Compared with the conventional filtration method using a tapered funnel and filter paper, the most obvious advantage of the laboratory vacuum vacuum filtration is that it is equipped with a vacuum pump to speed up the filtration rate of the laboratory sample by the pressure difference. However, in actual use, even if many vacuum pumps have been used, many customers will still think that the filtration speed is too slow. The filtrate will drip through the filter membrane even if it is not filtered. It takes dozens of minutes, even a few hours to filter hundreds of milliliters. sample. Greatly affected the efficiency of the experiment.
For the problem that the vacuum pumping speed should be too slow, first of all, the user should know what factors affect the filter speed, and do not blindly replace the equipment, so as not to return without success. The main factors affecting speed during the filtration process are:
1. Viscosity and content of the filtrate: If the content of the particles in the sample is high, the particles will directly cover the filter membrane due to the downward force during the filtration process, increasing the resistance and affecting the normal passage of the filtrate. Filter membrane.
2. Filter membrane quality: The quality of the membrane itself has a great influence on the filtration speed. Some membranes with poor quality, the pore size of the membrane is not uniform, and the difference in pore size is large, which will also affect the normal filtration rate. The difference in the quality of the filter is generally small when the first cup sample is filtered. Usually, it will be affected after filtering to 2-3 cups, and even the filter will not move.
3. Diameter of the filter: The larger the diameter of the filter, the more effective the filter area will become larger if there is no other factor, then the area of ​​the filtrate will be larger, and the filtration rate will naturally increase.
4. The structure of the filter: Whether the design of the filter itself is reasonable is also a very critical factor. For example, the Buchner funnel used conventionally, although the filter membrane used in the funnel is large in diameter, the portion of the filtrate that can pass through the filter membrane has only a round hole in the funnel, and the other portions are closed and cannot pass through the filtrate. Although the funnel opening is large, the effective filtration area is extremely limited and the filtration rate is correspondingly slow. In addition, some filters need to be equipped with extremely complicated conversion interfaces in order to be able to be connected to the reagent bottle, which also greatly reduces the filtrate flow rate, blocks the passage, and reduces the filtration speed.
5. Vacuum degree of the suction pump: The degree of vacuum will determine how much pressure is generated to squeeze the filtrate through the membrane. The higher the degree of vacuum, the higher the pressure of the extruded filtrate. Conversely, the lower the degree of vacuum, the pressure of the filtrate. The smaller the filtrate, the slower the rate at which the filtrate passes through the filter.
After understanding the above-mentioned main factors affecting the filtration rate, the user can increase the filtration rate from the following aspects:
FU-L1 with an effective filtration area of ​​up to 40.6 square centimeters exceeds most filter bottles, and samples with higher particulate content are especially suitable.
1. Replace the filter membrane and filter: use a filter with better quality or a larger effective filtration area. It can be used with FU-L1 vacuum filter bottle. This vacuum filter bottle can be matched with large-size filter membrane with diameter of 90mm. At the same time, the gasket supporting the filter membrane is designed with stainless steel mesh, which can be used for whole liquid discharge. The effective filtration area reaches 40.6. Square centimeter (usually 1000ml of ordinary sand core filter bottle effective filter area is only 9.6 square centimeters), several times the ordinary filter bottle. Can greatly improve aluminum plastic.
2. Dilute the sample: dilute the sample, and then filter it by multiple times and multiple filters. Thus the amount of particulate matter in the sample filtered relative to each filter bowl is reduced. However, this method has relative limitations and is not suitable for customers who need the filtrate for the final product. The dilution of the filtrate may affect the results and traits.
FS410V is a professional suction filter designed for samples with high viscosity and high particulate content, which can reach a higher degree of vacuum.
3. Replace the filter or filter pump: Replacing the suction pump is the simplest and most effective method. Using a pump with a higher vacuum means that a stronger thrust is generated and the filtrate is pushed through the filter. R410 oil-free vacuum pumping pump is recommended here, with a vacuum of 0.099MPa. It is especially suitable for environmental monitoring, sewage treatment, mining users to filter suspended solids in water, including algae samples, ore, sediment-containing sewage and so on.
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