Biomedical Engineering Reference
In-Depth Information
and capillary condensation in pores [20, 21]. If we know the
β
value (see above), we can determine the characteristic energy of
adsorption
values
for the adsorption of nitrogen and oxygen at 77 K are listed in
Table 4.2.
In Table 4.2 are also reported the adsorbent pore widths
calculated by the following equations [22, 47, 48]
E
(kJ/mol) for the adsorbents studied. The
E
0
0
-5 2.5
(4.4)
d
26.056/ -3.06×10 ; ln(41.25/ )/0.56
E
E
d
E
1
0
0
2
0
The pore size values obtained are in good agreement with the
results of measurements performed in Ref. [22]. It is to be noted that
these values, as those reported in Ref. [22], are almost an order of
magnitude higher than the limit pore size values (0.4 nm) for a pure
fullerene C
crystal [23, 49]. The pore size values given in Table 4.2
may be explained by the polycrystalline structure of the studied
fullerene sample.
The pores between separate crystals (grain boundaries) play
an important role in the adsorption on such samples. In addition,
it should be considered that adsorption measurements on fullerene
at 77 K are made using a material with a structure significantly
different from that existing at room temperature.
The total volumes of micropores in the adsorbents under
investigation are slightly larger than those obtained in Ref. [22, 23],
likely because the peculiarities of the sample structures, determined
by the degree of their aggregation.
60
Table 4.2
Sorption parameters calculated by Dubinin-Radushkevich
theory
Activated carbon
AG-3
Fullerene
Astralene
O
2
N
2
O
2
N
2
O
2
N
2
E
(kJ/mol) 4.655 6.05
5.04 5.53
5.54 6.51
0
W
(ml/g) 1.872 2.96
89.92 276.42
1.95 4.19
0
d
(nm) 5.59 4.34
5.17 4.71
4.69 4.0
1
d
(nm) 3.89 3.44
3.76 3.59
3.59 3.29
2
