Surface titration studies

It was noted that the content of functional groups on the surface of studied A1,03 was 0,92-10 mol/g of acid character for (I), FOS-IO mol/g of basic character for (II). The total content of the groups of both types was 1,70-lO mol/g for (III). The absence of appreciable point deviations from a flat area of titration curves in all cases proves simultaneously charges neutralization character on the same adsoi ption centers and non-depending on their density. The isoelectric points of oxide surfaces have been detenuined from titration curves and have been confirmed by drift method. 

Bacterial cell walls contain different types of negatively charged (proton-active) functional groups, such as carboxyl, hydroxyl and phosphoryl that can adsorb metal cations, and retain them by mineral nucleation. Reversed titration studies on live, inactive Shewanella putrefaciens indicate that the pH-buffering properties of these bacteria arise from the equilibrium ionization of three discrete populations of carboxyl (pKa = 5.16 0.04), phosphoryl (oKa = 7.22 0.15), and amine (/ Ka = 10.04 0.67) groups (Haas et al. 2001). These functional groups control the sorption and binding of toxic metals on bacterial cell surfaces. 

Surface science studies of CO oxidation on Au(llO) single crystals have been made previously in which a Pt filament was used to adsorb oxygen adatoms ( o 0.25) on the Au(llO) surface and a CO titration was performed subsequently (7). CO did react to form CO2 with Eapp = 2 1 kcal/mole. Since CO was not observed to adsorb on Au(llO) at 125 K, it is only physisorbed (as on Au(lll)) and we can estimate that Elh = 7 kcal/mol on Au(llO). The difference from Au(lll) is probably due to a weaker Au-O bond on Au(lll) which leads to a lower barrier for reaction. No surface carbonate was formed from CO2 + Oa on Au(llO) either (7). This is in contrast to the behavior on Ag. Exposing oxygen covered Ag(llO) (16) or Ag(lll) (17) to CO2 produces carbonate species which are stable to 485 K on the surface. 

Wangsakan, A., Chinachoti, P., McClements, D.J. (2001). Maltodextrin-anionic surfactant interactions isothermal titration calorimetry and surface tension study. Journal of Agricultural and Food Chemistry, 49, 5039-5045. 

Glazer and Dogan (4) studied BSA spread as a monomolecular film on water. In general, the surface titration curve resembled that of BSA in solution, with two inflections in the pH ranges 3.5 to 6.5 and 10.0 to... 

Double layer studies can also be used to characterize surfaces. Titrations, in combination with electrokinetics, are helpful to Identify charge-determining species and hence establish the relative acldity/basicity of a certain surface. These results may be compared with those from functional gas adsorption. In this way heterogeneous catalysts and pigments have been characterized. Trace... 

There are some studies that did not use in situ measurements. These include surface titration and desorption experiments in which surface cover-... 

The catalytic work on the zeolites has been carried out using the pulse microreactor technique (4) on the following reactions cracking of cumene, isomerization of 1-butene to 2-butene, polymerization of ethylene, equilibration of hydrogen-deuterium gas, and the ortho-para hydrogen conversion. These reactions were studied as a function of replacement of sodium by ammonium ion and subsequent heat treatment of the material (3). Furthermore, in some cases a surface titration of the catalytic sites was used to determine not only the number of sites but also the activity per site. Measurements at different temperatures permitted the determination of the absolute rate at each temperature with subsequent calculation of the activation energy and the entropy factor. For cumene cracking, the number of active sites was found to be equal to the number of sodium ions replaced in the catalyst synthesis by ammonium ions up to about 50% replacement. This proved that the active sites were either Bronsted or Lewis acid sites or both. Physical defects such as strains in the crystals were thus eliminated and the... 

Wesolowski, D.J. et al., Magnetite surface charge studies to 290 °C from in situ pH titrations, Chem. Geol.. 167. 193. 2000. 

Protein adsorption on solid surfaces is discussed from a colloid chemical and thermodynamic point of view. Information is mainly obtained from adsorption isotherms, (proton)titrations, electrokinetics and calorimetry. The adsorption behavior of human plasma albumin and bovine pancreas ribonuclease at various surfaces is studied. The differences in behavior between the two proteins are related to differences in the structural properties. Furthermore, the essential role of the low molecular weight electrolytes in the overall protein adsorption process is stressed. 

SO. For good working discussions of potentiometric titration methods, see G. H. Bolt, Determination of the charge density of silica soils, J. Phys. Chem. 61 1166 (1957), and D. E. Yates and T. W, Healy, Titanium dioxide-electrolyte interface. 2. Surface charge (titration) studies, J.C.S. Faraday 1 76 9 (1980), A critical discussion of the uses of potentiometric titration to measure (Th for soil clays is given in J. C. Parker, L. W, Zelazny, S. Sampath, and W. G. Harris, Critical evaluation of the extension of zero point of charge (ZPC) theory to soil systems. Soil Sci. Soc. Am. J. 43 668 (1979). 

Yates, D.E. and Healy, T.W., Titanium-dioxide electrolyte interface. 2. Surface-charge (titration) studies, J. Chem. Soc., Faraday Trans. 1, 76, 9, 1980. 

In this study gas adsorption, SEM, SAXS and surface titration methods were used to characterize the mor-... 

UV/vis titration studies on p-aryleneacetylene family of nanorings showed 1 1 supramolecular complexes with Cgo and C70, and the increased size of the aromatic surface yielded interesting supramolecular nanostructures (such as onion-type complexes). ... 

The superficial surface area of the metal working catalyst electrode is typically 2 cm and its true gas-exposed surface area is typically 5 to 10 cm as measured via surface titration of oxygen with CO or C2H4. The catalyst electrode is exposed to the reactive gas mixture (e.g., C2H4 -I- O2) in a continuous-flow, gradientless reactor (CSTR). Under open-circuit conditions (I = 0), it acts as a regular catalyst for the catalytic reaction under study, e.g., C2H4 oxidation. The counter and reference electrodes are usually exposed to ambient air. 

---