Environmental Engineering Reference
In-Depth Information
12,000
10,000
8000
6000
4000
2000
0
0
100
200
300
400
500
Time (min)
FIGURE 2.18
Swelling dynamics of a PNIPAm-based hydrogel.
2.3.7 Solute Partition in Hydrogels
Nanoporous hydrogels have polymer chains immersed in a water-rich environment.
However, while the nanopores are illed with aqueous solution, the polymer regions are
more hydrophobic in nature [118]. Therefore, the partition of water-soluble organic com-
pounds between the gel and the external solution will be inluenced by internal hydropho-
bic effects. Therefore, the gel can be considered as an immiscible solvent that could extract
organic solutes from aqueous solution [137].
Therefore, the partition coeficient between the gel and solution can be deined as
m
=
h
s
(2.6)
P
where
m
h
is the molality in the hydrogel (moles of substance in 1 kg of dry hydrogel) and
m
s
is the molality of the solution (moles of substance in 1 kg of solvent).
The partition coeficient is affected by the chemical composition of the hydrogel and
the conducting polymer present in a nanocomposite [68] (Table 2.2). As it can be seen,
large values (>1000) of partition coeficients for some molecules (e.g., tryptophan) are
TABLE 2.2
Partition Coeficients (
P
) of Different Compounds between Swollen Hydrogel Matrix
and Water at 20°C and pH 7
Hydrogels
Ribolavin
Methyl Orange
Propranolol
Tryptophan
PNIPAM/PANI
32
321
96
756
PNIPAM/PNMANI
29
4
302
1002
PNIPAM-co-2% AMPS/PANI
29
793
252
752
PNIPAM-co-2% AMPS/PNMANI
34
18
438
1211
