Alumina surface charge

In Regalbuto s most recent treatment of surface charging, pH shift data generated at different SLs are fit to the model so as to obtain the best values of and K2 [24], Representative experimental and model results are shown for alumina in Figure 6.15. Having obtained the oxide-charging parameters in the absence of metal adsorption, the parameters can be used with no adjustment in the RPA model to simulate metal uptake. This is described in the next section. 

Impregnating a basic colloidal suspension (pH = 12) on alumina does not induce proton liberation, thus the pH is constant (Fig. 13.25b). The system keeps its initial properties, i.e. negative charges for alumina support and PdO particles. Repulsive interactions are created between the alumina surface and the PdO particles so that the particles deposited on the support are redispersed, and finally isolated from each other. 

Fig. 32 Schematic representation of the correlation of surface charge and growth of the aggregates for the various regions of the adsorption isotherm of SDS on alumina based on fluorescence data and zeta potential measurement...

Fig. 4. Experimental surface charges on alumina gel, as measured by adsorption of counter-ions from 0.01 M NaCl electrolyte, and DLM simulated curves using parameters listed in Table 2.

Values of Sverjensky Sahai (1996) for gibbsite used to describe surface charge experiments on alumina gel (Fig. 4). Values optimized from surface charge experiments on silica gel (Fig. 3). 

Procedure. The solid used is a Merck alumina gel. The product is predominantly amorphous but its X-ray diffraction pattern exhibits small peaks characteristics of gibbsite. Its surface charge determined by counter-ions adsorption is reported in Fig. 4. Batch experiments were performed using 5 g/L solid contacted with ltr4 m uranyl carbonated solutions at pH 7... 

Further evidence for three distinct modes of adsorption can be seen in the electrophoretic behavior of alumina in the presence of sodium dodecyl sulfonate. Below 6 X 10 5M, the electrophoretic mobility is nearly independent of concentration, but at this concentration the slope of the mobility-us.-concentration curve abruptly changes. At 3 X 10"4M dodecyl sulfonate concentration, the electrophoretic mobility reverses its sign, indicating that the charge in the Stem layer now exceeds the surface charge in absolute magnitude. 

Rajan, S. S. S. (1978). Sulfate adsorbed on hydrous alumina, ligands displaced, changes in surface charge. Soil Sci. Soc. Am. J. 42, 39-44. 

Activated alumina can be regenerated by flushing with a solution of 4% sodium hydroxide which displaces F from the alumina surface (p. 51). This procedure is followed by flushing with acid to re-establish a positive charge on the surface of the alumina. 

Figure 3. Surface charge density of A-100 and A-300, titania, alumina/silica (23 wt.% A1203), titania/silica (35 wt% Ti02), and alumina/silica/titania (21, 8, and 71 wt% respectively) as a function of pH.

Keywords fumed silica alumina/silica, titania/silica alumina/silica/titania Ni(II) Cd(II) Pb(II) polyethylene glycol) poly(vinyl alcohol) adsorption potentiometric titration surface charge density... 

---