Influence of ionic strength and pH of dispersed systems on microfiltration

The influence of particle shape, ζ-potential and size with change of pH and ionic strength on permeate flux during the microfiltration of model dispersions (two different china clays with mean particle sizes of 3.5 μm and 1.5 μm) on flat sheet ceramic membranes (ZrO2, mean size of pores 0.2 μm) have been studied. The experiments include measurement of the basic characteristics of model dispersions. The description of the experimental system is also presented. The results of the experiments show that the ζ-potential of particles has indispensable impact on the permeate flux. This phenomenon is especially pronounced during the microfiltration of dispersion in the area close to the isoelectric point of dispersion, when the value of permeate flux increased to double value of non-treated dispersion. This phenomenon has caused the particle interaction. In the area close to the isoelectric point the dispersion had a tendency to instability, and particles tend to aggregate. It resulted in a higher porosity of the filter cake and thereby to a higher value of the permeate flux and a lower value of the filter cake resistance.