Membrane rejection of nonspherical particles: Modeling and experiment

Abstract

The rejection coefficient of nonspherical particles from ultrafiltration and microfiltration membranes has been examined from both theoretical and experimental perspectives. Modeling efforts focused on incorporating the convective hindrance factor for a capsule shaped particle in a cylindrical pore into predictions of the rejection coefficient. First, the convective hindrance factor was approximated using previously reported results for the hydrodynamic resistances experienced by a sphere in a pore. Second, computational fluid dynamics calculations predicted the convective hindrance factor for a capsule in a cylindrical pore. Results from both approaches indicate that including hydrodynamic interactions in predictions of the rejection coefficient has a greater effect for smaller particles and particles with smaller aspect ratio (i.e., close to spherical shape). Rejections of several rod-shaped Gram negative bacteria with aspect ratio from 2 to 5 by clean track-etched membranes were in general agreement with theoretical predictions.

The effect of particle rotation on the motion and rejection of capsular particles in slit pores

“…[2][3][4][5][6][7] Early review papers detailed the applications of hindered transport theories to biological membranes 8 as well as the impact of hindered transport of macromolecules in physiological applications. Hydrodynamic interactions are influenced by the particle size and shape 14 as well as the pore morphology. [10][11][12][13] Hindered transport of particles in porous membranes can be attributed to a combination of hydrodynamic, steric, and longrange particle-membrane interactions.…”

“…[10][11][12][13] Hindered transport of particles in porous membranes can be attributed to a combination of hydrodynamic, steric, and longrange particle-membrane interactions. 14,[16][17][18] In particular, our work has focused on examining the hindered transport of nonspherical capsule-shaped particles because many pathogenic bacteria, such as Escherichia coli, Brevundimonas diminuta, and Serratia marcescens are capsule shaped. 15 We, and others, have been interested in the effect of bacterial shape and flexibility on rejections from membrane filters.…”

“…Hydrodynamic interactions are influenced by the particle size and shape 14 as well as the pore morphology. 14,16 The impact of particle shape on transport in porous media and in attachment to environmentally relevant surfaces has also been studied. 14,[16][17][18] In particular, our work has focused on examining the hindered transport of nonspherical capsule-shaped particles because many pathogenic bacteria, such as Escherichia coli, Brevundimonas diminuta, and Serratia marcescens are capsule shaped.…”

“…14,16 Several studies examining particle transport in a confined environment have reported that the translational velocity of the particle is influenced by the velocity gradient, particularly when the particle is close to the channel wall. The mathematical equations involved in computing G are nonlinear and cannot be solved using analytical methods.…”

“…[10][11][12][13] Hindered transport of particles in porous membranes can be attributed to a combination of hydrodynamic, steric, and longrange particle-membrane interactions. Hydrodynamic interactions are influenced by the particle size and shape 14 as well as the pore morphology. 15 We, and others, have been interested in the effect of bacterial shape and flexibility on rejections from membrane filters.…”