Calcium exchange, degree

Except for A33 adsorbent, the experimental and theoretical curves are in good agreement. However the di sion curves of propane are even better. Moreover, at 523K, the theoretical and experimental curves are in better conformity with pentane, whatever the calcium exchange. The values of initial diffusion coefficients given as D/r/ versus calcium exchange degree are recapitulated in Table 1. 

The comparison of this time for the both molecules indirates the existence of a relationship with calcium exchange degrees. An example of idle times estimated at 373K for propane and... 

Fig. 7. Example of evolution of the idle period preceding the effective diffusion obtained at 373K versus calcium exchange degrees.

Ca variability in samples that have been subjected to varying degrees of calcium exchange... 

The data of Figure 2 indicate a complex relationship between the catalytic activity and degree of calcium exchange. Topchieva et al. (14) studied CaHY with calcium contents of 20, 40, 62, and 90% of the ex-... 

Considering that only 80%-wt. of each sample can adsorb the guest molecule, the number of molecules versus the degree of calcium exchange on CaA adsorbents is given in Fig. 1. 

Fig. 2. Number of propane and pentane moleeules per a cavity of CaA adsorbents versus the degree of calcium exchange.

Addition of a salt can transform the shale by cation exchange to a less sensitive form of clay, or reduce the osmotic swelling effect by reducing the water activity in the mud below that which occurs in the shale. These effects depend on the salt concentration and the nature of the cation. Salts containing sodium, potassium, calcium, magnesium, and ammonium ions ate used to varying degrees. 

To determine how the degree of exchange between an extrinsic isotope and the intrinsic calcium in the food or meal is affected by the method of incorporating the isotope, the calcium source itself or foods fed with it. 

What has happened to the bicarbonate and calcium delivered to the ocean by river runoff As described later, these two ions are removed from seawater by calcareous plankton because a significant fraction of their hard parts are buried in the sediment. In contrast, the only sedimentary way out of the ocean for chloride is as burial in pore waters or precipitation of evaporites. The story with sodium is more complicated— removal also occurs via hydrothermal uptake and cation exchange. Because the major ions are removed from seawater by different pathways, they experience different degrees of retention in seawater and uptake into the sediments. Another level of fractionation occurs when the oceanic crust and its overlying sediments move through the rock cycle as some of the subducted material is remelted in the mantle and some is uplifted onto the continents. 

Chemisorption of pyridine results in the disappearance of these groups and the formation of pyridinium ions. The concentration of pyridinium ions, and hence accessible Bronsted acid sites, follows a similar relationship to that of the hydroxyl group concentrations. Thus, the acid site concentration remains constant until about 16-18 calcium ions have been introduced. The acidity concentration then decreases rapidly as the calcium ions are exchanged for ammonium ions in accessible positions. At the same degree of exchange, the cation-pyridine band near 1444 cm" is observed first, confirming the appearance of calcium ions in accessible positions in the structure. 

The samples of zeolites prepared in our laboratory - sodium, calcium, strontium, barium, magnesium and decationated forms of Y-zeolites, which were denoted as NaY, CaY, SrY, BaY, MgY and DeY, were investigated. The degree of the cation exchange and decationation was more than 80%. For comparison porous silica Si02 and alumina (Y-AI2O3) were also studied. 

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