Colloidal Deposition On Membranes: Effects of Particle Shape and Deformation

Solvent permeation through filtration membranes results in an advective flux of material toward the membrane and, hence, increased deposition propensity. In general, a particle will translate towards the membrane surface at the same velocity as the background fluid. However, proximity to the membrane creates additional forces resulting from electrostatic, van der Waals, polar and hydrodynamic interactions. The balance between these forces ultimately dictates the deposition propensity of particles; hence, knowledge of the way these forces depend upon various characteristic parameters provides useful tools for predicting conditions leading to deposition and fouling.

Here, we present a theoretical treatment of the coupled hydrodynamic-colloidal interactions between a particle and a membrane surface, and demonstrate rational criteria for deposition. In particular, we include effects of particle shape and deformation, since these effects are present in many real systems where particles or aggregates are either inherently non-spherical or may deform under the applied stresses, whether colloidal or hydrodynamic in origin. Elastic deformation results in the coupling of surface and hydrodynamic forces, and generally leads to increased deposition propensity. The implications for deposition and fouling, arising from the elasto-hydro-molecular interactions and resulting particle deformation, are illustrated.