Prediction of optimum membrane design: pore entrance shape and surface potential

Particle rejection in membrane microfiltration and ultrafiltration depends on a balance between hydrodynamic and electrostatic forces. This balance defines a critical filtration velocity, which should be maximised to give fast process operation. The paper presents a quantification of the effects of pore entrance shape and membrane surface potential on these forces and on critical velocity. Three different shapes have been considered, sharp corner; rounded; and spiky. The effect of different surface potentials on the front face of the membrane and the pore wall are also considered. Repulsive electrostatic forces are found to be greatest for the spiky pore entrance. However, the greatest critical velocity is achievable for the rounded pore entrance. For such a rounded pore entrance, the benefits of a high surface potential on both the front surface of the membrane and the pore wall have been quantified.