Sorption temperature effects

The effect of a way of obtaining ChCS, time of realization of a sorption, temperature of a sorption, density and pH of sorbate on process of a sorption was studied. It is established, that chitincontaining sorbents ai e strong at pH<5 and are capable for effective heavy metals ions absorption from acid water solutions. 

Temperature Effects. The effect of a temperature increase from 25°C to 65°C is usually a small increase of the distribution coefficient (less than a factor of three). For the sorption of Cs on bentonite, which would correspond to an ion exchange process, the effect of increased temperature is the opposite. 

Temperature Effects. Equilibrium studies have been performed on the HC1, 10 2M NaCl system at temperatures of 2°, 25°, and 50°C. No significant differences were noted in the resulting isotherms, so that heats of sorption have not been calculated. The results of rate studies on the same systems at the three different temperatures are shown in Figures 13... 

Singleton and Pattee (84) investigated the various parameters necessary to optimize conditions for the analysis of TGs using a UV detector at 210 nm. The parameters tested were (a) the effect of sample solvent on TG analysis (b) the effect of mobile-phase composition on the sorption behavior of TGs (c) the effect of sample load level on TG analysis and (d) the temperature effects on TG analysis. 

Velazquez de la Cruz G, Torres J, Martin-Polo M. Temperature effects on the moisture sorption isotherms for methylcellulose and ethylcellulose films. / Food Engin 2001 48 91—94. 

Physical sorbents for carbon dioxide separation and removal were extensively studied by industrial gas companies. Zeolite 13X, activated alumina, and their improved versions are typically used for removing carbon dioxide and moisture from air in either a TSA or a PSA process. The sorption temperatures for these applications are usually close to ambient temperature. There are a few studies on adsorption of carbon dioxide at high temperatures. The carbon dioxide adsorption isotherms on two commercial sorbents hydrotalcite-like compounds, EXM911 and activated alumina made by LaRoche Industries, are displayed in Fig. 8.F23,i24] shown in Fig. 8, LaRoche activated alumina has a higher carbon dioxide capacity than the EXM911 at 300° C. However, the adsorption capacities on both sorbents are too low for any practical applications in carbon dioxide sorption at high temperature. Conventional physical sorbents are basically not effective for carbon dioxide capture at flue gas temperature (> 400°C). There is a need to develop effective sorbents that can adsorb carbon dioxide at flue gas temperature to significantly reduce the gas volume to be treated for carbon sequestration. 

Attempts to conduct kinetic experiments at varying temperatures are equally frustrating. Temperature effects are not limited to sorption kinetics, but the sorbent surfaces themselves can be affected by temperature. Cation exchange capacity, particularly of amorphous and organic surfaces (Wada and Harada, 1971) is temperature dependent, as is the stability of soil minerals (Mattigod and Kittrick, 1980). In turn, specific sorption will be affected by mineral stability due to associated surface changes. 

Two selected food materials are presented as an example in Figure 4.13. Potatoes exhibit a typical behavior. Equilibrium material moisture content is increased [173]. Raisins, on the other hand, exhibit an inverse temperature effect at large water activities [174], As shown in Figure 4.13, potatoes and raisins exhibit sorption isotherms of types II and III, respectively. 

The surrounding temperature affects the performance of a SAW device in two ways. Temperature changes the crystalline structure of the piezoelectric substrate that in turn affects the propagation property of the SAW. Temperature changes also affect the sorption and desorption property of the coating film. The effect that affects the property of the piezoelectric crystal can be reduced through installation of a reference SAW sensor that is isolated from the sample vapor. Temperature fluctuation affects not only the SAW sensors for the detection but also the reference sensor. Therefore, the temperature effect on the sensors could be compensated for by negating the similar effect experienced by the reference sensor. 

Overall, the anion systems have received fairly little attention and the experimental data only confirm the expected trends in part. There is need for more studies to clarify the actual trends and to understand the observed inversion of the temperature effect on organic acid sorption on kaohnite. 

Clearly, more systematic experimental studies on the temperature effect on anion sorption are required, which will explain the different observations, which have so far been pubhshed. 

From the data in Figure 1, a significant temperature effect on the solubility of n-pentane in PTMSP is also evident at all penetrant activities. As is typical for the sorption in glassy polymers, the solubility of the penetrant increases as the temperature decreases at each activity value. This effect is obviously associated with negative values of the mixing enthalpy, and it appears to be significantly pronounced in the case of n-pentane. 

In Figure 2 the solubility isotherms of n-hexane in PTMSP are reported at temperatures of 300 K and 330 K. The behaviour is qualitatively similar to that observed for n-pentane sorption. Both isotherms exhibit a downward curvature and the solubility coefficient in the low pressure limit. So, is high. For n-hexane. So 25 and 16 at 300 and 330 K, respectively. Also for n-hexane sorption, the effect of temperature on solubility indicates a large negative enthalpy of mixing since the solubility decreases substantially with increasing temperature. 

Many factors affect the mechanisms and kinetics of sorption and transport processes. For instance, differences in the chemical stmcture and properties, ie, ionizahility, solubiUty in water, vapor pressure, and polarity, between pesticides affect their behavior in the environment through effects on sorption and transport processes. Differences in soil properties, ie, pH and percentage of organic carbon and clay contents, and soil conditions, ie, moisture content and landscape position climatic conditions, ie, temperature, precipitation, and radiation and cultural practices, ie, crop and tillage, can all modify the behavior of the pesticide in soils. Persistence of a pesticide in soil is a consequence of a complex interaction of processes. Because the persistence of a pesticide can govern its availabiUty and efficacy for pest control, as weU as its potential for adverse environmental impacts, knowledge of the basic processes is necessary if the benefits of the pesticide ate to be maximized. 

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