Sorption carbon dioxide

Values of the uptake at saturation, of butane, carbon dioxide and nitrogen, by a sample of carbon, expressed as a volume of liquid v,. The carbon had been "burnt off" to different extents by heating in oxygen at 500°C on a sorption... 

Because of the delay in decomposition of the peroxide, oxygen evolution follows carbon dioxide sorption. A catalyst is required to obtain total decomposition of the peroxides 2 wt % nickel sulfate often is used. The temperature of the bed is the controlling variable 204°C is required to produce the best decomposition rates (18). The reaction mechanism for sodium peroxide is the same as for lithium peroxide, ie, both carbon dioxide and moisture are required to generate oxygen. Sodium peroxide has been used extensively in breathing apparatus. 

In air conditioning (qv) of closed spaces, a wider latitude in design features can be exercised (23,24). Blowers are used to pass room or cabin air through arrays of granules or plates. Efficiencies usuaHy are 95% or better. The primary limiting factor is the decreased rate of absorption of carbon dioxide. However, an auxHiary smaH CO2 sorption canister can be used. Control of moisture entering the KO2 canister extends the life of the chemical and helps maintain the RQ at 0.82. 

The scission reaction was carried out with a fixed addition of 1.50g of the dry resin, 10 mg of ferrous sulfate heptahydrate and 50 ml of 3% w/v hydrogen peroxide in a round Pyrex flask. The evolved carbon dioxide was vented to the atmosphere through serial traps containing sulfuric acid followed by a soda lime sorption tube. The magnetically stirred reaction flask was submerged in an oil bath heated with an immersed electrical coil and a magnetic stirrer positioned below the bath. The temperature was maintained at 50 +/- 1 C. After varied times 1.0 ml samples of liquid were withdrawn. There were fewer than six withdrawals in a given reaction sequence. 

To illustrate this a model transesterification reaction catalyzed by subtilisin Carls-berg suspended in carbon dioxide, propane, and mixtures of these solvents under pressure has been studied (Decarvalho et al., 1996). To account for solvent effects due to differences in water partitioning between the enzyme and the bulk solvents. Water sorption isotherms were measured for the enzyme in each solvent. Catalytic activity as a function of enzyme hydration was measured, and bell-shaped curves with maxima at the same enzyme hydration (12%) in all the solvents were obtained. The activity maxima were different in all media, being much higher in propane than in either CO2 or the mixtures with 50 and 10% CO2. Considerations based on the solvation ability of the solvents did not offer an explanation for the differences in catalytic activity observed. The results suggest that CO2 has a direct adverse effect on the catalytic activity of subtilisin. 

The importance of quadrupole interaction in zeolitic sorption has been pointed out by Barrer and Stuart (20). Such effects are clearly illustrated by the data for sorption of nitrogen and carbon dioxide in both H-chabazite and 5A zeolite. For these molecules, which have large quadrupole moments, the experimental values of K0 are much smaller than the theoretical values predicted from the idealized model suggesting either localized sorption at specific sites within the cavity or restricted rotational freedom. 

Sanders, E. S., Koros, W. J., Hopfenberg, H. B., Stannett, V. T. Pure and Mixed Gas Sorption of Carbon Dioxide and Ethylene in Poly(methyl methacrylate), to be pubhshed... 

Polyethylene terephthalate) (PET), with an oxygen permeability of 8 iiiuol/(ius-GPa), is not considered a barrier polymer by die old definition however, it is an adequate barrier polymer for holding carbon dioxide in a 2-L bottle for carbonated soft drinks. The solubility coefficients for carbon dioxide are much larger than for oxygen. For the case of the PET soft drink bottle, the principal mechanism for loss of carbon dioxide is by sorption in the bottle walls as 500 kPa (5 atm) of carbon dioxide equilibrates with the polymer. For an average wall thickness of 370 pm (14.5 mil) and a permeabdity of 40 nmol/(m-s-GPa), many months are required to lose enough carbon dioxide (15% of initial) to be objectionable. 

Figure 7. The effect of ethylene on the sorption level of carbon dioxide in poly(methyl methacrylate) at 35 °C.

The gas-polymer-matrix model for sorption and transport of gases in polymers is consistent with the physical evidence that 1) there is only one population of sorbed gas molecules in polymers at any pressure, 2) the physical properties of polymers are perturbed by the presence of sorbed gas, and 3) the perturbation of the polymer matrix arises from gas-polymer interactions. Rather than treating the gas and polymer separately, as in previous theories, the present model treats sorption and transport as occurring through a gas-polymer matrix whose properties change with composition. Simple expressions for sorption, diffusion, permeation and time lag are developed and used to analyze carbon dioxide sorption and transport in polycarbonate. 

In Section I we introduce the gas-polymer-matrix model for gas sorption and transport in polymers (10, LI), which is based on the experimental evidence that even permanent gases interact with the polymeric chains, resulting in changes in the solubility and diffusion coefficients. Just as the dynamic properties of the matrix depend on gas-polymer-matrix composition, the matrix model predicts that the solubility and diffusion coefficients depend on gas concentration in the polymer. We present a mathematical description of the sorption and transport of gases in polymers (10, 11) that is based on the thermodynamic analysis of solubility (12), on the statistical mechanical model of diffusion (13), and on the theory of corresponding states (14). In Section II we use the matrix model to analyze the sorption, permeability and time-lag data for carbon dioxide in polycarbonate, and compare this analysis with the dual-mode model analysis (15). In Section III we comment on the physical implication of the gas-polymer-matrix model. 

The solid line in Fig. 1 represents the sorption isotherm of carbon dioxide in polycarbonate calculated by fitting the solubility expression, eq. (11), to experimental data of Wonders and Paul (15). The best fit to the experimental data was achieved with the parameters ao=7.33cm3(STP)/cm3(polymer)-atm and a = 0.161 cm3(polymer)/cm3(STP). As can be seen in Fig. 1, eq. (11) describes the experimental data over the entire pressure range. The algorithm used to fit eq. (11) to the experimental data is described elsewhere (FI). 

Ongwandee, M. and Morrison, G.C. (2008) Influence of ammonia and carbon dioxide on the sorption of a basic organic pollutant to carpet and latex-painted gypsum board. Environmental Science and Technology, 42 (15), 5415-20. 

R. Ash, R.M. Barrer and P. Sharma, Sorption and Flow of Carbon Dioxide and Some Hydrocarbons in a Microporous Carbon Membrane, J. Membr. Sci. 1, 17 (1976). 

Rochette, E.A. and W.C. Koskinen (1996). Supercritical carbon dioxide for determining atrazine sorption by field-moist soils. Soil Sci. Soc. Am. J., 60 453 160. 

Additional studies by Menon (32) have indicated the p can occur at lower pressures then those predicted by Equation 1 depending on the pore structure associated with the adsorbent. Empirically, adsorbents possessing microporosity exhibit a p that is 0.6-0.8 of the value predicted by Equation 1. This observation is attributed to the overlapping of potential fields in the adsorbent pores, thereby enhancing sorption of the gas at lower pressures. Experimental studies by Ozawa (33) have verified this trend as shown in Figure 4 for the C02/activated carbon system. Here the adsorption maxima for the gas occurs at a lower pressure than the critical pressure of carbon dioxide. It should also be noted that the amount of gas adsorbed is decreased at higher reduced temperatures and that additional compression is required to reach a defined adsorption maxima (i.e., at very high values of T it is sometimes difficult to discern a well-defined adsorption maximum). The above trend has also been found for other adsorbent/adsorbate systems, such as silica gel/C02. 

Unfortunately values cannot be directly calculated from retention volume measurements by Equation 3 since the interfacial surface area is changing as a function of pressure due to the carbon dioxide sorption. However, the relative magnitude of the equilibrium shift of the sorbate from the solid adsorbent into the gaseous phase can be estimated by calculating the capacity factor, k, according to Equation A as given below ... 

Story, B. J., and Koros, W. J. (1991). Sorption of carbon dioxide/methane mixtures in poly(phenylene oxide) and a carboxylated derivative, J. Appl. Polym Sci. 42, 2613. 

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