Colloid stability ratio

This simplification is realized when the population of nuclei is much larger than the population of aggregates, which is the case at high levels of saturation where nucleation plays a dominant role. This simplification is also justified by the fact that the colloidal stability ratio, IF, is large for aggreate-aggregate collisions (i.e., is small) but small for... 

For the CSTR in problem 6 the average colloid stability ratio is 1.0 due to the high concentration of NH4CI in the solution. Determine the particle size distribution produced by the precipitator if aggregation is also considered. Use the viscosity of water 1 cp. 

When there are energy barriers between the particles, for example, attractive and repulsive interaction energy beirriers like those discussed in the previous section, Fuchs [57] showed that the rate of coagulation, J, should be divided by a factor W, the colloid stability ratio, where W is given by [58,59]... 

The W values [65] for a dispersion of AI2O3 as a function of pH and KNO3 salt concentration are shown in Figure 10.27. The AI2O3 particles are colloidally stable far away from their isoelectric point (i.e., pH 8.9). As the salt concentration is increased the zeta potential decreases and the colloid stability ratio, W, decreases. Near the isoelectric point there is no electrostatic repulsion, giving a rapid coagulation. 

FIGURE 10.26 Colloidal stability ratio for 0.57 gm SiOg particles as a function of solution pH for various 1 1 salt concentrations (i.e., KCl). Taken from Chang [62]. 

FIGURE 10.27 (a) Zeta potential as a function of pH for A1203 in an indifferent 1 1 electrolyte solution (i.e., l Os). (b) Colloid stability ratio for the same AI2O3 sol as a function of pH. The minimum values correspond to the isoelectric point at pH == 9. Data from Wiese and Healy [65]. 

LOG MOLAR CONCENTRATION FIGURE 10J29 Colloid stability ratio for different salt concentrations showing the critical coagulation concentration, CCC. Data from Barringer [25]. 

Studies of the doublet formation rate in polymer stabilized systems are far less numerous than those on electrostatically stabilized systems. Chang [68] has studied the doublet formation rate for 0.57 fim in diameter Si02 particles as a function of the amount of hydroxyl propyl cellulose (HPC) adsorbed onto their surface. Figure 10.32 is a plot of the colloid stability ratio as a function of the amount of HPC added to... 

FIGURE 10J32 Colloid stability ratio for 0.5 /lun Si02 sol at 1 Af KCI at pH 2 with various amounts of hs roxy propyl cellulose (HPC) added. Ri it axis shows the adsorption isotherm of HPC under these conditions. Taken from Chang [62]. 

This expression was obtained by setting the shear aggregation rate to the Brownian aggregation rate and solving for the size a to which this corresponds assuming the colloid stability ratio, W is unity. 

The pll dependence of (-potential, surface speciation and colloid stability ratios is presented in Figure 4. In panel (a) of Figure 4, the solid line represents the surface potential from the model, and the data points correspond to ( potential from electrokinetic measurements. The dashed line represents a reduced potential calculated at a distance of 4.0 nm from the surface. In panel (b). the surface species distribution is calculated by the SCF/DLM model. Under these conditions, the observed zero iiiterfacial potential is in the range pH 7.2 to 7.5, which suggests... 

Ma, L. Q., Y. Dong, and Q. Zhou. 2005. Relation of relative colloid stability ratio and colloid release in two lead-contaminated soils. Water, Air, and Soil Pollution 160, no. 1-4 343-355. doi 10.1007/sll270-005-3386-8. 

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