Activated adsorption chemical

The other case is that of slow adsorption of the substance, with fast chemical reaction at the surface. Such process is known as chemical adsorption or chemisorption. Here adsorbed molecules are glued to the surface by chemical forces of the same type as the forces of valence bonds. In order for these forces to reveal themselves, a molecule should come into a deformed state and overcome the activation barrier. Therefore the process of chemical adsorption requires a certain activation energy. Sometimes chemical adsorption is called activated adsorption. Chemical adsorption is closely related to the process of heterogeneous catalysis. The reaction rate of chemical adsorption is given by the expression ... 

On his return to Princeton after the war, Hugh Taylor organized catalytic research at the Frick Chemical Laboratory. He applied high vacuum technique, liquid air cryoscopy to the study of adsorptive characteristics of catalysts, correlating rates of catalytic reactions and rates of adsorption. He introduced the concept of activated adsorption and defended it against all comers. ... 

Steam stripping Air stripping Biological nitrification Chemical oxidation Ion exchange Solvent extraction Biological oxidation (aerobic) Wet oxidation Activated carbon Chemical oxidation Chemical precipitation Ion exchange Adsorption Nano-filtration Reverse osmosis Electrodialysis... 

In the pharmaceutical industry, surface area is becoming more important in the characterization of materials during development, formulation, and manufacturing. The surface area of a solid material provides information about the void spaces on the surfaces of individual particles or aggregates of particles [5], This becomes important because factors such as chemical activity, adsorption, dissolution, and bioavailability of the drug may depend on the surface on the solid [3,5]. Handling properties of materials, such as flowability of a powder, can also be related to particle size and surface area [4],... 

In surface-complexation models, the relationship between the proton and metal/surface-site complexes is explicitly defined in the formulation of the proposed (but hypothetical) microscopic subreactions. In contrast, in macroscopic models, the relationship between solute adsorption and the overall proton activity is chemically less direct there is no information given about the source of the proton other than a generic relationship between adsorption and changes in proton activity. The macroscopic solute adsorption/pH relationships correspond to the net proton release or consumption from all chemical interactions involved in proton tranfer. Since it is not possible to account for all of these contributions directly for many heterogeneous systems of interest, the objective of the macroscopic models is to establish and calibrate overall partitioning coefficients with respect to observed system variables. 

There are six primary in-plant control methods for removal of priority pollutants and pesticides in pesticide manufacturing plants. These methods include steam-stripping, activated carbon adsorption, chemical oxidation, resin adsorption, hydrolysis, and heavy metals separation. Steam-stripping can remove volatile organic compounds (VOCs) activated carbon can remove semi volatile organic compounds and many pesticides and resin adsorption, chemical oxidation, and hydrolysis can treat selected pesticides [7]. Heavy metals separation can reduce toxicity to downstream biological treatment systems. Discussion of each of these methods follows. 

The adsorption and reaction of methanol on metal surfaces has been widely studied (18-34). Methanol has C-0, C-H, and 0-H bonds, serving as one of the simplest systems for the selective activation of chemical bonds. The methoxyl (CH30(a)) species has been considered as an intermediate of the methanol decomposition. On many transition metal surfaces, adsorbed methanol molecules are usually decomposed to H2 and CO, although Ag and Cu are used as catalysts for the conversion of methanol to formaldehyde. The adsorption and reaction of alcohol molecules on Mo surfaces has been studied on the (100) (4) and (110) (35) surfaces. Alcohol molecules are decomposed effectively also on these surfaces. 

Activators are chemicals that permit or reinforce the adsorption of collectors onto particles, usually by complexing with the collector, or bridging between the collector and the solid. For example, sphalerite (ZnS) can only be floated using ethyl xanthate as a collector if the particles are first treated with copper sulfate. The copper species adsorbs first and acts as a bridge to the xanthate, allowing it to function as a collector for the sphalerite. 

Deposition occurs by adsorption or reaction from a gas phase. This method may ensure excellent dispersion and very well controlled distribution of the active species. Chemical vapour deposition is an example of gas-phase deposition. 

The highly catalytic oxides are unstable chemically and decompose readily into free oxygen and a lower oxide of the metal. They can be readily reduced by CO. The reaction must, therefore, involve two steps the first, a process of bond formation between CO and the catalyst, followed by a splitting off of C02. In the second step, activated adsorption of oxygen on the unsaturated manganese atoms would regenerate the catalyst. Any proposed mechanism for the reaction must also explain the poisoning effects of water vapor and of adsorbed alkali. 

The chemical potential Pk of tho free (unoccupied) active adsorption centers K on the surface can be defined in a similar way ... 

Activation is the process of enhancing a particular characteristic. Carbon whose adsorption characteristic is enhanced is called activated carbon. The activation techniques used in the manufacture of activated carbons are dependent on the nature and type of raw material available. The activation techniqnes that are principally used by commercial production operations are chemical activation and steam activation. As the name snggests, chemical activation nses chemicals in the process and... 

The term activated adsorption is, as originally designated by H. S. Taylor, a type of adsorption that takes place at a measurably slow rate, associated with a certain temperature coefficient. For the same type of adsorption, the term chemisorption has been used more frequently, in later years. We shall use here the term chemisorption when the heat of adsorption is comparable with the heat evolved in ordinary chemical reactions. 

Since chemical and field enhancement are sensitive to a number of variables, including substrate material, particle size and shape, laser wavelength, and the nature of the adsorbate-substrate interaction (including those requiring active adsorption sites), there is wide latitude in how a given substrate may be designed and optimized. Conversely, the observed enhancement can vary by orders of magnitude if the important substrate variables are not adequately controlled. Examples of SERS substrates that have been proposed for chemical analysis... 

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