MOISTURE SORPTION ISOTHERMS OF FOUR VEGETABLE SEEDS AS INFLUENCED BY STORAGE CONDITIONS

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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Moisture Sorption Isotherms And Thermodynamic Properties Of Urtica Dioica Leaves

European Scientific Journal ESJ ◽

10.19044/esj.2016.v12n24p376 ◽

2016 ◽

Vol 12 (24) ◽

pp. 376 ◽

Cited By ~ 1

Author(s):

Abdelkader Lamharrar ◽

Ali Idlimam ◽

Mohammed Kouhila ◽

Lamya Lahnine ◽

Hind Mouhanni

Keyword(s):

Water Activity ◽

Gravimetric Method ◽

Sorption Isotherms ◽

Moisture Sorption ◽

Storage Conditions ◽

Urtica Dioica ◽

Endemic Plant ◽

Clapeyron Equation ◽

Moisture Sorption Isotherms ◽

Different Temperatures

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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Sorption isotherms for oat flakes (Avena sativa L.)

Agronomía Colombiana ◽

10.15446/agron.colomb.v32n1.40652 ◽

2014 ◽

Vol 32 (1) ◽

pp. 52-58 ◽

Cited By ~ 2

Author(s):

José Edgar Zapata M. ◽

Oscar Albeiro Quintero C. ◽

Luis Danilo Porras B.

Keyword(s):

Sorption Isotherms ◽

Moisture Sorption ◽

Storage Conditions ◽

Percentage Error ◽

Relative Air Humidity ◽

Moisture Sorption Isotherms ◽

Relative Percentage Error ◽

The Mean ◽

Best Fit

Moisture sorption isotherms of oat flakes were determined at temperatures of 5, 25 and 37°C, using a gravimetric technique in an aw range of between 0.107 and 0.855. These curves were modeled using six equations commonly applied in food. The quality of the fit was assessed with the regression coefficient (r2) and the mean relative percentage error (MRPE). The best fit were obtained with the Caurie model with r2 of 0.996, 0.901 and 0.870, and MRPE of 7.190, 17.878 and 16.206, at 5, 25 and 37°C, respectively. The equilibrium moisture presented a dependence on temperature in the studied aw range, as did the security moisture (XS). These results suggest that the recommended storage conditions of oat flakes include: a relative air humidity of 50% between 5 and 25°C and of 38% up to 37°C.

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Simulation of Storage Conditions of Mixed Biomass Pellets for Bioenergy Generation: Study of the Thermodynamic Properties

Energies ◽

10.3390/en13102544 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2544

Author(s):

Lyes Bennamoun ◽

Merlin Simo-Tagne ◽

Macmanus Chinenye Ndukwu

Keyword(s):

Mathematical Modeling ◽

Thermodynamic Properties ◽

Standard Error ◽

Sorption Isotherms ◽

Moisture Sorption ◽

Storage Conditions ◽

Coefficient Of Determination ◽

Chi Square ◽

Bioenergy Generation ◽

Moisture Sorption Isotherms

Experimental and mathematical modeling of the moisture sorption isotherms for biomass pellets during storage is performed in this study. The tested pellets are a mixture of 50% wood: spruce or pine, and 50% switchgrass agricultural biomass. Storage conditions, i.e., temperature and humidity, are tested by varying the environment conditions in a conditioning chamber. The experimental results show that the moisture sorption isotherms are not affected by the temperature. Nevertheless, the equilibrium moisture content depends on the kind of the tested pellets. Mathematical modeling of the experimental isotherms is performed using four common models: the Oswin, GAB, Henderson and Peleg models. The Oswin model is defined as the most appropriate model to predict the moisture sorption isotherms of the spruce–switchgrass pellets. It presents a coefficient of determination equal to 0.998, a standard error around 0.049 and a chi-square approaching 0.007. On the other hand, Henderson and GAB models show the best results for pine–switchgrass pellets, with a coefficient of determination varying between 0.998 and 0.997, a standard error range 0.054–0.065 and chi-square error between 0.008 and 0.009. The thermodynamic properties, which include the net isosteric of heat and the entropy changes of sorption, are also determined for all tested samples.

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