Georges Grevillot

Temperature-Swing Gas Separation with Electrothermal Desorption Step

Abstract Results of an experimental investigation of a new method for heating adsorbent beds in the desorption step owing to Joules heat generated inside the adsorbent particles by passing an electric current through them are presented. Desorption of a previously saturated bed and cyclic separation with the electric potential applied to a fibrous activated carbon bed was performed.

Toxicity of Carbon Dioxide: A Review

The toxicity of carbon dioxide has been established for close to a century. A number of animal experiments have explored both acute and long-term toxicity with respect to the lungs, the cardiovascular system, and the bladder, showing inflammatory and possible carcinogenic effects. Carbon dioxide also induces multiple fetal malformations and probably reduces fertility in animals. The aim of the review is to recapitulate the physiological and metabolic mechanisms resulting from CO(2) inhalation. As smokers are exposed to a high level of carbon dioxide (13%) that is about 350 times the level in normal air, we propose the hypothesis that carbon dioxide plays a major role in the long term toxicity of tobacco smoke.

Adsorption of BSA and Hemoglobin on Hydroxyapatite Support: Equilibria and Multicomponent Dynamic Adsorption

Interactions of Bovin Serum Albumin and Hemoglobin with an hydroxyapatite gel (HA-Ultrogel, Sepracor), have been studied separately in batch experiments. The adsorption isotherms are of the Langmuir type and can be used directly to scale column operations.For adsorption of hemoglobin alone, in column at pH 6.8 (equal to its isoelectric point) we notice that a classical intraparticle transfer model, based on a constant effective diffusion coefficient represents perfectly the symmetrical breakthrough curve. For acid pH values (pH 5.8), Langmuir isotherms of BSA and hemoglobin adsorptions showed a strong curvature, sign of a quite irreversible adsorption and breakthrough curves obtained under these conditions, exhibit a high dissymmetrical shape for both proteins. In that case, a model of diffusion based on the adsorption on two types of independent sites, with two intraparticle transfer coefficients, gives a good representation of the breakthrough for adsorption of both proteins separately.Binary mixtures of these components were prepared and injected in columns packed with the same support. Competitive Langmuir equation, based on the results obtained in monocomponent batch experiments, give a very good fit to our system. The intraparticle transfer in that case seems to be facilitated, and one effective coefficient alone is enough to predict the breakthrough curves obtained. This behaviour may be the result of an increase of the solution ionic strength, and of the smaller irreversibility feature of the adsorption when proteins are in competition.

Equilibria and activity coefficients for non-ideal adsorbed mixtures from perturbation chromatography

Abstract This article presents a new method to construct binary co-adsorption isotherms and to obtain the thermodynamic parameters entering in their description. More precisely, we show how activity coefficients may be extracted from peak chromatography experiments in binary mixtures of co-adsorbed components. These activity coefficients are defined in the framework of the so-called non-ideal adsorbed solution theory. Explicit analytical expressions are established relating the overall adsorption coefficient (and thus the retention time of the peak), to the pure component adsorption isotherms, to the mixture composition, and to the activity coefficients. Owing to thermodynamic constraints (Gibbs–Duhem), the measurement of retention times furnishes enough information, in this framework, to retrieve the activity coefficients. The approach is independent of any model for the adsorption isotherms, but requires a model for the free energy of mixing, or for the dependence of activity coefficients on composition. Experimental examples illustrating the procedure are given for co-adsorption of the binary mixtures CH4/C2H6 (nearly ideal) and C2H6/CO2 (strongly non-ideal) on 5A zeolite.

Preparative scale separation of amino acids by using thermal ion exchange parametric pumping

Separation of amino acids by thermal parametric pumping is experimentally and theoretically investigated. A multicomponent, non-linear model that takes into account the dissociation reaction in liquid phase is used to predict the separation and to investigate the effect of the resin type on the performance of parametric pumping. Experiments have been done with different mixtures of glutamic acid, leucine, phenylalanine, proline, serine and valine. The experimental results demonstrate the capability of thermal parametric pumping of separating amino acids from aqueous mixtures. The simulations give the correct general behaviour of the experimental results and help to select the resin that is more suitable for the separation.

Separation of silver-copper mixtures by ion-exchange parametric pumping: I. Total reflux separations

Summary Silver-copper mixtures occur at various stages of metal recovery processes particularly in the refining of silver. Parametric pumping is proposed as a method of separating copper from silver. The process consists in making a periodic change in the temperature of a fixed bed of ion-exchange resin with a synchronized periodic relative flow of the liquid mixture. Experimental results at total reflux (batch) are presented that show that a good separation can be made by this method using Duolite C265 resin. The results are interpreted by a graphical approach using standard ion-exchange breakthrough curves obtained experimentally. Changes in total concentration are observed and interpreted as being the effect of temperature on Dorman electrolyte uptake.

Theoretical study of adsorptive parametric pumping and temperature swing chromatography with flow reversal

Different techniques of adsorptive parametric pumping have been theoretically studied with the help of a multicomponent, non-linear model. For calculations, a mixture of three components was considered. The effect of the initial concentration on the performance of parametric pumping was found to be significant. In the high initial concentration range (where the isotherm is non-linear), a combination of batch and continuous parametric pumping was investigated. It is shown that products with constant composition can be obtained. In the low initial concentration range (where the isotherm is linear), it is necessary to use a special type of adsorptive parametric pumping, called temperature swing chromatography, for separating the components. It is shown how the separation builds up from cycle to cycle, and how to influence the purity of the components with the help of the hot regeneration.

Carbon dioxide is largely responsible for the acute inflammatory effects of tobacco smoke

Tobacco smoking is responsible for a vast array of diseases, particularly chronic bronchitis and lung cancer. It is still unclear which constituent(s) of the smoke is responsible for its toxicity. The authors decided to focus on carbon dioxide, since its level of concentration in mainstream cigarette smoke is about 200 times higher than in the atmosphere. The authors previously demonstrated that inhalation of carbon dioxide concentrations above 5% has a deleterious effect on lungs. In this study, the authors assessed the inflammatory potential of carbon dioxide contained in cigarette smoke. Mice were exposed to cigarette smoke containing a high or reduced CO2 level by filtration through a potassium hydroxyde solution. The inflammatory response was evaluated by histological analysis, protein phosphatase 2 A (PP2A) and nuclear factor (NF)-κB activation, and proinflammatory cytokine secretion measurements. The data show that the toxicity of cigarette smoke may be largely due to its high level of CO2. Pulmonary injuries consequent to tobacco smoke inhalation observed by histology were greatly diminished when CO2 was removed. Cigarette smoke exposure causes an inflammatory response characterized by PP2A and NF-κB activation followed by proinflammatory cytokine secretion. This inflammatory response was reduced when the cigarette smoke was filtered through a potassium hydroxide column, and reestablished when CO2 was injected downstream from the filtration column.Given that there is an extensive literature linking a chronic inflammatory response to the major smoking-related diseases, these data suggest that carbon dioxide may play a key role in the causation of these diseases by tobacco smoking.

Amino acid separation by preparative temperature-swing chromatography with flow reversal

Abstract A special type of adsorptive parametric pumping called temperature-swing chromatography is experimentally investigated for a new application: the separation of amino acids. Experiments have been done with a mixture of arginine, histidine and lysine in acidic solution (HCl). A multicomponent equilibrium model has been used to simulate the experimental results and to investigate some possible ways to improve the separation. It is shown that it is possible to separate these amino acids, and the composition of the products strongly depends on the experimental conditions. Arginine with purity greater than 95% can be obtained by applying these methods.

Preparative-scale amino acid separation by thermal parametric pumping on an ion-exchange resin

Thermal parametric pumping was experimentally investigated for the concentration and separation of amino acids. Previous theories of parametric pumping were improved by taking into account dissociation equilibria in the liquid phase. Experiments were carried out with a mixture of glutamic acid, aspartic acid, serine and threonine in a highly acidic solution (HCl). A multi-component equilibrium model was mainly used to simulate the experimental results and to investigate the effect of chloride concentration over a wide range. It is shown that it is always possible to concentrate the amino acids and to separate some of them under certain conditions.