Method for measuring pore size and pore size distribution of filter membrane

A method for determining pore size and pore size distribution of a filter membrane, characterized in that, the method comprises the following steps:

• a) selecting a group of fluorescent pellets having different diameters and different emission wavelengths as a reference substance;
• b) plotting a standard curve between mass concentration and fluorescence intensity for each of the fluorescent pellets as the reference substance at its emission wavelength;
• c) uniformly dispensing the group of fluorescent pellets as the reference substance in water to prepare a mixed suspension of which mass concentration of each of the fluorescent pellets is C0;
• wherein C0 is 0.1-2.0 μg/mL;
• d) using the filter membrane to perform a one-time filtration by employing a needle-type filter on the mixed suspension prepared in step c), the amount of the mixed suspension used for filtration operation is 2-4 mL;
• then performing fluorescence detection on obtained filtrate sequentially at the emission wavelength corresponding to each constituent fluorescent pellet in the mixed suspension, and calculating mass concentration Ct of each of the fluorescent pellets in the filtrate according to the standard curve obtained in step b), and calculating retention rate R of the filtration membrane for each of the fluorescent pellets according to the following formula:
• R=(1−Ct/C0)×100%;
• and
• e) generating a nonlinear fitting curve between the diameter of the group of fluorescent pellets as a reference substance and their retention rate R, then obtaining the values of the pore diameter d50 and d90 according to the fitting curve, and finally calculating the pore size distribution f(d) according to the following pore size distribution formula:
• f
• ⁡
• (
• d
• )
• =
• 1
• d
• ⁢
• ln
• ⁡
• (
• d
• 90
• /
• d
• 50
• )
• ⁢
• 2
• ⁢
• π
• ⁢
• exp
• [
• -
• 1
• 2
• ⁢
• (
• ln
• ⁡
• (
• d
• /
• d
• 50
• )
• ln
• ⁡
• (
• d
• 90
• /
• d
• 50
• )
• )
• 2
• ]
• ,
• and
• plotting the pore size distribution figure, where d represents the pore size and π is the circumference ratio.