scholarly journals retention volumes in chromatography

2008 ◽  
Keyword(s):  
Retention Volumes

Adsorption of Vapours of Some Organic Compounds on Surface of Iron-Substituted Layered Vanadyl Phosphate

2000 ◽  
Vol 65 (1) ◽  
pp. 47-57 ◽  
Author(s):  
Pavel Hradil ◽  
Jiří Votinský ◽  
Karel Komárek ◽  
Vítězslav Zima ◽  
Jaroslava Kalousová ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Organic Molecules ◽  
Ferric Ions ◽  
Vanadyl Phosphate ◽  
Enthalpy Of Adsorption ◽  
Adsorbent Surface ◽  
Specific Retention Volumes ◽  
Specific Retention ◽  
Retention Volumes ◽  
Chromatographic Measurement

Gas chromatographic measurement of specific retention volumes of vapours of selected groups of organic compounds has been used to determine differential molar enthalpy of adsorption of their molecules on the surface of layered vanadyl phosphate substituted with ferric ions having the composition of [Fe(H2O)]0.20(VO)0.80PO4. Various types of bonds of the molecules to the surface of the layered adsorbent including their probable orientation with respect to the layers have been discussed. It was observed a dependence of the specific peak elution volume and shape of chromatographic peak on the sample size in the cases of those compounds whose molecules are chemically bound to the adsorbent surface. A connection is pointed out between the adsorption strength of the organic molecules on the layered adsorbent and the tendency of the system to undergo intercalation reaction.

Pore-Scale Transport Mechanisms and Macroscopic Displacement Effects of In-Situ Oil-in-Water Emulsions in Porous Media

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Chuan Lu ◽  
Wei Zhao ◽  
Yongge Liu ◽  
Xiaohu Dong
Keyword(s):  
Porous Media ◽  
Oil Recovery ◽  
Heavy Oil ◽  
Mobility Control ◽  
Pore Scale ◽  
Sweep Efficiency ◽  
Emulsion Droplets ◽  
Oil In Water ◽  
Retention Volumes

Oil-in-water (O/W) emulsions are expected to be formed in the process of surfactant flooding for heavy oil reservoirs in order to strengthen the fluidity of heavy oil and enhance oil recovery. However, there is still a lack of detailed understanding of mechanisms and effects involved in the flow of O/W emulsions in porous media. In this study, a pore-scale transparent model packed with glass beads was first used to investigate the transport and retention mechanisms of in situ generated O/W emulsions. Then, a double-sandpack model with different permeabilities was used to further study the effect of in situ formed O/W emulsions on the improvement of sweep efficiency and oil recovery. The pore-scale visualization experiment presented an in situ emulsification process. The in situ formed O/W emulsions could absorb to the surface of pore-throats, and plug pore-throats through mechanisms of capture-plugging (by a single emulsion droplet) and superposition-plugging or annulus-plugging (by multiple emulsion droplets). The double-sandpack experiments proved that the in situ formed O/W emulsion droplets were beneficial for the mobility control in the high permeability sandpack and the oil recovery enhancement in the low permeability sandpack. The size distribution of the produced emulsions proved that larger pressures were capable to displace larger O/W emulsion droplets out of the pore-throat and reduce their retention volumes.

scholarly journals Apex structures enhance water drainage on leaves

2020 ◽  
Vol 117 (4) ◽  
pp. 1890-1894 ◽  
Author(s):  
Ting Wang ◽  
Yifan Si ◽  
Haoyu Dai ◽  
Chuxin Li ◽  
Can Gao ◽  
...  
Keyword(s):  
Leaf Surface ◽  
Control Mechanisms ◽  
Water Drainage ◽  
Tropical Plants ◽  
Leaf Apex ◽  
Drainage Rate ◽  
Retention Volumes ◽  
Rapid Removal ◽  
Shape Changes ◽  
Surface Changes

The rapid removal of rain droplets at the leaf apex is critical for leaves to avoid damage under rainfall conditions, but the general water drainage principle remains unclear. We demonstrate that the apex structure enhances water drainage on the leaf by employing a curvature-controlled mechanism that is based on shaping a balance between reduced capillarity and enhanced gravity components. The leaf apex shape changes from round to triangle to acuminate, and the leaf surface changes from flat to bent, resulting in the increase of the water drainage rate, high-dripping frequencies, and the reduction of retention volumes. For wet tropical plants, such as Alocasia macrorrhiza, Gaussian curvature reconfiguration at the drip tip leads to the capillarity transition from resistance to actuation, further enhancing water drainage to the largest degree possible. The phenomenon is distinct from the widely researched liquid motion control mechanisms, and it offers a specific parametric approach that can be applied to achieve the desired fluidic behavior in a well-controlled way.

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