Cation-exchange capacity CEC

FIG. 4 Experimental (vertical bars) and simulated (symbols) values of the d-spacings for aUcy-lammonium-exchanged clay at three different cation exchange capacities (CECs) (a) SWy2 mont-morillonite, CEC = 0.8 meq/g (b) AMS montmorillonite (Nanocor), CEC = 1.0 meq/g (c) fluoro-hectorite (Dow-Corning), CEC = 1.5 meq/g. (Erom Ref. 30.)... 

The clay ion-exchange model assumes that the interactions of the various cations in any one clay type can be generalized and that the amount of exchange will be determined by the empirically determined cation-exchange capacity (CEC) of the clays in the injection zone. The aqueous-phase activity coefficients of the cations can be determined from a distribution-of-species code. The clay-phase activity coefficients are derived by assuming that the clay phase behaves as a regular solution and by applying conventional solution theory to the experimental equilibrium data in the literature.1 2 3... 

Some properties of the rock used in this study were measured The cation exchange capacity (cec) was determined by the barium sulfate method as described by Mortland and Mellor (33). Surface area was measured by using a Digisorb Meter (Micromeritics Instrument Corporation) through nitrogen adsorption. Estimation of mineral composition and indentification of the rock were performed by X-ray diffraction. 

In characterizing layered silicate, including layered titanate (HTO), the surface charge density is particularly important because it determines the interlayer structure of the intercalants as well as the cation exchange capacity (CEC). Lagaly proposed a method of calculation consisting of total elemental analysis and the dimensions of the unit cell [15] ... 

Soils were further characterized by the determination of pH in water and potassium chloride in the proportions 1 2.5, total organic carbon (TOC) and cation exchange capacity (CEC). Transfer coefficients between soil and plant and enrichment in soils were determined. The results for Pb were represented in the form of relative enrichments for soils (Kabata-Pendias, 1985) and transfer coefficients in plants (Kovalevskii, 1979). 

Heavy metals in rice and soils as well as several physicochemical indicators of soils including Organic matter (OM), pH, Cation- Exchange Capacity (CEC) and soil granularity were analyzed. As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Se, Zn and OM of soils, and As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Se and Zn of rice were determined at the central chemical lab of the Institute of Geophysical and Geochemical Exploration. The CEC of the soils was measured at the analytical institute of... 

Procedure 11.4 can also be used to determine the amount of all the individual cations present. The sum of these plus the pH can be used to determine the cation exchange capacity (CEC) of soil. 

Another type of reaction that responds to WD cycles is the fixation of K and NH4 ions by smectite (3-7). The fixation of K in smectite has been studied extensively by soil scientists because of its effect on the availability of plant nutrients. The reaction also decreases smectite s ability to swell, decreases its cation exchange capacity (CEC), and modifies its BrjSnsted acidity. Therefore, an understanding of this phenomenon is applicable to many fields of study that are concerned with swelling clays, fields such as soil fertility, soil mechanics, waste disposal, clay catalysis, and the geochemistry of ground and surface waters. 

XRD) and chemical extraction procedures, that much of the observed cation exchange capacity (CEC) arises from smectite impurities, the external surface CEC of kaollnite ranging from 0-1 meq/100 g. 

The sorption behavior of 11 PAH compounds (a training set, Table 11) on various solid phases (e.g., three soils and two sediments) with different properties to relevant sorption (e.g., organic carbon content, clay content, pH, cation exchange capacity CEC Table 12), was determined by batch equilibrium studies [1]. Batch equilibrium tests were designed to determine rates of equilibrium sorption under conditions of high mixing and high surface areas of the solid particles (see Chap. 3). 

Young, plastic walls were characterized both by a high level of branched and methylated rhamnogalacturonans which leads to swollen cell walls and by a low level of linear galacturonans which induces a low Cation Exchange Capacity (CEC). In contrast, stiff, mature cell walls are characterized by a low water content and a high CEC which favors cross-linking. 

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