Absorption onto silica particles

Morrissey 53) used transmission infrared spectroscopy to study protein adsorption onto silica particles in a heavy water (DzO) buffer. By observing the shift in the amide I absorption band, he could deduce the fraction of protein carbonyl groups involved in bonding to the silica surface. He found that bovine IgG had a bound fraction of 0.20 at low bulk solution concentrations, but only about 0.02 at high solution concentrations. However, neither prothrombin nor bovine serum albumin exhibited a change in bound fraction with concentration. Parallel experiments with flat silica plates using ellipsometry showed that the IgG-adsorbed layers had an optical thickness of 140 A and a surface concentration of 1.7 mg/m2 at low bulk solution concentration — in concentrated solutions the surface amount was 3.4 mg/m2 with a thickness of 320 A (Fig. 17). 

More recent x-ray absorption studies of Co sorption complexes on quartz [77] suggest that for quartz at relatively low density coverage, first-sorbed Co species provide energetically favorable nucleation sites for the subsequent formation of multinuclear hydroxide-like surface complexes. This is also seen for Ni " " adsorbed onto silica [78] where the first species adsorbed are seen as nickel phyllosilicates and not hydroxides. Subsequent layers are either more nickel phyllosilicate or nickel hydroxide depending on the activity of the sdica. If the silica is more active, for example due to smaller particles or greater surface area, then more metal-sUicate species are formed either at the... 

The kinetics of absorption of silica onto the surface of particles of thoria was determined at 100-200°C in an autoclave (77). 

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