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 (%)