Dissect the role of particle size through collision-attachment simulations for colloidal fouling of RO/NF membranes

Colloidal size affects the whole process of particle transport and membrane filtration. However, its compound effect on fouling remains controversial. In the present study, we adopt a collision-attachment approach to systematically investigate the role of colloidal size on fouling. Our study highlights the critical importance of four competing mechanisms: reduced specific cake resistance and enhanced foulant-membrane interaction of larger particles tend to mitigate flux decline, while the simultaneously increased hydrodynamic drag and reduced particle back-transport tend to promote fouling. The net effect of particle size on fouling is governed by the competition among these mechanisms. When strong foulant-membrane repulsion prevails, we show enhanced flux stability for larger particles as a result of a greatly increased energy barrier to resist particle deposition. Nevertheless, this trend could be reversed for weak foulant-membrane interaction. Our study reconciles the contradictory experimental observations of the effect of particle size on colloidal fouling and provide important insights for effective fouling mitigation.

Automated summary

This study systematically investigates the role of colloidal size on fouling using a collision-attachment approach, highlighting the importance of four competing mechanisms in governing the net effect of particle size on fouling. It shows that larger particles can enhance flux stability when strong foulant-membrane repulsion prevails, but this trend may be reversed for weak foulant-membrane interaction.