What Are the Details to Pay Attention to When Using Microporous Membranes?

What is microporous filter membrane?

Microporous filtration is a screening process and belongs to precision filtration. Microporous precision filtration refers to a filtration technology that filters out particles from 0.1 μm to 10 μm. Generally speaking, the filtration mechanism is divided into two types: surface type and deep layer type. The filtration mechanism of the MF membrane manufactured by advanced technology is surface filtration. Because the filter aperture is fixed, it can ensure the accuracy and reliability of the filter. Deep-layer filtration is divided into non-fixed irregular pore size and fixed irregular pore size. The former, such as a chemical fiber wound filter element, is generally only used as a rough pre-filter.

The microporous filtration includes flat sheet membrane, hollow fiber membrane, and tubular membrane. Among them, the flat thin paper filter membrane can be further subdivided into two types: “unsupported flat thin paper filter membrane” and “supported flat thin paper filter membrane”.

According to the requirements of the technology required for the manufacture of both, the production process of the “flat and thin paper filter membrane without support” is more sophisticated and complicated than the production process of the “flat and thin paper filter membrane with support”.

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How to use microporous filter membrane?

According to membrane manufacturer, there are many ways to use microporous membranes, most of which are used with filters or funnels, etc., depending on what type of microporous membrane you are using. The commonly used microporous filter membrane is generally a disc filter membrane, such as a 25mm disc microporous filter membrane, which can be used with a syringe filter connected to a syringe. The membrane filter 47mm, can be used with membrane filter, Buchner funnel, pressure vessel, etc. with the vacuum pump and pressure pump. There are also microporous membranes with larger diameters, which also require corresponding clamps and pressure. Other microporous membranes can be selected according to their needs.

Notes when using microporous filter membrane

Microporous membrane filter operations include dead-end filtration (vertical flow filtration) and cross-flow filtration (tangential flow filtration). But no matter what kind of operation there are precautions:
1. The microporous membrane should be cleaned before use, that is, soak in distilled water at 70-80 degrees for 4 hours, or soak in distilled water at room temperature for 12 hours.

2. Before using the microporous filter membrane, the pore size of the membrane must be selected accurately according to the needs, and the substance to be filtered must be larger than the pore size of the filter membrane.

3. The occasions with high requirements for use, such as the filtration of chromatographic samples or reagents. If it is water-based, wash it with distilled water and then pre-filter it with distilled water. If it is organic-based filtration, first put the product in pure toluene and 95% ethanol, soak them overnight, then pre-filter pure toluene and pure ethanol, and thoroughly wash the membrane before use. This product becomes significantly brittle after entering water, and the strength of organic solvents decreases slightly.

4. When there are many particles and bacteria in the filtrate, it should be pre-filtered, that is, pre-filtered with a pre-filter medium or a large-pore filter membrane to avoid too fast clogging.

5. Disinfection: The filter membrane is not sterilized before leaving the factory, so it needs to be sterilized before use. There are many sterilization methods, generally using autoclaving, that is, steam sterilization at 121°C for 30 minutes. During autoclaving, avoid steam directly rushing to the membrane in one direction and prevent the back of the membrane from being damaged due to negative pressure generated by the condensation of steam. Boiling sterilization, chemical sterilization, etc. are also possible. Use the bubble method to test whether the seal is sealed during sterilization and filtration and whether the filter membrane is damaged due to improper disinfection.

6. The filter membrane must be wetted when filtering liquid. If the filter membrane becomes dry due to disinfection, it must be wetted with sterile water. If the wettability is not good, the flow rate must be affected. Sterilize, then sterilize and filter in a sterile room, which should be carried out in strict accordance with the sterilization operating procedures.

7. The microporous filter membrane is flammable, not resistant to acids and alkalis, and not resistant to solvents. It is only suitable for aqueous solutions (PH5-10), oils, air, fruit juices, wines, etc. You must understand whether the filter material affects the membrane before use.

8. If pressurization, vacuum, position difference are adopted, the operator must pay attention to prevent bacteria in the outside air when vacuuming. If the particles are sucked into the contaminated filtrate and filtered under pressure, the filtration rate is faster, and the higher the pressure, the faster the filtration rate. If the pressure is high, consider whether the support of the filter is intact.