WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 14Citation - Scopus: 15Investigation of the Effect of Gel Properties on Supercritical Drying Kinetics of Ionotropic Alginate Gel Particles(Elsevier, 2019) Şahin, İbrahim; Uzunlar, Erdal; Erkey, CanA series of spherical ionotropic alginate gel particles with different diameters ranging from 2.8mm to 5.0mm and porosities ranging from 0.899 to 0.976 were prepared by dripping a Na-alginate solution into a solution of salts of divalent cations (Ca2+, Mn2+, Ni2+, Co2+, Cu2+ and Zn2+). After solvent exchange with ethanol, kinetics of supercritical drying of these ionotropic alginate gel particles in a packed bed was investigated at 308-338 K and 100-120 bar. Experimental data were compared with predictions of a model which considers diffusive transport inside the pores and convection in the flowing fluid stream. The model predicted drying profiles by taking into account only the changes in porosity and diameter of the gel particles. A convective mass transfer coefficient correlation that was originally developed for supercritical drying of Ca-alginate gel particles was found to be suitable for M-alginate gel particles. (C) 2019 Elsevier B.V. All rights reserved.Article Citation - WoS: 23Citation - Scopus: 24Investigation of Kinetics of Supercritical Drying of Alginate Alcogel Particles(Elsevier Ltd., 2019) Şahin, İbrahim; Uzunlar, Erdal; Erkey, CanSpherical calcium alginate gel particles were synthesized by dripping method. The effects of temperature, pressure, particle size and CO2 flow rate on kinetics of supercritical drying of alginate gel particles in a packed bed were investigated. Increase in CO2 flow rate, increase in temperature and decrease in particle size increased the drying rate and decreased the drying time. A mathematical model based on (i) the diffusion of the solvent inside the pores of gel particles, (ii) external mass transfer of the solvent from the surface of the gel particles into the flowing fluid stream, and (iii) convection and axial dispersion of the solvent in the flowing fluid stream was developed. A correlation for predicting external mass transfer coefficients for supercritical drying of alcogel particles was developed by fitting the model to experimental data. A good agreement between the experimental data and model results was achieved using the developed correlation.Article Citation - WoS: 13Citation - Scopus: 17Effect of Ultrasound on the Kinetics of Cation Exchange in Nax Zeolite(Elsevier Ltd., 2012) Erten Kaya, Yasemin; Çakıcıoğlu Özkan, FehimeIn this study, we focused on the effect of ultrasound on ion exchange kinetics to obtain the Li-, Ca- and Ce-rich NaX zeolite. The results were compared to those obtained from the traditional batch exchange method under similar conditions. Contact time and initial cation concentration (fold equivalent excess) were studied. Ultrasound enhanced the replacement of Na + ion with Li +, Ca 2+ and Ce 3+ ions in the extra-framework of zeolite up to 76%, 72% and 66%, respectively. The intraparticle diffusion is the rate limiting step in the ion exchange for both exchange methods. As compared to the traditional exchange method, the ultrasonic method applied in this study was found to be very effective on the exchange amount at equilibrium.Article Citation - WoS: 1Citation - Scopus: 2Kinetic Estimation of the Adsorbate Distribution on the Surface From Adsorbed Amounts(Elsevier Ltd., 2006) Polat, MehmetA phenomenological multilayer adsorption model for a well-dispersed, homogeneous, nonporous adsorbent and a molecular adsorbate is presented. The model provides explicit kinetic expressions associating the adsorbed amounts to the fraction of the surface occupied and reduces to the first- and second-order adsorption models for special cases. Parameters of the model are a pair of true rate constants related to the adsorbate-adsorbent and adsorbate-surface adsorbate affinities. A general graphical procedure and analytical equations for special cases are provided to estimate the rate constants from kinetic adsorption data. Data from the adsorption of sodium stearate onto α-alumina from water were used to test the model. The predicted values of the rate constants suggested that the stearate was distributed homogeneously on the alumina surface and essentially adsorbed as a monolayer before starting to form the second layer.Article Citation - WoS: 38Citation - Scopus: 43Degradation Kinetics of Anthocyanins From Sour Cherry, Pomegranate, and Strawberry Juices by Hydrogen Peroxide(John Wiley and Sons Inc., 2002) Özkan, Mehmet; Yemenicioğlu, Ahmet; Asefi, N.; Cemeroglu, BekirDegradations were studied at different hydrogen peroxide (H2O2] concentrations (9.31 to 27.92 mmol. L-1] over a range of 10 ° to 30 °C. Degradation of anthocyanins by H2O2 was described by first-order function. Comparison of t1/2 values revealed that sour cherry anthocyanins were the most resistant to H2O2, followed by pomegranate and strawberry anthocyanins. Thus, the removal of residual H2O2 from the juice contact surfaces of aseptically packaged strawberry juices should be controlled more carefully to prevent anthocyanin degradation. Respective Ea values were between 9.4 to 11.1, 9.5 to 11.4, and 11.4 to 12.2 kcal.mol-1; and Q10 values between 1.59 to 2.22, 1.62 to 2.05, and 1.76 to 2.36 for strawberry, sour cherry, and pomegranate anthocyanins.