Measuring membrane permeation rates through the optical visualization of a single pore

Sotiria Tsochataridou, Greg A. Mutch, Dragos Neagu, Evangelos I. Papaioannou, María Luisa Sanjuán, Brian Ray, Rosa I. Merino, Víctor M. Orera, Ian S. Metcalfe

Research output: Contribution to journalArticlepeer-review


Membranes are a critical technology for energy-efficient separation processes. The routine method of evaluating membrane performance is a permeation measurement. However, such measurements can be limited in terms of their utility: membrane microstructure is often poorly characterized; membranes or sealants leak; and conditions in the gas phase are poorly controlled and frequently far-removed from the conditions employed in the majority of real processes. Here, we demonstrate a new integrated approach to determine permeation rates, using two novel supported molten-salt membrane geometries. In both cases, the membranes comprise a solid support with laser-drilled pores, which are infiltrated with a highly CO2-selective molten carbonate salt. First, we fabricate an optically transparent single-crystal, single-pore model membrane by local laser drilling. By infiltrating the single pore with molten carbonate, monitoring the gas-liquid interface optically, and using image analysis on gas bubbles within the molten carbonate (because they change volume upon controlled changes in gas composition), we extract CO2 permeation rates with exceptional speed and precision. Additionally, in this arrangement, microstructural characterization is more straightforward and a sealant is not required, eliminating a major source of leakage. Furthermore, we demonstrate that the technique can be used to probe a previously unexplored driving force region, too low to access with conventional methods. Subsequently, we fabricate a leak-free tubular-supported molten-salt membrane with 1000 laser-drilled pores (infiltrated with molten carbonate) and employ a CO2-containing sweep gas to obtain permeation rates in a system that can be described with unprecedented precision. Together, the two approaches provide new ways to measure permeation rates with increased speed and at previously inaccesible conditions.
Original languageEnglish
Pages (from-to)16436-16441
Number of pages6
JournalACS Applied Materials and Interfaces
Issue number14
Early online date17 Mar 2020
Publication statusPublished - 8 Apr 2020


  • gas separation
  • image analysis
  • kinetics
  • membranes
  • thermodynamics


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