Water sorption, processing effects

The effect of physical aging on the crystallization state and water vapor sorption behavior of amorphous non-solvated trehalose was studied [91]. It was found that annealing the amorphous substance at temperatures below the glass transition temperature caused nucleation in the sample that served to decrease the onset temperature of crystallization upon subsequent heating. Physical aging caused a decrease in the rate and extent of water vapor adsorption at low relative humidities, but water sorption could serve to remove the effects of physical aging due to a volume expansion that took place in conjunction with the adsorption process. 

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... 

Sorption plays a significant role in the environmental fate and effects of compounds released into the aquatic environment, largely determining their distribution between different environmental compartments. Apart from affecting the mobility, and therefore the potential of a surfactant to reach groundwater and surface water, sorption can affect its toxicity and biodegradation by influencing bioavailability. This process is especially relevant for surfactants, since their molecular structure presents a pronounced tendency to sorb onto interfaces. 

Porous media have much larger solid-to-solution phase ratios (rsw) than surface waters (lakes and rivers). Therefore, even the transport of a chemical with moderate to small solid-water distribution ratios (/Q may be influenced by sorption processes. The basic mathematical tools which are needed to quantify the effect of sorption on transport are described in Section 18.4 and summarized in Box 18.5. 

For such starchy foods as noodles, cakes, pastries, processed potato food, and puddings, lipids improve the texture. The tendency of bread to staling is also related to the presence of lipids and emulsifiers. In order to satisfy market demands, it is important to optimize the water-binding capacity, the rate of water sorption, and the swelling power. The effects of lipids on these properties is under ongoing study. The mode of application of lipids is also a factor which controls functional properties.851-853 869 The effect of all these factors on bread quality has been recognized.870-873... 

Migration of water-soluble substances is a common process occurring in rocks and soils (Chapter 1, Section 1.3.6.2). This process is the net result of different hydrological and sorption processes. Hydrological processes (Chapter 1, Equation 1.127), that is, the movement of water, are governed by the water levels. Sorption processes can decrease the rate of water movement via interfacial processes (Chapter 1, Equations 1.128-1.131). In this chapter, the effect of sorption will be shown on the migration rate of water-soluble substances. 

Sorption processes are very effective and include adsorption/desorption (reversible binding at the solid-water interface), absorption (diffusion of pollutants into the solid matrix), precipitation and coprecipitation (incorporation into a freshly formed solid), and occlusion (sequestration of adsorbed pollutants during mineral growth). The most important factors for retention processes are pollutant concentration, the composition of the solid matrix, solution composition (e.g., complexing agents) and E/pH conditions (Brady and Boms 1997). 

Cosolute effects the presence of further organic solutes, as is the case in real waters, may significantly alter the solubility of the individual compounds. Suspended organic matter soil and sediment components (e.g. humic acids) may result in increased apparent solubilities by serving as a sink compartment due to sorption processes. 

In the majority of industrial processes where carbon dioxide capture can occur, the feed stream for separation is saturated with water vapour [42]. Therefore, competitive water sorption in the membrane, as well as plasticization and ageing effects, will have a much stronger influence on membrane performance compared to the previously mentioned... 

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