The structure and properties of activated carbon, activated carbon structure is more complex, not only is not like graphite, diamond like carbon atoms arranged according to a certain pattern, and not like carbon containing materials that contain organic complex and diverse, molecular structure is large. It has a unique structure. It consists of their nodes arranged the carbon atom layer composed of hexagonal plane, but the plane is not completely along the vertical axis are common but a layer and a layer of angular displacement messy and irregular, this structure is called "whorl like structure". In the process of activation, a variety of carbon containing compounds and disordered carbon that created the gap clearance between basic ceramics the remaining carbon accumulation. Quite loose, but mutual connection is very strong. So the ceramics that many different shapes, sizes and voids of a certain strength, according to the pore size is generally divided into big hole, hole and a small hole in the physical properties of.1972 International Union of fine former Soviet Union scholar Du Binning according to the classification of three activated carbon a gap in the specific provisions. 90% of the surface area of activated carbon in the pores, so the pores is an important factor to determine the adsorption performance of activated carbon pore. The pore diameter of the provisions of the classification association (nm) microporous <2 0= "" 2= "" 0= "" 50= "" >50 In the process, adsorption of activated carbon, the three kinds of pores which have special functions. The adsorption, pore is the most important, its surface area up to hundreds or even thousands of square meters of /g, pore volume is relatively large. The microporous determines the adsorption capacity of activated carbon to a great extent. The pore structure of adsorption the characteristics of activated carbon depends not only on it, but also depend on its chemical composition. Because the basic crystallite in the activation, a part of being burned, not by the whole interference graphite layer changes the electronic cloud of carbon skeleton arrangement, there is not fully saturated valence or paired electrons directly affecting the adsorption characteristics of activated carbon another effect of activated carbon adsorption is. In the structure of the heteroatom heteroatom. Activated carbon has two sources: one is the chemical combination of elements, such as oxygen and hydrogen, these elements are derived from raw materials, combined with carbon on the surface can not be finished. When carbonization in active carbon, in combination with other elements of N, CL so, the combination of these atoms on activated carbon decomposing legacy, while others are activated, and the activation agent for chemical reaction and on the surface. The other is the main source of ash, ash in activated carbon raw materials, there are a few into the production process. The crystal structure of ash activity carbon defects, oxygen chemisorption on these defects, In order to improve the adsorption effect of active carbon on polar molecules. The existence of ash on gas adsorption (such as sulfur dioxide, water vapor, acetic acid, etc.) has a direct impact. Some inorganic compounds added in active carbon (such as AlCl3, NaOH, CuO etc.) can make the modification of activated carbon, adsorption can occur in some obvious changes. Adsorption of certain substances can produce strange effect. The presence of oxygen and hydrogen adsorption performance of activated carbon affects them by chemical bond and carbon atoms, is an organic part of activated carbon structure. They are an important group of excellent activated carbon. According to solid surface multiphase theory. Oxygen, hydrogen and other With the heteroatom on the edge and angle of crystallite carbon atoms on the carbon atoms, because this is not fully saturated, high reactivity. In all elements combined, more oxygen attention than other elements. Because there is a major effect of oxygen on the activated carbon crystallite size. This arrangement and surface bound oxygen the water vapor and other polar or polarizable gas adsorption capacity of.C has significant effect on o surface compounds are diverse. For example: C - O surface complexes, surface oxide, surface oxidation and chemical adsorption oxygen compounds. These compounds are divided into two categories: one is at a temperature below 100 DEG C, and the gaseous oxygen the surface of the activated carbon. The reaction of oxygen complexes by hydration generated hydroxyl and other alkaline medium, the alkaline medium can play a role in ion exchange; when heated to 1000 DEG C, generating gaseous oxide, removal from the surface of activated carbon. The other is in the range of 300 ~ 500 DEG C, oxygen contact with activated carbon to generate acidic oxides after, hydration can generate acidic surface compounds, with ion exchange capacity. By the combination of surface oxygen functional groups are: hydroxyl, carboxyl, phenol, quinone. Fat, but only part of oxygen binding in these groups, the rest is based on the adsorption properties of the ether chain also has the obvious to sum up effect: In the activated carbon, due to the strong cross-linking between crystallites formed a well-developed porous structure, through the activation of the microporous expand the formation of many different sizes of pores, a part of the surface is burnt, structure is not complete, with ash and hetero atoms exist, the basic structure of activated carbon and unsaturated defects price, oxygen and other atoms adsorbed to these defects, the adsorption characteristics of activated carbon produced all kinds. It generates gaseous oxide, removal from the surface of activated carbon. The other is in the range of 300 ~ 500 DEG C, oxygen contact with activated carbon by acidic oxide, hydration can generate surface acidity compound, There are ion exchange capacity. By the combination of surface oxygen functional groups are: hydroxyl, carboxyl, phenol, quinone. Fat, but only part of oxygen binding in these groups, the rest is combined with the carbon surface with ether chain. In active carbon, in combination with other elements of N, CL so, the combination of these atomic adsorption properties of activated carbon also has obvious effect. Conclusion: in the activated carbon, due to the strong cross-linking between crystallites formed a well-developed porous structure, through the activation of the microporous expand the formation of many different sizes of pores, a part of the surface is burnt, structure is not complete plus, ash and heteroatoms exist The basic structure of activated carbon is defective and unsaturated, and oxygen and other hetero atoms are absorbed on these defects, so that activated carbon has a variety of adsorption characteristics.
Activated carbon adsorption and filtration mechanism of substance called adsorption on solid surfaces or micropore volume accumulated in the phenomenon. The mixture by certain equipment, some material was removed. The phenomenon is called filtering of indoor air, after activated carbon, some harmful substances are removed, the active carbon filtration effect; and some harmful material, active carbon adsorption.
For the physical adsorption and chemical adsorption adsorption process. A simple physical adsorption on the intermolecular pull of adsorbate adsorbed on the adsorbent surface. The physical adsorption is reversible, reduce the gas phase pressure to improve the quality of absorption, adsorption temperature, adsorption desorption quickly, without changing its chemical composition with selective chemical adsorption. Very high, a kind of adsorbent to specific physical adsorption. The chemical adsorption is irreversible, adsorption after the adsorbate has changed, changed the original characteristics. The physical adsorption process can be divided into the following steps: (a) pollution gas by adsorption of the boundary layer, the adsorbed molecular gas pollution may also be Can be taken away from the surface of activated carbon, the gas concentration difference depending on the components in the carrier gas and the boundary layer in the inside, this value determines the strength of adsorption. When air pollution by activated carbon, some harmful gas concentration difference is very big, so absorbed down, and the air concentration difference due to inherent component the basic is zero, so by normal, and some particles (smoke) due to too large, directly left big hole and in the hole. When the concentration of harmful gas difference is zero, the failure of activated carbon, the need to re activation. (b) molecule is adsorbed to the micropore diffusion (c). The molecule was firmly the bound on the adsorbent surface. The above three steps in Chemical reactions are also inevitable. Chemical adsorption, adsorbent and adsorbate combination is relatively strong, must be in high temperature to desorption. Chemical adsorption than physical adsorption driving force is greater, the combination is more solid, so for highly toxic pollutants, with chemical adsorption safer.
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