What is the difference between filter paper and microporous filter membrane?

Filter paper and microporous filter membrane are both particle filtration media and are commonly used in filtration applications in various industries. However, they are different in terms of composition, structure and filtration mechanism. For example, filter paper is mostly suitable for filtration of larger particles, while Microporous filtration membranes have the ability to filter smaller particles, microorganisms and special application conditions. Here is a brief summary of some of their differences.

1. Different materials. Filter paper is a semi-permeable porous material made of cellulose (such as wood pulp or cotton linters). Because it can retain solid particles while allowing liquid to pass, it is usually used in various applications. Filtration for solid-liquid separation; the size of filter paper pores varies greatly depending on the type of filter paper (from about 2-3 microns to 25 microns or larger). Therefore, filter paper has difficulty filtering very small particles due to its uneven pore size. The effect has certain limitations.

Microporous filtration membranes are membrane materials designed for precision filtration and separation applications. They are usually made of synthetic materials such as polymer films. On the other hand, microporous filtration membranes are usually made of synthetic materials such as polytetrafluoroethylene ( PTFE), polyvinylidene fluoride (PVDF), nylon or polysulfone, etc., have controlled uniformly sized pores, typically between 0.1 and 10 microns in diameter, which allow for more precise filtration compared to standard filter paper. Smaller particle size.

2. Structure and characteristics. Filter paper has a fiber structure and interconnected void spaces between fibers. The pore size and distribution of filter paper will change according to the manufacturing process and grade of the paper. When observed under a microscope, the fibers of the filter paper are visible, forming fibers. Network, there are open spaces between fibers, including particles trapped on the surface and within the void space are also visible; microporous filter membranes have a clear and uniform pore structure, and the pore size is strictly controlled during the manufacturing process to achieve precise filtration. Under the microscope, the membrane structure appears more uniform, the pore diameter is clear and regular, and the pores are smaller, which are usually invisible at lower magnifications, including some membranes that will have specific surface features or patterns due to the material.

3. Filtration mechanism. The filtration of filter paper is mainly a combination of surface filtration and depth filtration. Solid particles are captured on the surface of the paper fiber and in the void space between the fibers. The cotton fiber in the filter paper has a good affinity with water. It can absorb about 20% of water, of which 6% to 7% is bound to cellulose in the form of hydrogen bonds; the filtration of microporous membranes is mainly carried out through size exclusion, in which particles larger than the pore size are retained on the membrane surface , while liquids or smaller particles can pass through, and some membranes are naturally hydrophobic and can intercept water and liquids, while gases can pass through smoothly.

4. Filtration efficiency. Filter paper can effectively intercept larger particles, but due to its larger pore size, it may be limited in filtering smaller particles. Compared with microporous filter membranes, the filtration efficiency of filter paper is generally lower; In contrast, microporous membranes have high filtration efficiency, especially for smaller particles and microorganisms, and can provide reliable and consistent filtration results.

  5. Application industries, filter paper is usually used in various laboratory, industrial and environmental applications, such as qualitative analysis, routine filtration, clarifying liquids, and removing particles from air and water; microporous filtration membranes can be used in various industries, including pharmaceuticals, biology Technology, food and beverage, electronics, water treatment and research laboratories, etc. They are used for sterilization, clarification, particle removal, microbial analysis and other specialized filtration processes that require precise separation.

To sum up, most filter papers are suitable for general particle filtration and are suitable for the interception of larger particles, while microporous filter membranes can filter smaller particles, microorganisms, etc. The choice of filter paper and filter membrane depends on the specific filtration requirements, particles Various factors such as size range and required filtration efficiency.