3.1.3. BET analysis
BET analytical results showed that the adsorption average pore
sizes of PVDF100K–PVP, PVDF70K–PVP, PVDF100K and PVDF70K
membranes were 9.190 nm, 5.231 nm, 10.400 nm, 6.304 nm,
respectively. Fig. 3 indicates BET results of the PVDF100K and
PVDF100K–PVP membranes. According to the IUPAC classification,
the structures of the PVDF100K membrane and PVDF100K–PVP
membrane were almost the same since their N2 adsorption–desorption
isotherms were both belong to IV model which represented
tubular shape capillary pore structure with double open
ends. Besides, the relative pressure of abruption point of adsorption
curve and desorption curve decreased as a result of the trivial
alteration of pore size distribution and average pore size after
modification.
MWCO is an important evaluating parameter of ultrafiltration
membrane. The aqueous solutions containing PEG of different
MW were ultrafiltrated through the PVDF and PVDF–PVP membranes.
Then MWCO values of those membranes were determined
as selected PEGMW when the corresponding rejection ratio of PEG
reached 95%. Fig. 4 reveals the MWCO determination of PVDF100K
and PVDF100K–PVP membranes by PEG rejection ratio. As seen in
Fig. 4, actual MWCO value of PVDF100K membrane was close to
that of PVDF100K–PVP membrane.
3.1.3. BET analysisBET analytical results showed that the adsorption average poresizes of PVDF100K–PVP, PVDF70K–PVP, PVDF100K and PVDF70Kmembranes were 9.190 nm, 5.231 nm, 10.400 nm, 6.304 nm,respectively. Fig. 3 indicates BET results of the PVDF100K andPVDF100K–PVP membranes. According to the IUPAC classification,the structures of the PVDF100K membrane and PVDF100K–PVPmembrane were almost the same since their N2 adsorption–desorptionisotherms were both belong to IV model which representedtubular shape capillary pore structure with double openends. Besides, the relative pressure of abruption point of adsorptioncurve and desorption curve decreased as a result of the trivialalteration of pore size distribution and average pore size aftermodification.MWCO is an important evaluating parameter of ultrafiltrationmembrane. The aqueous solutions containing PEG of differentMW were ultrafiltrated through the PVDF and PVDF–PVP membranes.Then MWCO values of those membranes were determinedas selected PEGMW when the corresponding rejection ratio of PEGreached 95%. Fig. 4 reveals the MWCO determination of PVDF100Kand PVDF100K–PVP membranes by PEG rejection ratio. As seen inFig. 4, actual MWCO value of PVDF100K membrane was close tothat of PVDF100K–PVP membrane.
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