Opis: The solubility of supercritical carbon dioxide (scCO2) in poly(l-lactide) and poly(d,l-lactide-co-glycolide) at different temperatures (308, 313 and 323 K) and pressures (10-30 MPa) was measured using a magnetic suspension balance. The solubility data were also used for estimating the binary diffusion coefficients. The results show a good solubility of CO2 in both polymers: up to 43% in poly(l-lactide) and 30% in poly(d,l-lactide-co-glycolide). The diffusion coefficients have high values, which verify the liquid-like solvating properties of scCO2. The diffusion coefficient depends on the quantity of gas already absorbed by the polymer; its values decrease with increasing gas concentration. Ključne besede:SC CO2, solubility, diffusivity, magnetic suspension balance Objavljeno v DKUM: 31.05.2012; Ogledov: 1681; Prenosov: 102 Povezava na celotno besedilo

Opis: The extraction kinetics behaviour of lutein from Marigold flower petals and simultaneous alkali hydrolysis has been studied. Extraction was carried out by varying following operating conditions: type of organic solvent, temperature, ratio liquid: material, concentration of alkali solution, and particle size of plant material. Experimental extraction curves were analysed with a mathematical model derived from Fick's second law. The extraction of lutein appeared to be governed by slow and fast diffusion processes. Results showed that the intra-particle diffusion was the rate-governing step of the extraction process, and that the chosen model gives very good approximation of experimental data. Ključne besede:lutein, marigold, conventional extraction, diffusivity, mass transfer Objavljeno v DKUM: 31.05.2012; Ogledov: 2184; Prenosov: 108 Povezava na celotno besedilo

Opis: The note features the mathematical model of computing binary diffusion coefficient, thermal diffusion factor and viscosity in the real-gas region on the basis of nonequilibrium statistical mechanics. For the analytical calculation of transport properties, we have used the Kihara and Chapman-Cowling model up to the third order. In the presented note we calculated transport properties for mixtures between carbon monoxide and helium. We have developed the new mixing rules for the calculation of transport properties for mixtures. The analytical results obtained by statistical mechanics are compared with the experimental data and they show relatively good agreement. Ključne besede:thermodynamics, statistical thermodynamics, mathematical models, binary diffusion coefficient, thermal diffusivity, binary mixtures Objavljeno v DKUM: 30.05.2012; Ogledov: 2211; Prenosov: 70 Povezava na celotno besedilo