No abstract

It is very important to understand the equilibrium and dynamic characteristics of biospecific adsorption (affinity chromatography) for both scientific and application purposes. Experimental equilibrium and dynamic column data are presented on the adsorption of lysozyme onto antibody immobilized on nonporous silica particles. The Langmuir model is found to represent the equilibrium experimental data satisfactorily, and the equilibrium association constants and heats of adsorption have been estimated for two systems with different ligand densities. The effects of nonspecific interactions are more pronounced in the system with low-density ligand. The dynamic interaction kinetic parameters are estimated by matching the predictions of a fixed-bed model with the experimental breakthrough curves. The agreement between theory and experiment is good for the initial phases of breakthrough, where the mechanism of biospecific adsorption is dominant. In the later phase (saturation neighborhood) of breakthrough, the effects of nonspecific interactions appear to be greater in the low-density ligand system. The kinetics of the nonspecific interactions were estimated from the data of the later phase of breakthrough and were found to be considerably slower than those attributed to biospecific adsorption.

Utah tar sands have been pyrolyzed experimentally in a tubular furnace into a stream of nitrogen. Various condensate products have been collected and analyzed, and the pyrolyzed sands have been analyzed for coke and unreacted bitumen. The kinetics of the pyrolysis appeared to be second order under conditions of approximately constant temperature and in experiments with continuously changing temperatures. A lighter product with less sulfur, nitrogen, and arsenic was produced when more rapid heating rates were used. Other characteristics of the reaction and products are presented.Des sables bitumineux de 1'Utah ont Ct C pyrolysCs dans un four tubulaire sous un courant d'azote. Divers produits de condensats ont Ct C recueillis et analysCs et les sables pyrolysks ont ktC analysks pour dkterminer leur teneur en coke et en bitumes non rCagis. La cinktique de la pyrolyse s'avkre Ctre du second ordre dans des conditions de tempCrature a peu prks constante ainsi que dans des expkriences effectuees avec des temHratures changeant de facon continue.Un produit plus ICger avec moins de soufre, d'azote et d'arsenic a Ct C produit avec des vitesses de chauffe plus rapides. D'autres caractiristiques de la rCaction et des produits sont prksenttes.

When more components than desired are adsorbed, adsorption-desorption separation processes may not be satisfactory. However, in the cases of ethanol and water adsorption on activated carbon, propane and propylene adsorption on molecular sieves, and hydrogen sulfide, carbon dioxide, and propane adsorption on molecular sieves, it has been found that a variable-temperature stepwise desorption (VTSD) procedure following the adsorption stage can significantly increase the degree of separation achieved compared to a complete desorption of all adsorbed components. Studies indicate that these increased separations are in part due to nonequilibrium effects. An estimation of economic factors in separating low concentration propylene in propane indicates VTSD is favorable compared to distillation, because of lower energy costs. It appears that the VTSD method could be useful in bulk separations of mutlicomponent mixtures.Adsorption is a highly selective separation method in which a component (or components) in a fluid mixture is removed to the surface of a solid, usually by a highly specific physical or chemical interaction at the fluid-solid interface. As a separation method, physical adsorption is used to separate a desired component from a stream, and when the solid adsorbent is near saturation, the solid adsorbent is desorbed into a different stream by thermal, pressure, or diluent changes. Adsorption is a separation method that is most often useful in removing low concentration components from liquids or gases, with many applications in the removal of impurities or pollutants and in the recovery of solvents or other valuable components from air or water that is to be discharged. Adsorption has also found use in the petrochemical industry in separating xylenes and similar compounds by multistage operations. However, in most potential applications, adsorption is not an economical separation method for high volume products unless a satisfactory separation can be obtained in one stage of adsorption. This is because a large amount of adsorbent is usually required relative to the amounts adsorbed and because it is difficult and complex to handle solids in continuous processes and multiple stages. If undesired components are adsorbed along with the components that are desired to be adsorb, then further separation of the adsorbed components may be necessary, causing the complete separation process to be too costly. For these reasons, the applications of adsorption have not been widespread in bulk separations even though they may be more highly selective and use less energy than separations such as distillation, absorption, and extraction. Increased potential for adsorption separations could be achieved through methods of enhancing the separation in a minimum number of adsorption-desorption stages.Desorption of adsorbed components is necessary for the recovery of adsorbed compounds and for the regeneration of the adsorbent for repeated use. The desorption step of adsorption-desorption separations is usually carried out in a sin...

This study concerns rates of evaporation and mass transfer of water vapor from a heated salt solution through a water repellent porous membrane to a cooled water condensate. This transfer is a result of temperature differences and corresponding vapor pressure differences across the membrane. Three groups of experiments were carried out which indicate that the major factor influencing the rates of transfer is diffusion through a stagnant gas in the membrane pores. However, an equation considering film heat transfer coefficients, membrane thermal conductivity, and an empiricial correction based on temperature driving force appears to be necessary for representing all the data. The empirical correction appears to be related to internal condensation and possibly diffusion along surfaces.