Surface area pore size dependence

Effectiveness of selective adsorption of phenanthrene in Triton X-100 solution depends on surface area, pore size distribution, and surface chemical properties of adsorbents. Since the micellar structure is not rigid, the monomer enters the pores and is adsorbed on the internal surfaces. The size of a monomer of Triton X-100 (27 A) is larger than phenanthrene (11.8 A) [4]. Therefore, only phenanthrene enters micropores with width between 11.8 A and 27 A. Table 1 shows that the area only for phenanthrene adsorption is the highest for 20 40 mesh. From XPS results, the carbon content on the surfaces was increased with decreasing particle size. Thus, 20 40 mesh activated carbon is more beneficial for selective adsorption of phenanthrene compared to Triton X-100. 

No experimental method provides the absolute value of parameters such as porosity, surface area, pore size, etc. each gives a characteristic value which depends on the principles involved and the probe used. 

Alumina and amorphous silica-alumina are usually mesoporous materials with a wide distribution of pore sizes. The surface area, pore size and pore volume of alumina and amorphous silica-alumina depend greatly on the preparation method, hence their textural properties can be controlled to a certain extent by changing the synthesis conditions. These parameters are also highly relevant in determining the catalytic properties of these materials. 

An activated carbon in contact with a metal salt solution is a two-phase system consisting of a solid phase, which is the activated carbon surface, and a liquid phase which is the salt solution. The solution contains varying amounts of different metal ion species and their complexes so that the interface between the two phases will behave as an electrical double layer and determine the adsorption processes taking place in the system. The adsorptive removal capacity of an activated carbon for metal cations from the aqueous solutions generally depends on the physicochemical characteristics of the carbon surface, which include the surface area, pore-size distribution, electrokinetic properties, and the chemical structure of the carbon surface, as well as on the nature of the metal ions in the solution. 

It is apparent from the perusal of the literature that the investigations concerning the adsorptive removal of different pesticides from water have generally been directed toward determining the efficiencies of powdered and granulated activated carbons for their removal. None of the studies have discussed the effect of such parameters as the surface area, pore-size distribution, or the chemistry of the carbon surface on the adsorption and its mechanism. Only in one paper Prakash indicated that the adsorption of diquat and paraquat depended on the surface area of the carbon. Thus, there is need to study the influence of these parameters on the adsorption of pesticides. 

The adsorptive properties of an adsorbent depends mainly on the pore structure (surface area, pore size and pore volume) and surface chemical properties of the adsorbent. The sol-gel derived ceramic adsorbents possess unique pore structure defined by the microstructure of the sol-gel derived materials. This section describes the synthesis and microstructure of several crystalline and amorphous adsorbents prepared by the sol-gel method in our laboratory. 

The yield of products from catalytic pyrolysis depends on catalyst type and catalyst to feed ratios besides pyrolysis temperature and residence time (Ojha and Vinu, 2015). Different types of catalysts have different properties such as surface acidity, specific surface area, pore size, and pore size distributions which also determine the yield and selectivity of various products. The range of different functionalities of the catalysts should be matched to the various pyrolysis feedstocks as each feedstock may have a preferred pyrolysis catalyst. Therefore research has been precise in developing particular catalysts for specific raw material (depending on pyrolysis reactor). The section below describes the properties and effect specific catalysts have on pyrolysis vapor upgrading. 

All packing materials produced at PSS are tested for all relevant properties. This includes physical tests (e.g., pressure stability, temperature stability, permeability, particle size distribution, porosity) as well as chromatographic tests using packed columns (plate count, resolution, peak symmetry, calibration curves). PSS uses inverse SEC methodology (26,27) to determine chromatographic-active sorbent properties such as surface area, pore volume, average pore size, and pore size distribution. Table 9.10 shows details on inverse SEC tests on PSS SDV sorbent as an example. Pig. 9.10 shows the dependence... 

The characterization of colloids depends on the purposes for which the information is sought, because the total description would be an enormous task. Among the properties to be considered are the nature and/or distributions of purity, crystallinity, defects, size, shape, surface area, pores, adsorbed surface films, internal and surface stresses, stability, and state of agglomeration [57,58],... 

The parameters of the pore structure, such as surface area, pore volume, and mean pore diameter, can generally be used for a formal description of the porous systems, irrespective of their chemical composition and their origin, and for a more detailed study of the pore formation mechanism, the geometric aspects of pore structure are important. This picture, however, oversimplifies the situation because it provides a pore uniformity that is far from reality. Thorough attempts have been made to achieve the mathematical description of porous matter. Researchers discussed the cause of porosity in various materials and concluded that there are two main types of material based on pore structure that can be classified as corpuscular and spongy systems. In the case of the silica matrices obtained with TEOS and other precursors, the porous structure seems to be of the corpuscular type, in which the pores consist of the interstices between discrete particles of the solid material. In such a system, the pore structure depends on the pores mutual arrangements, and the dimensions of the pores are controlled by the size of the interparticle volumes (1). 

Interfacial processes take place on the surface of solid (rock or soil), so the specific surface area (area per mass) is one of the most important parameters. The specific surface area depends on the particle size or the particle size distribution, and the roughness of the surface. These factors determine the external specific surface area. In addition, rocks and soils contain a network of pores with different sizes and shapes. Some of them are in a direct connection with the external surface (open pores). Therefore, depending on the relative sizes of the pores and the particles of the substance, the different substances of the surroundings can enter the pores. Two especially important types of pores are... 

Adsorbent surface area, pore volume, and pore diameter are the properties of significant importance. HPLC retention is generally proportional to the surface area accessible for a given analyte (Chapter 2). Surface area accessibility is dependent on the analyte molecular size, adsorbent pore diameter, and pore size distribution. 

The binding capacity and the site availability of MIPs depend on parameters such as surface area, pore diameter and pore size distribution. These parameters are therefore often determined, by gas sorption or mercury penetration, when MIPs are characterized. 

The surface area, pore volume, and pore size of the deposited film depend on such factors as the size and structure (fractal dimension) of the entrained inorganic species, the relative rates of condensation and evaporation during deposition, and the magnitude of the capillary pressure (122). The fractal dimension influences porosity through steric control. Mandelbrot (47) showed that if two objects of radius R are placed independently in the same region of space, the number of intersections (Mi,2) is expressed as... 

Molecular sieves arc aluminum silicate ion exchangers, whose pore size depends on the kind of cation present. Commercial preparations of these materials arc available in particle sizes of 40 to 60 mesh to 00 to 120 mesh. The sieves are classified according to the maximum diameter of molecules that can enter the pores. Commercial molecular sieves come in pore sizes of 4, 5, 10, and 1,1 A, Molecules smaller than Ihese dimensions penetrate into the interior of the panicles where adsorption takes place. For such molecules, the surface area is enormous when compared with the area available to larger molecules. Thus, molecular sieves can be used to separate small molecules from large. For... 

The size of water droplets dispersed in the starting organic monomer liquid and the stability of the emulsion depend on the water-to-AOT molar ratio IV. The smallest droplets and the most stable emulsion are formed when IV=1. This ratio may change from 1 to 18, but, beyond this value, the initial system becomes unstable and macro phase separation takes place. In principle, IV determines the surface area, pore volume, and pore size... 

In certain papers (Aroutiounian and Ghulinyan, 2000 Aroutiounian et al., 2000), a fractal model of a porous layer formation was proposed.The consideration of the time-dependent pore growth process has allowed us to calculate important parameters of the porous matrix, such as the formed surface area, and the surface and volume porosity values. We have theoretically shown that the formed surface area is strongly dependent on the difference between the pore size growth velocities parallel and perpendicular to the surface (i.e. the crystallographic orientation of the silicon surface). The volume and surface porosity values and the formed porous surface area are linear functions of the density of the anodization current. These results are in agreement with other theoretical and experimental data. 

---