Principles of Adsorption at Solid Surfaces and their Significance in Gas/Solid and Liquid/Solid Chromatography

Adsorption and Aggregation of C8E4 and C8G1 Nonionic Surfactants on Hydrophilic Silica Studied by Calorimetry

“…The enthalpies of displacement of water by the nonionic surfactants were measured by flow sorption experiments with the same TAM calorimeter as used for the titration experiments. The calorimeter was connected to a differential refractometer, which allowed a simultaneous measurement of the adsorption isotherm, on the principle of flow frontal analysis solid/liquid chromatography. , The measuring system represents an improved version of the design of van Os and Haandrikman . The system consisted of two three-channel degassers, an electric seven-port valve, an HPLC Micropump (each unit Knauer, Berlin, Germany), a back pressure regulator (SSI, State College, PA), a six-way valve (Knauer), the sample vessel (designed by van Os 55 ) attached to the holder of the calorimeter perfusion cell, a differential refractometer (Knauer), and a liquid microflowmeter (PhaseSep, Clwyd, England).…”

Temperature Dependence of the Artificial Photosynthesis Reactions Catalyzed by Nanostructured Co/CoO

“…In reality, they are not constants but a function decreasing with the temperature increasing. 18 − 20 Taking this into account, the underestimation at temperature lower than 360 K and overestimation at about 490 K as shown in Figure 5 might be improved. However, as shown in the inset of Figure 5 , the experimental value at about 330 K is more than 10 times larger than that of the calculation with eq 8 .…”

“…[1][2][3][4][5]18 Chem- isorption may increase with increased temperature, while physisorption decreases with increased temperature. H 2 O molecules are less likely to be absorbed when they are in the gas phase than in the liquid phase, 19,20 and this decrease in physisorption greatly reduces effective amount of reactants and thus bottlenecks the reaction rate. Using the vapor pressure as a function of temperatures 21 and estimating the reaction chamber pressure as a function of temperature, we obtain a critical temperature T v at which water has a phase transition.…”

“…The adsorbed CO 2 and H 2 O molecules on the CoO surfaces are the sources of carbons and hydrogen in the process of artificial photosynthesis, respectively. − CO 2 molecules are mainly chemisorbed on the CoO surfaces, and H 2 O molecules are mainly physisorbed on the CoO surfaces. − , Chemisorption may increase with increased temperature, while physisorption decreases with increased temperature. H 2 O molecules are less likely to be absorbed when they are in the gas phase than in the liquid phase, , and this decrease in physisorption greatly reduces effective amount of reactants and thus bottlenecks the reaction rate. Using the vapor pressure as a function of temperatures and estimating the reaction chamber pressure as a function of temperature, we obtain a critical temperature T v at which water has a phase transition.…”

“…The adsorbed CO 2 remained in the form of chemisorption, and its concentration is not very sensitive to the temperature, while H 2 O concentration is very sensitive to the temperature, considering the vapor pressure effect because of the physisorption . In the temperature range from 273 to 500 K, [(CO)*] is simply considered as a constant, while [( H 2 )*] abruptly decreases above T v due to evaporation; − we may express [( H 2 )*] with d is the portion of [( H 2 )*] comparing to temperature lower than T v , b describes the temperature range in which water evaporates. Eq indicates that when temperature is lower than T v , [( H 2 )*] is a constant and is a different constant if the temperature is higher than T v , as shown in Figure .…”