Nanostructured micrometric-pore membranes for nanofiltration: Micrometric geometry may optimize performance, energy efficiency and operational lifetime

TL;DR

This study demonstrates that micrometric pore geometry significantly influences nanofiltration efficiency, lifetime, and energy use, with certain geometries outperforming simple cylindrical pores by up to four times.

Contribution

It reveals the impact of micrometric-scale geometry on nanofiltration performance and lifetime, using stochastic modeling to optimize pore design for specific filtration goals.

Findings

Certain geometries like decreasing-conical and sinusoidal-corrugated pores enhance performance.

Optimized pore shapes can extend operational lifetime by about four times.

Pore geometry effects depend on the desired nanofiltration removal level.

Abstract

Media and membranes composed of micrometric-diameter pores are well known in academia and industry to be capable of efficacious nanofiltration of fluids once the pore inner surfaces are coated with nanostructures. Given the large mismatch between the two very different scales of these hybrid systems, it could be expected that trapping of nanoimpurities would almost entirely depend on the characteristics of the nanostructures. However, we show here that the micrometric-scale nominal geometry does have noticeable impact on the nanofiltration performance, on its evolution with time, and on the energy spent per trapped impurity. For that, we apply stochastic calculations customized to combine the cumulative probabilities of wall-impurity attraction and binding, supplemented with continuity equations as the fluid flows; this allows tracking the nanofiltration without a many-particle simulation, prohibitive in such multi-scale system. We focus on the influence of the micrometric nominal geometry over filtration features like logarithmic removal value LRV, operational lifetimes, energy balances, or spatial profiles of the trapped-impurity layer in the pore inner walls. Our results identify some pore geometries (e.g., decreasing-conical and sinusoidal-corrugated) with about 4-fold larger initial nanofiltering performance and operational lifetime than simple cylinders of the same average diameter. The optimal geometry is also shown to depend on the LRV value acceptable for each specific application.