Dissecting the role of membrane defects with low-energy barrier on fouling development through A collision Attachment-Monte Carlo approach

Abstract

Membrane defects with low energy-barrier characteristics are unavoidable in membrane fabrication. However, their influences on fouling have not been fully understood. This work systematically investigates the critical role of membrane defects on fouling development and characteristics by adopting a collision attachment-Monte Carlo approach. Simulations show that membrane defects influencing on fouling is highly governed by foulant-clean-membrane interaction (F-M) and foulant-fouled-membrane interaction (F–F). When F–F energy barrier (Ef) is above a critical value (Ec), the long-term stability of water flux is not affected by the presence of defects, thanks to high F–F repulsion preventing further particles deposition. At low Ef (<Ec) but high F-M energy barrier Em (≥Ec), there appears an extended metastable flux for defect-free membrane. Since the local defects serve as hotspots to accelerate fouling, increased coverage or lowered energy barrier of defects shortens or even vanishes metastable period. For both low Ef (<Ec) and Em (<Ec), severe fouling occurs at the beginning of filtration with/without defects as a result of the rapid fouling transition from F-M to F–F. Furthermore, membrane defects have less remarkable influences at higher initial flux where permeate drag plays a primary role. Our simulation provides important implications to membrane design and fouling mitigation.