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Adsorbate
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a fluid (the ''absorbate'') is dissolved by or permeates a liquid or solid (the ''absorbent''). Adsorption is a '' surface phenomenon'', while absorption involves the whole volume of the material, although adsorption does often precede absorption. The term ''sorption'' encompasses both processes, while ''desorption'' is the reverse of it. Like surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent or metallic) of the constituent atoms of the material are fulfilled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates. The exact nature of the bond ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adsorption Chillers
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a fluid (the ''absorbate'') is dissolved by or permeates a liquid or solid (the ''absorbent''). Adsorption is a '' surface phenomenon'', while absorption involves the whole volume of the material, although adsorption does often precede absorption. The term ''sorption'' encompasses both processes, while ''desorption'' is the reverse of it. Like surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent or metallic) of the constituent atoms of the material are fulfilled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates. The exact nature of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterogeneous Catalysts
In chemistry, heterogeneous catalysis is catalysis where the phase of catalysts differs from that of the reactants or products. The process contrasts with homogeneous catalysis where the reactants, products and catalyst exist in the same phase. Phase distinguishes between not only solid, liquid, and gas components, but also immiscible mixtures (e.g. oil and water), or anywhere an interface is present. Heterogeneous catalysis typically involves solid phase catalysts and gas phase reactants. In this case, there is a cycle of molecular adsorption, reaction, and desorption occurring at the catalyst surface. Thermodynamics, mass transfer, and heat transfer influence the rate (kinetics) of reaction. Heterogeneous catalysis is very important because it enables faster, large-scale production and the selective product formation. Approximately 35% of the world's GDP is influenced by catalysis. The production of 90% of chemicals (by volume) is assisted by solid catalysts. The chemical an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Desorption
Desorption is the physical process where a previously adsorbed substance is released from a surface. This happens when a molecule gains enough energy to overcome the activation barrier of the bounding energy that keeps it in the surface. There are a lot of different types of desorption, depending on the mechanism that separates the adsorbate from the substrate; therefore there is no one equation that describes the process. Note that desorption is the opposite of adsorption, which differs from absorption because it refers to substances being stuck to the surface, as opposed to being absorbed into the bulk. Desorption can occur after a reaction between a catalyst and an adsorbed compound; or during stripping or chromatography which are types of separation processes. Desorption mechanisms Depending on the nature of the adsorbent-to-surface bond, there are a multitude of mechanisms for desorption. The surface bond of a sorbant can be cleaved thermally, through chemical react ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemisorption
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, and subtler effects associated with heterogeneous catalysis, where the catalyst and reactants are in different phases. The strong interaction between the adsorbate and the Substrate (chemistry), substrate Interface (matter), surface creates new types of electronic chemical bond, bonds. In contrast with chemisorption is physisorption, which leaves the chemical species of the adsorbate and surface intact. It is conventionally accepted that the energetic threshold separating the binding energy of "physisorption" from that of "chemisorption" is about 0.5 eV per adsorbed Chemical species, species. Due to specificity, the nature of chemisorption can greatly differ, depending on the chemical identity and the surface structural properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Phenomenon
Surface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid–liquid interfaces, solid–gas interfaces, solid–vacuum interfaces, and liquid–gas interfaces. It includes the fields of ''surface chemistry'' and ''surface physics''. Some related practical applications are classed as surface engineering. The science encompasses concepts such as heterogeneous catalysis, semiconductor device fabrication, fuel cells, self-assembled monolayers, and adhesives. Surface science is closely related to interface and colloid science. Interfacial chemistry and physics are common subjects for both. The methods are different. In addition, interface and colloid science studies macroscopic phenomena that occur in heterogeneous systems due to peculiarities of interfaces. History The field of surface chemistry started with heterogeneous catalysis pioneered by Paul Sabatier on hydrogenation and Fritz Haber on the Haber process. Irving ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Science
Surface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid–liquid interfaces, solid–gas interfaces, solid–vacuum interfaces, and liquid–gas interfaces. It includes the fields of ''surface chemistry'' and '' surface physics''. Some related practical applications are classed as surface engineering. The science encompasses concepts such as heterogeneous catalysis, semiconductor device fabrication, fuel cells, self-assembled monolayers, and adhesives. Surface science is closely related to interface and colloid science. Interfacial chemistry and physics are common subjects for both. The methods are different. In addition, interface and colloid science studies macroscopic phenomena that occur in heterogeneous systems due to peculiarities of interfaces. History The field of surface chemistry started with heterogeneous catalysis pioneered by Paul Sabatier on hydrogenation and Fritz Haber on the Haber process. Irving ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physisorption
Physisorption, also called physical adsorption, is a process in which the electronic structure of the atom or molecule is barely perturbed upon adsorption. Overview The fundamental interacting force of physisorption is Van der Waals force. Even though the interaction energy is very weak (~10–100 meV), physisorption plays an important role in nature. For instance, the van der Waals attraction between surfaces and foot-hairs of geckos (see Synthetic setae) provides the remarkable ability to climb up vertical walls. Van der Waals forces originate from the interactions between induced, permanent or transient electric dipoles. In comparison with chemisorption, in which the electronic structure of bonding atoms or molecules is changed and covalent or ionic bonds form, physisorption does not result in changes to the chemical bonding structure. In practice, the categorisation of a particular adsorption as physisorption or chemisorption depends principally on the binding en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vroman Effect
The Vroman effect, named after Leo Vroman, describes the process of competitive protein adsorption to a surface by blood serum proteins. The highest mobility proteins generally arrive first and are later replaced by less mobile proteins that have a higher affinity for the surface. The order of protein adsorption also depends on the molecular weight of the species adsorbing. Typically, low molecular weight proteins are displaced by high molecular weight protein while the opposite, high molecular weight being displaced by low molecular weight, does not occur. A typical example of this occurs when fibrinogen displaces earlier adsorbed proteins on a biopolymer surface and is later replaced by high molecular weight kininogen. The process is delayed in narrow spaces and on hydrophobic surfaces, fibrinogen is usually not displaced. Under stagnant conditions initial protein deposition takes place in the sequence: albumin; globulin; fibrinogen; fibronectin; factor XII, and HMWK. Molecular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absorption (chemistry)
In chemistry, absorption is a physical or chemical phenomenon or a process in which atoms, molecules or ions enter some bulk phase – liquid or solid material. This is a different process from adsorption, since molecules undergoing absorption are taken up by the volume, not by the surface (as in the case for adsorption). A more common definition is that "Absorption is a chemical or physical phenomenon in which the molecules, atoms and ions of the substance getting absorbed enters into the bulk phase (gas, liquid or solid) of the material in which it is taken up." A more general term is ''sorption'', which covers absorption, adsorption, and ion exchange. Absorption is a condition in which something takes in another substance. In many processes important in technology, the chemical absorption is used in place of the physical process, e.g., absorption of carbon dioxide by sodium hydroxide – such acid-base processes do not follow the Nernst partition law (see: solubility). For ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metallic Bond
Metallic bonding is a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons (in the form of an electron cloud of delocalized electrons) and positively charged metal ions. It may be described as the sharing of ''free'' electrons among a structure of positively charged ions ( cations). Metallic bonding accounts for many physical properties of metals, such as strength, ductility, thermal and electrical resistivity and conductivity, opacity, and luster. Metallic bonding is not the only type of chemical bonding a metal can exhibit, even as a pure substance. For example, elemental gallium consists of covalently-bound pairs of atoms in both liquid and solid-state—these pairs form a crystal structure with metallic bonding between them. Another example of a metal–metal covalent bond is the mercurous ion (). History As chemistry developed into a science, it became clear that metals formed the majority of the periodic ta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of Colloid And Interface Science
The ''Journal of Colloid and Interface Science'' is a peer-reviewed scientific journal published by Elsevier. It covers research related to colloid and interface science with a particular focus on colloidal materials and nanomaterials; surfactants and soft matter; adsorption, catalysis and electrochemistry; interfacial processes, capillarity and wetting; biomaterials and nanomedicine; and novel phenomena and techniques. The editor-in-chief is Martin Malmsten (Uppsala University). The journal was established in 1946 as ''Journal of Colloid Science''. It obtained its current name in 1966. Abstracting and indexing The journal is abstracted and indexed in: According to the ''Journal Citation Reports'', the journal has a 2021 Impact Factor of 9.965, ranking it 32nd out of 162 journals in the category "Chemistry, Physical". See also * '' Colloids and Surfaces A: Physicochemical and Engineering Aspects'' * '' Colloids and Surfaces B: Biointerfaces'' * ''Advances in Colloid and Inter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Van Der Waals Force
In molecular physics, the van der Waals force is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The van der Waals force quickly vanishes at longer distances between interacting molecules. Named after Dutch physicist Johannes Diderik van der Waals, the van der Waals force plays a fundamental role in fields as diverse as supramolecular chemistry, structural biology, polymer science, nanotechnology, surface science, and condensed matter physics. It also underlies many properties of organic compounds and molecular solids, including their solubility in polar and non-polar media. If no other force is present, the distance between atoms at which the force becomes repulsive rather than attractive as the atoms approach one another is called the van der Waals contact distance; this phenomenon resul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
