Monte Carlo simulation of pore blocking and cake formation by interfacial interactions during membrane filtration

The interactions between membrane and particles or among particles were examined based on DLVO theory in order to probe complex membrane fouling phenomena. The strength of the interactions depends on the competition between van der Waals attraction and electrostatic double layer repulsion. An on-lattice Monte Carlo model was developed for two-dimensional membrane pore and surface to simulate pore blocking and cake formation. Effects of interactions on membrane retention, membrane resistance, and cake layer density were studied with the microstructural changes in cake layer formation. The model can be widely applied to the analysis of membrane fouling for a variety of foulants.

In summary, Monte Carlo method and DLVO theory are simultaneously used to study the fouling of membranes by foulants. Interaction energy increases with the augmentation of surface potential as well as Debye length and with the decline of Hamaker constant. The capture probability mainly depends on interaction energy barrier and flow modes. The morphology and density of the cake layer varies with different capture probability and flow modes. In dead-end flow mode, particles aggregate symmetrically on the membrane surface and with a looser packing mode than that in cross-flow mode. The packing density decreases with the increase of the capture probability. Membrane resistances are examined and found that although the resistance of the pore keeps unaltered, the resistance of cake layer increases with the raise of the capture probability.