Diffusion into and adsorption of polyethylenimine on porous silica gel

Abstract

SynopsisThe polyethyleneimine (PE1)-water-silica gel absorption system was used as a model system to investigate the relationship between diffusion into the porous structure, adsorption rate, and molecular weight of the polymer. Three silica gels, Porasil A, B, and and C having a range of characteristic porosity were used as adsorhents. Adsorption of PEI on Porasil C, which has the majority of its pores much larger than the dimensions of the adsorbate molecule, increased initially with increased molecular weight but became nearly constant at higher molecular weight. Little increase in adsorption occurred for this silica gel with increased ionic strength or with increased p H between 9.5 and 10.8. In contrast, adsorption increased sharply with increased ionic strength and for the same p H range on Porasil A.Adsorption decreased with increased molecular weight on Porasil A. In this case, the molecular size of PEI investigated was the same as the majority of pore apertures in the adsorbent. Solution environments (i.e., p H and ionic strength) that decrease the size of the PEI molecule and its affinity for the anionic silica gel surface, thus enabling it to more readily diffuse into the smaller porous regions of the adsorbent, are the apparent causes of the very large adsorption increase. Electrostatic repulsion between PEI molecules do not appear greatly to affect adsorption. Similar adsorption behavior has been reported in the literature for the PEI-cellulosic fiber adsorption system. bIaximum adsorption on Porasil A occurred at p H 10.8, the same maximuni generally reported for adsorption of PEI on cellulosic fibers. In this case, the silica gel (Porasil A ) was found to have a pore size distribution and specific surface area of the same magnitude as cellulosic fibers prepared in the expanded state.Molecular weight dependence was reversed.

Adsorption of Polyethylenimine on Nanosized Zirconia Particles in Aqueous Suspensions

“…On titration with HNO 3 , the apparent degree of dissociation ␣ increases and causes insignificant variation of the pH values of the solution. However, in the region pH Ͻ 2, the polymer will completely dissociate and undergo a transition from a compact coiled conformation to one that is stretched (11). Figures 3 and 4 show the adsorption isotherms of PEI on nanosized ZrO 2 particles at 25°C.…”

Dissolved and Colloidal Substances (Dcs) and the Charge Demand of Papermaking Process Waters and Suspensions: A Review

“…In particular, an effective "surface charge" can be estimated by tests involving the adsorption of highmass cationic polyelectrolytes (Wågberg et al 1989;Horvath and Lindström 2007). The principle of such analyses was pioneered by Hostetler and Swanson (1974), who used silica gel as a model mesoporous substrate. The validity of such an approach rests upon a number of assumptions, including (a) there is a 1:1 stoichiometry of interactions between the test polymer and the surface groups, and (b) the selected polyelectrolyte does not permeate into the cell wall to a significant extent during the time of testing.…”

“…One of the consequences of fibers' mesoporous nature is that low-mass cationic polymers tend to adsorb in greater amounts compared to their higher-mass analogues (Hostetler and Swanson 1974;Lindström and Söremark 1976;Petlicki and van de Ven 1994;Farley 1997;Taipale et al 2011).…”

Enhancement of polyelectrolyte precipitation through the genetic fusion of charged polypeptides to enzymes

“…The hydrodynamic radii of the 470 kDa P-galactosidase and the 65 kDa glucoamylase were estimated to be 84.1 Â and 37.8 Â, respectively, using the correlation of Teller [18] for monomeric and multimeric proteins. The highly branched form of polyethyleneimine (PEI) used in the precipitations has been shown to assume a spherically symmetric compact shape in solution [19]. The hydrodynamic radius of the 55 kDa polyelectrolyte was estimated to be 130 Â at I = 0.1 M, using the correlation between molecular weight and size from Lindquist and Stratton [20] and Hostetler and Swanson [19].…”

“…The highly branched form of polyethyleneimine (PEI) used in the precipitations has been shown to assume a spherically symmetric compact shape in solution [19]. The hydrodynamic radius of the 55 kDa polyelectrolyte was estimated to be 130 Â at I = 0.1 M, using the correlation between molecular weight and size from Lindquist and Stratton [20] and Hostetler and Swanson [19]. The maximum number of proteins which could sterically interact with the polyelectrolyte was estimated by treating both the protein and polyelectrolyte as hard spheres to determine how many proteins could pack on the surface of the polyelectrolyte.…”