Ion-exchange membranes are the selectivity layer that decides whether your stack splits salts, concentrates acids, or shuttles protons across a working cell. This collection groups the polymer films we stock for ion separation: cation-exchange membranes (CEMs), anion-exchange membranes (AEMs), and bipolar membranes (BPMs) used in electrodialysis (ED), electrodeionization (EDI), diffusion dialysis, and bipolar membrane electrodialysis (EDBM). Membranes intended primarily for energy conversion or storage (fuel-cell MEAs, water electrolyzers, redox-flow stacks) are catalogued separately under Membranes and MEA; many PFSA grades appear in both because the chemistry overlaps.
Cation-exchange membranes (CEMs)
CEMs carry fixed sulfonate groups (-SO3-) and pass cations such as Na+, Ca2+, Li+, and H+ while rejecting anions. We stock three structural families: perfluorosulfonic-acid (PFSA) films for high chemical stability and high proton conductivity; sulfonated hydrocarbon membranes (sulfonated polyaryl/PPSU/PEEK-type backbones) for higher selectivity and lower vanadium or co-ion crossover; and homogeneous and heterogeneous economy grades for cost-driven ED and EDI duty. Within PFSA, thicker grades favour barrier and lifetime; thinner reinforced grades favour low area resistance.
Anion-exchange membranes (AEMs)
AEMs use fixed quaternary ammonium (-NR4+) groups to transport OH-, Cl-, and other anions. Reinforced polyaromatic AEMs are the workhorse for industrial ED stacks and brackish or seawater desalination; specialised acid-blocking grades are engineered for low proton crossover, which is what makes acid concentration and EDBM feasible. For alkaline electrolysis and AEM fuel cells, see the dedicated energy collection.
Bipolar membranes (BPMs)
A BPM laminates a CEL and an AEL into one composite so that, under reverse bias, water at the interface dissociates into H+ and OH- in situ. This makes BPMs the active component in EDBM lines that convert salt streams into matched acid and base products without adding reagents.
If you are building a desalination or salt-splitting stack, start with the CEM and AEM grades here. If you need acid concentration or on-site acid & base generation, pair an acid-blocking AEM with a BPM. For proton-conducting membranes used in fuel cells, electrolyzers, and flow batteries, continue to Membranes and MEA.
