Figure 3 Vertical cross-section SEM images of Fc (a,b), and horizental
cross section SEM image of Fc (c), CN-Fc (d), CN-Fc1 (e) and AO-Fc(f),
HAADF-STEM images of CN-Fc (g), CN-Fc1(h), AO-Fc (i), and EDS elemental
maping images of CN-Fc (j,k), CN-Fc1(l,m), AO-Fc (n,o)
The bet surface area, pore volume and pore size of Fc, CN-Fc, CN-Fc1 and
AO-Fc were analyzed and the results were reported in Table 2. After
functionalization of Fc, both surface area and pore volume were
decreased from 155 m2/mg to 46 m2/mg
and 0.07 cm3/g to 0.007 cm3/g
(Figure 4 a,b), because of the large number of amidoxime groups
occupying the pores space of Fc. Compared with amidoxime modified bamboo
charcoal36, AO-HNTs41, and
fiber45 used for uranium extraction, the specific
surface area of AO-Fc was relatively higher which might increase uranium
adsorption capacity in seawater. The super-hydrophilicity of the
material was determined by analyzing water contact angle measurements.
The water contact angle of Fc and CN-Fc showed hydrophilicity and
reached the water contact angle of 149o and
82.3o at the time of water contact with the adsorbent
surface for 13 seconds (see video S1 and S2). On the other side, the
water angle of AO-Fc reached 0o angle at a time gap of
0.02 seconds indicating AO-Fc possessed super-hydrophilicity due to the
presence of enough hetero groups onto the surface of AO-Fc (see video
S3).
Figure 4 Nitrogen adsorption and desorption isotherms (a) and
distribution of pore size (b)
Table 1 Elemental analysis by weight percentage (%)