Sorbed components

In the sorption experiments of Icopini et al. (2004), the measured isotopic contrast between Fe(II)aq and the goethite starting material was -0.8%o after Fe(II) had sorbed to the surface over 24 hours in this case, the isotopic fractionation between sorbed Fe(II) and Fe(II)aq is not the 0.8%o measured difference, but is approximately +2.1%o based on an inferred 8 Fe value for the sorbed component as calculated from Fe mass balance (Fig. 4), as was noted in that study. Measured differences in Fe isotope compositions between ferric oxide/hydroxide and Fe(II)aq during dissimilatory Fe(III) reduction and photosynthetic Fe(II) oxidation have been proposed to reflect fractionation between soluble Fe(II) and Fe(III) species, where the soluble Fe(III) component is postulated to be bound to the cell and is not directly measured (Beard et al. 2003a Croal et al. 2004). In the case of dissimilatory Fe(III) reduction, assuming a static model simply for purposes of illustration, if 50% of the Fe in a pool that is open to... 

The Cb term becomes significant with rapidly eluted but poorly sorbed components. The value of Cb depends upon the particle size of the packing. 

REQUIRED PLATE NUMBER. Knowing the capacity factor, k1, and the separation factor, a, one is able to calculate the required number of plates (n ) for the separation of two components (the k value refers to the more readily sorbed component). 

Unfortunately, Equation 2.113 is of little practical importance because the h value for the more readily sorbed component must be known and this is not readily available from independent data. 

So far most of the pertinent literature interprets interactions between polymer and a second sorbed component on the basis of the colligative properties of the system. This information is summarized in Sect. 2 of this review. From those reports, I inferred that some sort of association of the small penetrant molecules with the repeat unit of the polymer is a prerequisite condition for the sequential changes described above. This implies that the magnitude of polymer swelling should be directly related to how well the molecular structure of the small molecule can be accommodated by the molecular structure of the polymer repeat unit in view of the macrostructure of that polymer (i.e. the crosslink density). The results obtained in our laboratory, which are summarized in Sect. 3 of this Review, are thoroughly consistent with that hypothesis. In Sect. 4 these interpretations are extended to correlate the colligative properties of Sect. 2. 

As a result of the fact that the selectivity of the ion exchanger toward mixture components is different the more weakly sorbed component is gradually concentrated in the top of column I while the more strongly sorbed one is concentrated at the bottom of column II. Once the required degree of enrichment is achieved it is possible to remove the product while adding the original mixture of components at the bottom of column I. 

Either a more strongly or a more weakly sorbed component may be recovered from mixtures in the separating column with flow reversal at one-end if the column is long enough. The recovery and purification of mix-... 

A. Preliminary Separation from More Strongly Sorbed Component Mixtures and Subsequent Resolution of Pure Product... 

Figure 9 A scheme for recovery of a component with sorbability both stronger and weaker than other components after removing the weaker sorbed components.

Rgure 10 Schemes for complete separation of four-component mixtures after removal of (a) more strongly and (b) less strongly sorbed components. 

Further clarification is provided by Fig. 11. Given in Fig. 11a is the scheme for conventional ion-exchange separation in a countercurrent column to obtain a more effectively sorbed component. To displace the separated ions from the ion-exchange resin auxiliary ions are applied. The distribution of the concentrated component along the column height is... 

Figure 11 Concentration of a more strongly sorbed component (a,b) the process with flow reversal (c,d) the process with changes of interphase transfer direction (a,c) schemes for the process (b,d) distribution of the concentrated component along the column height.

Dual-temperature based theory for linear equilibrium isotherms has been developed [26]. From the results of this analysis the optimal value of flow ratio in the simplest case of nonselective conditions for concentrating the least strongly sorbed component can be found with the following expression ... 

At the border between the different pH zones the transfer of a portion of the ions from the solution to the ion exchanger proceeds by sorption of phenolic groups, thereby combining two-temperature" separation with partial flow reversal. Upon separation with flow reversal in the upper part of zone II the weaker sorbed component should be concen-... 

Diffusion The sorbed components diffuse across the swollen membrane under a chemical potential gradient. 

Absorption Sorption characterized by penetration of the sorbed component into the bulk structure of the solid. The amount of water absorbed does not depend on surface area. 

Desorption The spontaneous loss of the sorbed component (water) to the atmosphere. 

The mechanism of transport by pervaporation can be described in the light of the sample diffusion model [159], which comprises the following steps (a) evaporation of the analyte into the air gap (b) sorption into the membrane on the sample side (c) diffusion of the sorbed component through the polymer matrix and (d) desorption into a liquid or gas phase on the acceptor side. The last three steps are also included in industrial pervaporation processes. 

As indicated clearly for sorption of TCB on diagenetically altered organic matter in natural systems, linear models do not suffice to describe all potentially important local-sorption phenomena. For such nonlinear systems, the relative contributions of different sorbing components and surfaces will vary... 

The experimental results given in Figure 7 provide confirmation of the importance of such small but highly reactive nonlinearly sorbing components to the overall sorption behavior of hydrophobic contaminants in subsurface systems. This figure presents a comparison of the carbon-normalized contribution of the nonlinear local TCB isotherm for the shale isolated from the Wagner soil to the composite sorption isotherm for the soil itself. 

The nonlinearity (n = 0.77) of the composite isotherm is significant and reflects the dominance by the nonlinearly sorbing components of the overall... 

Zn(0H)2 the -composition curves only differ by the fact that sorption capacities of Cu(0H)2 and Zn(OH)2 are not equal and consequently, in the Vs -composition curves the sorption maxima are shifted towards the most actively sorbed component (Fig.6). 

In this case the position of maxima in the Ssp -composition curve fully coincides with those in the Vj -composition curves of synthesized porous materials. Depending on the value of the sorption capacity, the positions of maxima in the composition axis can be shifted towards the most sorbed component or be in its center when the sorption capacities of individual components in a binary mixture are equal. 

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