Search results
Results from the WOW.Com Content Network
Thus, the use of alternative probe molecules can often result in different obtained numerical values for surface area, rendering comparison problematic. The model also ignores adsorbate–adsorbate interactions. Experimentally, there is clear evidence for adsorbate–adsorbate interactions in heat of adsorption data.
Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbent surface. Examples include macroscopic phenomena that can be very obvious, like corrosion [clarification needed], and subtler effects associated with heterogeneous catalysis, where the catalyst and reactants are in different pha
gas molecules only interact with adjacent layers; and; the Langmuir theory can be applied to each layer. the enthalpy of adsorption for the first layer is constant and greater than the second (and higher). the enthalpy of adsorption for the second (and higher) layers is the same as the enthalpy of liquefaction. The resulting BET equation is
The Langmuir isotherm is nonetheless the first choice for most models of adsorption and has many applications in surface kinetics (usually called Langmuir–Hinshelwood kinetics) and thermodynamics. Langmuir suggested that adsorption takes place through this mechanism: A g + S ⇌ A S {\displaystyle A_{\text{g}}+S\rightleftharpoons AS} , where ...
Vapor-solid reactions: formation of an inactive surface layer and/or formation of a volatile compound that exits the reactor. [22] This results in a loss of surface area and/or catalyst material. Solid-state transformation : solid-state diffusion of catalyst support atoms to the surface followed by a reaction that forms an inactive phase.
Adsorption is the adhesion of ions or molecules onto the surface of another phase. [1] Adsorption may occur via physisorption and chemisorption. Ions and molecules can adsorb to many types of surfaces including polymer surfaces.
The active layers tend to be extremely thin and relatively nonporous. The chemistry of these layers often imparts selectivity. Meanwhile the support layers tend to need to be both extremely porous and robust to higher pressures. [7] Other materials, usually zeolites, are also used in the manufacture of TFC membranes.
The result is the same as in the locally attract strategy, the difference being in the way this is achieved. The major techniques that use this strategy are: [33] Scanning tunneling microscope; The scanning tunneling microscope can remove SAM molecules in many different ways. The first is to remove them mechanically by dragging the tip across ...