Velocity lag, solute

Rejection of the solute (or dispersed colloid) is, together with permeate flux, one of the two key performance parameters of any ultrafiltration membrane. The values of rejection coefficients are of crucial Importance in many applications of ultrafiltration. The objective of this contribution is to consider and analyze the individual factors affecting rejection of polymer solutes by ultrafiltration membranes. The factors that will be considered include, sterlc rejection (sieving), solute velocity lag and solute-membrane Interaction. 

In a steady-state situation, the drag force has to be zero and a constant solute velocity lag can be described by an equation ... 

The magnitude of the solute velocity lag correction Is shown in Figure 2. As seen, for a rigid sphere in a cylinder, this correction is not too large. Nevertheless, we will keep considering it in further discussions. The correction calculated from Equation (16b) of Anderson and Quinn (7), applicable for X<0.4, is in agreement with our results. 

Figure 2. Effect of solute velocity lag with solute rejection as a function of A. The line without symbols is calculated from Equation lb, the line with triangles is from Equation 4, and the circles are calculated from Equation 16b of Anderson and...

---