What is the difference between an unsupported filter membrane and a supported filter membrane?

Unsupported membranes and supported membranes are two types of membrane materials with different structural characteristics. Unsupported filter membranes, also known as pure membranes, consist entirely of active filter materials without any underlying support structure. They are called "pure" because they only contain filter material and no additional support material. These membranes are generally thinner and more flexible, which can lead to higher permeability and better filtration efficiency. However, unsupported membranes can be more fragile and easily damaged, especially when used under high pressure or in applications with significant mechanical stress.

Composite supported filter membranes are made by lamination or coating processes, and are mainly composed of filter layers attached to porous support structures. This support layer provides extra strength and stability to the membrane, making it less likely to be damaged or cracked during use. Support structures can be made of various materials, such as polymers or fibers, and can have different pore sizes and shapes. Supported membranes are often used in high pressure or mechanically demanding applications where membrane strength is a critical factor.

The main difference between unsupported and supported membranes can be understood from the following points:

1. Composition: The unsupported filter membrane is entirely made of active filter materials, which is suitable for a relatively stable filtration environment under low pressure, while the supported filter membrane includes a support structure in addition to the filter layer, which has the characteristics of high tensile strength and can be applied It is more common in industrial production.

2. Strength and stability: Supported filter membranes are usually stronger and more stable than unsupported membranes, making them suitable for applications with high pressure or high mechanical requirements. The support protects the filter membrane to a certain extent. On the one hand, the support also has filtering ability; on the other hand, the adhesion between the support layer and the filter layer increases the toughness and strength of the overall composite membrane.

3. Permeability and filtration efficiency: The unsupported pure filter membrane also has its unique advantages, which may have higher permeability and better filtration efficiency due to its thinner and more flexible structure.

The choice between unsupported and supported filtration membranes will depend on the specific needs and requirements of the filtration application, such as pressure and flow rate, mechanical stress and desired filtration efficiency. Taking filtration pressure as an example, unsupported membranes are more easily damaged and deformed under pressure, so they require lower filtration pressures than supported membranes. The recommended filtration pressure range for unsupported membranes is typically 1 to 10 Bar (14.5 to 145 psi), depending on the specific membrane material and pore size. Supported membranes can withstand higher filtration pressures due to their reinforced structure, and the recommended pressure can be higher, typically 5 to 20 Bar (72.5 to 290 psi), depending on the specific membrane material and support structure. Exceeding the recommended filtration pressure Membrane fouling, damage and reduced membrane performance can result. Therefore, the appropriate filtration pressure must be carefully selected according to membrane specifications and operating conditions to maximize membrane performance and service life.

Citation

1.Rautenbach, R., & Vrouwenvelder, J. S. (2013). Membrane filtration: pressure-driven processes. In Encyclopedia of Membrane Science and Technology (pp. 1-26). John Wiley & Sons, Inc.

2.Baker, R. W. (2012). Membrane technology and applications. John Wiley & Sons.

3.Mulder, M. (1996). Basic principles of membrane technology. Kluwer Academic Publishers.

4.Chung, T. S., & Weber, M. (2002). Recent advances in polymeric membranes for membrane reactors. Advances in Polymer Technology, 21(4), 299-315.