A new method for estimating cake height and porosity during crossflow filtration of particulate suspensions

An indirect method was developed to estimate the height and porosity of the cake deposited on the membrane surface during crossflow filtration of a pa rticulate suspension. The method was based on reconstructing the cake recov ered from the membrane unit by static filtration on a 0.22 mu m filter for the same time and transmembrane pressure (TMP) as used in the crossflow mic rofiltration (CFMF) run. The accuracy of the porosity measurements was conf irmed using uniform sized glass spheres. The developed method was then used to estimate the cake properties during CFMF of lactalbumin suspensions in a tubular membrane. The estimated cake heights (10-81 mu m) were in the sam e order as that measured using techniques like scanning electron micrograph y and NMR micro-imaging under similar experimental conditions reported in t he literature. This study revealed the decrease in cake porosity with time of Filtration to a steady-state value of similar to 0.2 that demonstrated t he marked penetration of smaller particles into cake voids. The steady-stat e cake height increased with an increase in TMP and with a decrease in cros sflow velocity (CFV). However, there was no significant effect of TMP or CF V on the steady-state porosity of the cake. The method is particularly usef ul for small diameter tubular membranes, for which most direct height measu rement techniques are not applicable. (C) 2000 Elsevier Science B.V. All ri ghts reserved.