Adsorption and trapping

The present study investigates the adsorption and trapping of polymer molecules in flow experiments through unconsolidated oil field sands. Static tests on both oil sand and Ottawa sand indicates that mineralogy plays a major role in the observed behavior. Effect of a surfactant slug on polymer-rock interaction is also reported. Corroborative studies have also been conducted to study the anomalous pressure behavior and high tertiary oil recovery in surfactant dilute-polymer systems(ll,12). 

There are several physical mechanisms for the removal of cells and particles. These include sieving, adsorption, and trapping in the matrix. Membrane filters work mainly by sieving, whilst filters such as fibrous pads and sintered glass are depth filters, and work by adsorption and entrapment. Depth filters can suffer from microbial multiplication within the filter, which causes contamination in the filtrate, a problem known as grow through. 

Answer by Author Adsorption and trapping could and probably does account for the removal of some of the noncondensables. No data were taken with the mechanical pumps sealed from the chamber. Subsequent runs have been made with only one mechanical pump, resulting in no significant change in pumping speed. 

When an atom or molecule approaches a surface, it feels an attractive force. The interaction potential between the atom or molecule and the surface, which depends on the distance between the molecule and the surface and on the lateral position above the surface, detemiines the strength of this force. The incoming molecule feels this potential, and upon adsorption becomes trapped near the minimum m the well. Often the molecule has to overcome an activation barrier, before adsorption can occur. 

Schematic diagram of a purge-and-trap system. Anaiyte is coiiected in the primary adsorption trap. The secondary adsorption trap is monitored for evidence of breakthrough.

The sulfur is thus removed from the gas stream and trapped in the sorbent as iron sulfide [1317-37-9]. Over time all of the iron oxide becomes sulfided and the adsorptive capacity of the sorbent becomes exhausted. The bed can be partially regenerated by oxidation, as follows ... 

Evaporative emissions from the fuel tank and carburetor have been controlled on all 1971 and later model automobiles sold in the United States. This has been accomplished by either a vapor recovery system which uses the crankcase of the engine for the storage of the hydrocarbon vapors or an adsorption and regeneration system using a canister of activated carbon to trap the vapors and hold them until such time as a fresh air purge through the canister carries the vapors to the induction system for burning in the combustion chamber. 

Organic traps contain isoporous, macroporous, or other specifically designed resins (such as reticulated, cross-linked polystyrene resins devoid of ionic function) and take up organics by a combination of ion exchange, adsorption, and other mechanisms. They typically are installed to precede the DI plant. 

Here we shall be concerned with the interaction of inacming diatomic molecules (H-/ 0.) with either types of potential energy wells The molecular InteractJjon (responsible for elastic and direct-inelastic scattering with extremely short residence times of the irpinglng molecules in the potential) and the chemisorptive interaction (leading to dissociative adsorption and associative desorption, reflectively, and associated with H (D) atoms trapped in the chemisorption potential for an appreci le time). 

The catalyst for the in situ FTIR-transmission measurements was pressed into a self-supporting wafer (diameter 3 cm, weight 10 mg). The wafer was placed at the center of the quartz-made IR cell which was equipped with two NaCl windows. The NaCI window s were cooled with water flow, thus the catalyst could be heated to 1000 K in the cell. A thermocouple was set close to the sample wafer to detect the temperature of the catalyst. The cell was connected to a closed-gas-circulation system which was linked to a vacuum line. The gases used for adsorption and reaction experiments were O, (99.95%), 0, (isotope purity, 97.5%), H2 (99.999%), CH4 (99.99%) and CD4 (isotope purity, 99.9%). For the reaction, the gases were circulated by a circulation pump and the products w ere removed by using an appropriate cold trap (e.g. dry-ice ethanol trap). The IR measurements were carried out with a JASCO FT/IR-7000 sprectrometer. Most of the spectra were recorded w ith 4 cm resolution and 50 scans. 

Particles may be trapped on the biofilm surface or in voids of the biofilm where any organics may be hydrolyzed and further take part in the transformation processes. A number of factors influence adsorption and desorption of particles, such as particle size, surface charge, pH, etc., as well as biofilm surface properties and bulk water flow pattern. Studies of model biofilms have shown that water flows into the biofilm in small channels, making the prediction of transport of particles as well as soluble compounds complex (Norsker et al., 1995). 

Purge, adsorption processes, 7 613, 614 Purge-and-trap methods... 

Various sample enrichment techniques are used to isolate volatile organic compounds from mammalian secretions and excretions. The dynamic headspace stripping of volatiles from collected material with purified inert gas and trapping of the volatile compounds on a porous polymer as described by Novotny [3], have been adapted by other workers to concentrate volatiles from various mammalian secretions [4-6]. It is risky to use activated charcoal as an adsorbent in the traps that are used in these methods because of the selective adsorption of compounds with different polarities and molecular sizes on different types of activated charcoal. Due to the high catalytic activity of activated charcoal, thermal conversion can occur if thermal desorption is used to recover the trapped material from such a trap. 

Chapter 5 discusses contaminant adsorption on geosorbents and includes a short description of the surface properties of adsorbents and the methodology for quantifying adsorption. The chapter continues with a presentation of adsorption of various types of toxic chemicals on the subsurface solid phase. In addition to physicochemical adsorption, contaminants can be retained in the subsurface by precipitation, deposition, and trapping. These topics, as well as hysteresis phenomena and formation of bound residues, are discussed. 

Contaminants may be adsorbed on the solid phase or on suspended particles in the liquid phase. Environmental factors, such as temperature, pH, and water content in the subsurface prior to contamination, also affect the nature of contaminant adsorption. Other physical processes of retention include precipitation, deposition, and trapping. Under natural conditions, pollutants often consist of more than a single contaminant, comprising a mixture of organic and inorganic toxic compounds. Each of these compounds can react differently with the existing minerals and chemicals in the subsurface. 

Figure 13. Schematic representation of the setup used for the infrared characterization of liquid-solid interfaces [63], The main cell consists of a platinum disk used for adsorption and reaction, a Cap2 prism for guidance of the infrared beam, and a liquid solution trapped between those two elements. The overall arrangement includes gas and liquid sample introduction stages as well as the electronics used for the electrochemical oxidation-reduction cycles needed to preclean the platinum surface.

Adsorption and phase formation of uracil on massive Au[ (lll)-(110)] singlecrystal and Au (111 - 20 nm) film electrodes in 0.1 M IT2SO4 has been studied in electrochemical measurements and applying ATR surface-enhanced infrared reflection absorption spectroscopy [299]. At E < 0.15 V (versus trapped hydrogen electrode), uracil molecules are disordered and planar oriented. Close to the pzc, a 2D condensed physisorbed film of planar-oriented molecules interconnected by directional hydrogen bonds, is formed. 

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