Negative charged silica

NaLS promotes the reaction as both Ru and MV++ are bound, and the product Ru is maintained at the micelle while MV+ regresses to the aqueous phase (12 -15). The use of a Ru1 derivative with a long hydrocarbon chain also assists the reaction. If a negatively charged silica colloid is used in place... 

Fig. 12. Salt retention by colloidal particles. The curved dashed and solid lines represent the surface of a negatively charged silica particle. Around this there is a layer of counter sodium cations outside there is a layer in which sulfate anions (Q) are more concentrated than in the bulk solution.

Figure 26-20 (a) Electric double layer created by negatively charged silica surface and nearby cations. (fc>) Predominance of cations in diffuse part of the double layer produces net electroosmotic flow toward the cathode when an external field is applied. 

The adsorption of ionic or polar surfactants on charged or polar surfaces involves coulombic (ion-surface charge interaction), ion-dipole, and/or dipole-dipole interaction. For example, a negatively charged silica surface (at a pH above the isoelectric point of the surface, i.e., pH >2-3)... 

As a rule the adhesion increased with increasing amounts of salts, cations being the important ions with the negatively charged silica the... 

Of course, the decrease in the number of positive charge carriers in the polyelectrolyte layer results in a decrease in the number of electrostatic interactions between the negatively charged silica surface centers and polyelectrolyte molecules. Advantageously, despite the limitation of electrostatic interactions of the polyelectrolyte layer and silica, the PVFA-co-PVAm cannot be removed because the cross-linking process forms a cage-like network covering the silica particle. 

For most electrophoretic separations of small ions, the smallest analysis time results when the analyte ions move in the same direction as the electroosmotic flow. Thus, for cation separations, the walls of the capillary are untreated, and the electroosmotic flow and the cation movement are toward the cathode. For the separation of anions, however, the electroosmotic flow is usually reversed by treating the walls of the capillary with an alkyl ammonium salt, such as cetyl trimethylammonium bromide. The positively charged ammonium ions become attached to the negatively charged silica surface and in turn create a negatively charged double layer of solution, which is attracted toward the anode, reversing the electroosmotic flow. 

The level of HPAM retention in the sand pack decreases as the degree of hydrolysis increases (Lakatos et al., 1979 Chen and Chen, 2002). Figure 5.45 presents the HPAM adsorption data on unconsolidated Miocene sand. It shows that the adsorption decreased with hydrolysis, but there was a degree of hydrolysis at which the adsorption was at a minimum. The minimum adsorption is related to the charge interaction between the negatively charged silica surface... 

Fig. 15 (a) A hole of a photonic crystal fiber with inner side coated with poly-L-lysine (PLL) and DNA in monolayers of thicknesses tcNA) pll and refractive indices dna. Jpll- (b) The molecular structure of poly-L-lysine with positive charges immobilized onto the negatively charged silica surface (Si02). The negatively charged DNA is immobilized on the PLL. Reprinted from [34]... 

Pu(HP04)44 in 2M nitric acid. The formation of the phosphate complex, in effect, increases the average negative charge of the ionic or colloidal plutonium species. As in the case of the bicarbonate complex, this should reduce sorption onto the negatively charged silica surface. However, as is shown in Table V, the sorption increased. In another experiment in which the phosphate concentration was varied between zero and 1.25 X 10 2M, there was no significant difference in the sorption constants. 

There is little or no evidence of micelle adsorption in these systems, and, indeed, it is not to be expected owing to the coulombic repulsion between the negatively charged silica or clay and the micelles. Surfactant anion adsorption at positive (cationic) sites followed by further surfactant adsorption induced by lateral attraction between the hydrocarbon tails to form... 

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