Effect of physicochemical conditions on crossflow microfiltration of mineral dispersions using ceramic membranes
Advancing the chemical engineering fundamentals
Filtration (T2-11P)
Keywords: Microfiltration, pH, ionic strength, coagulation, membrane fouling
Crossflow microfiltration experiments were performed on aqueous dispersions of titanium dioxide through a 0.1 micron pore size ceramic membrane at various operating parameters. The influence of a coagulant type, the dispersion pH, and ionic strength on the process performance was analyzed. The initial transient flux decline follows dead-end filtration theory, with the membrane resistance determined from the initial flux and the cake resistance determined from the rate of flux decline due to cake build-up. For long times, the observed fluxes reach steady or nearly steady state values, presumably as a result of the cake growth being arrested by the shear exerted at its surface. The steady state fluxes increase with increasing inlet crossflow velocity and decreasing feed concentration.
The extreme sensitivity with the nature of the coagulant and dispersions pH was observed, whereby the dispersion particle size can be changed by as much as an order of magnitude with pH variation at constant volume fraction.
The steady state permeate flux values were determined from the steady state model based on the Kozeny-Carman equation for cake resistance and Darcy's law applied over the filter area to relate filtration rate to average pressure difference between the feed and permeate sides of the filter. The model includes a cake resistance of the cake layer, which was determined for the titanium dioxide dispersions by fitting the experimental flux data to the model.
The resulting fluxes obtained from the model using simple values for the membrane resistance, cake resistance, and physicochemical parameters for each data set are in good agreement with the measured fluxes.
Acknowledgements
This work was financially supported by the Ministry of Education, Youth and Sports of the Czech Republic, Project MSM0021627502.
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Presented Tuesday 18, 13:30 to 15:00, in session Filtration (T2-11P).
