Carbonaceous materials definition

By definition, benzene is standardized as the reference compound for carbonaceous materials, and thus the value of its affinity coefficient //is 1. The relevant parameters of the D-R isotherm can be found in paragraph 1.4, Appendix I. 

Many nanoproducts either release ENMs into the wastewater stream during use (collected and treated) or release the bulk of the ENMs only during end-of-life-treatment. In this indirect release, ENMs are potentially removed in the effluent or discharge from treatment (waste incineration plant, wastewater treatment). One should, however, keep in mind that only carbonaceous materials can be definitively destroyed in treatment. Metals and metal oxides may be retained but will persist. Measures to prevent the entry of ENMs into the environment for products with indirect ENM release could be taken at the product design and manufacturing stage or at the treatment stage. 

The microscopic image shows a juxtaposition of differently orientated areas whose sizes, varying between a few microns and several tens of microns, are associated particularly with the elementary composition of the initial carbonaceous material (4, 18, 19). The formation of a texture of this type, often called a mosaic structure, can be compared (20) to the crystallization of a supersaturated solution areas, each characterized by a definite orientation, develop from nuclei up to the total consumption of the isotropic material surrounding them. 

There is no precise definition of an active carbon , but it is generally understood to be a carbonaceous material of appreciable specific surface area. If it is to be an effective adsorbent, an active carbon must have a surface area of at least 5 m2 g1. Active carbons used as industrial adsorbents have much larger BET-areas, which may extend well above 2000 m2 g1. In accordance with this broad definition, an active carbon may be porous or non-porous. The term activated carbon has a more specific connotation, however, since it is reserved for a highly porous carbon produced from a carbon-rich material by some form of chemical or physical activation. 

Oxidation of SO2 in droplets, which contain various products, detectable in the atmosphere, is the measurement accepted as being real as it approaches atmospheric conditions. Studies upon the oxidation of SO2 in droplets, which contain soot particles, definitely show the effect of carbonaceous material in performing the conversion to SO"4. This process seems to be of relevant importance in polluted areas. As far as liquid phase oxidation of SO2 is concerned, it seems that the uncatalyzed oxidation of SO2 by ozone or hydrogen peroxide is probably the dominant mechanism in the droplet phase. 

As employed in atmospheric chemistry, the term elemental carbon refers to carbonaceous material that does not volatilize below a certain temperature, usually about 550°C. Thus, this term is an operational definition based on the volatility properties of the material. The term soot is also used to refer to any light-absorbing, combustion-generated carbonaceous material. Perhaps the most widely used term for light-absorbing... 

All natural waters contain some carbonaceous material. Even rainwater has been shown to include about 1 mg C/L (Thurman, 1985). Some of this organic material is in the form of truly dissolved, soluble compounds, whereas other fractions consist of colloidal or particulate organic matter. The definitions of dissolved and particulate carbon that have been more or less established by convention among aquatic scientists are somewhat elastic and arbitrary one criterion that is widely used sets the boundary between the two at 0.45 /tM (the pore size of some common filter media). These demarcations tend to disguise the fact that there is a continuum of organic particles in water that ranges in relative size from molecules to microorganisms. 

Attempts were made to discover the correlation between the crystalline structure of carbonaceous materials and their capability to reversibly intercalate lithium. This correlation has not been definitely established, but still, one can assume as a certain general principle that the optimum materials would contain an amorphous matrix with inclusions of a mesophase nuclei of graphite crystallites. Such materials are various cokes, pyrographite, and products of pyrolysis (carbonization) of various polymers. For practical purposes, the industry mastered some special materials providing high characteristics of negative electrodes in lithium ion batteries. The most popular material is manufactured by the Japanese company of Osaka Gas Co. under the name of mesocarbon microbeads, MCMB it represents the carbonization product of pitchy resins under a certain temperature regime. 

The classic definition of asphaltenes is based on the solution properties of petroleum residuum in various solvents. This generalized concept has been extended to fractions derived from other carbonaceous sources, such as coal and oil shale. With this extension there has been much effort to define asphaltenes in terms of chemical structure and elemental analysis as well as by the carbonaceous source. This effort is summarized by Speight and Moschope-dis (i) in their chapter in this volume along with a good summary of the current thinking. Thus, there are petroleum asphaltenes, coal tar asphaltenes, shale oil asphaltenes, tar sands bitumen asphaltenes, and so on. In this chapter I will attempt to show how these materials are special cases of an overall concept based directly on the physical chemistry of solutions and that the idea that they have a specific chemical composition and molecular weight is incorrect even for different crude oil sources. 

Carbonaceous solids that are inside the triangle in Fig. 2.4 obviously contain mixtures of the three hybridization states. Japanese researchers [33, 34] recently coined the term carbon alloys to designate materials typically made up of carbon atoms in multicomponent systems, where the components undergo physical or chemical interactions with each other. This very broad concept extends to mixtures of different phases (as occurs, for instance, in carbon-carbon composites), and also to materials containing heteroatoms. The interesting point in the present context is that, according to the above definition, carbon atoms with different hybrid orbitals are considered as different components. 

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