Activation Energy For Moisture Diffusion Research Articles

PEA GRAINS IN DRYING: UNRAVELING THE KINETICS OF HOT-AIR DRYING AND EXPLORING MATHEMATICAL MODELS FOR MOISTURE DIFFUSION

Pea drying studies were assessed to learn more about the kinetics and properties of drying in a hot-air dryer. Research was done on impact of temperatures and pre-treatments on drying behaviours. The drying rate graphs demonstrated that the entire drying procedure took place when rates were declining. To properly understand the experimental data, four mathematical models (Henderson & Pabis, Page, Wang & Singh, and Aghbashlo et al.) were used. The Page model was discovered to be the ideal one to depict peas' curves of drying. The identification of the Page model as the most suitable for depicting pea drying curves underscored the applicability in modeling drying behaviors in similar agricultural products. With Fick's second law of diffusion, effective moisture diffusivity (Deff) sorted from 2.45x10-10 to 6.55x10-10 m2/s at given temperature. Deff was expressed as a function of temperature with an Arrhenius type equation. For samples from Potas, Blanch, and Control codes, the activation energy for moisture diffusion was computed as 21.48, 22.82, and 22.32 kJ/mol, respectively. The computation of activation energy for moisture diffusion for different samples offered practical information for optimizing drying processes under various conditions. The results showed the importance of pea drying kinetics and practical implications for industry on drying efficiency and product quality.

Drying Kinetics and Mass Transfer Characteristics of Walnut under Hot Air Drying

This study was conducted to investigate the drying kinetics and internal and external mass transfer characteristics of walnuts for an understanding of the drying mechanism. The drying characteristics, mass transfer characteristics, and color of walnut during hot air drying (HAD) were investigated under different initial moisture content (IMC) (0.35, 0.39, and 0.43 g water/g wet mass) and drying temperatures (50, 60, 70, and 80 °C). The results indicated that the IMC and drying temperature both have significant effects on the drying process of walnut, showing the higher the IMC, the longer the preheating time, the smaller the effective moisture diffusivity (Deff) and mass transfer coefficient (hm), and the longer the drying time, but reverse results for drying temperature. The values of Deff and hm for walnut ranged from 4.94 × 10−10 to 1.44 × 10−9 m2/s and 1.24 × 10−7 to 3.90 × 10−7 m/s, respectively. The values of activation energy for moisture diffusion and mass transfer ranged from 21.56 to 23.35 kJ/mol and 28.92 to 33.43 kJ/mol, respectively. Multivariate linear prediction models were also established for estimating the Deff and hm as a function of the HAD process parameters. The drying temperature has a greater effect on the walnut kernel lightness than the IMC. The Verma et al model could be used to describe the HAD process of the walnut. The findings contribute to the understanding of moisture transfer mechanisms in walnuts and have practical value for the evaluation and improvement of drying systems.

Thermal efficiency and drying Behaviour of Yam slices in a dryer driven by the waste heat of exhaust gases

This study investigated the thermal efficiency and thin-layer drying characteristics of yam tuber in a crop dryer driven by the waste heat of exhaust gases. Experiments were conducted at three different progressive levels of drying air temperature (T) of 55 - 75°C; air velocity (va) of 1.0 - 2.0 m/s; and sample slice thickness (X) of 1.0 - 2.0 cm with a batch size of 2200 ± 0.5 g of the blanched yam tubers. Results demonstrate that at varying process conditions, the mean drying time varied between 195 and 705 mins, with the average drying rate, dA in the range of 2.039 - 7.374 gwater/min. The diffusion coefficient of moisture for the tuber samples (De), fluctuated between 7.27 × 10−10 m2/s and 5.60 × 10−9 m2/s, obtained at (55°C, 1 m/s and 1 cm) and (75°C, 2 m/s, and 2 cm) treatment combinations. The thermal efficiency (ηth) of the dryer improved with increasing T, whereas an increase in either va or X caused a reduction in the value of ηth. The range of thermal efficiency values obtained varied in the order: 9.42% ≤ ηth≤ 44.95%. The activation energy for moisture diffusion showed no exact relationship with va. The values ranged from 34.36 to 53.4 kJ/mol. The results obtained in this investigation will come in handy in the design and development of agro-crop commercial dryers that are inexpensive, eco-friendly, energy-efficient and sustainable.

Mathematical modeling of infrared drying of red pitaya pulp (Stenocereus queretaroensis) for potential use of its betalains

AbstractRed pitaya fruit has an important concentration of betalains (68.7 mg/100 g fresh sample) that potentially can be used as natural colorants for food, textiles, dye‐sensitized solar cells, etc. Nevertheless, this fruit has a short shelf life. To overcome this problem and to take advantage of their varied and attractive colors, pitayas can be infrared dried. In this work, we evaluated the kinetics of infrared drying of red pitaya pulp in the temperature range of 40–70°C. The drying rate was found to increase with temperature. The time required to diminish moisture content of red pitaya pulp from 80.5% to around 0.1%–0.3% (dry basis) decreased from 625 min at 40 to 240 min at 70°C. The experimental drying data were fitted to nine empirical drying models reported in literature and to one new model herein proposed. Based on statistical criteria, the proposed model was found the best for characterizing drying behavior of red pitaya pulp for the whole range of temperature. Effective moisture diffusivity was moisture content‐dependent, the average values for diffusivity coefficients at each drying temperature were derived from Fick's law and varied from 0.98–4.43 × 10−9 m2/s over the temperature range. Activation energy for moisture diffusion in red pitaya pulp was determined as 42.89 kJ/mol. Best drying temperature was found to be at 70°C, where a higher betalain content and a faster drying process conditions were achieved.Practical applicationsBetalains can be used as healthy natural colorants for food, among others. A limitation for which pitayas have not been exploited as a source of colorants is because of their short shelf life. Due to the important concentration of betalains present in this fruit, it is highly desirable to have methodologies that allow access to their use. To overcome this problem and to take advantage of their varied and attractive colors, red pitaya pulp was infrared dried for its study. Herein the proposed model exhibited an excellent fit to the red pitaya pulp drying process. The commercial exploitation of pitayas as an alternative source of natural colorant betalains may not only provide a wider color spectrum than red beetroot, but also contribute to the sustainable development of the usually underdeveloped semiarid regions.

Evaluating the heat and mass transfer effective coefficients during the convective drying process of paddy (Oryza sativa L.)

AbstractThis work investigates important heat and mass transfer parameters of a variety of paddy named Fajr, during a thin layer convective drying. The experiments on drying are conducted at air temperatures in the domain of 30–80°C with air velocities between 0.54 and 3.27 m s−1. Mathematical equations are developed to adjust the experimental data obtained for the thin layer drying. The drying results show that the Henderson and Pabis' model satisfactorily fit all the experimental data for the convective drying behavior of paddy. The effective diffusivity of moisture transfer, calculated by the Fick's second law of diffusion, varies from 1.109 × 10−11 to 5.858 × 10−10 m2 s−1 and the highest values of the Dincer, Biot, Reynolds, and Nusselt numbers obtained are 2.383 × 105; 0.2026; 1.833 × 107; and 8,434, respectively. The obtained results demonstrate that the coefficient of mass transfer (hm) for paddy lies between 5.118 × 10−8 and 4.807 × 10−6 m s−1, while the heat transfer coefficient (hc) ranges from 811 to 2,474 W m−2 K−1. Furthermore, the values of the energies of activation obtained for moisture diffusion (Ed) and convective mass transfer (Ec) are in the range of 50.538–61.825 kJ mol−1 and 72.325–87.386 kJ mol−1, respectively. Therefore, knowledge regarding to the determination process of heat and mass transfer characteristics can help to distinguish the suitable operating conditions for saving the maximum value of energy.Practical ApplicationsSome grains have a short shelf life that limits their commercialization as fresh products and increase postharvest losses. Drying is an interesting alternative to the development of new products of grains like paddy with added value. This research work involved the estimation of heat and mass transfer properties during convective drying by using two calculation methodologies, allowing estimating the diffusivity and the mass and heat transfer coefficients for paddy. Also, the activation energy for moisture diffusion and for convective mass transfer was determined, assuming that the temperature dependence of the diffusion coefficient and the mass transfer coefficient follows an Arrhenius type relationship. Therefore, also the study presents a simple method to greatly enhance the shelf life of wet paddy by convective drying and it can be applied for the better preservation of this product.

Evaluation of Thin-layer Models for Kinetic Analysis in Unbleached Kraft Pulpboard Drying

The drying characteristics of unbleached Kraft pulpboard has been studied in a convective drying equipment under different hot air temperature and velocity. In this work, the drying experiments were conducted in the range of 80-100℃ and 1.87-2.48m/s, respectively. The drying characteristics results indicated that high air temperature and velocity is beneficial to increase drying rate and decrease drying time. Ten thin-layer drying models were evaluated to describe the drying kinetic of unbleached Kraft pulpboard for its suitability. Based on the statistical analysis, the Yun model could predict the pulpboard drying kinetic better than others in terms of fitting performance. Through calculation and fitting, the effective moisture diffusivity varied from 2.07710-10 to 3.63110-10m2/s over the investigated temperature range, and the average activation energy for moisture diffusion was 22.818kJ/mol.

Drying kinetics and mass transfer properties in the drying of thistle flower

Abstract Thistle flowers, and particularly their stigmas, are used to coagulate milk in the production of a number of traditional Portuguese cheeses due to their high milk-clotting activity provided by the high content of aspartic proteases. The aim of the present work was to determine the mass transfer properties of thistle flower under different drying conditions: natural drying and convective drying. Convective drying took place in a convection chamber set at different temperatures (35 to 65 °C) and the process was terminated when the sample presented a moisture content of about 5% or less. The traditional drying method was also used, placing the thistle flowers in a dry place sheltered from the sun, and leaving them to dehydrate at the variable room temperature. The present work allowed for the conclusion that convective drying was much faster than natural drying, and that the drying rate increased with temperature. The drying curve revealed an initial constant rate period followed by a falling rate. All the five thin layer models tested to fit the experimental data were shown to adequately describe the drying of the thistle flowers, but the best one was the Page model. The drying constant increased with temperature as did the effective diffusivity and the mass transfer coefficient. The results allowed one to estimate the activation energy for moisture diffusion (57 kJ/mol) and for convective mass transfer (78 kJ/mol). Thus this study showed the possibilities for designing efficient drying processes for the thistle flower used for milk-clotting in the manufacture of traditional cheeses.

Effect of Vacuum Drying Temperature on Drying Kinetics, Effective Moisture Diffusivity and Quality of Peeled Litchi (Litchi chinensis Sonn.)

AbstractThis study aimed at investigating the effect of vacuum drying temperature on drying kinetics, drying rates, effective moisture diffusivity and quality parameters of litchi fruits. Peeled litchi quarters were dried at 50–70 °C at an absolute pressure of 8 kPa. Results show that the vacuum drying occurred in the falling rate period. Drying rates increased with drying temperature. The Page model provided the best fit to the drying kinetics. Effective moisture diffusivity ranged between 1.997 × 10−9 and 5.012 × 10−9 m2/s. The temperature dependence of the effective moisture diffusivity was well described by an Arrhenius‐type equation. The activation energy for moisture diffusion was 41.81 kJ/mol. Drying temperature did not significantly affect product sensory acceptance, density, shrinkage and rehydration. The products dried at 50 and 70 °C presented slightly superior texture and flavor, while the product dried at 60 °C presented significantly higher lightness and lower water activity.Practical ApplicationsThis work provides valuable information on the vacuum drying of litchi fruits, which are appreciated in many countries due to their pleasant sensory characteristics. Vacuum drying is not a costly drying method. At the same time, vacuum drying produces dried foods of relatively good quality. This study could be used as a reference by small and medium scale food processors interested in producing dried litchi of good quality with relatively low investment in equipment. The understanding of the influence of drying temperature on quality parameters is useful for deciding which temperature is more appropriate depending on the desired quality aspects, while the calculation of engineering parameters is important for designing the drying process.

Weibull distribution for modeling drying of Angelicae Sinensis Radix and its application in moisture dynamics

To establish the water dynamics model for drying process of Angelicae Sinensis Radix, the Weibull distribution model was applied to study the moisture ratio variation curves, and compared the drying rate and drying activation energy with the drying methods of temperature controllable air drying, infrared drying under different temperatures (50, 60, 70 degrees C). The Weibull distribution model could well describe the drying curves, for the moisture ratio vs. drying time profiled of the model showed high correlation (R2 = 0. 994-0. 999). The result proved that the drying process of Angelicae Sinensis Radix belonged to falling-rate drying period. For the drying process, the scale parameter (a) was related to the drying temperature, and decreased as the temperature increases. The shape parameter (β) for the same drying method, drying temperature had little impact on the shape parameter. The moisture diffusion coefficient increase along with temperature increasing from 0.425 x 10(-9) m2 x s(-1) to 2.260 x 10(-9) m2 x s(-1). The activation energy for moisture diffusion was 68.82, 29.60 kJ x mol(-1) by temperature controllable air drying and infrared drying, respectively. Therefore, the Weibull distribution model can be used to predict the moisture removal of Angelicae Sinensis Radix in the drying process, which is great significance for the drying process of prediction, control and process optimization. The results provide the technical basis for the use of modern drying technology for industrial drying of Angelicae Sinensis Radix.

Evaluation of semi-empirical and non-linear drying models by Bayesian inference

Current analysis investigates thin layer drying experiments on passion fruit seeds. Drying characteristics of passion fruit seeds were examined using ambient air for temperature range between 40 and 65oC and air flow velocity range between 0.6 and 1.2 m s -1 . The semi-empirical models were then fitted to the drying data by Bayesian inference, based on the ratios of the difference between the initial and final moisture contents and equilibrium moisture content. The effective diffusivity varied between 1.70 x 10 -10 and 4.68 x 10 -10 m 2 s -1 with temperature and air flow rate increase. Temperature dependence on the diffusivity coefficient was described by an Arrhenius-type relationship. The activation energy for moisture diffusion was 24.36, 35.24 and 13.86 kJ moL -1 for drying air speeds respectively equal to 0.6, 0.9 and 1.2 m s -1 .

KINETICS OF HYDRATION AND DIMENSIONAL CHANGES OF BROWN RICE

ABSTRACT Hydration kinetics and dimensional changes of brown rice kernels during soaking at below gelatinization temperature, 30 to 60C, were studied. Image analysis was implemented to determine changes in length, width, perimeter and projected area of kernels as a function of time. Water absorption was described by the Fick's second law of diffusion. The effective diffusivity varied from 5.30 × 10−11 to 1.56 × 10−10 m2/s. The temperature dependence of the effective diffusivity was described by an Arrhenius-type relationship and the activation energy for moisture diffusion was 30.46 kJ/mol. The dimensional changes were first-order kinetic and the activation energy values for changes in kernel length, width, perimeter and projected area were 25.27, 23.01, 26.39 and 31.05 kJ/mol, respectively. Five semi-theoretical models including the Lewis, Page, Modified Page, Henderson and Pabis, and Two term models were proposed to describe the soaking behavior of brown rice kernels. It was noted that the Page model presented the best fit and represented an excellent tool for estimating moisture content and dimensions of brown rice kernels at any soaking time. PRACTICAL APPLICATIONS Soaking is one of the hydrothermal processes and it is an essential step of the brown rice process. The present study was undertaken to investigate the hydration characteristics and dimensional changes of brown rice kernels during soaking. The results of processing variables are needed for practical applications to optimize and characterize the soaking condition, design grain processing equipment, and predict water absorption as a function of time and temperature. Thus, a suitable mathematical model was applied to predict accurately the water absorption and dimensional changes of brown rice kernels during soaking.

Optimization of Drying Kinetics and Quality Parameters of Broccoli Florets

Drying kinetics of broccoli florets in a tunnel dryer was studied. Effective moisture diffusivity (Deff) and activation energy for moisture diffusion (E0) were estimated. The effect of air temperature, air flow rate and particle size on antioxidant capacity, greenness and texture were calculated through a 23 factorial design. Air flow rate and temperature significantly affected drying time. Deff fluctuated between 2.82 x 10-10 and 2.00 x 10-9 (m2/s), and E0 was around 42 KJ/mol, agreeing with values reported in literature. The maximum antioxidant activity was obtained at 60°C, air flow rate of 4 m/s and 1.5 cm particle diameter, resulting in a 70 percent reduction in free radical scavenging ability and a 29 percent increase in total reductive capability. Air temperature had significant effect on greenness, and air flow rate significantly affected texture. The optimization of convective drying of broccoli allows maximizing antioxidant activity and minimizing cost by saving energy and time.

Thin layer drying characteristics of rapeseed ( Brassica napus L.)

This study was performed to determine the most appropriate thin layer drying model and the effective moisture diffusivity of rapeseed. The thin layer drying tests were conducted at three different combinations of drying air temperature levels of 40, 50, and 60 °C and relative humidity levels of 30, 45, and 60%. The thin layer drying characteristics of rapeseed were determined. The Page (1949) model was the most adequate model for describing the thin layer drying of rapeseed. Drying occurred in the falling rate period and the rate of moisture removal from rapeseed was governed by the rate of water diffusion to the surface of the seed. Effective moisture diffusivities were calculated based on the diffusion equation for a spherical shape using Fick’s second law. Effective moisture diffusivity during drying varied from 1.72 × 10 −11 to 3.31 × 10 −11 m 2 s −1 over the temperature range. The dependence of moisture diffusivity on temperature was described by an Arrhenius-type equation. The activation energy for moisture diffusion during drying was 28.47 kJ mol −1.

EFFECT OF PRETREATMENTS ON AIR‐DRYING PATTERN AND COLOR OF DRIED PUMPKIN (CUCURBITA MAXIMA) SLICES

ABSTRACT Effect of pretreatments on air‐drying pattern and color of pumpkin slices was investigated. Fresh, sulfited (1,000 ppm), blanched (100C for 3 min) and osmotically pretreated pumpkins (40, 50 and 60 °Brix) were air dried at 50–80C. Moisture transfer from fresh and pretreated pumpkin was modeled using Fick's diffusion model, and effective moisture diffusivity (m2/s) was calculated. Moisture ratio decreased with increased drying temperature and time. No constant drying rate period was observed in the drying process. Pre‐osmosed pumpkin recorded lower moisture contents and drying rate. Effective moisture diffusivity was in the range of 6.50 E‐10–2.45 E‐09 m2/s. Arrhenius relation with activation energy for moisture diffusion of 24.49–43.27 kJ/mol expressed the effect of temperature on moisture diffusivity. L*, a*, b*, color intensity (ΔE) and chroma (ΔC) values of dried pumpkin increased with increase in drying temperature from 50 to 60C.PRACTICAL APPLICATIONSPumpkin is usually sun dried during the season of production, packaged and rehydrated in water prior to use. However, some problems are associated with the drying of the commodity. Use of pretreatments such as blanching, sulfiting and osmotic dehydration (OD) prior to forced convection air drying would result in minimal quality degradation, savings in energy and, in the case of OD, the production of eat‐out‐of‐hand snack items. The effects of the pretreatment are mainly related to the improvement of some nutritional, organoleptic and functional properties of the product. Also, pretreatments aid the inhibition of enzymatic browning, provide an adjustment of water activity and the achievement of structural, textural and sensory, and other functionalproperties. These properties are obtained with a reduced energy input over traditional drying processes. Air drying following the pretreatment could be adopted for the production of shelf‐stable dried fruit and vegetable commodities with acceptable quality attributes.

Evaluation of Mathematical Models for Prediction of Thin-Layer Drying of Banana Slices

Drying characteristics of bananas were experimentally determined. The drying experiments were carried out in a hot air dryer at four inlet temperatures of 50, 60, 70 and 80°C, at a constant air velocity of 2.4 m/s and relative humidity of 4–25%. The experimental results were fitted to five thin-layer drying models and it was found that the Page and Logarithmic models gave better fit that the other models. Values of the effective diffusivity ranged from 7.374 × 10−11 to 2.148 × 10−10 m2/s. Activation energy for moisture diffusion of the banana slices was found to be 32.65 kJ/mol.

Modelling of air drying of fresh and blanched sweet potato slices

SummaryEffects of blanching, drying temperatures (50–80 °C) and thickness (5, 10 and 15 mm) on drying characteristics of sweet potato slices were investigated. Lewis, Henderson and Pabis, Modified Page and Page models were tested with the drying patterns. Page and Modified Page models best described the drying curves. Moisture ratio vs. drying time profiles of the models showed high correlation coefficient (R2 = 0.9864–0.9967), and low root mean squared error (RMSE = 0.0018–0.0130) and chi‐squared (χ2 = 3.446 × 10–6–1.03 × 10–2). Drying of sweet potato was predominantly in the falling rate period. The temperature dependence of the diffusion coefficient (Deff) was described by Arrhenius relationship. Deff increased with increasing thickness and air temperature. Deff of fresh and blanched sweet potato slices varied between 6.36 × 10–11–1.78 × 10–9 and 1.25 × 10–10–9.75 × 10–9 m2 s–1, respectively. Activation energy for moisture diffusion of the slices ranged between 11.1 and 30.4 kJ mol–1.

Mass Transfer Coefficients for the Drying of Pumpkin (Cucurbita moschata) and Dried Product Quality

The aim of this work was to determine the mass transfer properties of pumpkin (Cucurbita moschata) exposed to air drying. The drying temperatures tested ranged between 30°C and 70°C, and the kinetic behavior was studied in this temperature band. The samples were analyzed in terms of moisture content, acidity, proteins, lipids, and crude fiber, both in the fresh state and after drying. From the chemical analyses made, it was possible to conclude that drying induces some reductions in acidity, lipids, fibers, and proteins. As to the influence of the drying temperature on the process, it was observed that a temperature rise from 30°C to 70°C led to a 70% saving in drying time. The results obtained by fitting the experimental data to the kinetic models tested allowed concluding that the best model for the present case is Henderson–Pabis, and the worst is Vega–Lemus. Furthermore, in this work, it was possible to determine the values of the diffusion coefficient at an infinite temperature, De0, and activation energy for moisture diffusion, Ed, which were, respectively, 0.0039 m2/s and 32.26 kJ/mol. Similarly, the values of the Arrhenius constant and the activation energy for convective mass transfer, respectively, hm0 and Ec, were also calculated, the first being 3.798 × 108 m/s and the latter 86.25 kJ/mol. These results indicate that the activation energy for convective mass transfer is higher than that for mass diffusion.

유채 종자의 수본확산계수에 관한 연구

The effective moisture diffusivity and its dependence on drying temperature during drying of rapeseed were experimentally investigated. The data were recorded from thin layer drying experiments at nine different combinations of drying air temperatures of 40, 50, and <TEX>$60^{\circ}C$</TEX> and the relative humidities of 30, 45, and 60%. The moisture diffusion equation was analyzed using stepwise multiple regression analysis. Effective moisture diffusivities were calculated based on the moisture diffusion equation for a spherical shape using Fick's second law. The effective diffusivities during the drying of rapeseed were <TEX>$l.72{\times}10^{-11}$</TEX>, <TEX>$2.41{\times}10^{-11}$</TEX> and <TEX>$3.31{\times}10^{-11}\;m^2{\cdot}s^{-1}$</TEX> at 40, 50 and <TEX>$60^{\circ}C$</TEX>, respectively. The activation energy for moisture diffusion during drying was <TEX>$28.47\;kJ{\cdot}mol^{-1}$</TEX>. The dependence of moisture diffusivity on temperature was described by an Arrhenius-type equation. Drying occurred in the falling rate period and the internal moisture diffusion phenomenon is the governing physical mechanism of the moisture movement in the particles.

Drying behaviour of green beans

This paper presents the thin layer drying experiments and mathematical modelling of green bean grown in Iskenderun, Turkey. Drying characteristics of green bean were examined for average moisture content from 90.53 ± 0.5% to 14 ± 0.3% using hot air of the temperature range of 50–70 °C. The results have shown that, increasing the drying air temperature causes shorter drying times. The experimental drying curves obtained were fitted to a number of semi-theoretical models, namely Handerson and Pabis, Lewis and Page models. Comparing the determination of coefficient, reduced chi-square and root mean square error values of three models, it was concluded that the Page model represents drying characteristics better than the others. The effective diffusivity coefficient of moisture transfer varied from 2.641 × 10 −9 to 5.711 × 10 −9 m 2/s over the temperature range. The temperature dependence of the diffusivity coefficients was described by Arrhenius type relationship. The activation energy for moisture diffusion was found to be 35.43 kJ/mol.

Effect of ethyl oleate on drying characteristics of mulberries

In this study, air-drying experiments in thin layers of mulberry grown in Istanbul, Turkey, were conducted. The effect of ethyl oleate solution on drying time of mulberry samples was investigated in a pilot air-dryer. When ethyl oleate was used as pretreatment solution, the drying time of samples was decreased. Drying curves were obtained using the Page model. The effective diffusivity varied from 2.326 x 10(-10) to 1.809 x 10(-9) m2/s the temperature range. The temperature dependence of the diffusivity coefficient was described by the Arrhenius type relationship. The activation energy for moisture diffusion was found to be 50.87 kJ/mol for treated samples and 51.85 kJ/mol for untreated samples.