Poly , sorption sites

Corundum is aluminum oxide, q -A1203, which has a hexagonal crystalline structure that is analogous to hematite. However, water treatment systems most often use activated alumina, which is typically produced by thermally dehydrating aluminum (oxy)(hydr)oxides to form amorphous, cubic (y), and/or other polymorphs of corundum (Clifford and Ghurye, 2002, 220 Hlavay and Poly k, 2005 Mohan and Pittman, 2007). When compared with corundum, amorphous alumina tends to have higher surface areas, greater numbers of sorption sites, and better sorption properties. 

Consistent with the preceding discussion concerning sorption and flux reductions by relatively nonin-teracting penetrants, the data shown in Fig. 20.4-11 clearly illustrate the progressive exclusion of CO] from Langmuir sorption sites in poly(mediyl methacrylate) (PMMA) as ethylene partial pressure (og) is increased in the presence of an essentially constant CO] partial pressure of T 0.13 atm. The... 

Dole [67, 68] observed that small molecules associate firmly with functional sites in polymeric materials. He studied sorption of water and organic vapors by synthetic high molecular weight polymers. He noted that the ratio (a/N) of sorbed molecules (a) to available adsorption sites (N, i.e. the total number of functional groups in the polymer) increases with the partial pressure of the vapor being sorbed. In the case of water sorption at 100% RH by poly(/V-vinyl 2-pyrrolidinone) a/N was almost one, and in the case of water sorption by poly(vinyl methoxyacetal) [68] it was even greater than one. 

Consistent with the preceding discussion concerning sorption and flux reductions by relatively noninteracting penetrants, the data shown in Fig. 20.4-11 clearly illustrate the progressive exclusion of CO2 from Langmuir soiption sites in poly(methyl methaciylate) (PMMA) as ethylene partial pressure (Pb) increased in the presence of an essentially constant CO2 partial pressure of 3-05 7 0.13 atm. The tendency of the CO2 soiption shown in Fig. 20.4-11 to decrease monotonically with ethylene pressure provides impressive support for the competition concept on which E. . 4-17) and (20.4-18) are based. Pemreation data are not available for this stem to determine if changes in the values of Dp and Dh occur in the mixed gas situation. If offsettiiig increases in these transport coefficients do not occur in the presence of ethylene, the CO2 permeability will be depressed in the mixed gas peimeation situations. 

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