Bubble Pressure Pore Size Analysis of Filter Paper

As known to all, there are two general classifications of filter paper, qualitative and quantitative filter paper. Generally, qualitative filter paper is used for solution filtration, and for qualitative tests such as chloride and sulfate that do not require calculated values and it can separate most insoluble fiber-insoluble organic and inorganic suspensions; while quantitative filter paper is used for filtration of precisely calculated values, such as the determination of residues, insoluble, etc. In the manufacturing process of quantitative filter paper, treat the pulp with hydrochloric acid and hydrofluoric acid, and use distilled water to wash it to remove the paper fiber impurities, so there is little residual ash after burning, which has little effect on the analysis results, suitable for precise quantitative analysis. There are two different shapes of filter paper available, square and round. For the round filter papers, there are different diameters to meet specific requirements. For the square ones, it could be 60cm×60cm and 30cm×30cm.

HAWACH is a professional manufacturer of filter paper specializing in the production of qualitative filter paper, quantitative filter paper, and various specifications of chromatography filter paper, etc. They are widely used in scientific research, industry, agriculture, medicine and health, colleges and universities, teaching experiments, environmental protection testing, etc. Today, HAWACH will discuss the bubble pressure pore size analysis for filter paper. Welcome to contact the HAWACH team for further discussion.

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Pore size test

Qualitative filter paper is a filter paper commonly used in chemical laboratories to filter precipitates and suspended solids. After burning, it has some amount of ash, with silicon content higher than that of quantitative filter paper.

The pore size of the through holes of the filter material tested by the bubble pressure pore size analyzer can accurately test the maximum pore size, minimum pore size, and average pore size of the through holes of filter materials such as filter membranes, diaphragms, fabrics, fibers, ceramics, sintered metals, etc., pore size distribution and permeability, suitable for research and development, production of filter materials and related scientific research.

Taking a certain membrane material as an example, the membrane is fully wetted with a liquid that can be infiltrated with it. Due to the existence of surface tension, the infiltration liquid will be bound in the pores of the membrane; gradually increasing the gas pressure on one side of the membrane. When the gas pressure reaches a pressure greater than the pressure generated by the surface tension of the infiltrating liquid in a certain aperture, the infiltrating liquid in the aperture will be pushed out by the gas; since the smaller the aperture, the higher the pressure generated by the surface tension, so it is necessary to push out the infiltrating liquid in it. The gas pressure to be applied is also higher; in the same way, it can be seen that the infiltrating liquid in the hole with the largest pore size will be pushed out first, allowing the gas to permeate, and then with the increase of the pressure, the pore size will change from large to small, and the infiltration liquid in the hole will be pushed out first. The liquid is pushed out in turn, allowing the gas to permeate until all the pores are opened to achieve the same permeability as the dry membrane;

The qualitative filter paper pore size is irregular. Usually, the pore size of the qualitative filter paper is large and the quantitative one is small. According to the pore size of the filter paper, it is divided into three types: fast, medium, and slow. The markings on the ribbon on the packaging box are white, blue, and red respectively, which should be selected and used according to different types of precipitation. When filtering colloidal precipitates such as ferric hydroxide, the fast type should be used; when filtering fine crystal forms such as barium sulfate precipitates, the slow type should be used.

For the technical indicators specified for qualitative filter paper products, please refer to the national standards. There are 80-120 microns, 30-50 microns, and 1-3 microns pore sizes available. The pressure corresponding to the hole that is opened first is the bubble point pressure, and the pore size corresponding to this pressure is the maximum pore size; during this process, the pressure and flow are recorded in real-time, and the pressure-flow curve is obtained; the pressure responds to the information of the pore size, the flow rate It can reflect the information of the number of pores of certain pore size; then test the pressure-flow curve of the dry membrane, and calculate the maximum pore size, average pore size, minimum pore size, pore size distribution, and transmittance of the membrane sample according to the corresponding formula.