Physically bound water

Water taken up by solid materials is generally classified as water bound by physical forces or water bound by chemical bonds. Physically bound water includes adsorbed water, trapped or liquid-inclusion water, and absorbed water. The physical adsorption of water occurs when water condenses or is held on the surface the surface includes the cracks, crevices, etc. of real materials. Liquid inclusion occurs during the crystallization process when bubbles of water are trapped. 

Quite often fireclay is burnt to chamotte at the place where it is found. The most common clay mineral in fireclay is kaolinite with the ideal formula Al4[(OH)8/Si4O10], or in the notation applied in world of ceramics Al203.2Si0r2 H20. Kaolinite contains chemically and physically bound water. When you heat it to about 1500 °C, the physically bound form is first released and subsequently the chemically bound one. In the last phase chamotte is formed ... 

The physically bound water in the raw material clay is determined by drying the sample at 105 °C until it has a constant mass. In order to determine the chemically bound water it is necessary to heat the sample to 1100 °C. Remember that between the clay sheets water molecules are bound to the ions of the sheets an ionic dipole bond. In addition some molecules are interconnected by means of H-bridges,... 

Differential thermal analysis. The phenomena of adsorption and desorption of water and the loss of physically bound water have been investigated by differential thermal analysis (112,151a). In this method, a small amount of the sample to be examined and a sample of inert material (e.g., calcined alumina) are placed in separate wells in a nickel block. A thermocouple junction is placed in each of the samples and the thermocouple leads are connected in series but with opposing e.m.f. s. The nickel... 

Activation by heating at 150-200°C removes the physically bound water. The assumption that one silica is most suitable for adsorption and another for liquid-liquid partition chromatography is questionable and, beyond that, irrelevant because pure adsorption or partition retention mechanisms generally do not occur. 

Coldry is a recently proposed method that is mainly an evaporative drying process based on brown coal densification. In the process, the coal is sheared and attritioned, which results in particle size reduction and releasing water naturally in the porous coal structure (Moore, 2012). This dispersal of surface and/or physically bound water is then evaporated at or near ambient temperature. The extra benefit of brown coal densification is that some chemically bound water is also removed without the need of high tanperature/pressure. The new structure of a dried coal by this method also reduces the tendency to self-heat. 

The physically bound water in the paste, as well as the water in the hydrates can be determined by means of elastic neutron scattering, without sample drying [43, 44]. For this reason it is an very interesting method, and obtained results give the possibility to explain many discrepancies linked with the sorption methods. The results of one study have shown that the free water content (Fig. 5.23) is consistent with that calculated earlier as the capillary water [44]. 

In hygroscopic materials, there is large amount of physically bound water and the material often shrinks during heating. In hygroscopic materials there is a level of moisture saturation below which the internal vapor... 

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