Method for measuring pore size and pore size distribution of filter membrane
A method for determining the pore size and pore size distribution of a filtration membrane comprises: selecting a group of fluorescent pellets having different diameters and emission wavelengths as a reference; plotting the standard curve between the concentration and fluorescence intensity for each fluorescent pellet at its emission wavelength; uniformly dispensing a group of fluorescent pellets as a reference substance in water to prepare a mixed suspension of which the mass concentration of each fluorescent pellet; using the filter membrane to be tested to perform one-time filtration on the mixed suspension prepared, then performing fluorescence detection on the obtained filtrate, calculating the concentration of each fluorescent pellet in the filtrate the retention rate of the filtration membrane to be tested for each fluorescent pellet; and calculating the pore size and pore size distribution of the filter membrane to be tested accordingly.
1 . 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 C 0 ; wherein C 0 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 C t 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− C t /C 0 )×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 d 50 and d 90 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.
2 . The method according to claim 1 , wherein the fluorescent pellets are polystyrene fluorescent pellets.
3 . The method according to claim 1 , wherein step a) selects the following group of polystyrene fluorescent pellets as the reference substance:
polystyrene fluorescent pellets having a diameter of 20 nm and an emission wavelength of 488 nm;
polystyrene fluorescent pellets having a diameter of 77 nm and an emission wavelength of 695 nm;
polystyrene fluorescent pellets having a diameter of 100 nm and an emission wavelength of 460 nm; and
polystyrene fluorescent pellets having a diameter of 200 nm and an emission wavelength of 615 nm.
4 . The method according to claim 1 , wherein step a) selects the following group of polystyrene fluorescent pellets as the reference substance:
polystyrene fluorescent pellets having a diameter of 20 nm and an emission wavelength of 488 nm;
polystyrene fluorescent pellets having a diameter of 100 nm and an emission wavelength of 460 nm;
polystyrene fluorescent pellets having a diameter of 200 nm and an emission wavelength of 615 nm; and
polystyrene fluorescent pellets having a diameter of 300 nm and an emission wavelength of 695 nm.
5 . The method according to claim 1 , wherein step a) selects the following group of polystyrene fluorescent pellets as the reference substance:
polystyrene fluorescent pellets having a diameter of 77 nm and an emission wavelength of 695 nm;
polystyrene fluorescent pellets having a diameter of 100 nm and an emission wavelength of 460 nm;
polystyrene fluorescent pellets having a diameter of 200 nm and an emission wavelength of 615 nm; and
polystyrene fluorescent pellets having a diameter of 500 nm and an emission wavelength of 488 nm.
6 . The method according to claim 1 , wherein step a) selects the following group of polystyrene fluorescent pellets as the reference substance:
polystyrene fluorescent pellets having a diameter of 100 nm and an emission wavelength of 460 nm;
polystyrene fluorescent pellets having a diameter of 200 nm and an emission wavelength of 615 nm;
polystyrene fluorescent pellets having a diameter of 300 nm and an emission wavelength of 695 nm; and
polystyrene fluorescent pellets having a diameter of 500 nm and an emission wavelength of 488 nm.