How To Use Vacuum Filtration?
In the laboratory vacuum filtration experiment, customers often filter some samples with a lot of particles or very viscous. When these samples are filtered, they often fail to pump.
This situation is generally due to the liquid in the liquid. It is caused by the solids completely blocking the microporous filter membrane. In this case, the following methods are generally recommended:
1. Dilute the sample: In the detection and filtration of suspended solids, it is often the case that the high particle content in the water sample blocks the microporous filter membrane and can not move. You can dilute the sample that needs to be filtered and then filter it.
2. Increase the filtration area: now the common vacuum filter bottle on the market can be placed with a 50mm diameter microporous filter membrane. Replace a set of filters that can place a larger diameter filter membrane, so that the solids in the sample are not so easy to block the filter. membrane.
3. Increase the vacuum degree: replace a vacuum filter pump with a higher vacuum degree. The suction filter pump with a higher vacuum degree has more force during suction and may alleviate the phenomenon of inability to filter to a certain extent.
300ml glass solvent filters are to suck out the solvent and it will evaporate. The loss of solvent pressure filtration is to squeeze out the solvent. Generally, there will be more solvent residue in the filter cake. It is better to use a centrifuge to separate the material, fully enclosed, and automatically unloading. Both environmental protection and low labor intensity. If you don’t care whether the loss of solvent and residue is the same as pressure filtration and reduced pressure filtration, both can be used.
1. Install the instrument, check whether the connection between the Buchner funnel and the suction filter bottle is tight and whether the connection port of the suction pump is leaking;
2. Trim the filter paper to be slightly smaller than the Buchner funnel but cover all the holes, add distilled water dropwise to wet the filter paper, and slightly open the exhaust valve to make the filter paper and the funnel tightly connected;
3. You should turn on the air pump switch, pour the solid-liquid mixture, and start suction filtration. Try to keep the material to be filtered in the center of the Buchner funnel to prevent it from flowing directly through the gap between the funnel and the filter paper without being filtered.
4. After filtering, first remove the suction filter bottle to take over, and then turn off the suction pump.
5. When taking out solids from the funnel, remove the funnel from the suction filter flask, hold the funnel tube in your left hand, turn it upside down, and “slap” the left hand with your right hand to make the solids fall onto the clean paper or watch glass together with the filter paper . Remove the filter paper and dry the solid.
The solution in the suction filter bottle should be poured out from the upper mouth.
1. When installing the instrument, the inclined surface of the lower end of the funnel tube should face the branch nozzle. But not too close to avoid the filtrate being pumped away.
2. When the filtered solution has strong acidity, strong alkalinity, or strong oxidation, glass fiber should be used instead of filter paper or glass sand funnel should be used instead of the Buchner funnel.
3. It is not suitable to filter the colloidal precipitate or the precipitate with too small particles.
4. In the process of suction filtration, when cracks appear in the solid layer in the funnel, use glass plugs or the like to compress them to block the cracks. If it is not compacted, the suction efficiency will be reduced.
5. When stopping suction filtration, first unscrew the cock on the safety bottle to restore normal pressure, and then close the suction pump.