Total exchange capacity

Monomer Milling time min Yield of copolymer Character of copolymer Copolymer (comp.) % PE Modifying monomer Total exchange capacity mg equiv./g... 

Important chemical characteristics of the soil include the total exchange capacity for cations, expressed as total meq of cations per 100 gm of soil, and the base status, which is the percentage saturation of the negative charge with cations such as calcium, magnesium and sodium. The more productive soils are about 80% saturated with calcium and magnesium. Excessive hydrogen and aluminum saturation (much over 15%) is termed soil acidity. Excess sodium saturation (12% or more) leads to dispersiveness of the soil and poor productivity. 

The total exchange capacity (TEC) of a aluminosilicate zeolite is a function of the framework, that is, the Si/Al ratio. It is easy to get a numerical relation between the TEC in mequiv/g, C, and the number of A1 atoms per framework unit cell, NA1 [104] ... 

To estimate the total exchange capacity of the AAH, a method of potentiometric suspension titration was employed. The values of TEC that were determined below the isoelectric point are shown in Fig. 2. The value of TEC above 8 eq/kg AI2O3 indicates a great number of surface active groups present as well as a well-developed interfacial surface of active aluminium hydroxide. 

Most laboratory and industrial applications of ion exchange employ resins in columns or cylindrical pressure vessels respectively. Hence a value for total exchange capacity on a bulk (apparent) volume basis is more meaningful. Elution methods are used in volume capacity determinations whereby the total number of equivalents of exchangeable ions per unit volume of the resin is measured and the result usually expressed as equivalents per litre of resin (eqlR ). See Box 4.6. 

To estimate an apparent selectivity coelTicient K, p the total exchange capacity of the H form resin in mequiv. per swollen gram is required. This value may be obtained by titration of the swollen resin or from the dry weight capacity DWG (Box 4.5) and the resin water content IF% (Box 4.4), where ... 

Let Q be the total exchange capacity of the IX resin ( /L) and C be the total ionic concentration in the solution (eq/L), and also let X and X represent the percentage of species in solution and solid phases. We then have... 

In the case of vermiculite, the short-chain organic cations do not penetrate into the interlayer space, and are adsorbed only on the external surface of the mineral. This is clearly seen from the analytical measurements, showing that only 0.06 meq/g of Na" " ions is substituted when Na-vermiculite is treated with tetramethylammonium salt solution, the total exchange capacity being equal to 1.5 meq/g. Therefore, the values of specific surface area obtained from water and hexane adsorption isotherms for the initial and [(CH3)4N] modified vermiculite are virtually the same (Table 3). Such a pronounced difference in the... 

Total exchange capacity = 5% of this = 0.64 peq Molar mass of NaCl 0.64 mmol of NaCl =... 

Since each bead of a given external diameter that is made by the inert diluent process will contain some void volume, there is actually less polymer available per unit volume for the introduction of functional groups. Therefore, these macroporous resins are inherently of lower total exchange capacity than gel-type resins of the same composition. 

The total exchange capacity, the porosity, the operating capacity and the efficiency of regeneration need to be evaluated in the laboratory when comparing resins for a given application. 

The total exchange capacity is usually determined by titrating the resin with a solution of acid or base to a specific end point. This type of information is readily available fi om the manufacturers of commercial ion exchange resins. 

The same roughly linear correlation was found for all three zeolites. The higher absolute content of iron as well as higher Fe/Al values reached for Fe-FER sample are probably due to the higher total exchange capacity of ferrierite (SEAl 8.4) in comparison to BEA and MFI, with Si/Al values of 13.5 and 13.2, respectively. 

The sorption capacity of the soil depends on its mineralogical composition, dispersion humus content and pH of the medium. In an acid medium, the negative charge of acidoids is decreased, which results in decreasing the total exchange capacity. A very acid medium can induce a change of the... 

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