PREDICTION OF STEADY-STATE CROSS-FLOW FILTRATION USING A FORCE BALANCE MODEL

A model to predict steady state flux of a crossflow filter is presented. A frictional force balance is applied to a particle at the cake surface - it is assumed that if the ratio of net axial force to net normal force exceeds the coefficient of friction, deposition does not occur. Unlike previous frictional models, both hydrodynamic and interparticle forces are considered. Experiments filtering spherical monodisperse latex particles with sizes of 0.55 and 1.8 micrometers were used to test the theory. The variables examined were membrane type, crossflow, pressure, particle diameter and system pH. The model successfully predicts both the linear nature of permeate velocity dependence on shear stress and the associated gradient as being a function of particle diameter. The system can be characterized by a single empirical parameter, the form of which is dictated by the force balance.