Fluid Sorption Data and Modeling

Prediction of the breakthrough performance of molecular sieve adsorption columns requires solution of the appropriate mass-transfer rate equation with boundary conditions imposed by the differential fluid phase mass balance. For systems which obey a Langmuir isotherm and for which the controlling resistance to mass transfer is macropore or zeolitic diffusion, the set of nonlinear equations must be solved numerically. Solutions have been obtained for saturation and regeneration of molecular sieve adsorption columns. Predicted breakthrough curves are compared with experimental data for sorption of ethane and ethylene on type A zeolite, and the model satisfactorily describes column performance. Under comparable conditions, column regeneration is slower than saturation. This is a consequence of non-linearities of the system and does not imply any difference in intrinsic rate constants. 

DEA DeAngelis, M.G., Meikel, T.C., Bondar, V.I., Freeman, B.D., Doghieri, F., and Sard, G.C., Gas sorption and dilation in poly(2,2-bistrifluorometltyl-4,5-difluoro-l,3-dioxole-co-tetra-fluoroethylene) comparison of experimental data with predictions of the nonequilibrium lattice fluid model, Macromolecules, 35, 1276, 2002. 

It has long been known that the solubilities of sulfide ore minerals in hydrothermal fluids results from the complexation of metals such as Cu, Zn and Fe by Cl and HS ligands (Seward and Barnes 1997). Complexation of heavy metals such as As, Pb and Cd by mineral surfaces controls the mobility of such metals in the environment. Geochemists need to have a reliable thermodynamic data set to predict mineral solubilities and metal sorption reactions. Such data are found by fitting measured solubilities and sorption isotherms to a set of stability constants for aqueous and surface complexes. However, fits to experimental data are often non-unique and depend on the speciation model an independent way to determine the nature of metal complexes in aqueous solutions and on mineral surfaces is needed. 

In order to compare the model calculations with experimental calorimetric data, PS samples were modified in a transitiometer used, in this case, as a small reactor to modify PS under equilibrium conditions in the presence of a chosen fluid. Modifications of PS have been done in the presence of N2 and CO2, along isotherms at a given pressure. For these two fluids, a final temperature of 398.15 K and a final pressure of 80 MPa have been attained. The Tg of modified and nonmodified PS samples were determined by temperature-modulated DSC (TMDSC). The solubilities of the different gases were measured using the YW-pVT sorption technique [48, 49] along different isotherms, and the mass fraction of the gas in the polymer was then determined with the following equation ... 

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