The effect of surface active agents on the mass transfer coefficient in vertical film flow of liquid over the surface of expanded metal sheet packing

1986 ◽  
Vol 51 (2) ◽  
pp. 302-313 ◽  
Author(s):  
Zdeněk Brož ◽  
Mirko Endršt
Keyword(s):  
Mass Transfer ◽  
Film Flow ◽  
Metal Sheet ◽  
Expanded Metal ◽  
Surface Active Agents ◽  
Interfacial Surface ◽  
Interfacial Mass Transfer ◽  
Poorly Soluble ◽  
Surface Active ◽  
Moving Liquid

Experimental data have been used on absorption of poorly soluble gases, helium, carbon dioxide, and propane, to study the mechanism of interfacial mass transfer in vertical gravitational film flow down the surface of the expanded metal sheet. It has been found that upon addition of surface active agents into water, the original almost freely moving liquid-gas interfacial surface behaves similarly as a liquid-solid surface. Two adjustable hydrodynamic parameters have been evaluated on the basis of the film penetration theory with the physical meaning of the dimensionless thickness of an unmixed region near the interface ϑ+ = 0.4 and the characteristic length < scale of the disturbance λ+ = 26.4.

Drug Solubilization by Surfactants: Experimental Methods and Theoretical Perspectives

2021 ◽  
Vol 21 ◽  
Author(s):  
Nisar Ahmad Malik
Keyword(s):  
Theoretical Models ◽  
Experimental Methods ◽  
Poorly Soluble Drugs ◽  
Drug Solubilization ◽  
Theoretical Perspectives ◽  
Surface Active Agents ◽  
Poorly Soluble ◽  
Surface Active ◽  
Mixed Systems ◽  
Insight Into

: This mini review will give an insight into the need and usefulness of investigating the solubilization of poorly soluble drugs. Commonly used experimental and theoretical models are outlined to study the efficacy of the carrier or excipient for the poorly soluble drugs. Furthermore, the use of surface active agents for drug solubilization is discussed in correlation with the mathematical models suggested from time to time. A few experimental techniques are also discussed which would be very helpful in elucidating the interactions prevailing in the mixed systems of poorly soluble drugs and surface active agents.

The effects of surface films in damping eddies at a free surface of a turbulent liquid

1966 ◽  
Vol 290 (1423) ◽  
pp. 515-526 ◽  
Keyword(s):  
Mass Transfer ◽  
Liquid Surface ◽  
Active Material ◽  
Surface Films ◽  
Surface Renewal ◽  
Elastic Stresses ◽  
Hydrodynamic Behaviour ◽  
Surface Active Agents ◽  
Surface Active ◽  
Surface Active Material

Mass-transfer rates across a gas liquid surface into a turbulent liquid depend markedly on the hydrodynamic behaviour of the liquid immediately subjacent to the interface. Though turbulence is always somewhat damped at a free liquid surface, there may remain significant movements of liquid into the plane of a clean surface. A very small amount of surface-active material, however, sets up gradients of surface tension between different parts of the surface, and the accompanying (elastic) stresses are shown to damp very strongly eddies approaching the surface, thus reducing the rate of ‘surface renewal’: mass-transfer of a solute across the liquid surface is correspondingly retarded. This paper treats these phenomena quantitatively, and includes five predictions of the effects of surface-active agents. Comparison is made with published experimental data.

Effects of surface-active agents on mass transfer inside drops

1979 ◽  
Vol 34 (2) ◽  
pp. 217-224 ◽  
Author(s):  
L. Mekasut ◽  
J. Molinier ◽  
H. Angelino
Keyword(s):  
Mass Transfer ◽  
Surface Active Agents ◽  
Surface Active

scholarly journals Nanocrystals of Poorly Soluble Drugs: Drug Bioavailability and Physicochemical Stability

Pharmaceutics ◽  
2018 ◽  
Vol 10 (3) ◽  
pp. 134 ◽  
Author(s):  
Maria Gigliobianco ◽  
Cristina Casadidio ◽  
Roberta Censi ◽  
Piera Di Martino
Keyword(s):  
Drug Delivery ◽  
Particle Size ◽  
Colloidal Particles ◽  
Poorly Soluble Drugs ◽  
Drug Bioavailability ◽  
Free System ◽  
Surface Active Agents ◽  
Carrier Free ◽  
Poorly Soluble ◽  
Surface Active

Many approaches have been developed over time to overcome the bioavailability limitations of poorly soluble drugs. With the advances in nanotechnology in recent decades, science and industry have been approaching this issue through the formulation of drugs as nanocrystals, which consist of “pure drugs and a minimum of surface active agents required for stabilization”. They are defined as “carrier-free submicron colloidal drug delivery systems with a mean particle size in the nanometer range, typically between 10–800 nm”. The primary importance of these nanoparticles was the reduction of particle size to nanoscale dimensions, with an increase in the particle surface area in contact with the dissolution medium, and thus in bioavailability. This approach has been proven successful, as demonstrated by the number of such drug products on the market. Nonetheless, despite the definition that indicates nanocrystals as a “carrier-free” system, surface active agents are necessary to prevent colloidal particles aggregation and thus improve stability. In addition, in more recent years, nanocrystal properties and technologies have attracted the interest of researchers as a means to obtain colloidal particles with modified biological properties, and thus their interest is now also addressed to modify the drug delivery and targeting. The present work provides an overview of the achievements in improving the bioavailability of poorly soluble drugs according to their administration route, describes the methods developed to overcome physicochemical and stability-related problems, and in particular reviews different stabilizers and surface agents that are able to modify the drug delivery and targeting.

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