Anion-Exchange Membrane (Fumasep, FAD Series) for Diffusion Dialysis, CDDAEMFAD
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The Fumasep FAD series (produced by Fumatech BWT) is a specialized range of anion exchange membranes (AEMs) designed specifically for Diffusion Dialysis (DD). Unlike the FAA or FAAM series, which are optimized for carrying electrical current (electrolysis/fuel cells), the FAD series is engineered to facilitate the passive diffusion of mineral acids while blocking metal cations. This makes them the industry standard for acid recovery from waste streams.
The FAD membranes are used to recover "free" acid from spent pickling or etching liquors in the metal finishing, semiconductor, and mining industries. In a diffusion dialysis stack, the waste acid solution flows on one side of the membrane and water flows on the other. Because of the concentration gradient, the acid (H+ and the anion) diffuses through the membrane into the water. he membrane’s fixed positive charges (quaternary ammonium) allow anions to pass easily. Protons (H+) can tunnel through as well. However, multi-charged metal cations (like Fe3+ or Ni2+) are strongly repelled by the membrane and stay in the waste stream. FAD membranes typically recover 80–90% of the free acid while rejecting 90–95% of the metal contaminants.
| Part Number |
CDDAEMFAD55 |
CDDAEMFADPET75 |
| Membrane Name |
FAD-55 |
FAD-PET-75 |
| Thickness (um) |
~55 μm (50–60 range) |
~75 μm (70–80 range) |
| Reinforcement |
None (Self-Supporting) |
Yes (PET Mesh) |
| Area Resistance (Cl-, Ω·cm²) |
0.20–0.25 |
0.20–0.25 |
| Specific Conductivity (mS/cm) |
25-30 |
15-25 |
| Selectivity |
>85% |
91-95% |
| Tensile Strength (MPa) |
24-26 |
40-70 |
| Proton Transfer Rate |
8000 - 10000 µmol•min-1•cm-2 |
2000 - 5000 µmol•min-1•cm-2 |
| Ion Exchange Capacity (IEC) |
~2.0-2.5 meq/g (in Cl- form) |
~2.0-2.3 meq/g (in Cl- form) |
| Application Cases |
Diffusion dialysis for acid concentration and recovery |
Electrolysis stack for industrial-scale recovery unit with excellent mechanical stability |
| Package Grade |
10cm * 10cm/pcs/pack |
10cm * 10cm/pcs/pack |
Use Note:
To ensure the longest possible life for these membranes, specific preparation is required:
Hydration: These membranes are supplied dry. They must be soaked in water or a 1–3% HCl solution for at least 12–24 hours before assembly.
Avoid Drying Out: Once the membrane is hydrated, it must remain wet. If an FAD membrane dries out, it may develop micro-cracks that allow metal ions to "leak" into the recovered acid stream, ruining the purity.
Chemical Limits: While highly stable in acids, avoid exposing them to strong oxidizing agents (like chromic acid or concentrated nitric acid at high temperatures) unless specifically rated for those conditions.
References:
- Z. Palatý, et al., Permeability of a Fumasep-FAD Membrane for Selected Inorganic Acids, Chem. Engineering Tech., 2018, 41, 385-391.
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Helena Bendová, et al., Comparison of Anion-Exchange Membranes for Diffusion Dialysis of Mixtures of Acids and Their Iron Salts, Membranes 2024, 14, 6.
- P. Długołęcki, et al., Transport limitations in ion exchange membranes at low salt concentrations, 2010, 346, 163-171.