Fluid flux represents one of the key evaluators to assess the functionality of membranes. At present, fluid flux is determined by experimental measurement, and it is in urgent need of developing quantitative prediction models towards rational design of high-performance membranes.

In this work, we report an analytical yet convenient model for flux prediction, and the discrepancy between predictions and experimental measurements is surprisingly small. Importantly, for the first time we unravel that the fluid flux varies with pore diameter non-monotonically, and the optimal flux is identified when the pore size of a membrane is 5 times the fluid molecule size (~1.50 nm for water/CNTs systems). In addition, we find a thin membrane with neutrally wettable exterior surface (with contact angle θ ≈ 60°) can greatly boost the water flux.

This work not only provides a workhorse for predicting fluid flux but also casts insights for designing high-performance membranes.

An Analytical Model for Evaluating Fluid Flux across Carbon-based Membrane. Journal of Membrane Science, 2022, 644, 120157.  ( DOI :10.1016/j.memsci.2021.120157 )