frameworks (MOFs) having the highest H2 sorption capacity. [Zn(bdc)(ted)0.5]·2,DMF·0.2,H2O adsorbs a very large amount of hydrocarbons, including methanol, ethanol, dimethylether (DME), n -hexane, cyclohexane, and benzene, giving the highest sorption values among all metal,organic based porous materials reported to date. In addition, these materials hold great promise for gas separation. [source] Sub-micron spongiform porosity is the major ultra-structural alteration occurring in archaeological boneINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 6 2002G. Turner-Walker Abstract Total pore volume and pore size distribution are indicators of the degree of post-mortem modification of bone. Direct measurements of pore size distribution in archaeological bones using mercury intrusion porosimetry (HgIP) and back scattered scanning electron microscopy (BSE-SEM) reveal a common pattern in the changes seen in degraded bone as compared to modern samples. The estimates of pore size distribution from HgIP and direct measurement from the BSE-SEM images show remarkable correspondence. The coupling of these two independent approaches has allowed the diagenetic porosity changes in human archaeological bone in the >0.01 µm range to be directly imaged, and their relationship to pre-existing physiological pores to be explored. The increase in porosity in the archaeological bones is restricted to two discrete pore ranges. The smaller of these two ranges (0.007,0.1 µm) lies in the range of the collagen fibril (0.1 µm diameter) and is presumably formed by the loss of collagen, whereas the larger pore size distribution is evidence of direct microbial alteration of the bone. HgIP has great potential for the characterization of microbial and chemical alteration of bone. Copyright © 2002 John Wiley & Sons, Ltd. [source] Microporous activated carbon spheres prepared from resole-type crosslinked phenolic beads by physical activationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Arjun Singh Abstract Microporous activated carbon spheres (ACSs) with a high specific Brunauer,Emmet,Teller (BET) surface area were prepared from resole-type spherical crosslinked phenolic beads (PBs) by physical activation. The PBs used as precursors were synthesized in our laboratory through the mixing of phenol and formaldehyde in the presence of an alkaline medium by suspension polymerization. The effects of the gasification time, temperature, and flow rate of the gasifying agent on the surface properties of ACSs were investigated. ACSs with a controllable pore structure derived from carbonized PBs were prepared by CO2 gasification. Surface properties of ACSs, such as the BET surface area, pore volume, pore size distribution, and pore diameters, were characterized with BET and Dubinin,Reduchkevich equations based on N2 adsorption isotherms at 77 K. The results showed that ACSs with a 32,88% extent of burn-off with CO2 gasification exhibited a BET surface area ranging from 574 to 3101 m2/g, with the pore volume significantly increased from 0.29 to 2.08 cm3/g. The pore size and its distribution could be tailored by the selection of suitable conditions, including the gasification time, temperature, and flow rate of the gasifying agents. The experimental results of this analysis revealed that ACSs obtained under different conditions were mainly microporous. The development of the surface morphology of ACSs was also studied with scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis and simple method of estimating macroporosity of methyl methacrylate,divinylbenzene copolymer beadsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Muhammad Arif Malik Abstract Macroporous methyl methacrylate,divinylbenzene copolymer beads having diameter , 300 ,m were synthesized by free radical suspension copolymerization. The macroporosity was generated by diluting the monomers with inert organic liquid diluents. The macroporosity was varied in the range of ,0.1 to , 1.0 mL/g by varying a number of porosity controlling factors, such as the diluents, solvent to nonsolvent mixing ratios when employing a mixture of the two diluents, degree of dilution, and crosslinkage. Increase in pore volume from 0.1 to 0.45 mL/g resulted in a sharp increase in mesopores having diameters in the range of 3,20 nm whereas the macropores remained negligible when compared with mesopores. Increase in pore volume from 0.45 to 1 mL/g resulted in a sharp increase in macropores, whereas mesopores having diameters in the range of 3,20 nm remained almost constant. The mesopores having diameters in the range of 20,50 nm showed an increase with the increase in pore volume throughout the whole range of pore volume studied. Macroporosity characteristics, i.e., pore volume (Vm), surface area (SA), and pore size distributions were evaluated by mercury penetration method. Statistical analysis of the data obtained in the present study shows that the macroporosity characteristics can be estimated with a reasonable accuracy from the pore volumes, which in turn are determined from the densities of the copolymers. These results are explained on the basis of pore formation mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Thermal analysis of merino wool fibres without internal lipidsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007M. Martí Abstract Merino wool is made up of cuticle and cortical cells held together by the cell membrane complex (CMC), which contains a small amount of internal lipids (IWL) (1.5% by mass). IWL have been extracted from wool on account of their considerable dermatological interest owing to their proportion of ceramides. IWL have been extracted by different methods and solvents, methanol and acetone at laboratory and pilot plant levels. Thermal analysis of these extracted wool fibers is presented using thermogravimetry (TG) and differential scanning calorimetry (DSC). TG provides a measurement of the weight loss of the sample as a function of time and temperature. DSC gives information about possible structure modification of extracted wool fibers. Thermoporometry was applied to evaluate the pore size distribution of extracted wool fibers. The results showed that the extraction process increased the pore size distribution and the cumulated pore volume, which is consistent with some changes in the extracted wool CMC. Extracted fiber becomes more hydrophilic and absorbs a large amount of water. We can conclude that the lipid extraction of wool produced no relevant changes in the crystalline fraction when extracted with acetone. However, part of the amorphous keratin material was extracted with methanol, the rest of the crystalline material becoming more stable. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 545,551, 2007 [source] Kinetic behaviour of the adsorption and photocatalytic degradation of salicylic acid in aqueous TiO2 microsphere suspensionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2004XZ Li Abstract A new photocatalyst, named TiO2 microspheres, prepared by a sol-spraying-calcination method, can freely suspend with air bubbling in its aqueous suspension and easily settle down from a water phase under gravity. The experimental results demonstrated that TiO2 microspheres had better adsorption capacity than conventional TiO2 powders, due to large surface area, large pore volume, and also a porous structure. The photocatalytic activity of TiO2 microspheres in aqueous suspension was evaluated using salicylic acid (SA) as a model substrate. It was found that the Langmuir,Hinshelwood model in its integral form described the kinetics of SA photocatalytic degradation in the TiO2 microsphere suspensions better than its simplified form as a first-order reaction model, since the significant substrate adsorption on the catalysts was not negligible. The kinetics of SA photocatalytic degradation with different initial concentrations and pH was further investigated. The experiments demonstrated that the change of pH could significantly affect the adsorption of SA in the TiO2 microsphere suspensions. The effects of substrate adsorption rate and photoreaction rate on the overall performance of photocatalytic degradation is also discussed on the basis of experimental data. Copyright © 2004 Society of Chemical Industry [source] Capacity of activated carbon derived from pistachio shells by H3PO4 in the removal of dyes and phenolicsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2003Amina A Attia Abstract Two activated carbons were obtained from pistachio shells by impregnation with H3PO4 under standard conditions of acid concentration (50 wt%) and heat treatment at 773 K for 2 h. The soaking time was 24 and 72 h for the two samples before thermal pyrolysis. Analysis of the N2/77 K adsorption isotherms proved that both were highly adsorbing carbons with considerable microporosity, and that the prolonged contact with activant enhanced total porosity (surface area and pore volume) and increased the amount of mesoporosity. Adsorption isotherms of probe molecules, viz methylene blue (MB), rhodamine B (RB), phenol (P) and p -nitrophenol (PNP), were determined at room temperature, from aqueous solutions. Both the Langmuir and Freundlich model adsorption equations show satisfactory fit to experimental data. Both carbons exhibit similar adsorption parameters irrespective of their porosity characteristics. The sequence of uptake per unit weight was: PNP > MB > RB > P. Low affinity towards phenol may be associated with its competition with water molecules which are more favourably attracted to the acid surface which has a high oxygen functionality. Preferred adsorption in the order PNP > MB > RB is proposed to be a function of carbon porosity, related to the increased molecular dimensions of the solutes. Adsorption from a binary mixture of equal concentrations of MB and RB showed reduced uptake for both sorbates in comparison to the single component experiments. RB removal surpasses that of MB in the binary test and may be attributed to lower water solubility and higher molecular dimensions. Copyright © 2003 Society of Chemical Industry [source] Pore-size effects on activated-carbon capacities for volatile organic compound adsorptionAICHE JOURNAL, Issue 8 2002Mei-Chiung Huang Gas-phase adsorption of acetone and n-hexane by activated carbons with different pore structures was investigated. The carbons were prepared from a bituminous coal with KOH activation. Increasing the activation temperature increased both the porosity and pore size. The equilibrium adsorption capacity for the organic compounds increased with the carbon porosity, but not proportionally. The percentage of pore volume utilized showed a decreasing trend with the porosity development for acetone adsorption, while an increasing trend was observed for n-hexane. By incorporating pore size distribution with the Dubinin-Radushkevich equation using an inverse proportionality between the micropore size and adsorption energy, the isotherms for adsorption onto different carbons can be well predicted. Simulations indicated that the adsorption energy, which is an inverse function of the micropore size, determines the adsorption capacity. Different effects of porosity development were observed for different adsorbates. [source] Direct drug loading into preformed porous solid dosage units by the controlled particle deposition (CPD), a new concept for improved dissolution using SCF-technologyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2008Ragna S. Wischumerski Abstract The controlled particle deposition (CPD), a supercritical fluid precipitation process, is used to load porous tablets with ibuprofen to improve drug dissolution. Porous tablets (porosity 44.3,±,5.5%), consisting of microcrystalline cellulose pellets and hydroxyethylcellulose, or sugar cubes (porosity 37.2,±,0.5%), are used as carrier material. Loading experiments are conducted at 313 K and 25 MPa, drug concentrations between 6.25 and 33.3 mg ibuprofen/mL supercritical carbon dioxide and contact times of 15.5 h or 5 min. The resulting products have drug contents of 3,5 g ibuprofen/mL void volume in the carrier. Comparison of a predicted value, calculated from pore volume and loading concentration to the actual drug concentrations yielded by the loading process demonstrates the efficiency and controllability of the process. The mean particle size d50 of deposited ibuprofen is around 25 µm, half the size of the starting material. Drug dissolution from loaded carriers is significantly increased by a rise in the dissolution coefficient from 0.07 min,1 for the starting material to 0.13 or 0.14 min,1 for the CPD products. The CPD method therefore is presented as a feasible and controllable process to load porous solid dosage forms with drug particles in order to improve dissolution. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4416,4424, 2008 [source] Triboelectrification of Spray-dried Lactose Prepared from Different Feedstock ConcentrationsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 1 2000ORLA E. CASSIDY Powder systems may acquire electrostatic charge during various pharmaceutical processing operations and may give rise to difficulties in handling and powder flow, mainly due to adhesion/cohesion effects. We have investigated the electrostatic charging of spray-dried lactose prepared from different feedstock concentrations using a laboratory spray-dryer. Triboelectrification of the spray-dried lactose samples was effected through contact with the stainless steel surface of either a mixing vessel or a cyclone separator. Results from both techniques showed differences in charge accumulation and particle-steel adhesion between the spray-dried lactose samples. As the feedstock concentration used to produce the spray-dried lactose was increased in the range 10,50% w/v, the mean charge on the lactose decreased from ,20.8 to ,1.3 nC g,1 and ,54.9 to ,4.1 nC g,1 for the mixing vessel and cyclone separator, respectively, with a corresponding decrease in adhesion. In addition, as the feedstock concentration was increased from 10 to 50% w/v, decreases were obtained in surface area values (1.06 to 0.56 m2 g,1), pore diameter (198.7 to 83.5 ,m) and pore volume (1.09 to 0.75 cm3 g,1), and together with differences in crystal form correlated with the charge and adhesion results. The results suggested that the feedstock concentration could have a considerable influence on the charging and adhesional properties of spray-dried lactose. This may have relevance during pharmaceutical processing and manufacturing operations. [source] The influence of porosity on the Phillips Cr/silica catalyst 2.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2009Polyethylene elasticity Abstract The Phillips Cr/silica catalyst produces low levels of long chain branching (LCB) in polyethylene, which have a powerful influence on industrial molding behavior. Although many catalyst and reactor variables determine the degree of LCB, perhaps the most significant of these is the morphology of the silica support. In this study many different types of silicas were converted into Cr/silica catalysts, which were tested in ethylene polymerization, and the resultant polymer elasticity was then determined. In some experiments, the surface area of the catalyst seemed to correlate quite well with polymer elasticity. In other tests, however, no connection with surface area was evident but the pore volume was quite influential. Together, all these studies suggest that it is the degree of structural reinforcement of the silica matrix, rather than any one physical measurement of porosity, that influences elasticity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 845,865, 2009 [source] Aryl acrylate based high-internal-phase emulsions as precursors for reactive monolithic polymer supportsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2005Peter Krajnc Abstract Water-in-oil high-internal-phase emulsions (HIPEs), containing 4-nitrophenyl acrylate and 2,4,6-trichlorophenyl acrylate as reactive monomers, were prepared and polymerized, and highly porous monolithic materials resulted. The novel materials were studied by combustion analysis, Fourier transform infrared spectroscopy scanning electron microscopy, mercury porosimetry, and N2 adsorption/desorption analysis. With both esters, cellular macroporous monolithic polymers were obtained; the use of 4-nitrophenyl acrylate resulted in a cellular material with void diameters between 3 and 7 ,m and approximately 3-,m interconnects, whereas the use of 2,4,6-trichlorophenyl acrylate yielded a foam with void diameters between 2 and 5 ,m, most interconnects being around 1 ,m. The resulting monoliths proved to be very reactive toward nucleophiles, and possibilities of functionalizing the novel polymer supports were demonstrated via reactions with amines bearing additional functional groups and via the synthesis of an acid chloride derivative. Tris(hydroxymethyl)aminomethane and tris(2-aminoethyl)amine derivatives were obtained. The hydrolysis of 4-nitrophenylacrylate removed the nitrophenyl group, yielding a monolithic acrylic acid polymer. Furthermore, functionalization to immobilized acid chloride was performed very efficiently, with more than 95% of the acid groups reacting. The measurement of the nitrogen content in 4-nitrophenyl acrylate poly(HIPE)s after various times of hydrolysis showed the influence of the total pore volume of the monolithic polymers on the velocity of the reaction, which was faster with the more porous polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 296,303, 2005 [source] Calcium carbonate solubilization through H-proton release from some legumes grown in calcareous saline-sodic soilsLAND DEGRADATION AND DEVELOPMENT, Issue 1 2010A. R. Mubarak Abstract Increasing levels of CO2 and H+ proton in the rhizosphere from some legumes may play an important role in calcite dissolution of calcareous salt affected soils. Soils planted with white and brown varieties of cowpea (Vigna unguiculata L.) and hyacinth bean (Dolichos lablab L.) relying on either fertilizer N (KNO3) or N-fixation were compared against soils to which gypsum was applied and a control without plants and gypsum application to study the possibility of Ca2+ release from calcite and Na+ leaching. As compared to plants relying on inorganic N, leachates from all pore volumes (0·5, 1·0, 1·5, 2·0 pore volume) in lysimeters planted with N-fixing hyacinth bean contained significantly higher concentrations of HCO with lower concentrations from lysimeters planted with white cowpea relying on N-fixation. However, the lowest concentrations of HCO were recorded in the gypsum and control treatments. In initial leaching, lysimeters planted with N-fixing plants maintained similar leachate Ca2+ and Na+ concentrations compared to gypsum amended soils. However, gypsum amended soils were found to have a prolonged positive effect on Na+ removal. It might be concluded that some legumes that are known to fix N in calcareous salt affected soils may be an alternative ameliorant to the extremely expensive gypsum through calcite solubilization and a consequent release of Ca2+. Copyright © 2009 John Wiley & Sons, Ltd. [source] Preparation of Water-Absorbing Polyacrylonitrile Nanofibrous MembraneMACROMOLECULAR RAPID COMMUNICATIONS, Issue 2 2006Haiqing Liu Abstract Summary: Hydrophilic acrylic nanofibers were prepared from alkaline hydrolysis of hydrophobic polyacrylonitrile (PAN) nanofibers. Water contact angle, pore volume, and liquid retention capacity of PAN nanofibrous membranes were measured to determine their dependence on hydrolysis parameters such as base concentration, temperature, and time. Vertical water retention capacity of hydrolyzed PAN nanofibrous membrane could reach as large as 200 times of that of original membrane. Fiber twinning in post-hydrolyzed PAN nanofibrous membrane. [source] Loading of Bacterial Cellulose Aerogels with Bioactive Compounds by Antisolvent Precipitation with Supercritical Carbon DioxideMACROMOLECULAR SYMPOSIA, Issue 2 2010Emmerich Haimer Abstract Bacterial cellulose aerogels overcome the drawback of shrinking during preparation by drying with supercritical CO2. Thus, the pore network of these gels is fully accessible. These materials can be fully rewetted to 100% of its initial water content, without collapsing of the structure due to surface tension of the rewetting solvent. This rehydration property and the high pore volume of these material rendered bacterial cellulose aerogels very interesting as controlled release matrices. Supercritical CO2 drying, the method of choice for aerogel preparation, can simultaneously be used to precipitate solutes within the cellulose matrix and thus to load bacterial cellulose aerogels with active substances. This process, frequently termed supercritical antisolvent precipitation, is able to perform production of the actual aerogel and its loading in one single preparation step. In this work, the loading of a bacterial cellulose aerogel matrix with two model substances, namely dexpanthenol and L-ascorbic acid, and the release behavior from the matrix were studied. A mathematical release model was applied to model the interactions between the solutes and the cellulose matrix. The bacterial cellulose aerogels were easily equipped with the reagents by supercritical antisolvent precipitation. Loading isotherms as well as release kinetics indicated no specific interaction between matrix and loaded substances. Hence, loading and release can be controlled and predicted just by varying the thickness of the gel and the solute concentration in the loading bath. [source] Topographical and Wettability Effects of Post-Discharge Plasma Treatments on Macroporous Polystyrene-Divinylbenzene Solid FoamsPLASMA PROCESSES AND POLYMERS, Issue 10 2009Cristina Canal Abstract The aim of this study was to evaluate the morphological characteristics and wetting properties of polystyrene-divinylbenzene (PS-DVB) solid foams and their modification through post-discharge plasmas. The low-density solid foams are mainly macroporous, but show a small fraction of mesopores; their characterization revealed differences in topography between the smoother surface and the rougher bulk, while from the chemical point of view both regions of the PS-DVB solid foams are hydrophobic. The macroporous structure of these materials with high pore volume makes them interesting for the design of new drug delivery systems, but some active principles and the physiological media are hydrophilic; therefore, it would be of interest to modify the wettability of the materials via post-discharge plasma treatments. [source] Influence of fibre length and filler particle size on pore structure and mechanical strength of filler-containing paperTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2000Noriyoshi Kinoshita Abstract Test sheets were prepared by incorporating softwood pulp with silica filler, PW-5 (diameter 4.5 ,m) or PW-20 (15 ,m). Length-weighted averages of fibre were 2.5 (uncut fibre) and 1.25 mm (short-cut fibre). Pore sizes less than 150 urn were measured by mercury porosimeter. Sheets of short-cut fibres and mixed with uncut fibres at ratio of 3:1 or 1:3 had larger pore volumes than others tested. When filler content increased, the total pore volume increased for PW-20 sheets, but it did not for PW-5 sheets with short-cut fibres. Tensile index and folding endurance were very much affected by fibre length. Contact number on a fibre was calculated by computer simulation, and it had a linear relation with tensile index of sheet. Des échantillons de feuilles ont été préparés en incorporant dans de la pâte de bois tendre une charge de silice, soit du PW-5 (diamètre 4,5 ,m) ou du PW-20 (15 ,n). Les moyennes pondérées de la longueur des fibres sont de 2,5 (fibre non coupée) et 1,25 mm (fibre courte). Des distributions de taille des pores inférieures à 150 ,m ont été mesurées à l'aide d'un porosimètre au mercure. Les feuilles fabriquées avec des fibres courtes et celles mélangées à des fibres non coupees dans des rapports de 3:1 et 1:3 présentent de plus grands volumes de pores que les autres. Lorsque la charge augmente, le volume total des pores augmente pour les feuilles ayant du PW-20, ce qui n'est pas le cas pour les feuilles contenant du PW-5 avec des fibres courtes. L'indice de traction et l'endurance au pliage sont très influencés par la longueur des fibres. Le nombre de contacts sur une fibre a été calculé au moyen de simulations par ordinateur et il varie linéairement avec l'indice de traction des feuilles. [source] TiO2 -Modified Macroporous Silica Foams for Advanced Enrichment of Multi-Phosphorylated PeptidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2009Jingjing Wan Abstract Enriching peptides: Novel TiO2 -modified macroporous materials (Ti-MOSF, see figure) have been synthesized with high surface area, large pore volume, and functional surfaces that are rich in coordinatively unsaturated TiIV species, which can be applied in the specific extraction of phosphopeptides and which show a preferential capture of multi-phosphorylated peptides with low detection limits and high selectivity. [source] An Efficient Hybrid, Nanostructured, Epoxidation Catalyst: Titanium Silsesquioxane,Polystyrene Copolymer Supported on SBA-15CHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2007Lei Zhang Abstract A novel interfacial hybrid epoxidation catalyst was designed with a new immobilization method for homogeneous catalysts by coating an inorganic support with an organic polymer film containing active sites. The titanium silsesquioxane (TiPOSS) complex, which contains a single-site titanium active center, was immobilized successfully by in-situ copolymerization on a mesoporous SBA-15-supported polystyrene polymer. The resulting hybrid materials exhibit attractive textural properties (highly ordered mesostructure, large specific surface area (>380,m2,g,1) and pore volume (,0.46,cm3,g,1)), and high activity in the epoxidation of alkenes. In the epoxidation of cyclooctene with tert -butyl hydrogen peroxide (TBHP), the hybrid catalysts have rate constants comparable with that of their homogeneous counterpart, and can be recycled at least seven times. They can also catalyze the epoxidation of cyclooctene with aqueous H2O2 as the oxidant. In two-phase reaction media, the catalysts show much higher activity than their homogeneous counterpart due to the hydrophobic environment around the active centers. They behave as interfacial catalysts due to their multifunctionality, that is, the hydrophobicity of polystyrene and the polyhedral oligomeric silsesquioxanes (POSS), and the hydrophilicity of the silica and the mesoporous structure. Combination of the immobilization of homogeneous catalysts on two conventional supports, inorganic solid and organic polymer, is demonstrated to achieve novel heterogeneous catalytic ensembles with the merits of attractive textural properties, tunable surface properties, and optimized environments around the active sites. [source] Control of Drug Release through the In Situ Assembly of Stimuli-Responsive Ordered Mesoporous Silica with Magnetic ParticlesCHEMPHYSCHEM, Issue 17 2007Shenmin Zhu Dr. Abstract A site-selective controlled delivery system for controlled drug release is fabricated through the in situ assembly of stimuli-responsive ordered SBA-15 and magnetic particles. This approach is based on the formation of ordered mesoporous silica with magnetic particles formed from Fe(CO)5 via the surfactant-template sol-gel method and control of transport through polymerization of N-isopropyl acrylamide inside the pores. Hydrophobic Fe(CO)5 acts as a swelling agent as well as being the source of the magnetic particles. The obtained system demonstrates a high pore diameter (7.1 nm) and pore volume (0.41 cm3,g,1), which improves drug storage for relatively large molecules. Controlled drug release through the porous network is demonstrated by measuring the uptake and release of ibuprofen (IBU). The delivery system displays a high IBU storage capacity of 71.5 wt,%, which is almost twice as large as the highest value based on SBA-15 ever reported. In vitro testing of IBU loading and release exhibits a pronounced transition at around 32,°C, indicating a typical thermosensitive controlled release. [source] | ||||||||||||||||||||||||||||||||||