Evaluation of Vapor Deposition Techniques for Membrane Pore Size Modification

Document Type: Research Paper

Authors

Department of Chemical & Biological Engineering, Colorado School of Mines, Golden, CO 80401, USA

Abstract

The suitability of three vapor deposition techniques for pore size modification was evaluated using polycarbonate track etched membranes as model supports. A feature scale model was employed to predict the pore geometry after modification and the resulting pure water flux. Physical vapor deposition (PVD) and pulsed plasma-enhanced chemical vapor deposition (PECVD), naturally, form asymmetric nanopores that retain high flux as pore size is reduced. But PVD-modified supports exhibited poor control and reproducibility. In contrast, pulsed PECVD and plasma-enhanced atomic layer deposition (PEALD) were shown to deliver digital control over pore size. Moreover, good agreement was obtained between model predictions and flux measurements. Exposure limitations during PEALD introduce a degree of asymmetry, though net growth rates were 1-2 orders of magnitude smaller than pulsed PECVD and PVD. Filtration experiments using bovine serum albumin as a model solute showed that pulsed PECVD-modified membranes can be engineered to simultaneously deliver both high flux and high selectivity. For example, pulsed PECVD-modified supports were demonstrated to deliver high retention (~ 75%) while maintaining 70% of their initial pure water flux.

Graphical Abstract

Evaluation of Vapor Deposition Techniques for Membrane Pore Size Modification

Highlights

• Nanopore membranes modified by PVD, ALD, and pulsed PECVD.
• Feature scale model used to design membranes and analyze performance.
• Pulsed PECVD forms asymmetric membranes with nanoscale control.
• The membranes have high pure water fluxes and good protein rejection.

Keywords

Main Subjects