Artículos de revistas: "Isosteric method"

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Zheng, Qing Rong, Shuai Gao y Chen Jie. "Determination of the Isosteric Heat of Adsorption of Hydrogen on the Multi-Walled Carbon Nanotubes". Advanced Materials Research 512-515 (mayo de 2012): 1484–91. http://dx.doi.org/10.4028/www.scientific.net/amr.512-515.1484.

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The isosteric heat of adsorption was used to study the interaction between hydrogen molecules and the Multi-Walled Carbon Nanotubes (MWCNTs). Characterizations of the MWCNTs sample were carried out based on the N2 adsorption isotherm at 77 K and the images from TEM and HRTEM. Step by step method was used to volumetrically measure hydrogen adsorption isotherms at equilibrium temperature-pressures from 123-310 K and 0-12.3 MPa. Isosteric heats of adsorption at seven excess adsorption amounts and that at zero surface loading were respectively determined by the slopes of the adsorption isosteres and the plot of the temperature dependence of the Henry’s constants. Results show that the limit of the isosteric heat of adsorption at zero surface loading is about and the mean under the experimental condition is about . The values are in the same grade as those of hydrogen on the activated coconut charcoal but smaller than those of hydrogen on the graphitized carbon black P33, the activated carbon AX-21 and the Single-Walled Carbon Nanotubes (SWCNTs). Conclusions are drawn that relatively lower adsorption amounts and the isosteric heat of hydrogen adsorption on the MWCNTs could be ascribed to the small specific surface area and the large mesopores.

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Giraldo, Liliana, Paola Rodriguez-Estupiñán y Juan Carlos Moreno-Piraján. "Isosteric Heat: Comparative Study between Clausius–Clapeyron, CSK and Adsorption Calorimetry Methods". Processes 7, n.º 4 (10 de abril de 2019): 203. http://dx.doi.org/10.3390/pr7040203.

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This work presents the calorimetric study of five adsorbents with different chemical and textural characteristics: MOF-199, MCM-41, SBA-15, activated carbon prepared from corn cob (GACKP) and graphite. These solids were used to establish the differences between isosteric heats evaluated by three different methods: Clausius–Clapeyron (C-C), Chakraborty, Saha and Koyama (CSK) and Adsorption Calorimetry (A-Cal). The textural characterization results show solids that have values of specific surface area between 2271 m2·g−1 for the MOF-199 and 5.2 m2·g−1 for the graphite. According to the results obtained for the isosteric heats for each sample, the magnitude varies depending on the coverage of the adsorbate and the textural characteristics of each adsorbent. Solids with an organized structure have isosteric heat values that are coincident among the three methods. Meanwhile, heterogeneous solids such as activated carbon values evaluated by the CKS and C-C have a high dispersion method regarding the adsorption calorimetry method. The results obtained show that the adsorption calorimetry, being a direct experimental measurement method, presents less dispersed data. At low quantities, the isosteric heat of nitrogen adsorption decreased in the order MOF-199, GACKP, MCM-41, SBA-15 and Graphite. The order for the isosteric heats values was coherent with the surface characteristics of each of the solids, especially with the pore size distribution. Finally, throughout the coverage examined in this work, the isosteric heats for nitrogen adsorption determined by adsorption calorimetry (A-Cal) were larger than the evaluated by C-C and CSK indirect methods of vaporization. According to the results, it is shown that the adsorption calorimetry allows values of the isosteric heats of adsorption with an error of less than 2% to be established and also reveals the complex nature of the heterogeneity or homogeneity of the adsorbent.

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Yonova, Albena. "Experimental studies on equilibrium adsorption isosteres and determination of the thermodynamic quantities of polar media on alumina Al2O3". Acta Scientifica Naturalis 4, n.º 1 (1 de marzo de 2017): 34–45. http://dx.doi.org/10.1515/asn-2017-0006.

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Abstract The present work is a revieif of theoretical and experimental study on the adsorption performance of the adsorbent Alumina (Al2O3) used in the adsorption system. An experimental investigation on the equilibrium adsorption isosteres at low pressure (< 1 atm) of working pairs Al2O3/H2O and Al2O3/C2H6O2 is carried out. The isovolume measurement method is adopted in the test setup to directly measure the saturated vapor pressures of working pairs at vapor-liquid equilibrium (dG=0 and dμi=0). Quantity adsorbed is determined from pressure, volume and temperature using gas law. The isosteric heat of adsorption is calculated from the slope of the plot of lnP versus 1/T different amounts of adsorbate onto adsorbent as follows: 0,01 vol% Al2O3/H2O; 0,03 vol% Al2O3/H2O; 0,1 vol% Al2O3/H2O; 0,01 vol% Al2O3/C2H6O2; 0,03 vol% Al2O3/C2H6O2; 0,1 vol% Al2O3/C2H6O2. This study shows that adsorption working pair Al2O3 C2H6O2 has better adsorption performances than those of the A2O3/H2O. Surface acidity! is a most important property! far both adsorption and catalysis and therefore is examined structure of active sites of alumina surface. Thermodynamic parameters such as isosteric heat of adsorption, isosteric enthalpy and entropy of adsorption are critical design variables in estimating the performance and predicting the mechanism of an adsorption process and are also one of the basic requirements for the characterization and optimization of an adsorption process

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Štencl, Jiří. "Effect of temperature and water activity on heat transfer in parsley leaves in the range of temperatures 10–30 °C". Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 55, n.º 5 (2007): 181–86. http://dx.doi.org/10.11118/actaun200755050181.

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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 determined. Henderson equation was found to be a good model both for moisture adsorption and desorption. Isosteric heat of sorption was defined 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 temperature in the analysed range was observed. The isosteric heats of sorption (qnst) were indicated graphic in the form qnst versus moisture content. Values for isosteric heat of sorption ranged from 54.41 to 46.85 kJ/mol.

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Li, Dong. "Study on the Calculation method of the Coal and Gas Outburst Threshold". International Journal of Innovative Research in Advanced Engineering 10, n.º 02 (28 de febrero de 2023): 10–17. http://dx.doi.org/10.26562/ijirae.2023.v1002.01.

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The four undetermined parameters of the temperature-pressure-adsorption equation (TPAE) were obtained by regression of the series isothermal adsorption data of the measured middle-rank deformed coal and normal coal. The unit isosteric adsorption enthalpy (UIAE) was obtained. According to the negative value of the UIAE, adsorption is an exothermic process, desorption is an endothermic process. The coal and gas outburst threshold (OT) is defined as the product of the firmness coefficient and the unit isosteric desorption enthalpy (UIDE) to show the combined effect of adsorption thermodynamics and tectonic stress. The UIDE difference between the two coals was from 1.91 times expanded to OT difference of 5.74 times.

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Kloutse, A. F., R. Zacharia, D. Cossement, R. Chahine, R. Balderas-Xicohténcatl, H. Oh, B. Streppel, M. Schlichtenmayer y M. Hirscher. "Isosteric heat of hydrogen adsorption on MOFs: comparison between adsorption calorimetry, sorption isosteric method, and analytical models". Applied Physics A 121, n.º 4 (11 de septiembre de 2015): 1417–24. http://dx.doi.org/10.1007/s00339-015-9484-6.

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7

Cavalcante, Maisa D., Geovana R. Plácido, Daniel E. C. de Oliveira, Bheatriz S. M. de Freitas, Caroline Cagnin y Déborah de S. Oliveira. "Isotherms and isostatic heat of foam-mat dried yellow mombin pulp". Revista Brasileira de Engenharia Agrícola e Ambiental 22, n.º 6 (junio de 2018): 436–41. http://dx.doi.org/10.1590/1807-1929/agriambi.v22n6p436-441.

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ABSTRACT Yellow mombin has high nutritional value but is very perishable. Foam mat drying is a method that has been widely used to preserve liquid and semi-solid powdered foods. In this context, the aim of this study was to determine desorption isotherms and isosteric heat of yellow mombin (Spondias mombin L.) foam for different conditions of temperature and water activity. Powdered yellow mombin pulp was obtained by drying in forced-air oven regulated to 60 ° C. The indirect static method was used to determine the isotherms and isosteric heat, whereas water activity (aw) was determined using the Hygropalm-HP23AW-A analyzer. A B.O.D. incubator, set at 10, 20, 30 and 40 °C, was used to control the temperature, and the water activity for each temperature was between 0.220 and 0.832. The experimental data were fitted to mathematical models frequently used to represent the hygroscopicity of agricultural products, and the best model was the Modified Halsey. Integral isosteric heat of desorption of yellow mombin powder, within the water content range of 17.22 to 57.58 (% d.b.), ranged from 3198.56 to 2598.38 kJ kg-1. It was concluded that the equilibrium water content of yellow mombin pulp powder increased with the increment in water activity; desorption isotherms obtained for yellow mombin pulp powder showed sigmoid form and, with the reduction of water content, the isosteric heat increases.

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Liu, Xiu Ying, Wei Guo Sun, Zhi Qin Fan y Li Ying Zhang. "Adsorption of Methane on Several Zeolites by Monte Carlo Method". Advanced Materials Research 512-515 (mayo de 2012): 1353–57. http://dx.doi.org/10.4028/www.scientific.net/amr.512-515.1353.

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Grand Canonical Monte Carlo (GCMC) method is employed to simulate the adsorption of methane in several nanoporous zeolites. Adsorption isotherms over the temperature 177-398K and the pressure 0-12MPa are simulated. And their adsorption capacities of methane in these zeolites at different temperatures and pressures are also compared. The results show that: (1) the methane uptake is in the order of LTA>MOR>MFI at the same condition. The isosteric heat can support this conclusion: the value of isosteric heat in LTA is the largest, intermediate in MOR and the least in MFI. (2) The effects of the pore volume, channel size and the energetic interactions between zeolite and methane on adsorption amounts are considered. A large pore volume and a suitable channel size near to the kinetic diameter of a methane molecule are very important for improving the storage capacity of zeolites. Based on this, we conclude that LTA zeolite with a large pore volume and a suitable channel diameter exhibit a most efficient methane storage capacity than MOR and MFI zeolites.

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9

Tautz, Markus, César Saldías, Antonio Diego Lozano-Gorrín y David Díaz Díaz. "Use of a bis-1,2,3-triazole gelator for the preparation of supramolecular metallogels and stabilization of gold nanoparticles". New Journal of Chemistry 43, n.º 35 (2019): 13850–56. http://dx.doi.org/10.1039/c9nj03427g.

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10

Poyet, Stéphane, Gaëtan Touzé, Jean-Luc Adia, Laurent Charpin y Sylvie Michel-Ponnelle. "A simple method to measure the isosteric energy of adsorption". Cement and Concrete Research 147 (septiembre de 2021): 106520. http://dx.doi.org/10.1016/j.cemconres.2021.106520.

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11

Cao, J. y D. P. Kamdem. "Moisture adsorption thermodynamics of wood from fractal-geometry approach". Holzforschung 58, n.º 3 (12 de mayo de 2004): 274–79. http://dx.doi.org/10.1515/hf.2004.042.

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Abstract The fractal-geometry approach was used to calculate the thermodynamic properties of moisture sorption by wood from the adsorption isotherms in this study. The results were compared with those from an isosteric approach and a calorimetric approach. The adsorption isotherms of Southern yellow pine (Pinus spp.) were measured at 4, 15, 30, and 40°C to provide source data for the calculation of both fractal-geometry and isosteric approaches. The results show that the fractal dimensions of the internal surfaces of wood vary between 2.4 and 2.5. The curves of the differential heat of adsorption −∆H against moisture content from the fractal-geometry approach are similar to those from calorimetric measurements in previous research. The −∆H values from the isosteric approach increased with moisture content within a moisture content range up to 3%. And, at moisture contents higher than 3%, the −∆H values from this method are much higher than those from the fractal-geometry approach and calorimetric approach. As a result, the fractal-geometry approach is applicable to calculate the differential thermodynamic properties of moisture sorption by wood in future research.

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12

Liu, Xiuying, Jie He y Rui Li. "High-Pressure Hydrogen Adsorption in the Zeolites: A Grand Canonical Monte Carlo Study". ISRN Renewable Energy 2012 (8 de julio de 2012): 1–4. http://dx.doi.org/10.5402/2012/491396.

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The adsorption of hydrogen molecules on different zeolites at near room temperature and extremely high pressures has been simulated employing Grand Canonical Monte Carlo (GCMC) method. Some important physical amounts under different temperatures and pressures, such as adsorption isotherms, adsorption amounts, and isosteric heats were studied. We predict the storage capacity of hydrogen in ZON and CHA zeolites at different conditions. The results show that the hydrogen storage capacity of CHA is superior to that of ZON. The different hydrogen adsorption behavior between them is explained by the isosteric heats of adsorption at different temperatures. These results may help us to understand different hydrogen adsorption properties of these two zeolites, thus facilitate exploring new hydrogen storage candidates experimentally.

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13

Li, Dong, Qinghua Ma, Xuemei Zhang, Yaling Wei y Jingyuan Hao. "STUDY ON THE CALCULATION AND APPLICATION OF THE UNIT ISOSTERIC ADSORPTION ENTHALPY". International Journal of Innovative Research in Advanced Engineering 9, n.º 11 (30 de noviembre de 2022): 453–58. http://dx.doi.org/10.26562/ijirae.2022.v0911.03.

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A series of isothermal adsorption experimental data of lean coal and fat coal has been converted into a temperature-pressure-adsorption equation. The slop of the lnP vs 1/T straight line of Clausius-Clapeyron equation proves that physical adsorption is an exothermic process. The Unit Isosteric Adsorption Enthalpy (UIAE, KJ•mol-1•cm-3•g) is defined as a unit adsorbed amount enthalpy at a fixed adsorbed amount andthe calculation method is presented. The UIAE calculation results prove the surface of the adsorption medium is not uniform, and the interaction between the adsorption molecules occurs. At the same isosteric adsorption condition, lean coal has higher priority to carry out the exothermic process than the fat coal.

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Ouaabou, Rachida, Said Ennahli, Chira Di Lorenzo, Hafida Hanine, Aadil Bajoub, Rachid Lahlali, Ali Idlimam, Ahmed Ait Oubahou y Mohamed Mesnaoui. "Hygroscopic Properties of Sweet Cherry Powder: Thermodynamic Properties and Microstructural Changes". Journal of Food Quality 2021 (1 de diciembre de 2021): 1–11. http://dx.doi.org/10.1155/2021/3925572.

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Understanding sorption isotherms is crucial in food science for optimizing the drying processes, enhancing the shelf-life of food, and maintaining food quality during storage. This study investigated the isotherms of sweet cherry powder (SCP) using the static gravimetric method. The experimental water sorption curves of lyophilized sweet cherry powder were determined at 30°C, 40°C, and 50°C. The curves were then fitted to six isotherm models: Modified GAB, Halsey, Smith, Oswin, Caurie, and Kühn models. To define the energy associated with the sorption process, the isosteric sorption heat, differential entropy, and spreading pressure were derived from the isotherms. Among the six models, the Smith model is the most reliable in predicting the sorption of the cherry powder with a determination coefficient (R2) of 0.9978 and a mean relative error (MRE) ≤1.61. The values of the net isosteric heat and differential entropy for the cherry increased exponentially as the moisture content decreased. The net isosteric heat values varied from 10.63 to 90.97 kJ mol−1, while the differential entropy values varied from 27.94 to 273.39 J. mol−1K−1. Overall, the enthalpy-entropy compensation theory showed that enthalpy-controlled mechanisms could be used to regulate water adsorption in cherry powders.

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Sousa, Kelly A. de, Osvaldo Resende y Bruno de S. Carvalho. "Determination of desorption isotherms, latent heat and isosteric heat of pequi diaspore". Revista Brasileira de Engenharia Agrícola e Ambiental 20, n.º 5 (mayo de 2016): 493–98. http://dx.doi.org/10.1590/1807-1929/agriambi.v20n5p493-498.

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ABSTRACT The objective was to determine water sorption isotherms of diaspores of pequi fruits in order to obtain information on the amount of water that this product desorbs at the temperatures of 10, 20, 30 and 40 °C and water activities from 0.20 to 0.89, adjusting different mathematical models to experimental data, and to determine its latent heat and isosteric heat. The equilibrium moisture content was obtained through the indirect static method, using the device Hygropalm Model Aw 1. The Modified Henderson model was the one that best fitted the data and was selected to predict the equilibrium moisture content of pequi diaspore. It was observed that the higher the temperature for the same equilibrium moisture content (% d.b.), the higher the water activity values. As temperature values increased, there was a reduction in the vaporization latent heat of the product. Isosteric heat values of diaspores of pequi fruits in the moisture content range of 4.02 to 16.63 (% d.b.) varied from 2,776.49 to 2,558.39 kJ kg-1.

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Oliveira, Daniel E. C. de, Osvaldo Resende, Lílian M. Costa, Weder N. Ferreira Júnior y Silva Igor O. F. "Hygroscopicity of baru (Dipteryx alata Vogel) fruit". Revista Brasileira de Engenharia Agrícola e Ambiental 21, n.º 4 (abril de 2017): 279–84. http://dx.doi.org/10.1590/1807-1929/agriambi.v21n4p279-284.

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ABSTRACT With the knowledge on the hygroscopic equilibrium of the baru (Dipteryx alata Vogel) fruit, the product can be adequately handled to maintain the moisture content at the levels recommended for safe storage. Thus, this paper aimed to determine the water desorption isotherms of baru fruits at temperatures of 20, 25, 30 and 35 °C, and water activity between 0.14 and 0.80, and obtain the values of isosteric heat of desorption as a function of the equilibrium moisture content of the product. The equilibrium moisture content was obtained using the static-gravimetric method. Modified Halsey was the best model recommended to represent the hygroscopicity of baru fruits. The recommended moisture contents for safe storage of baru fruits are not more than 19.9, 19.3, 18.6 and 18.0 (%, d.b.) for the respective temperatures of 20, 25, 30 and 35 °C. The integral isosteric heat of desorption increases as the water content decreases, leading to an increment in the energy required to remove water from the product.

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Oliveira, Daniel E. C. de, Osvaldo Resende, Lílian M. Costa, Glicélia P. Silva y Juliana de F. Sales. "Hygroscopicity of ‘sucupira-branca’ (Pterodon emarginatus Vogel) fruits". Revista Brasileira de Engenharia Agrícola e Ambiental 21, n.º 4 (abril de 2017): 285–89. http://dx.doi.org/10.1590/1807-1929/agriambi.v21n4p285-289.

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ABSTRACT ‘Sucupira-branca’ (Pterodon emarginatus Vogel) is a tree from ‘Cerrado’ and stands out mainly for its pharmacological properties; however, there are no technological information about its post-harvest operations. Thus, the aim of this study was to determine the sorption isotherms of ‘sucupira-branca’ fruits for different air conditions and obtain the values of desorption isosteric heat, depending on the equilibrium moisture content of the product. The equilibrium moisture content of ‘sucupira-branca’ fruits was determined by dynamic method for temperatures of 25, 30, 35 and 40 °C and water activities for each temperature between 0.270 and 0.775. The models Chung-Pfost, Copace, Modified Halsey, Oswin Modified and Sigma Copace obtained high coefficient of determination (R2) and low chi-square (χ2), relative mean error (P) and estimated mean error (SE), and the Copace model was selected to represent the desorption isotherms. The isosteric heat increases with the reduction of equilibrium moisture content and required more energy to remove water from the ‘sucupira-branca’ fruit.

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Barbosa, Karine F., Juliana de F. Sales, Osvaldo Resende, Daniel E. C. de Oliveira, Jacson Zuchi y Kelly A. de Sousa. "Desorption isotherms and isosteric heat of 'cajuzinho-do-cerrado' achenes". Revista Brasileira de Engenharia Agrícola e Ambiental 20, n.º 5 (mayo de 2016): 481–86. http://dx.doi.org/10.1590/1807-1929/agriambi.v20n5p481-486.

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ABSTRACT The objective of this study was to determine the desorption isotherms of 'cajuzinho-do-cerrado' achenes (Anacardium humile St. Hil.) in various conditions of temperature and water activity, as well as to select the one that best represents the phenomenon and to determine the isosteric heat of desorption. The fruits were collected at the Emas National Park, in the municipality of Mineiros-GO, Brazil, pulped and then subjected to drying in silica gel at temperature of 25 ± 2 °C until the moisture contents of 17.6, 13.6, 11.1, 8.7 and 5.3 (d.b.%). After drying, the desorption isotherms were determined by the indirect static method. The water activity (Aw) was determined at different temperatures, and the achenes were placed in a B.O.D. chamber, regulated at 10, 20, 30 and 40 °C. Data of hygroscopic equilibrium moisture content were fitted to different mathematical models through non-linear regression analysis, using the Gauss-Newton method. The Copace model was the one that best represented the hygroscopicity of 'cajuzinho-do-cerrado' achenes, while the integral isosteric heat of desorption of 'cajuzinho-do-cerrado' achenes for the moisture content range of 4.51 to 13.40 (% d.b.) varied from 2,734.82 to 2,548.49 kJ kg-1.

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Ferreira Junior, Weder N., Osvaldo Resende, Kelly A. de Sousa, Melícia I. A. Gavazza, Juliana de F. Sales y Daniel E. C. de Oliveira. "Desorption isotherms and isosteric heat of araticum (Annona crassiflora Mart.) seeds". Revista Brasileira de Engenharia Agrícola e Ambiental 24, n.º 9 (septiembre de 2020): 630–36. http://dx.doi.org/10.1590/1807-1929/agriambi.v24n9p630-636.

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ABSTRACT The objective of this study was to determine the desorption isotherms and isosteric heat of Annona crassiflora Mart. seeds, using Akaike information criterion (AIC) and Schwarz’s Bayesian information criterion (BIC) to assist in the choice of the nonlinear regression model. The desorption isotherms were determined by indirect static method and water activity was obtained using the instrument HygroPalm; the product was put in the device in B.O.D. chamber set at 10, 20, 30 and 40 °C. Several nonlinear regression models were fitted to the experimental data by the Gauss-Newton method. The desorption isotherms of Annona crassiflora Mart. seeds can be represented by the models of Chung-Pfost, Copace, Modified GAB, Modified Henderson, Modified Oswin, Sabbah and Sigma Copace. However, the Sigma Copace model showed better fit to the experimental data, with lower AIC and BIC values, being chosen to represent the desorption isotherms of Annona crassiflora Mart seeds. Isosteric heat increased with decreasing moisture content, requiring a greater amount of energy to remove water from seeds, with values ranging from 2541.64 to 2481.56 kJ kg-1, for the moisture content range from 5.69 to 14.93% on a dry basis.

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Ren, Zhong Yang, Yan Yan Wu, Zhen Hua Duan, Lai Hao Li y Xian Qing Yang. "Experimental Study and Modelling of Moisture Sorption Isotherms of Salted Largehead Hairtail (Trichiurus lepturus) at 25 and 35°C". Advanced Materials Research 1033-1034 (octubre de 2014): 681–89. http://dx.doi.org/10.4028/www.scientific.net/amr.1033-1034.681.

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The moisture sorption characteristics of salted largehead hairtail (Trichiurus lepturus) were investigated within the limits of water activity (0.11-0.98) at 25 and 35°C using a self-made instrument for the measurement of the equilibrium moisture content according to the static gravimetric method. The shape of the sorption isotherms was sigmoidal. The moisture sorption isotherms exhibited significant hysteresis. The hysteresis of salted fish may be due to the salt permeating into the body of the fish as a result of desorption and adsorption processes. Seventeen mathematical models were fit to the experimental data for the equilibrium moisture content at different water activity levels. The Ferro-Fontan equation provided the best fit for the experimental data of the equilibrium moisture content among the 17 models assessed for the sorption isotherms at 25 and 35°C. The net isosteric heats of sorption decreased gradually with increases in moisture content. The isosteric heats of sorption ranged from 44.59 kJ/mol to 45.61 kJ/mol between the moisture contents of 22.22% and 43.25% for salted largehead hairtail.

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Mohamad Efendi, Yusuf Hendrawan, La Choviya Hawa, Bambang Dwi Argo, Sumardi Hadi Sumarlan y Bambang Susilo. "Moisture adsorption isotherms properties of dried overripe barlin fruit (Musa acuminata AA.) powder". World Journal of Advanced Research and Reviews 18, n.º 2 (30 de mayo de 2023): 1386–95. http://dx.doi.org/10.30574/wjarr.2023.18.2.0977.

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Moisture sorption of dried overripe barlin banana powder using the static gravimetric method. The materials were conditioned at 5, 10, and 25 oC with a water activity range of 0.16 to 0.86. Five mathematical models to describe the suitability of the phenomenon of adsorption experimental data using non-linear regression. The thermodynamic properties such as isosteric heat and Gibbs free energy are evaluated in this paper. The experimental results indicated that the equilibrium moisture content of dried overripe barlin banana powder increased with increasing water activity and decreasing temperature. The results of the model are based on the goodness of fit, and the Peleg model is the most suitable for describing the adsorption phenomenon with the type II sigmoidal shape. Monolayer moisture content and adsorption surface area using the GAB model are in the range of 6.18-7.81%d.b and 219.09-246.39 m2/g d.b, respectively, which increases with increasing temperature. Moreover, isosteric heat decreases with an increase in equilibrium moisture content and is opposite to the value of Gibbs free energy. In addition, the hygroscopicity of the dried overripe barlin banana powder increased with temperature and water activity.

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Suntaro, Kiattisak, Supawan Tirawanichakul y Yutthana Tirawanichakul. "Determination of Isosteric Heat and Entropy of Sorption of Air Dried Sheet Rubber Using Artificial Neural Network Approach". Applied Mechanics and Materials 541-542 (marzo de 2014): 374–79. http://dx.doi.org/10.4028/www.scientific.net/amm.541-542.374.

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Equilibrium moisture contents (EMC) of air dried sheet (ADS) rubber were determined by commonly gravimetric-static method with saturated salt solution among surrounding temperatures of 40-70°C correlated to water activity (aw) ranges between 0.10 and 0.9. The experimental results was analyzed by 5 commonly EMC model. The results showed that equilibrium moisture content of ADS rubber decreased with increase of surrounding temperature at constant water activity and the simulated data using Chung-Pfost model has a good relation to experimental data with R2, RMSE and χ2 equal 0.9565, 0.0235 and 0.0006, respectively. However some physical property of ADS rubber sample affects to evaluate EMC modeling. Due to avoid this effect, thus the aim of this research work was to determine EMC value by using Artificial neural network (ANN) method and also evaluate the isosteric heat of sorption by following the Clausius-Clapeyron equation. The results showed that simulated results using ANN approach has relatively high accuracy compared to common EMC model. Finally determination of isosteric heat of sorption and entropy of sorption of ADS rubber were carried on. The results stated that the enthalpy and entropy of heat sorption was power function and polynomial function of moisture content respectively. These two parameters of ADS rubber can be used for prediction suitable storage condition and drying condition for ADS rubber drying in the near future work.

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Zálešák, František, Jan Slouka y Jakub Stýskala. "General Synthesis of 1-Aryl-6-azaisocytosines and Their Utilization for the Preparation of Related Condensed 1,2,4-Triazines". Molecules 24, n.º 19 (1 de octubre de 2019): 3558. http://dx.doi.org/10.3390/molecules24193558.

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A simple general synthesis of 1-aryl-6-azaisocytosine-5-carbonitriles 4 is described. This method is based on coupling diazonium salts with cyanoacetylcyanamide 2 and then cyclization of the formed 2-arylhydrazono-2-cyanoacetylcyanamides 3. The 6-azaisocytosines 4 were studied with respect to tautomeric equilibrium and the transformation of functional groups, and used in the synthesis of the condensed heterocyclic compounds: Purine isosteric imidazo[2,1-c]-[1,2,4]triazine 8 and the 1,2,4-triazino[2,3-a]quinazolines 9–12.

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Costa, Lílian Moreira, Osvaldo Resende, Weder Nunes Ferreira Junior, Daniel Emanuel Cabral de Oliveira y Igor Olacir Fernandes Silva. "Isotermas e calor isostérico de dessorção das sementes de tungue". Revista Principia - Divulgação Científica e Tecnológica do IFPB 1, n.º 54 (5 de abril de 2021): 163. http://dx.doi.org/10.18265/1517-0306a2021v1n54p163-171.

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The tung is a species that has potential for biodiesel production, so for safe storage there is a need to get to know its hygroscopicity. The objective of this work was to determine the desorption isotherms based on the recommendation of a mathematical model, to define the safe moisture content for storage, and to obtain the isosteric heat for the tung seeds. In order to obtain the hygroscopic equilibrium water content, the static method was used, with 20g of seeds surrounded by a permeable tissue, and placed inside the desiccators containing salt solutions, in a BOD chamber with temperatures of 20, 25, At 30 and 35 ºC, water activity ranged from 0.14 to 0.812 decimal.The Akaike information criterion (AIC) and Bayesian Schwarz information criterion (BIC) were used to adjust the mathematical models and to help choose the best one. Among the tested models, ChungPfost was elected to represent the desorption isotherms of tung seeds. Integral isosteric desorption heat values in the equilibrium moisture content range from 2.08 to 8.35 (% b.s.) ranged from 3754 to 2555 kJ kg-1

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Echeverría, Jesús C., Ignacio Calleja, Paula Moriones y Julián J. Garrido. "Fiber optic sensors based on hybrid phenyl-silica xerogel films to detect n-hexane: determination of the isosteric enthalpy of adsorption". Beilstein Journal of Nanotechnology 8 (21 de febrero de 2017): 475–84. http://dx.doi.org/10.3762/bjnano.8.51.

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We investigated the response of three fiber optic sensing elements prepared at pH 10 from phenyltriethoxysilane (PhTEOS) and tetraethylsilane (TEOS) mixtures with 30, 40, and 50% PhTEOS in the silicon precursor mixture. The sensing elements are referred to as Ph30, Ph40 and Ph50, respectively. The films were synthesized by the sol–gel method and affixed to the end of optical fibers by the dip-coating technique. Fourier transform infrared spectroscopy, N2 adsorption–desorption at 77 K and X-ray diffraction analysis were used to characterize the xerogels. At a given pressure of n-hexane, the response of each sensing element decreased with temperature, indicating an exothermic process that confirmed the role of adsorption in the overall performance of the sensing elements. The isosteric adsorption enthalpies were obtained from the calibration curves at different temperatures. The magnitude of the isosteric enthalpy of n-hexane increased with the relative response and reached a plateau that stabilized at approximately −31 kJ mol−1 for Ph40 and Ph50 and at approximately −37 kJ mol−1 for Ph30. This indicates that the adsorbate–adsorbent interaction was dominant at lower relative pressure and condensation of the adsorbate on the mesopores was dominant at higher relative pressure.

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Siqueira, Valdiney Cambuy, Fernanda Pimentel Da Silva, Wellytton Darci Quequeto, Rodrigo Aparecido Jordan, Rafael Araujo Leite y Geraldo Acácio Mabasso. "Desorption isotherms and isosteric heat of niger grains (Guizotia abyssinica (L. f.) Cass.)". REVISTA AGRO@MBIENTE ON-LINE 12, n.º 2 (30 de junio de 2018): 124. http://dx.doi.org/10.18227/1982-8470ragro.v12i2.4908.

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Niger seed oil has excellent quality and quantity (30-50%) and is rich in polyunsaturated fatty acids, mainly linoleic acid (about 70%). Thus, control of environmental temperature and relative humidity, and of seed moisture content is essential to maintain seed oil quality during storage. Thus, the objective of this study was to determine the desorption isotherms of niger seeds under different temperature and water activity conditions, to test the experimental data with different mathematical models, and discover which best represents the phenomenon, as well as calculate the isosteric heat value for the product. Hygroscopicity was determined by the static gravimetric method, at temperatures of 30, 35 and 40 ºC, and water activity between 0.07 and 0.79 (decimal). For the experimental data, mathematical models commonly used to test hygroscopicity in agricultural products were evaluated. From the results obtained, it was concluded that: water activity increases as moisture content rises; based on the statistical parameters, the models of Chung and Pfost, modified Henderson, Oswin, Sabbah, Sigma Copace, Halsey, Smith and Copace appropriatrely represented the desorption phenomenon of niger seeds; total isosteric desorption heat increased with reduction of moisture content, with values varying from 2539.62 to 3081.48 kJ kg-1, within the range of equilibrium moisture content of 2.4 to 12.2 (% dry basis).

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Agbor, Agbor Evelyn, Charles Chukwuma Ariahu, Peter A. Adie y E. C. Ariahu. "Moisture Transfer Characteristics and Microbiological Stability of Fermented Pre-gelatinized Plantain and Soybean Based Complementary Food Flours". Asian Food Science Journal 23, n.º 4 (27 de abril de 2024): 44–53. http://dx.doi.org/10.9734/afsj/2024/v23i4710.

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The effect of gelatinization and fermentation on the moisture sorption characteristics and microbial stability of complementary foods from unripe plantain fruits and soybean seeds was evaluated. The plantain was heated to obtain 10%, 18%, 23%, 33%, 74% and 100% starch gelatinization. The samples were fermented, dried and ground to flour. Plantain and soybean flour were mixed by material balance to produce 16% protein complementary foods. Moisture sorption isotherms wereinvestigated at 10, 20, 30, and 40 ° C using the gravimetric method. The BET equation was fitted to the experimental sorption data, and the Clausius-Clapeyron equation was used to determine the isosteric heat of sorption. The microbial stability of the gruels was evaluated using the microbial challenge test with Staphylococcus aureus. With better results from fully gelatinized samples, gelatinization and fermentation reduced the hygroscopic properties of the dehydrated products, with the gelatinized fermented samples having the least equilibrium moisture contents, monolayer moisture values, surface area of sorbent, and net isosteric heats of sorption, an indication that these samples could be stored at temperatures as high as 40 ° C with extended shelf life. The microbiological stability of foods was enhanced by fermentation, since microbial growth was suppressed in fermented samples, offering perspectives for microbial stability of the products.

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Ferreira Junior, Weder N., Osvaldo Resende, Daniel E. C. de Oliveira y Lílian M. Costa. "Isotherms and Isosteric Heat Desorption of Hymenaea stigonocarpa Mart. Seeds". Journal of Agricultural Science 10, n.º 10 (15 de septiembre de 2018): 504. http://dx.doi.org/10.5539/jas.v10n10p504.

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The Brazilian Cerrado is one of the most important ecosystems and due to the extractivism it is necessary to recover the degraded areas. The tree of Hymenaea stigonocarpa Mart. is used in this reforestation system, so the study of post-harvest management of the seed is necessary for the propagation. The objective of this work was to determine the isotherms and the isosteric desorption heat of Hymenaea stigonocarpa Mart. Seeds, and to test the methodology of the Akaike’s information criterion (AIC) and Schwarz’s bayesian information criterion (BIC) for the choice of the best mathematical model. Different mathematical models were fitted to the experimental data and the model that best represents the phenomenon was selected, from the statistical parameters. To obtain the equilibrium moisture content was used static method using desiccants in incubators cameras with control of relative humidity by salt solution. The Oswin Modified model obtained better results according to analyzed parameters, being this model the one selected for prediction of the hygroscopic balance of the Hymenaea stigonocarpa Mart. seeds. It was found that the higher the temperature for the same equilibrium moisture content, the higher the water activity values. The AIC and BIC methodology contributed to the choice of the best mathematical model to predict the hygroscopicity phenomenon. The isosteric heat increased with the decrease in the equilibrium moisture content requiring a greater amount of energy to remove water from the seeds.

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Shim, Wang-Geun, Min-Joo Lee, Hyun-Chul Kang, Chan Kim, Jae-Wook Lee, Sang-Chai Kim y Hee Moon. "Surface Energy Heterogeneity and Heterogeneous Adsorption of Benzene on Double-Walled Carbon Nanotubes". Journal of Nanoscience and Nanotechnology 7, n.º 11 (1 de noviembre de 2007): 3896–901. http://dx.doi.org/10.1166/jnn.2007.057.

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We examined the adsorption properties of double walled carbon nanotubes (DWCNTs) synthesized by using a catalytic chemical decomposition vapor method. To analyze the structural and energetical surface characteristics of the DWCNTs, nitrogen and benzene adsorption isotherms were measured. The Toth isotherm equation was used to correlate the adsorption data and evaluate the thermodynamic properties such as Henry's constant and the adsorption second virial coefficient. The existence of heterogeneous surface in DWCNTs was confirmed by the analysis of pore size distribution, the isosteric heat of adsorption, and the adsorption energy distribution determined for nitrogen and benzene.

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Akmel, Djedjro C., Kouassi E. Kakou, Kisselmina Y. Kone, Nogbou E. Assidjo y Patrice Kouame. "Desorption Isotherms and Isosteric Heats of Fermented Cocoa Beans (Theobroma cocoa)". Journal of Food Research 4, n.º 3 (6 de abril de 2015): 138. http://dx.doi.org/10.5539/jfr.v4n3p138.

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Water desorption isotherms of fermented cocoa beans from Ivory Coast were determined using the gravimetric static method of saturated salts solutions at 30 °C, 40 °C and 60 °C, and isosteric heats of desorption were calculated from Clausius-Clapeyron equation. The experimental data were fitted to several isotherm equations. The best fittings were obtained for the BET equation for aw<0.50 (with an average mean relative deviation (MRD) value of 1.56%) and for the Harkins-Jura equation for aw?0.50 (with an average value MRD equation of 4.17%). The isotherms obtained at 30 °C and 40 °C are practically coincident and overlapped for aw below 0.40. Fermented cocoa beans presented a monolayer moisture content of 0.083 dry basis (d.b.) at 30 °C and this value decreases with increasing temperature. The net isostheric heats of desorption for fermented cocoa beans for the temperature range studied (30-60 °C) were estimated as a function of moisture content. The maximum net isosteric heat of desorption for fermented cocoa beans was estimated at around 13.51 kJ/mol corresponding to a moisture content value of 2.85%. The energy requirement for maintaining the moisture content low of 8.7% (d.b.) or 8% wet basis (w.b.) for safe storage of this product or for reducing the moisture content during drying was estimated at around 9.58 kJ/mol.

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31

Pedro, Maria Angélica Marques, Javier Telis-Romero y Vânia Regina Nicoletti Telis. "Effect of drying method on the adsorption isotherms and isosteric heat of passion fruit pulp powder". Ciência e Tecnologia de Alimentos 30, n.º 4 (diciembre de 2010): 993–1000. http://dx.doi.org/10.1590/s0101-20612010000400024.

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32

Du, Zhenyu, Xianhua Nie, Shuai Deng, Li Zhao, Shuangjun Li, Yue Zhang y Jie Zhao. "Comparative analysis of calculation method of adsorption isosteric heat: Case study of CO2 capture using MOFs". Microporous and Mesoporous Materials 298 (mayo de 2020): 110053. http://dx.doi.org/10.1016/j.micromeso.2020.110053.

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33

Verdier Abouo, N., K. Ernest Kakou, E. Edwige Akoa y N. Emmanuel Assidjo. "MODELING OF THE WATER ADSORPTION ISOTHERM OF MANGO SLICES (MANGIFERA INDICA L.) DRIED UNDER HOT AIR". International Journal of Advanced Research 11, n.º 05 (31 de mayo de 2023): 603–12. http://dx.doi.org/10.21474/ijar01/16913.

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The general objective of this work is to contribute to the reduction of post-harvest losses of mangoes by the transformation into stable dried products.This research aims to determine the best storage conditions for dried mangoes.Thus, the water adsorption isotherms of mango slices dried under hot air were experimentally determined by the static thermogravimetric method at 25Ã‚Â°C.Eight mathematical models from the literature were used (GAB, BET, Hasley, Henderson, Harking and Dura, Oswin, Chung and Pfost, Smith) to describe the hygroscopic behavior of dried mango slices.Regression analysis was performed using MatLab R2016a software to determine the coefficients, model parameters and statistical parameters of the smoothing.The results revealed that the equilibrium is obtained from 35 days for the two samples and the adsorption isotherms determined are of type II characterized by a sigmoidal shape.In addition, the three-parameter (GAB) model showed good agreement with the experimental data (r= 0.999 and 0.997 respectively for slices with thicknesses of 1cm and 1.5cm) at 25Ã‚Â°C.The water content of the mono-molecular layer is 2.295% at 25Ã‚Â°C for the 1cm slices and 2.289% at 25Ã‚Â°C for the 1.5cm slices.The net isosteric heat of adsorption tends towards zero for high water contents (0.052KJ/mol at 44.472% water).The linearity between enthalpy (net isosteric heat) and differential entropy of adsorption shows their compensation.

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34

Ajala, A. S., P. O. Ngoddy y J. O. Olajide. "Sorption isotherms and their fitted equations for dried chips of cassava roots (Manihot Esculenta Crantz; Tme-7 variety) and the resulting isosteric heats of sorption". Food Research 4, n.º 3 (17 de enero de 2020): 703–11. http://dx.doi.org/10.26656/fr.2017.4(3).340.

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Cassava roots are susceptible to deterioration with 24 hrs of harvest; it needs processing into a more stable material such as dried cassava chips to extend its shelf life for long storage. However, improper knowledge of the effect of atmospheric relative humidity on these dried chips during storage makes it mouldy and unacceptable. This work aimed at studying the effect of sorption isotherms on the dried cassava chips. In this study, adsorption and desorption isotherm were carried out using static gravimetric method and data for equilibrium moisture content (EMC) were generated at five (5) temperatures (53, 60, 70, 80, 86oC). These were fitted into four (4) isotherm-models [Oswin, Peleg, the Modified Oswin and GAB]. The statistical criteria to test the models were coefficient of determination (R2 ), reduced chi-square (χ 2 ), root mean square error (RMSE) and mean bias error (MBE). The values of EMC ranged from 7.21-12.44% wb. The values of R2 ranged from 0.95-0.99; χ 2 ranged from 0.008-0.14; RMSE values ranged from 0.06-0.254 while MBE values ranged from -0.0004-1.1E-5. The values of isosteric heat of sorption calculated from the isosteres recorded a range from 6.579 to 67.829 kJ/mole. The Pelegmodel gave the best fit in the relative humidity range of 10 to 80%. The values of EMC show that the chips can have a stable shelf life without spoilage.

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Larbi, Ahmed Amine, Akil Loumani, Ahmed Mediani, Asma Masmoudi, Fatima Zohra Bnoumachich, Djaber Abdelkarim, Tigani Cherif y Ahmed Harrouz. "Inﬂuence of temperature and Thermodynamic Analysis on Adsorption/Desorption Isothermss for green menth." Algerian Journal of Renewable Energy and Sustainable Development 5, n.º 1 (15 de junio de 2023): 85–93. http://dx.doi.org/10.46657/ajresd.2023.5.1.11.

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The objective of this study is to experimentally determine the sorption isotherms and thermodynamic properties of green mint after undergoing thermal and biochemical treatment. The method employed is the gravimetric method using saturated saline solutions at various temperatures. In order to model and predict the hygroscopic behavior during drying and storage, we have utilized developed mathematical models (such as the Langmuir, GAB, modified BET, Peleg models, etc.). The adjustment and optimization of these models will be conducted using statistical techniques to analyze the obtained data. The isosteric desorption heats of green mint will be calculated using the Clausius-Clapeyron equation. This study will provide an expression to predict the thermodynamic properties of green mint.

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Corrêa, P. C., A. L. D. Goneli, C. Jaren, D. M. Ribeiro y O. Resende. "Sorption Isotherms and Isosteric Heat of Peanut Pods, Kernels and Hulls". Food Science and Technology International 13, n.º 3 (junio de 2007): 231–38. http://dx.doi.org/10.1177/1082013207079601.

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This study was carried out to evaluate the sorption isotherms of peanut pods, kernels and hulls for several temperature and humidity conditions and to fit different mathematical models to the experimental data, selecting the one best fitting the phenomenon. The dynamic method was applied to obtain the hygroscopic equilibrium moisture content. The environmental conditions were provided by means of an atmospheric conditioning unit, in which removable perforated trays were placed to allow air to pass through peanut mass, each one containing 50 g of the product. The mathematical models frequently used for the representation of hygroscopicity of agricultural products were fit to the experimental data. Based on those results, it was concluded that peanut pods, kernels and hulls presented differentiated hygroscopicity. The equilibrium moisture content for peanut pods, kernels and hulls increased with an increase in the relative humidity at any particular temperature and decreased with increase in temperature at constant relative humidity. At a constant water activity, peanut hulls samples had higher equilibrium moisture content than the pods and kernels samples. Based on statistical parameters, the modified Henderson and Chung-Pfost models were found to adequately describe the sorption characteristics of peanut pods, kernels and hulls. Isosteric heat of desorption were evaluated by applying the Clausius—Clapeyron equation to experimental isotherms and decreased with increasing moisture content. The peanut hulls had higher isosteric heat of sorption than that peanut pods and kernels.

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Jiang, Xiuping, Xiuping Jiang, Huanhuan Li, Hosahalli S. Ramaswamy, Songming Zhu, Yong Yu, Huanhuan Li, Hosahalli S. Ramaswamy, Songming Zhu y Yong Yu. "Moisture Sorption Isotherms and Isosteric Heats of Sorption of High-Pressure Treated Paulownia Wood under Different Storage Conditions". Transactions of the ASABE 62, n.º 1 (2019): 105–14. http://dx.doi.org/10.13031/trans.12899.

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Abstract. Understanding of moisture sorption isotherms (MSI) is critical for predicting the stability of wood during handling, transport, and storage. The aim of this study was to evaluate the adsorption and desorption isotherm characteristics of high-pressure (HP) treated paulownia wood and to identify the best-fitting model to describe its sorption behavior. The equilibrium moisture contents (EMCs) of HP-treated paulownia wood were obtained using a static gravimetric method under different storage conditions: three temperatures (20°C, 30°C, and 40°C) and five water activity (aw) levels (0.32 to 0.95). Results showed that HP parameters did not significantly affect the MSI trend of treated groups. Eight modified models (modified Chung-Pfost, modified Henderson, modified Oswin, modified Halsey, Chen-Clayton, Guggenheim-Anderson-de Boer (GAB), simply modified GAB, and Peleg) were fitted to the experimental data. The Chen-Clayton model (temperature-dependent) produced randomized residuals and the best prediction performance for both adsorption and desorption among all models. Net isosteric heat of adsorption and desorption decreased from 7.55 to 4.84 kJ mol-1 and from 18.1 to 12.2 kJ mol-1, respectively, with an increase in EMC from 7.5% to 10%. The isosteric temperature (Tß) was 352 K for adsorption and 335 K for desorption, between which all the adsorption and desorption reactions proceeded at the same rate. All thermodynamic functions were adequately characterized by a power law model. Keywords: Equilibrium moisture content, High-pressure treatment, Modeling, Moisture sorption isotherm, Paulownia wood, Temperature, Thermodynamic analysis.

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Mentasty, L., A. M. Woestyn, E. Basaldella, A. Kikot y G. Zgrablich. "High-Pressure Methane Adsorption on NaX and NaY Zeolites with Different Si/Al Ratios". Adsorption Science & Technology 11, n.º 4 (diciembre de 1994): 209–16. http://dx.doi.org/10.1177/026361749401100403.

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One method of increasing the storage capacity of compressed natural gas, an alternative for vehicular fuel, is by adsorbing it on to microporous solids such as zeolites or activated carbons. NaX and NaY zeolites with different Si/Al ratios have been synthesized and characterized. Experimental adsorption isotherms for CH4 on these zeolites have been obtained at different temperatures over a pressure range of 0–5 MPa using a high-pressure volumetric apparatus. Isosteric heats of adsorption have been estimated and the isotherms analyzed applying a statistical thermodynamic model. The efficiency of this solid as a methane storage system has been evaluated and compared with other sorbents. Encouraging results have been obtained.

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Makowski, Wacław. "Quasi-equilibrated temperature programmed desorption and adsorption: A new method for determination of the isosteric adsorption heat". Thermochimica Acta 454, n.º 1 (febrero de 2007): 26–32. http://dx.doi.org/10.1016/j.tca.2006.12.015.

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40

Zhang, Dongqing. "Modelling Methane Adsorption Isotherms on Shale at Different Temperatures". Atmosphere 13, n.º 6 (25 de mayo de 2022): 865. http://dx.doi.org/10.3390/atmos13060865.

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Prediction of adsorption isotherms under different temperatures is significant to reserve estimation of shale gas reservoirs. Based on the Polanyi adsorption potential theory and Langmuir adsorption theory, a method was presented to predict adsorption isotherms at different temperatures. In this method, the relationship between Langmuir pressure and temperature was quantified. By utilizing this method, we predicted adsorption isotherms of Longmaxi shale from 45 °C to 120 °C according to experimental data at 30 °C. Meanwhile, by considering the pressure and temperature gradients, we also predicted the adsorption capacity of Longmaxi shale with geologic depth. Results show that the adsorption data predicted by our method are in accord with experimental data and the error coefficient is less than 5%. In addition, the isosteric heat of adsorption for Longmaxi shale can be calculated by predicted adsorption data based on the Clausius–Clapeyron equation of capillary systems. Therefore, our study illustrates theoretical foundations for the efficient evaluation of adsorbed gas content in shale gas reservoirs at geologic conditions.

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Cakicioglu-Ozkan, Fehime. "Adsorption of carbon dioxide on MIL53(Al), CuBTC and K- NaX zeolite". ICONTECH INTERNATIONAL JOURNAL 4, n.º 3 (17 de diciembre de 2020): 30–42. http://dx.doi.org/10.46291/icontechvol4iss3pp30-42.

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CO2 adsorption on K exchanged NaX zeolites, and metal organic frameworks (MOFs), namely Cu-BTC and MIL53 (Al) was studied at 5 °C and 25 °C. Exchange via ultrasonic and traditional methods, was conducted at 50 °C and 70 °C. The maximum replacement of Na+ ion with K+ ion in the extra framework of zeolite was increased from 76% to 83% with increasing temperature from 50 °C to 70 °C in the ultrasonic method which is more effective than traditional one. Compared with the zeolites, the MOF adsorbents used in this work have higher Langmuir specific surface area values namely 1278, 1473 and about 1000 m2/g for MIL 53, Cu-BTC and zeolite adsorbents respectively. The resulting CO2 isotherms can be well represented by the Toth equation. Comparison of the isosteric heat of adsorption at zero loading shows that CO2 was adsorbed more weakly on MOFs than zeolites.

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42

Saad, Amel, Boumediene Touati, Belkacem Draoui, Boufeldja Tabti, Asma Abdenebi y Said Benaceur. "Mathematical Modeling of Moisture Sorption Isotherms and Determination of Isosteric Heats of Sorption ofZiziphusLeaves". Modelling and Simulation in Engineering 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/427842.

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Desorption and adsorption equilibrium moisture isotherms ofZiziphus spina-christileaves were determined using the gravimetric-static method at 30, 40, and 50°C for water activity(aw)ranging from 0.057 to 0.898. At a givenaw, the results show that the moisture content decreases with increasing temperature. A hysteresis effect was observed. The experimental data of sorption were fitted by eight models (GAB, BET, Henderson-Thompson, modified-Chung Pfost, Halsey, Oswin, Peleg, and Adam and Shove). After evaluating the models according to several criteria, the Peleg and Oswin models were found to be the most suitable for describing the sorption curves. The net isosteric heats of desorption and adsorption ofZiziphus spina-christileaves were calculated by applying the Clausius-Clapeyron equation to the sorption isotherms and an expression for predicting these thermodynamic properties was given.

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43

Talla, André. "Predicting Sorption Isotherms and Net Isosteric Heats of Sorption of Maize Grains at Different Temperatures". International Journal of Food Engineering 10, n.º 3 (1 de septiembre de 2014): 393–401. http://dx.doi.org/10.1515/ijfe-2014-0047.

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Abstract In Sub-Saharan Africa, drying maize on their stem was the traditional technique frequently used; this technique must be improved to avoid contaminations and to increase the quality of drying. However, the method of storage is accountable for the most significant losses after harvest, because mildew develops when the conditions of storage (too high temperature and moisture of the air) do not tally with the final content of the dried product. Sorption isotherms of products are most important to model moisture uptake during storage and distribution. Sorption isotherms of intermediate moisture content maize grains were determined using the gravimetric static method of saturated salt solutions at 30°C, 40°C, 50°C, and 60°C, and GAB equation was applied to discuss the results. This model correctly describes the evolutions of maize sorption isotherms, with maximum deviation of 0.0080 kg water/kg db. The net isosteric heat of sorption was determined also, using the Clausius–Clapeyron equation, and it was varied from 463 kJ/kg to 1,264 kJ/kg, decreasing with increasing moisture content. This effect was well described by an exponential function with a regression coefficient R2 > 97%. The monolayer moisture content was found to decrease with increasing temperature. These results can be used to predict the potential changes in the stability of maize grains and later for the development of a system of suitable drying.

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Sears, W. M. "Isosteric Heat of Adsorption of Water Vapor on Bismuth Iron Molybdate Measured by the Method of Constant Surface Conductance". Langmuir 17, n.º 17 (agosto de 2001): 5237–44. http://dx.doi.org/10.1021/la001005c.

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Zhang, Yongchun, Aiguo Hu, Pei Xiong, Hao Zhang y Zhonghua Liu. "Experimental Study of Temperature Effect on Methane Adsorption Dynamic and Isotherm". Energies 15, n.º 14 (11 de julio de 2022): 5047. http://dx.doi.org/10.3390/en15145047.

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Knowing the methane adsorption dynamic is of great importance for evaluating shale gas reserves and predicting gas well production. Many experiments have been carried out to explore the influence of many aspects on the adsorption dynamic of methane on shale rock. However, the temperature effect on the adsorption dynamic as a potential enhanced shale gas recovery has not been well addressed in the publications. To explore the temperature effect on the adsorption dynamic of methane on gas shale rock, we conducted experimental measurement by using the volumetric method. We characterized the adsorption dynamic of methane on gas shale powders and found that the curves of pressure response at different pressure steps and temperatures all have the same tendency to decrease fast at first, then slowly in the middle and remain stable at last, indicating the methane molecules are mainly adsorbed in the initial stage. Methane adsorption dynamic and isotherm can be well fitted by the Bangham model and the Freundlich model, respectively. The constant z of the Bangham model first decreases and then increases with equilibrium pressure increasing at each temperature, and it decreases with temperature increasing at the same pressure. The adsorption rate, constant k of the Bangham model, is linearly positively correlated with the natural log of the equilibrium pressure, and it decreases with temperature increasing at the same pressure. Constant K and n of the Freundlich model all decrease with temperature increasing, indicating that low temperatures are favorable for methane adsorption on shale powders, and high temperatures can obviously reduce constant K and n of the Freundlich model. Finally, we calculated isosteric enthalpy and found that isosteric enthalpy is linearly positively correlated with the adsorption amount. These results will be profoundly meaningful for understanding the mechanism of methane adsorption dynamic on shale powders and provide a potential pathway to enhance shale gas recovery.

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Zlatovic, Mario, Vladimir Sukalovic, Goran Roglic, Sladjana Kostic-Rajacic y Deana Andric. "The influence of dispersive interactions on the binding affinities of ligands with an arylpiperazine moiety to the dopamine D2 receptor". Journal of the Serbian Chemical Society 74, n.º 10 (2009): 1051–61. http://dx.doi.org/10.2298/jsc0910051z.

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Several isosteric 1,3-dihydro-5-[2-(4-aryl-1-piperazinyl)ethyl]-2H-benzimidazole-2-thiones were used to investigate the interactions of different ligands with the binding site of the D2 receptor. Due to limitations of the simulation methods, docking analysis failed to show precisely the interactions that influence the binding affinity of the ligands. It is presumed that dispersive forces or more precisely edge-to-face interactions play an important role in the binding process, especially for the lipophilic part of the ligands. In order to confirm this hypothesis, ab initio calculations were applied on a model system in order to find the stabilization energies of potential edge-to-face interactions and then to correlate them with the ligand affinity. The obtained results indicate that there is a significant correlation between the strength of dispersive interactions and ligand affinity. It was shown that for the calculation of stabilization energies of modeled receptor-ligand complexes the Becke 'half-and-half' hybrid DFT method can be used, thus speeding up the usually long calculation time and reducing the required computer strength.

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Meriama, Foullanine, Bennaceur Said, Loumani Akil, Mediani Ahmed, Moungar Houcine, Djaber Abdelkrim, Tigani Cherif, Larbi Ahmed Amine y Draoui Belkacem. "Experimental Determination and Modeling of the Moisture-Sorption Isotherms and Isosteric Heat of Tobacco Leaves". Instrumentation Mesure Métrologie 20, n.º 5 (31 de octubre de 2021): 269–77. http://dx.doi.org/10.18280/i2m.200504.

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During a forced convection sun drying and storage operation, the equilibrium water content of a product to be dried is critical. These figures are frequently derived using isothermal sorption curves. The calculation of isotherms is a necessary step in determining the distribution and intensity of water connections in products. for that this paper concentrates on the experimental determination of the adsorption-desorption isotherms for various temperatures (40, 50, and 60℃) of the Nicotiana Tabacum L plants. From which we had established the relationship between the water activity and the water content in the product. However, the aforementioned determination was carried out by the static gravimetric method. Eight saturated salt solutions have been utilized in applications such as (KOH, KCl, MgCl2, MgNO3, K2CO3, BaCl2, K2SO4, and NaCl). Hygroscopic equilibrium was completed after 13 days for temperature 40℃, 11 days for 50℃, and 9 days for 60℃. The overall experimental sorption curves are summarized by six models (HENDERSON, modified HALSEY, OSWIN, GAB, modified BET, and PELEG). The sorption isotherms built using the Clausius–Clapeyron equation were used to determine the net isosteric temperatures of desorption and adsorption of Nicotiana Tabacum L. The results for the adsorption-desorption isotherms found are type III according to IUAPC. Following the smoothing of the experimental results by different used models, it was found that the models of GAB and Peleg allow having the lowest mean relative errors and correlation coefficient.

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Lamharrar, Abdelkader, Ali Idlimam, Mohammed Kouhila, Lamya Lahnine y Hind Mouhanni. "Moisture Sorption Isotherms And Thermodynamic Properties Of Urtica Dioica Leaves". European Scientific Journal, ESJ 12, n.º 24 (30 de agosto de 2016): 376. http://dx.doi.org/10.19044/esj.2016.v12n24p376.

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Urtica dioica is a Moroccon endemic plant of used for its virtues in traditional medicine. Thus, it is necessary to study the effect of preservation processes on the storage conditions of the plant. The static gravimetric method was used to determine sorption isotherms of Urtica dioica leaves at three temperatures (40, 50 and 60 °C) and in the range of water activity ( w a ) ranging from 0.0572 to 0.898. Six mathematical models were used to fit the experimental data. The Enderby and Peleg models were found to be the most suitable for describing the sorption curves. The optimal water activity for conservation of Urtica dioica leaves was determined. Isosteric heats of desorption and adsorption were calculated by applying the Clausius- Clapeyron equation to the sorption isotherms at different temperatures; it decreased with increasing moisture content. A linear relation exists between the enthalpy and entropy of the sorption reaction.

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Majd, Kamran Maleki, Seyed H. Karparvarfard, Asgar Farahnaky y Sara Ansari. "Thermodynamic properties of water sorption isotherms of grape seed". International Agrophysics 28, n.º 1 (1 de marzo de 2014): 63–71. http://dx.doi.org/10.2478/intag-2013-0028.

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Abstract In this study the moisture sorption isotherm of grape seed was determined by using a static gravimetric method at 35-65°C and 0.108-0.821 water activity range. The sorption isotherms were found to be typical sigmoid shape of most food materials. Five models including the Brunauer-Emmett-Teller (2-parameter), Guggenheim, Anderson and De Boer (3-parameter), Oswin (2-parameter), Ferro-Fontan (3-parameter) and Peleg (4-parameter) models were considered to fit the experimental data. The Ferro- Fontan and Peleg equations (at three temperatures 35, 45, 65°C) having R2 greater than 0.97 and lower values of standard error of estimate and deviation modulus gave the best fit of the experimental data throughout the entire range of water activity. The net isosteric heat of sorption, calculated by Calusius-Clapeyron equation on experimental data, was found to be a polynomial and exponential function of equilibrium moisture content within the temperature range investigated.

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Sun, Yangzesheng, Robert F. DeJaco, Zhao Li, Dai Tang, Stephan Glante, David S. Sholl, Coray M. Colina et al. "Fingerprinting diverse nanoporous materials for optimal hydrogen storage conditions using meta-learning". Science Advances 7, n.º 30 (julio de 2021): eabg3983. http://dx.doi.org/10.1126/sciadv.abg3983.

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Adsorptive hydrogen storage is a desirable technology for fuel cell vehicles, and efficiently identifying the optimal storage temperature requires modeling hydrogen loading as a continuous function of pressure and temperature. Using data obtained from high-throughput Monte Carlo simulations for zeolites, metal-organic frameworks, and hyper–cross-linked polymers, we develop a meta-learning model that jointly predicts the adsorption loading for multiple materials over wide ranges of pressure and temperature. Meta-learning gives higher accuracy and improved generalization compared to fitting a model separately to each material and allows us to identify the optimal hydrogen storage temperature with the highest working capacity for a given pressure difference. Materials with high optimal temperatures are found in close proximity in the fingerprint space and exhibit high isosteric heats of adsorption. Our method and results provide new guidelines toward the design of hydrogen storage materials and a new route to incorporate machine learning into high-throughput materials discovery.

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