Sorption composite kinetics

Effect of size of AMP-PUF on Cs" sorption. To elucidate the above, AMP-PUF was milled and sieved to fragmentize by size. Effect of the size on sorption kinetics of Cs was studied for 10 mL solution containing 500 pg of Cs. Fig. 4 shows the results by decreasing the size of the composite, sorption kinetics was effectively improved. Comparison of the results between milled fragments and 5 mm cube suggests that sorption kinetics is considerably improved by increase in an effective surface area of the composite and will be strongly influenced by osmotic behavior of solution into PUF. 

COSY fiKSS, Germany 48 since 01/1 t/06 Sorption kinetics and reactive hydride composites, for energy efficient hydrogen storage 3.5... 

The phenomenon of polymer swelling, owing to sorption of small molecules, was known even before Staudinger reported [1] in 1935 that crosslinked poly(styrene) swells enormously in certain liquids to form two-component polymer gels. The physical state of such systems varies with the concentration (C) and molecular structure of the sorbed molecules thus, the system undergoes transition at constant temperature from a rigid state (glassy or partially crystalline) at C < Cg to a rubbery state at Cg (the transition state composition). When C > Cg and the second component is a liquid, its subsequent sorption proceeds quickly to gel-saturation and of course a solution is produced if the polymer lacks covalently bonded crosslinks or equivalent restraints. Each successive physical state exhibits its own characteristic sorption isotherm and sorption kinetics. 

Sorption Kinetics. The adsorption and desorption data were analyzed in terms of a model based on the following main assumptions. Micropore diffusion within the sieve crystals is the rate-controlling process. Diffusion may be described by Fick s law for spherical particle geometry with a constant micropore diffusivity. The helium present in the system is inert and plays no direct role in the sorption or diffusion process. Sorption occurs under isothermal conditions. Sorption equilibrium is maintained at the crystal surface, which is subjected to a step change in gas composition. These assumptions lead to the following relation for the amount of ethane adsorbed or desorbed by a single particle as a function of time (Crank, 4). 

Gordeeva, L.G. Mrowiec-Bialon, J. Jarzebski, A.B. Lachowski, A.I. Malinowski, J. Aristov, Y.I. Selective water sorbents for multiple applications, 8. Sorption properties of CaCl2-Si02 sol-gel composites. React. Kinet. Catal. Lett. 1999, 66 (1), 113-120. 

Aramid fibers are popular in the reinforcement of various matrix materials. It is frequently the case that low water uptake by a composite is required, which cannot be regulated by the matrix. Figure 16.15 shows that aramid fibers differ in water sorption kinetics. Fiber E gives better performance due to a hydrophobic coating. This lower water sorption of the fiber decreases water sorption of the composite, as was established in the study. ... 

Beside the appropriate design of their chemical composition, the control of morphology and size of PCP crystals at the nanoscale provides an additional mean to modulate their physicochemical properties, in particular their sorption capacity. Recent studies showed that when PCP crystals are downsized to the nanometer scale and for peculiar morphologies, the external surface of the crystal starts to influence the sorption kinetics and sorption type. This phenomenon was explained by the decrease of the diffusion length toward the adsorption sites and by the enhanced accessibility of speciflc pore entrances. Contribution of the size and shape of the crystals upon the sorption properties is an inherent feature of porous materials, which was exploited for facilitating their integration into catalysis, separation, or sensing systems. 

In section 3 the phenomenon of hydrogen sorption in intermetallic compounds is described. Topics dealt with in this section are activation treatment, pressure-composition isotherms, miscibility gap, sorption hysteresis, lattice expansion, diffusion, sorption kinetics, surface effects, poisoning, impurity effects and decomposition of ternary hydrides. The sorption characteristics of all ternary rare-earth hydrides investigated are listed in several tables given in the appendix. For comparison the sorption characteristics of some selected ternary hydrides based on non-rare-earth metals are given in a separate table. 

Since an understanding of the nature of water sorption by materials is of extreme interest to the formulator, an evaluation of the degree of hygroscopicity associated with a given material is crucial to the development process. A systematic approach for these types of studies has been outlined, in which the kinetics of water adsorption can be deduced [84]. This work should be performed at the preformulation stage, where the effect of water on the various components (and mixtures of these) needs to be addressed prior to any final decision as to the formulation composition [85]. It would be far better to discover any... 

Solubility and kinetics methods for distinguishing adsorption from surface precipitation suffer from the fundamental weakness of being macroscopic approaches that do not involve a direct examination of the solid phase. Information about the composition of an aqueous solution phase is not sufficient to permit a clear inference of a sorption mechanism because the aqueous solution phase does not determine uniquely the nature of its contiguous solid phases, even at equilibrium (49). Perhaps more important is the fact that adsorption and surface precipitation are essentially molecular concepts on which strictly macroscopic approaches can provide no unambiguous data (12, 21). Molecular concepts can be studied only by molecular methods. 

There are four major transformation pathways leading from the DOM pool into the microbial loop direct uptake and photolysis-, ectoenzyme-, and sorption-mediated uptake (Fig. 1). Each of these pathways or processes is regulated by a combination of intrinsic and extrinsic factors. Intrinsic factors are elements of the pathway itself and include DOM characteristics, enzyme kinetics, and microbial diversity. For instance, the uptake characteristics of the resident microbial community will affect which monomers are assimilated from the pool of DOM. Conversely, the composition of the DOM pool is likely to affect which microbial consortia are present and active at any given time. 

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