Abstract. Based on a thermodynamic approach, a mathematical model of charge transfer processes in the polymeric ionites (ion-exchange materials) during the water vapor sorption was developed. Theoretical dependences of the resistance of a polymeric ionite on the relative air humidity over the range 10-100% at physically reasonable values of the parameters of the system were obtained. The comparison of theoretical and experimental dependences has been performed. Possible reasons for and criteria of the phase transitions that lead to stepwise change of ionite resistance were discussed. The developed mathematical model adequately describes the available experimental data and allows formulating practical recommendations on selecting optimal polymeric coatings for the electrode units of molecular-electronic humidity gauges.
and a less reduction in the magnetic properties as well. In ad- dition, the Zn vapor sorption treatment was applied to NdFeB magnetic powders. Similar effect on the thermal stability of magnetic properties could be obtained in the Zn coated Nd- FeB bonded magnets. 6) The improvements in the corrosion resistance and the thermal stability of magnetic properties are attributed to the changes in microstructure of the powder by the Zn vapor sorption treatment. In the present work, the modification in the microstructures of practical NdFeB pow-
ABSTRACT: Nanocomposite films have been developed where a galactomannan (guar) matrix was reinforced with cellulose nano- whiskers and plasticized using sorbitol. The properties of these films were compared with films made from guar only. The films were examined using scanning electron microscopy and dynamic vapor sorption. The sorption kinetics properties were analyzed using parallel exponential kinetics (PEK) and this data interpreted using the Kelvin-Voigt (K-V) viscoelastic model. Substantial differences in sorption behavior were noted between the guar and cellulose reinforced guar films. Addition of cellulose nanowhiskers (CNWs) to the guar resulted in a change in the shape of the isotherm, as well as a reduced equilibrium moisture content throughout the hygroscopic range. With the guar film, hysteresis between the adsorption and desorption branches of the isotherm occurred up to 75% RH, where it collapsed. Dynamic mechanical analysis showed that the collapse of the hysteresis loop occurred at the glass transi- tion temperature of the guar film. However, addition of CNWs to the guar produced a film where sorption hysteresis was found to occur throughout the hygroscopic range. The applicability of the K-V interpretation of the sorption kinetics is discussed. V C 2013
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RH in vapor sorption analyzers and/or thermogravimetric an- alyzers can be calibrated/verified by determining the DRH of a reference material with a well-defined DRH (ASTM, 2007). In this work, NaBr provided by TA Instruments is used as the reference material (Waguespack and Hesse, 2007). We compare our measured DRHs of NaBr at six dif- ferent temperatures with those reported by a previous study (Greenspan, 1977). The results are summarized in Table 1, suggesting that the differences between our measured and previous reported DRHs is < 1 % RH for temperatures rang- ing from 5 to 30 ◦ C. The agreement is excellent, especially considering that (1) the RH has a stated accuracy of ± 1 % for our instrument and (2) DRH values reported by Greenspan (1977) typically have errors of ± 0.5 %. Further inspection of results compiled in Table 1 reveals that the difference is larger at lower temperature and becomes smaller at higher temperature.
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fraction of closed nanopores where o-Ps are trapped . After final drying (in a vacuum at 120 °C for 4 h) of the cer- amics samples previously exposed to water vapor, the initial pore size tends to be restored (Table 2 and Fig. 3). However, it does not recover entirely, suggesting that some fraction of water molecules remain adsorbed. The intensity I 4 does
Following synthesis, the crude SLI was successively recrystallized in methanol with accompanying purity analyses at each stage. A polythermal solubility turdimetric analysis was subsequently completed to determine the optimum crystallization parameters for the scalable purification of SLI. There is a notable lack of published literature concerning the fundamental properties and characteristics of sodium acyl isethionates. The resultant purified surfactant was therefore subjected to a detailed physicochemical characterisation and analysis which included melting, decomposition, vapor sorption and surface tension measurements. The fundamental data reported in the study provides a much needed insight into how the physicochemical properties influence the commercial scale manufacture, performance and synthesis of acyl isethionate surfactants from biorenewable sources.
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Various modifications were used to convert waste materials into heavy metal sorbents. In this study, simple thermal treatment was applied on rice husk and its sorption potential to remove Zn (II) ions from aqueous solution was investigated. Equilibrium sorption data were evaluated with two commonly used isotherms i.e. Langmuir and Freundlich isotherms. Coefficient of determination (R 2 ) of the models were used to determine the best fitted isotherm. The correlation coefficients were
The equilibrium conditions of copper (II), zinc, cadmium and lead ions have been studied, sorption isotherms have been constructed and calculating formulas that meet isotherms respective to the Langmuir and Freundlich equations has been suggested. The submission of isotherms to the Langmuir equation indicates that the monomolecular layer was formed on the sorbent surface. Being the kinetic mechanism of the processes under the control of internal diffusion is determined by known methods, and the values of diffusion coefficients and substitution period are calculated. It was noted that thermodynamic parameters for rapidly occurring sorption processes are characterized by minimal values, a significant change of the sorption speed has been occurred in cases where the activation energy is high with the temperature change. Enthalpy values from direct calorimetric measurements and theoretical calculations can be normal with 5-7% error. The studied sorbents are lined up according to their sorption capability and kinetic indicator. Since Dowex MAC-3 is characterized by a very high (10,4 mg- ekv/g) exchange capacity, its large number of functional groups make the sorption processes more effective in comparison with other sorbents. The values of the diffusion coefficients and other kinetic and thermodynamic parameters calculated with it also prove the statement. The sorption speed of Cu 2+ ion with this sorbents 3,77; 4,80; 6,0 times higher than the sorption speed of the same sorbent with Duolite C 467, Amberlite IRC 748 and Amberlite IR 120 ions. The values of semi-exchange period calculated for all systems also prove the mentioned statements.
All the parameters of isotherms for sorption the methylene blue by biomass waste mint are determined from the straight linearity (Figure 5, 6, 7 and 8) according to the equations of the models described in Table 1. In considering the reliability of the proposed isotherms models, we calculated the correlation coefficients of the equations and the constants of each model. These are grouped in Table 2.
The performance of a bed depth is obtained through the concept of breakthrough curve. The time or volume for breakthrough appearance and the shape of the breakthrough curve are important characteristics for determining the operation and dynamic response of sorption column. Again, successful design of a sorption column requires prediction of the concentration–time or concentration–volume profile from breakthrough curve for the effluent discharged from the column. When the sorption zone moves up and the upper edge of this zone reaches the top of the column, the effluent concentration starts to rise rapidly; this is called the breakthrough point.
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Abstract. The article deals with the actual problem of improving the vacuum cooling efficiency systems during the biodiesel production by using vacuum devices account for the liquid-vapor ejector, which operates on the princi- ple of jet thermal compression. The purpose of this study is the feasibility of using vacuum devices, that based on the liquid-vapor ejector, and takes as a basis the principle of jet thermal compression in vacuum cooling systems of bio- diesel production units. This article describes the basic scheme of the cooling system devices during the biodiesel production, which includes a three-stage steam-jet ejector and the proposed scheme based on the liquid-vapor ejector. A comparative analysis of the vacuum cooling systems during biodiesel production units was realized, where the schemes were compared on the basis of existent three-stage steam-jet ejectors and a new single-stage vacuum unit based on a liquid-vapor ejector. An exergy method of assessing the effectiveness of the proposed equipment was used as a comparison, because in the working process there is a transformation of two energy types: electric for the pump drive and heat for heating the working fluid of the active flow in the exchanger-heater. The intermediate pressure be- tween the liquid-vapor ejector and the liquid-ring vacuum pump can help to achieve the highest characteristics of the new technology on the optimization parameters.
Abstract: - The study under investigation discovers the sorption conduct of resin used as an adsorbent toward metal ions and specified the percent sorption for the metal that reduced with rise in pH, above pH 6.The degree of uptake for resin initially was fast (88-90 %), creating equilibrium within sixty minutes for Copper. The resin exhibit the extreme percent sorption (86 - 88 %) for Nickel ranging contact time between sixty minutes; further than the described range the surge in % sorption was not recognized. The flow rate, isotherms and thermodynamic parameters were also examined for both the metal ions. PMBMNen effectively eradicated heavy amounts of metals from the real water samples.
by the amount of sorbents HA, MHA I and MHA II in range from 0.01 g to 0.13 g in 10 mL congo red solution. For the sorbent of 0.05 g in 10 mL, it was found that after 60 min agitation time, the amount of dye being adsorbed were 45.78 % for HA, 70.04 % for MHA I and 92.51 % for MHA II. The percent removal of methylene blue increases with respect to increase in sorbent dosage. The percent removal were 37.67 % for HA, 50.61 % for MHA I and 82.91 % for MHA II with respect to 0.05 g in 10 mL of methylene blue solution after the equilibrium time. The higher percent removal capacity may be attributed to the greater quantity of sorbent dose being used. This is due to increased in sorbent dosage attributed to increase in surface area and availability of adsorption site. The dosage method involves the use of different masses of sorbent, but a fixed initial concentration of the sorbate at a certain temperature. Here, to reveal the significance of the removal of congo red and methylene blue, the well-known isotherms were applied such as Langmuir isotherm, Freundlich isotherm and Temkin isotherm. Table (1 - 6) represent the data and Figures ( 1- 18 ) showed the Langmuir, Freundlich and Temkin isotherms pertaining to sorption equations. The calculated results of the Langmuir, Freundlich and Temkin isotherm constants are presented in Table 7.
Cavitation is known as a repeated formation and violent collapse of bubbles in a liquid, which generates very large hydrodynamic stresses. These bubbles can be either gas or vapor filled and can occur in a variety of liquids under a wide range of operating conditions. The collapse of a spherical bubble causes the origin of an impacting microjet. This leads to arising local high pressures and shears. The magnitude of pressure pulse may be as high as 10 3 MPa.
With a view to study phosphate sorption characteristics of soils, an experiment was conducted in the laboratory of the Department of Soil Science, University of Chittagong, Bangladesh. Five different soil series namely the Borkal (Typic Dystrudepts), the Pahartoli (Aeric Endoaquepts), the Raojan (Aeric Endoaquepts), the Noapara (Typic Endoaquepts) and the Manu (Aeric Dystrudepts) were used in the study. Soil samples at a depth of 0–15 cm were collected and mixed together to form a composite sample. The soils were then air dried at room temperature (25±2 0 C) for a week, ground and passed through a 2 mm sieve.
The administration of cholestyramine reduces cholesterol absorption by sequestering bile acid conjugates and decreasing the micellarisation of exogenous cholesterol (Hassan & Rampone 1979; McNamara et al. 1980). Owing to its interrupt- ing the enterohepatic circulation of bile acids, cholestyramine increases their faecal excretion and triggers a compensatory increase in the cholesterol oxidation in the liver. However, this polymeric resin also binds anionic drugs, vitamins, and salts (Johansson et al. 1978; Harmon & Seifert 1991). The competition for cholestyramine binding sites in the digestive tract decreases the binding capacity for bile acids, so large doses are required for the effective sorption (Stedronsky 1994). In some patients, the large doses of cholestyramine required to produce the desired cholesterol level
mixture is used as refrigerant in this vas system. All the remaining parts of the system i.e. condenser, expansion device and evaporator will be same as that of simple vapor compression refrigeration system. This system of ammonia- water refrigerant can provide up to -5 ºc temperature but we can achieve nearly 5-6 ºc temperature range because of some losses. In this project our aim is to achieve the sufficient temperature range for the human comfort. Concentration of this project is to utilize the exhaust gas heat which is wasted to the surrounding and lead to the increase in temperature of atmosphere.
Another possible explanation for the sorption behavior shown in Figure 4.7 is a difference in the initial amount of columnar structure in each sample relative to other structures before sorption. It is known that rapid precipitation of α- and γ-CD from aqueous solution does not result in complete crystallization in the columnar structure. 40 Amorphous and cage structures can precipitate as well, which have different sorption behaviors compare to columnar structure. 29,31 The integral sorption isotherms in Figure 4.7, which are from different precipitations of α-CD, could then be composite sorption isotherms of multiple crystal types containing mostly columnar structure.
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ŠTENCL, J.: Effect of temperature and water activity on heat transfer in parsley leaves in the range of temperatures 10–30 °C. Acta univ. agric. et silvic. Mendel. Brun., 2007, LV, No. 5, pp. 181–186 The equilibrium moisture contents of parsley leaves were measured by the gravimetric dynamic method with continuous recording of changes in sample weight. Consequently water activity values were deter- mined. Henderson equation was found to be a good model both for moisture adsorption and desorption. Isosteric heat of sorption was defi ned and determined in the temperature range of 10–30 °C. Clausius- Clapeyron equation was used to calculate the isosteric heat of sorption since no dependence on tempe- rature in the analysed range was observed. The isosteric heats of sorption (q n st ) were indicated graphic
With vapor phase systems, heat is transferred at the saturation tem- perature of the vapor. As a result, such units can provide uniform, precisely controlled temperatures. The heating of synthetic fiber spin- nerettes represents just one of the many applications that take advan- tage of these vapor properties. In liquid phase systems, the tempera- ture of the heating medium decreases as it gives up its sensible heat. Thus, the temperature of the medium at the inlet will be higher than its temperature at the outlet. This non- uniformity of temperature can be harmful to heat-sensitive products, even when it is reduced by increasing the circulation rate of the medium. However, for heat-insensitive products, such changes in tempera- ture are of little consequence. In systems with multiple heat users, a combination of both vapor and liquid phase may be superior to either by itself. Economics is the deciding factor when considering line sizing, distances, pressure drop, type of equipment, method of tem- perature control, and temperature requirements.
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