Anion-Exchange Membrane (Fumasep, FAB-PK Series) for Flow Battery and Electrodialysis, CFBEAEMFABPK

The Fumasep FAB-PK series is a specialized line of reinforced anion exchange membranes (AEMs) designed specifically for acid processing and bipolar membrane electrodialysis (EDBM). While the FAA series is the general-purpose choice for electrolysis and fuel cells, the FAB series is engineered with a proprietary "low proton crossover" chemistry. This makes it the preferred choice for applications where you need to block protons (H+) from leaking across the membrane, such as in the production of highly concentrated acids.

The primary applications of the FAB-PK series membranes are: (1) Acid/Base Production (EDBM): In a Bipolar Membrane Electrodialysis stack, the FAB membrane is used as the anion-selective layer. Its unique chemistry prevents protons generated at the bipolar interface from migrating into the salt chamber. This allows for the production of much higher concentrations of acid (e.g., HCl or H2SO4) than standard anion membranes. (2) Acid Concentration and Recovery: The FAB series is highly effective in processes designed to concentrate acidic solutions. Because of its high proton-blocking capability, it ensures that the acid remains on one side of the membrane while other ions are transported. (3) Non-Aqueous Redox Flow Batteries: Due to the stable polyaromatic backbone and PEEK reinforcement, the FAB-PK-130 is often cited as a candidate for organic redox flow batteries using solvents like acetonitrile. The reinforcement prevents the membrane from excessive swelling or "gelation" when exposed to organic electrolytes.

Use Note:

Proper activation is essential to transition the membrane from its stable shipping form to its active operational state.

Shipping Form: Delivered dry in the Bromide (Br-) form.

Activation: Soak the membrane in 0.5 M NaCl at 25°C for 72 hours, exchanging the solution several times. This hydrates the polymer and converts it to the Chloride (Cl-) form.

Dimensional Stability: Because it is reinforced with a PK mesh, it has excellent dimensional stability (< 2% swelling in water). However, once hydrated, never let it dry out. Shrinkage can cause micro-cracks in the polymer resin around the rigid reinforcement fibers.

Cutting: Always use a new, sharp blade and wear protective gloves to avoid micro-punctures or scratches that cause internal leaks.

References:

1. M. F. Rochow, et al., Methodology for Selecting Anion and Cation Exchange Membranes Based on Salt Transport Properties for Bipolar Membrane Fabrication, ACS Appl. Polym. Mater. 2025, 7, 9, 5456–5464. 
2. S. Changkhamchom, et al., Anion exchange membranes composed of quaternized polybenzimidazole and quaternized graphene oxide for glucose fuel cell, I. J. International Hydrogen, 2021, 46, 5642-5652.