Sorption properties

Other processes of structural modification of cellulose, e.g., mercerization, treatment with amines or liquid ammonia, and regeneration from solutions, lead to a decrease in crystallinity, length, and lateral size of crystallites these treatments cause transformation of the initial cellulose structure into another structure in which small crystallites are surrounded by non-crystalline matrix [Fig. 7.28]. 

Finally, it may be concluded that natural cellulose has a complicated multilevel structural organization. The linear cellulose macro molecules joined by hydrogen bonds form the crystallites, noncrystalline domains, and elementary nanofibrils. The elementary nanofibrils are aggregated into bundles called microfibrils, which form lamellas and layers of the cell wall of natural cellulose fibers. At last, the fibers are constituents of various cellulosic materials papers, paperboards, cardboards, textiles, nonwoven materials, etc. 

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A rationalization of the complex behavior of pectins in solutions and gels with respect to their stmcture, solvation, and the presence of ions and other saccharides has been presented (123). The solution and sorption properties of gum tragacanth and the pectin isolated from the roots of Hibiscus mani/)ot F (Tororoaoi) contributes to their use in specialty paper manufacture (124—126). 

The purpose of these work are consist in comparative research of sorption properties unmodified aerosile A-300 and its modified analogue - K-7-30 for selective evolving of microquantities of Al (111), Ga (111), In (111) at consistent presence, as well as Mo (VI) and W (VI). 

The results of sorptional properties investigation have shown the possibility of SN-SiO, application for Pb +, ClC+, Zn +, Cd + selective preconcentration. The preconcentrated Cu, Pb, Cd, Zn ions at pH 6-7 were eluted by acid and determined by atomic-absoi ption method. 

Petropoulos, J. H. Membranes with Non-Homogeneous Sorption Properties. Vol. 64, pp. 85-134. Pino, P. Optically Active Addition Polymers. Vol, 4, pp. 393-456. 

Note The amino acid residues of lysine (K) and arginine (R) which may be responsible for the binding of POs to polysaccharides are in bold. According to Demand et al. (2002), the mutual substitution of these amino acids has no influence on the sorption properties of the ATg08770 PO of Arabidopsis with pectins, and the deletion of the fragment results in the loss of this function. 

Precoated layers sorbents with wide range of sorption properties for selectivity optimisation (HPTLC)... 

The main characteristic features of HPTLC (use of fine particle layers for fast separations, sorbents with a wide range of sorption properties, high degree of automation for sample application, development and detection) are the exact opposite of conventional TLC. Expectations in terms of performance, ease of use and quantitative information from the two approaches to TLC are truly opposite [419], Modern TLC faces an uncertain future while conventional TLC is likely to survive as a general laboratory tool. 

Factors that affect the accessibility of chemicals to plant roots include hydrophobicity, polarity, sorption properties and solubility. In order to apply phytoremediation techniques to soils polluted by organic contaminants, the contaminant must come into contact with the plant roots and be dissolved... 

Even if 5A zeolite is widely used in iso-paraffin separation from an n/iso paraffin mixture, the adsorbent is affected by a slow deactivation mainly due to coke formation inside the molecular sieve porosity. Its aging phenomenon decreases its sorption properties. According to previous studies, 5A zeolite deactivation results essentially from heavy carbonaceous compound formation in a-cages blocking the 5A zeolite microporosity [1-2]. 

Means, J.C., Hassett, J.J., Wood, S.G., Banwart, W.L. (1979) Sorption properties of energy-related pollutants and sediments. In Polynuclear Aromatic Hydrocarbons. P.W. Jones and P. Leber Editors, pp. 329-340, Ann Arbor Science Publishers, Ann Arbor, Michigan. 

Polymers are among the most widely used materials for chemical sensing since they are able to collect and concentrate molecules on sensor surfaces by reversible sorption they can be deposited on several substrates as thin adherent films with easy processing techniques they are available in many kinds having different chemical and sorption properties, which can be used to enhance the selectivity of the sensors last but not least, they are of low cost. 

N2 injection rapidly increases the methane production rate. The timing and magnitude depends on the distance between injection and production wells, on the natural fracture porosity and permeability, and on the sorption properties. N2 breakthrough at the production well occurs at about half the time required to reach the maximum methane production rate in this ideal case. The N2 content of the produced gas continues to increase until it becomes excessive, i.e., 50% or greater. 

The preparation methods of aluminum-deficient zeolites are reviewed. These methods are divided in three categories (a) thermal or hydrothermal dealumination (b) chemical dea-lumination and (c) combination of thermal and chemical dealumination. The preparation of aluminum-deficient Y and mordenite zeolites is discussed. The structure and physico-chemical characteristics of aluminum-deficient zeolites are reviewed. Results obtained with some of the more modern methods of investigation are presented. The structure, stability, sorption properties, infrared spectra, acid strength distribution and catalytic properties of these zeolites are discussed. 

Sorption. Lohse et al. (36,47,48) have studied the sorption properties of acid-dealuminated Y zeolites that contain about 99% SiC, and compared them with those of the... 

Beyer and Belenykaia (27) have investigated the sorption properties of DAY zeolites prepared from Y zeolite and SiCl vapors. They reported a very low adsorption capacity for water and ammonia, similar to that of the almost aluminum-free silicalite (49). The low adsorption capacity for water is indicative of a hydrophobic zeolite surface. The adsorption isotherms for n-butane, benzene and n-hexane obtained on the aluminum-deficient zeolite have a shape similar to those obtained on NaY zeolite and are characteristic for micropore structures. They show the absence of secondary pores in this DAY zeolite. 

Structural characteristics. Both natural and synthetic mordenite have an orthorhombic structure that consists of parallel, 12-membered ring channels in the c-direction, having an eliptical cross-section with dimensions of 6,7 x 7.0 A (Figure 9). Smaller 8-membered ring channels with dimensions of 2.9 x 5.7 A, which are perpendicular to the main channels, are too small to allow the movement of molecules from one main channel to another. Mordenite has been synthesized in a "large -port" and "small-port" form that have different sorption properties. A typical unit cell content is Na0[(A10o)o(Si0o)/rJ. 24 HO. 8 28 2 40... 

Sorption. The sorption properties of aluminum-deficient mordenite are strongly affected by the dealumination procedure used and by the degree of dealumination. Materials prepared by procedures that do not involve high temperature treatments show a relatively high sorption capacity for water (15,70), due to the presence of silanol groups, which are hydrophilic centers. However, aluminum-deficient mordenite zeolites prepared by methods requiring heat treatment show a lower sorption capacity for water due to fewer silanol groups. This was shown by Chen (71), who studied the sorption properties of aluminum-deficient mordenite prepared by the two-step method. 

Dispersion of POMs onto inert solid supports with high surface areas is very important for catalytic application because the surface areas of unsupported POMs are usually very low (—10 m2g). Another advantage of dispersion of POMs onto inert supports is improvement of the stability. Therefore, immobilization of POMs on a number of supports has been extensively studied. Silica and active carbon are the representative supports [25], Basic supports such as MgO tend to decompose POMs [101-104], Certain kinds of active carbons firmly entrap POMs [105,106], The maximum loading level of POMs on active carbons is 14 wt% [107], Dispersion of POMs onto other supports such as zeolites, mesoporous molecular sieves, and apatites, is of considerable interest because of their high surface areas, unique pore systems, and possibility to modify their compositions, morphologies, and sorption properties. However, a simple impregnation of POM compounds on inert supports often results in leaching of POMs. 

Many models have been developed that deal with the sorption properties of wood in the presence of moisture these have been discussed in a number of works (e.g. Skaar, 1972 Siau, 1984). They can be approximately divided into sorption models, such as the Brunauer-Emmett-Teller (BET) model, or solution models (such as the Hailwood-Horrobin, H-H, model). The sigmoidal shapes of sorption or desorption isotherms can be deconvoluted into two components. These are often taken to represent a monomolecular water layer (associated with the primary sorption sites, OH groups), and a multilayer component where the cell wall bound water molecules are less intimately associated with the fixed cell wall OH groups. 

Popper and Bariska (1972) studied the moisture sorption properties of wood chemically modified with acetic (or phthalic) anhydride and analysed the results using Brunauer-Emmett-Teller (BET) theory and the H-H model. Acetylation was found to reduce the number of sorption sites, whereas little effect was noted with phthaloylation. By dividing the sorption isotherm into a monolayer component and a multilayer component using the H-H model, it was shown that there was a large reduction in the... 

Martins and Banks (1991) modified pine and wood samples with phenyl or butyl isocyanate and investigated the water vapour sorption properties of the modified wood. Modification resulted in a reduction in EMC at a given RH up to about 35 % WPG with butyl isocyanate, although reaction with phenyl isocyanate above 25 % WPG resulted in an increase in sorption due to cell wall damage caused by the reaction. The butyl derivative was more effective at reducing hygroscopicity over all the WPGs studied. 

Clemons, C., Young, R.A. and Rowell, R.M. (1992). Moisture sorption properties of composite boards from esterified aspen fiber. Wood and Fiber Science, 24(3), 353-363. 

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