NaCl, charge density

Assume is -25 mV for a certain silica surface in contact with O.OOlAf aqueous NaCl at 25°C. Calculate, assuming simple Gouy-Chapman theory (a) at 200 A from the surface, (b) the concentrations of Na and of Cr ions 10 A from the surface, and (c) the surface charge density in electronic charges per unit area. 

FIG. 8 Density profiles p z) and running integrals n z) of the ion densities for cations (full lines) and anions (dashed lines) at three different surface charge densities in units of pC cm as indicated. Left NaCl solutions right CsF solutions. 

The effects of ion valence and polyelectrolyte charge density showed that at very low ionic strength found that when the counterion valence of added salt changes from monovalent (NaCl) to divalent (MgS04), the reduced viscosity decreases by a factor of about 4.5. If La(N03)3 is used, the reduced viscosity will be further decreased although not drastically. As for polyelectrolyte charge density, the intrinsic viscosity was found to increase with it because of an enhanced intrachain electrostatic repulsion (Antonietti et al. 1997). 

Unlike the sand used above, the adsorption of HPAM on SiC at 20g/l NaCl is significant even in the absence of Ca2+ (Figure 5). This is mainly due to the lower charge density of SiC, hence the weaker electrostatic repulsion. The higher affinity of HPAM for SiC may also explain the attainment of maximum adsorption at lower Ca2+ level, and may also be the reason that the higher interaction of HPAM with Ca2+ can induce an adsorption level higher than that of PAM. 

Figure 3. Charge density about a chloride anion in molten NaCl (simulation as per Fig. 2), taken from Ref. [239]. Solid Results of simulation data. Dashed Best-fit based on Eq. 3. Cation-cation and cation-anion radial distribution functions for molten NaCl, obtained from simulation (force field given in Ref. [285]).

Figure 5. Surface charge density on silica unmodified and modified by adsorbed PVA (0.15 g/g) and PEG (0.125 g/g) as a function of pH at 0.001 M NaCl.

Figure 7. Adsorption of Ni(II) on (1) titania Figure 8. Surface charge density of (1) titania, (2) and (2) silica/titania ST94 as a function of pH titania/Ni(II), (3) ST94, and ST94/Ni(II) at 0.001 at 0.001 M NaC104. M Ni(II) and 0.001 M NaCl.

The numerical optimization, that include surface charge densities as well as electrolyte ion adsorption data, was performed for TiC>2 (anatase)-NaCl... 

The intrinsic surface charge density reflects particle charge developed from either isomorphic substitutions or adsorption involving H+ or OH-. A widely used technique for measuring intrinsic surface charge density is the Schofield method. In this method [3], clay mineral particles are reacted with an electrolyte solution (e.g., NaCl) at a given pH value and ionic strength the specific surface excess of the cation and the anion adsorbed from the electrolyte is determined and the value of is calculated with the equation... 

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