Sorption behaviour

Due to the chemical structure, fimctionality and composition of their constituents, ordinary variations of the processing conditions as well as the quality of the raw materials have been observed to lead to changes of the fine structure which are often responsible of lower ageing resistence of the polymer. The data reported here correlate the morphology of some widely utilized epoxy matrices to the informations that can be obtained from the study of the sorption behaviours. 

In order to evaluate the effect of hygrothermal fatigue on the physical and mechanical properties of composites in actual service, it is crucial to resolve the basic phenomena driving the complex water sorption behaviour and degradation mechanisms in various combinations of moist environment and temperature. 

Table 1.9. Sorption behaviour as percentage of silver, cadmium and zinc in artificial seawater [54]... 

The sorption behaviour of trace elements depends on a variety of factors which, taken together, make sorption losses rather difficult to predict. However, the data from the study and from the literature indicate for which elements sorption losses may be expected as a function of a number of factors, such as trace element concentration, container material, pH, and salinity. 

Dooley CA, Homer V (1983) Organotin compounds in the marine environment uptake and sorption behaviour. Technical report no. 917. Naval Ocean Systems Center, San... 

Unger et al. [87] have studied the sorption behaviour of tributyltin on estuarine sediments. 

Fig. 5.4.5. Schematic diagram of the typical surfactant sorption behaviour [5,11] related to surfactant concentration at constant temperature.

Popper, R. and Bariska, M. (1972). Acylation of wood. Part I The sorption behaviour of water vapour. Holz als Roh- und Werkstoff, 30(8), 289-294. 

Schneider, A. and Rusche, H. (1973). Sorption behaviour of beech and spruce wood after heat treatment in air and in vacuum. Holz als Roh- und Werkstoff, 31(8), 313-319. 

Arsenic and antimony are Group VB elements and both occur in soils predominantly in - -3 and - -5 oxidation states and they have similar redox and sorption behaviour. The oxidized forms are rather insoluble in soils and the reduced forms much more soluble. 

The redox and sorption behaviour of Sb is similar, but no volatile forms are produced. The oxidized form of Sb, antimonite, Sb(V), has the anionic form Sb(OH)e at pH > 4, and is sorbed on oxides and sihcate clays. The reduced form, antimonite, Sb(III), is present as the uncharged Sb(OH)3 molecule except at very low or very high pH where the Sb(OH)2 cation and Sb(OH)4 anion form, respectively. The uncharged Sb(OH)3 is little sorbed on soil surfaces. 

S. Deledda, B.C. Hauback, H. Fjellvag, H-sorption behaviour of mechanically activated Mg-Zn powders, J. Alloys Compd. 446 47 (2007) 173-177. 

Peuravuori, J., Paaso, N., and Pihlaja, K. Sorption behaviour of some chlorophenols in lake aquatic huttric matter, Talanta, 56(3) 523-538, 2002. 

The sorption behaviour of antibiotics, in particular, can be very complex and therefore difficult to assess. As an example, ciprofloxacin has a log ATqw equal to 0.28, conferring it with a small tendency to leave the aquatic phase however, it does sorb well onto active sludge or sediments [62, 63] in WWTP. Tetracyclines (log A ow equal to 1.4), on the other hand, form complexes with double cations (calcium and magnesium) present in the water [64] and also tend to adsorb onto the surface of complexes between humic acids and hydrous Al oxide [65]. 

This paper is devoted to the sorption of uranyl, which exhibits a complex aqueous and surface chemistry. We review briefly the sorption behaviour of An in the environment, and illustrate the variety of environmental processes using published data of uranyl sorption in the Ban-gombe natural reactor zone. After summarizing the general findings of the mechanisms of An sorption, we then focus particularly on the current knowledge of the mechanisms of uranyl sorption. A major area of research is the influence of the aqueous uranyl speciation on the uranyl surface species. Spectroscopic data of U(VI) sorbed onto silica and alumina minerals are examined and used to discuss the role of aqueous uranyl polynuclear species, U02(0H)2 colloids and uranyl-carbonate complexes. The influence of the mineral surface properties on the mechanisms of sorption is also discussed. 

Water sorption isotherms may be determined experimentally by gravimetric determination of the moisture content of a food product after it has reached equilibrium in sealed, evacuated desiccators containing saturated solutions of different salts. Data obtained in this manner may be compared with a number of theoretical models (including the Braunauer-Emmett-Teller model, the Kuhn model and the Gruggenheim-Andersson-De Boer model see Roos, 1997) to predict the sorption behaviour of foods. Examples of sorption isotherms predicted for skim milk by three such models are shown in Figure 7.12. 

The sorption behaviour of a number of dairy products is known (Kinsella and Fox, 1986). Generally, whey powders exhibit sigmoidal sorption isotherms, although the characteristics of the isotherm are influenced by the composition and history of the sample. Examples of sorption isotherms for whey protein concentrate (WPC), dialysed WPC and its dialysate (principally lactose) are shown in Figure 7.13. At low aw values, sorption is due mainly to the proteins present. A sharp decrease is observed in the sorption isotherm of lactose at aw values between 0.35 and 0.50 (e.g. Figure 7.13). This sudden decrease in water sorption can be explained by the crystallization of amorphous lactose in the a-form, which contains one mole of water of crystallization per mole. Above aw values of about 0.6, water sorption is principally influenced by small molecular weight components (Figure 7.13). 

Despite some conflicting evidence (Kinsella and Fox, 1986), it appears that denaturation has little influence on the amount of water bound by whey proteins. However, other factors which may accompany denaturation (e.g. Maillard browning, association or aggregation of proteins) may alter protein sorption behaviour. Drying technique affects the water sorption characteristics of WPC. Freeze-dried and spray-dried WPC preparations bind more water at the monolayer level than do roller-, air- or vacuum-dried samples, apparently due to larger surface areas in the former. As discussed above, temperature also influences water sorption by whey protein preparations. The sorption isotherm for /Mactoglobulin is typical of many globular proteins. 

For Am there is no evident particle size dependence. The kinetics are considerably slower than for Cs (and Sr). Possibly the sorption process is a volume dependent adsorption with contributions from ion exchange. The sorption and also the diffusion into the particles should be governed by the complicated hydrolysis reactions to be expected at environmental pH. Other tri- and tetra-valent elements would be expected to show a similar slow non-surface related sorption behaviour. 

The isotherm model of Schirmer et al. (T.) for sorption in molecular sieves is based on statistical thermodynamics in which the configuration integrals describing the sorption behaviour are extracted from the available data. The model does not presuppose any specific kind of sorption mechanism. The multi-component form of this isotherm derived by Loughlin and Roberts (8 ) is also not limited to any particular sorption mechanism,... 

H. Irth, R. Tocklu, K. Welten, G. J. de Jong, R. W. Frei and U. A. Th Brinkman, Trace enrichment on a metal-loaded thiol stationary phase in liquid chromatography effect of analyte structure and pH value on the (de)sorption behaviour , J. Pharm. Biomed. Anal. 7 1679-1690(1989). 

McCubbin, D. and Leonard, K.S. (1995) Influence of some seawater components on the sorption behaviour of Npv. Radiochim. Acta, 69, 97-102. 

Frobe, Z., Drevenkar, V., Stengl, B. (1989) Sorption behaviour of some organophosphorus pesticides in natural sediments. Toxicol. Environ. Chem. 19, 69-82. 

Demertzis P G, Johansson F, Lievens C and Franz R, 1997, Studies on the development of a quick inertness test procedure for multi-use PET containers - sorption behaviour of bottle wall strips. Packaging Technology and Science 10,45-58. 

The observed sorption behaviour can therefore be described by a combined Langmuir-Henry absorptions isotherm. Equation 1 was fitted to the calibration curves of the three methods and the Henry-Langmuir-behaviourwas verified. 

Type I is of course the ideal sorption behaviour according to Henry s law. As said before, it is observed in the sorption of permanent gases at moderate pressures. 

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