Ion Exchange Membranes: Comprehensive Selection Guide

A: The relationship can be easily understood as three levels of concentric circles.

• The most general is CEM. CEM can be used to transport common type of cations: Na⁺, K⁺, Ca²⁺, Mg²⁺, Cu²⁺, NH₄⁺, …
• The next is PEM which is a functional subclass of CEM. A PEM is a type of CEM that is engineered to transport protons (H⁺ ions). By definition it is still a CEM but the PEM name was preferred because it implies its major function is about transporting protons.
• PFSA membrane is the most important commercial example of PEM. PFSA is a subclass of materials not of functions. Its chemical composition is the reason it has outstanding performance: PTFE backbone for exceptional chemical/mechanical stability; and Perfluorinated side chains terminating in sulfonic acid (-SO₃H) functional groups to give the proton conductivity.

A: This is hard to define in general since there are many factors affecting the lifetime. In general, in a benign environment, with good pre-treatment, our membranes can last 2-5 years in water treatment applications and 1-3 years in more demanding industrial processes. The duration can also be longer in some more specialized applications such as in certain fuel cells, in excess of 5000 hours.

A: In general, heterogeneous membranes provide better mechanical properties and lower costs. Homogeneous membranes have better electrochemical properties.

A: In most applications, membranes should be pretreated for better performance, some common procedures are washing with deionized water, soaking in proper solutions, etc. Slow ramping up to operating parameters. Protocols for pretreatment are slightly different for different membranes and applications, please refer to the specific product data sheet.

A: Higher temperatures generally increase ion migration rates but may compromise membrane integrity. Most standard membranes perform optimally at 20-40°C. Special high-temperature membranes are available for applications up to 80-90°C.

A: Many membranes can be regenerated and reused after proper cleaning. The possibility depends on the membrane type and the nature of fouling.

A: Thinner membranes (10-50μm) offer lower electrical resistance but may sacrifice mechanical strength. Thicker membranes (100-500μm) provide better durability but higher resistance. The optimal choice depends on your specific application requirements.

A: Membranes should be stored in a cool, dark place away from direct sunlight. Most are best kept slightly moist in sealed packaging. Specific storage conditions vary by membrane type, and we provide detailed storage instructions with each product.

A: Reinforcement (with ePTFE, PET, PK, or PP) enhances mechanical strength, dimensional stability, and durability. Reinforced membranes can withstand higher pressures and are less prone to damage during handling and operation.

A: Membrane area requirements depend on process parameters including flow rates, current density, and desired separation efficiency. Our technical team can help calculate optimal membrane area based on your specific application details.