31.2. Elemental analysis
Table 1 illustrates the elemental analysis results of PVDF70K,
Polyalcohol and PVDF70K–PVP membranes. As demonstrated in
Table 1, after defluorination process, the F/C ratio decreased in
polyalcohol than in PVDF, which was possibly due to a change in
the chemical structure of the PVDF, that is, from CH2ACF2 to
CH@CF as reported by Brewis [22] and Kise [23]. It is well known
that an increase in O/C ratio of defluorinated membranes occurs
together with the decrease of F/C ratio because of the formation
of hydroxyl groups and carbonyl groups in the defluorination process
[24]. Nitrogen content increased from zero in PVDF membrane
to 10.83% in PVDF–PVP membrane, which proved that the PVP
molecules had been introduced on the membrane surface. These
results were in consistent with those of FTIR analysis.