Sorption calculations

As a consequence of the assumed temperature dependence of the molecular volume of the sorbate, the isosteric heats of sorption, calculated... 

A set of five programs known as The Geochemist s Workbench or GWB was developed by Bethke (1994) with a wide range of capabilities similar to EQ3/6 and PHREEQC v. 2. GWB performs speciation, mass transfer, reaction-path calculations, isotopic calculations, temperamre dependence for 0-300 °C, independent redox calculations, and sorption calculations. Several electrolyte databases are available including ion association with Debye-Huckel activity coefficients, the Pitzer formulation, the Harvie-M0ller-Weare formulation, and a... 

The second example considers a blend formed by LDPE, with 30% crystallinity, and PVC. The polymer matrices examined are pure LDPE, the blends LDPE (80%)-PVC (20%) and LDPE (50%)-PVC (50%), and pure PVC, with toluene as the penetrant. Experimental data by Markevich etalS report solubiUty of toluene in the above blends, at the temperature of 30° C, while toluene solubiUty in pure PVC was taken from Berenst l The glassy transition temperature is equal to —25° C for LDPE and to +75° C for pure PVC. Therefore, pure PVC is a glass at 30° C however, due to the large swelling and plasticization of the polymer induced by toluene sorption, it can be seen that the sorption of toluene lowers the glass transition of PVC to temperatures below 30° C, already at relatively low toluene activities. That is also confirmed by the sorption isotherm which is concave to the concentration axis as is typical of rubbery polymers. The glass transition temperatures for the blends are estimated to be — 10°C for the 80% LDPE blend and +17° C for the 50% LDPE blend, all below the temperature of the sorption experiment. The crystalline fraction of LDPE is assumed, as is usual, not to contribute to the sorption process, therefore we consider only the amorphous fraction of LDPE in the sorption calculations based on EoS. For the sake of simplicity, we present here only the results obtained with the LF equilibrium model. 

Figure 4. Contribution of hole-filling to total sorption calculated by the Freundlich slope method for 1,3-dichlorobenzene in (a) Cheshire fsl. and (b) Pahokee peat soil and its humin and humic acid fractions for a 48-h equilibration time. Data taken from isotherms in Figures 2 and 5.

In sorption calculations, the energy is determined by summing the interaction energy between all atoms using defined potentials. The sorbed molecule is positioned into the zeolite cavity surrounded by framework atoms which extend to infinity. The zeolite and molecule are then allowed to relax to their lowest energy configuration. The calculated heats of adsorption (q j) of the molecule in the zeolite is obtained from - r(Z+mol) +... 

Fig. 10-17. Response surface for Np(V) sorption calculated using the DLM. Data are plotted from 10 to 10 atm (C02-free results not shown for clarity). Np(V)(o,ai 1 x 10 M, M/V=4 g x L . DLM parameters are from Table 10-1.

Plasticization and Other Time Effects Most data from the literature, including those presented above are taken from experiments where one gas at a time is tested, with Ot calculated as a ratio of the two permeabihties. If either gas permeates because of a high-sorption coefficient rather than a high diffusivity, there may be an increase in the permeabihty of all gases in contact with the membrane. Thus, the Ot actually found in a real separation may be much lower than that calculated by the simple ratio of permeabilities. The data in the hterature do not rehably include the plasticization effect. If present, it results in the sometimes slow relaxation of polymer structure giving a rise in permeabihty and a dramatic dechne in selectivity. 

The capacity factors of SN-SiO, for metal ions were determined under a range of different conditions of pH, metal ions concentrations and time of interaction. Preconcentration of Cd ", Pb ", Zn " and CvS were used for their preliminary determination by flame atomic absorption spectroscopy. The optimum pH values for quantitative soi ption ai e 5.8, 6.2, 6.5, 7.0 for Pb, Cu, Cd and Zn, respectively. The sorption ability of SN-SiO, to metal ions decrease in line Pb>Cu> >Zn>Cd. The soi ption capacity of the sorbent is 2.7,7.19,11.12,28.49 mg-g Hor Cd, Zn, Pb, andCu, respectively. The sorbent distribution coefficient calculated from soi ption isotherms was 10 ml-g for studied cations. All these metal ions can be desorbed with 5 ml of O.lmole-k HCl (sorbent recovery average out 96-100%). 

In conditions of a dynamic sorption the calculation of pai ameters sorbate pillai s was conducted at usage initial curve in co-ordinates C/C - f(t). 

Chiesa and Consonni [1 gave another detailed analysis for this plant in comparison with Cycle A1. They found that the efficiency dropped by 5% from that of the basic CCGT plant this is. somewhat surprising as the ab.sorption plant is smaller than that for Cycle A1 and it might have been expected that the penalty on efficiency of intrcxlucing the absorption plant would have been much less than that of Cycle Al. With this calculated efficiency and a detailed estimate of capital cost, the price of electricity was virtually the same as that of Cycle Al, i.e. 40% greater than that of the basic CCGT plant. 

Besides shear-induced phase transitions, Uquid-gas equilibria in confined phases have been extensively studied in recent years, both experimentally [149-155] and theoretically [156-163]. For example, using a volumetric technique, Thommes et al. [149,150] have measured the excess coverage T of SF in controlled pore glasses (CPG) as a function of T along subcritical isochoric paths in bulk SF. The experimental apparatus, fully described in Ref. 149, consists of a reference cell filled with pure SF and a sorption cell containing the adsorbent in thermodynamic equilibrium with bulk SF gas at a given initial temperature T,- of the fluid in both cells. The pressure P in the reference cell and the pressure difference AP between sorption and reference cell are measured. The density of (pure) SF at T, is calculated from P via an equation of state. 

Since the mechanism of interaction between proteins polyfunctional with respect to ionogenic groups and CP is complex, an approximate method of calculation of sorption selectivity constants according to the inverse form of Langmuir isoterm should be used. Hence, the approximate values of AG, AH and AS obtained from Eq. (3.5) should be applied (Table 7). 

For slow diffusion of organic ions, one of the most suitable methods for the determination of quasi-diffusion in the grain is the use of the calculation of mean sorption time t [108]... 

Sorption curves obtained at activity and temperature conditions which have been experienced to be not able to alter the polymer morphology during the test, i.e. a = 0.60 and T = 75 °C, for as cast (A) and for samples previously equilibrated in more severe conditions, a = 0.99 and T = 75 °C (B), are shown in Fig. 13. According to the previous discussion, the diffusion coefficient, calculated by using the time at the intersection points between the initial linear behaviour and the equilibrium asymptote (a and b), for the damaged sample is lower than that of the undamaged one, since b > a. The morphological modification which increases the apparent solubility lowers, in fact, the effective diffusion coefficient. 

However, it has been concluded from sorption and diffusion experiments that plutonium exists largely in the tetravalent state (53) and clearly not as Pu(V), in the intermediate pH-range under oxic conditions and at low carbonate concentration. This would be representative of many groundwaters and also in agreement with the calculated curves of Figure 2. 

The values of kj calculated by Bacon and Anderson (1982), and used in most models of Th scavenging, varied with particle concentration and ranged from 0.2 to 1.2 Such values are appreciably longer than expected from sorption rates onto particle surfaces. The discrepancy can be explained if dissolved Th is initially sorbed to surfaces of very small particles (colloids) that pass through the typical filters (0.1-0.4 im) used to separate dissolved from particulate fractions (Santschi et al. 1986). 

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