Search results for "Chemical engineering"

Buildup of Ultrathin Multilayer Films by a Self-Assembly Process: II. Consecutive Adsorption of Anionic and Cationic Bipolar Amphiphiles and Polyelec…

1991

We have recently reported on the consecutive physisorption of anionic and cationic bipolar amphiphiles onto charged surfaces, adsorbed out of aqueous solutions [1]. Here, we extend our previous concept to multipolar compounds such as polyelectrolytes. In contrast to the bipolar amphiphile system, it is not necessary to separate single charges by a rigid unit, when the polyelectrolyte is adsorbed from sufficiently concentrated solutions. In this case the physisorbed layer does not bind with all ionic groups to the surface and exposes free ionic groups at the new film/solution interface. Therefore a polyelectrolyte layer can replace a layer of bipolar amphiphiles in the consecutive buildup of…

Fast Measurements of Adsorption on Porous Materials Using Jäntti's Method

1999

In 1972, Jäntti et al. formulated a method to shorten the time taken for adsorption measurements. We suggested at the Kiev International Conference on Vacuum Microbalance Techniques (1999) that the applicability of this method could be widened by considering a number of parallel adsorptions. There is, however, a more complicated but perhaps more interesting variant possible when extra mass transport is considered to occur in series. Such an application could involve adsorption within a porous structure where diffusion must be considered as a process occurring in series with adsorption on the surface.

Study and Modelling of the Vacuum Swing Adsorption (VSA) Process Employed in the Production of Oxygen

1999

An isothermal and non-equilibrium mathematical model was provided for the multi-component adsorption process. In addition, the software was developed for the VSA-based production of oxygen with the use of a CaX zeolite molecular sieve. The mathematical model and computer software were verified on the basis of experimental data. The study employed a test stand comprising two adsorption columns. The adsorption pressure P A = 150 and 135 kPa and desorption pressure P D = 20 kPa were adopted in the experiments. The tests produced oxygen with the purity of 90–94% O 2 (vol), at an efficiency of 55–73% and productivity of 570–850 kg O 2 per ton per day. The calculation results showed good consiste…

Zeolithe als Adsorbentien für die Trennung, Reinigung und Konzentrierung von organischen Wertprodukten in der präparativen Säulen-Flüssig-Chromatogra…

1995

Self-assembled titania-silica-sepiolite based nanocomposites for water decontamination

2009

WOS: 000264524200020

Pore Length Effect on Drug Uptake and Delivery by Mesoporous Silicas

2012

The capability of UVM-7 silicas to work as supports for drug storage and delivery is investigated using ibuprofen as a model. UVM-7 silicas are surfactant-assisted synthesised mesoporous materials displaying a characteristic bimodal pore architecture related to their nanoparticulate texture. Strict control of the drug-charge protocol allows the achievement of high ibuprofen loads, not only because of the availability of intra-nanoparticle mesopores and large textural voids, but also owing to the decrease in pore-blocking effects (with regard to related unimodal mesoporous materials such as MCM-41) achieved through the shortening of the mesopore length. The UVM-7/ibuprofen nanocomposites are…

High-resolution physisorption techniques for the characterization of adsorbents and catalysts

1991

Abstract High-resolution physisorption techniques performed in the continuous volumetric mode have been developed to investigate the surface and pore structure properties of porous solids. Physisorption data on well-defined microporous solids (zeolites and aluminophosphates) provide novel information on the mechanism of micropore filling, the behavior of the adsorbed phase and the pore structure of the adsorbent. The combination of physisorption with high-resolution analytical techniques such as calorimetry and neutron diffraction further expands our knowledge and understanding of physisorption processes. The results are not only important for fundamental research but can be applied in the …

Sorption Kinetics of Xenon on MFI-Type Zeolite Molecular Sieves

1990

Kinetic uptake data for xenon adsorbed onto large and uniform silicalite-I crystals are presented over a temperature range of 121 K to 296 K. — Adsorption isotherms and corrected diffusion coefficients derived from the uptake curves are given. The heat of adsorption and activation energy of diffusion were estimated from the plots of reciprocal temperature against the logarithm of equilibrium pressure and corrected diffusion coefficients, respectively. — While the corrected diffusion coefficient is independent of coverage for the higher temperatures, it decreases significantly at the lower temperatures investigated (<170 K) when the limiting adsorption capacity has been reached. — Comparing …

Neutrophil‐mediated enhancement of angiogenesis and osteogenesis in a novel triple cell co‐culture model with endothelial cells and osteoblasts

2017

Repair and regeneration of critical‐sized bone defects remain a major challenge in orthopaedic and craniomaxillofacial surgery. Until now, attempts to bioengineer bone tissue have been hindered by the inability to establish proper angiogenesis and osteogenesis in the tissue construct. In the present study, we established a novel triple cell co‐culture model consisting of osteoblasts, endothelial cells, and neutrophils and conducted a systematic investigation of the effects of neutrophils on angiogenesis and osteogenesis. Neutrophils significantly increased angiogenesis in the tissue construct, evidenced by the formation of microvessel‐like structures with an extensive lattice‐like, stable t…

Transdermal nortriptyline hydrocloride patch formulated within a chitosan matrix intended to be used for smoking cessation.

2010

The aim of this study was to prepare and characterize both physically and biopharmaceutically, a nortriptyline hydrochloride (NTP-HCl) patch formulated in chitosan.16 g of each chitosan patch formulation (I, II and III, see Table 1 ) was poured onto rectangular glass plates (64 cm²) at a height of 1 mm and dried for 24 h at room temperature. In order to characterize the chitosan patches, polarized microscopy, in vitro skin permeation studies by passive diffusion and iontophoresis and rheological and bioadhesion studies were performed.Polarized microscopy revealed the absence of aggregates and crystal forms of NTP-HCl in all transdermal patches after 30 days of storage. The rheological behav…