Civil Engineering Reference
In-Depth Information
values up to 63.5 emu.g
-1
were reported at room temperature [262], whereas for pure mag-
netite the typical saturated magnetization value is 77 emu.g
-1
at room temperature [267].
One of the main applications of the BC/Fe
x
O
y
NPs composites involves their use for
the absorption of heavy metals for water detoxii cation, namely As
4+
(90 mg.g
-1
) [257];
Pb
2+
(~50 mg.g
-1
), Mn
2+
(~25 mg.g
-1
) and Cr
3+
(~20 mg.g
-1
) [258]; Cd
2+
[262]. Although
the elution capacity ranks oppositely to the absorption order, it was demonstrated that
heavy metals can be eluted from the BC/Fe
x
O
y
NPs with a concentrated sodium citrate
solution and reused again ef ectively for several cycles [258].
Apart from magnetic properties, these NPs also confer improved mechanical prop-
erties to the nanocomposites [257], and the materials tend to be l exible and mallea-
ble [259, 264, 265, 267], which in general is important for most of the applications
mentioned above. h e functional character of BC/Fe
x
O
y
can be further extended for
example by the
in situ
oxidative polymerization of aniline into polyaniline, leading to
a material that is simultaneously magnetic and conductive [209, 261]. h is approach,
conjugated with the above mentioned preparation of the BC/Fe
x
O
y
NPs during biosyn-
thesis leads to materials where both the magnetite NPs and the polyaniline phase are
uniformly distributed over the 3D nanoi brillar network of BC (Figure 2.27) [209].
W i t h a d i f erent objective, BC/Fe
x
O
y
NPs nanocomposite membranes were treated
with a perl uoroalkylsilane (CF
3
(CF
2
)
7
(CH
2
)
2
Si(OCH
3
)
3
) leading to highly biphobic
materials with water and oil contact angles of 130
(Figure 2.28), respectively,
opening the opportunity for the production of liquids resistant or even self-cleaning
l exible devices for applications such as in electronic actuators, magnetographic
printing, information storage, electromagnetic shielding coating and anti-counterfeit
[256, 259].
°
and 112
°
Figure 2.26
Typical aspect of spherical BC and spherical BC/Fe
x
O
y
NPs nanocomposites produced in
agitated culture media. Reproduced with permission from [258].
Figure 2.27
Distribution of B) magnetite NPs, C) polyaniline and D) magnetite and polyaniline in the
3D nanoi brillar network of BC. Reproduced with permission from [209].
