Environmental Engineering Reference
In-Depth Information
TABLE 8.3
Extraction of Polar Compounds from Water by Osorb
Solute Percent Extraction a
Octanoic acid 90%
p -Ethylphenol 55%
2-butoxyethanol 42%
1-Butanol 28%
1,4-Dioxane 20%
Phenol 15%
Methanol 6%
Acetone 4%
a Conditions: 0.5% w/v Osorb, TDS = 0 ppm, T = 25°C, [solute] = 100 ppm.
organics can be increased by changing the surface chemistry through the use of alternate
derivatization routes. Derivatization using a silane with an extended polyethylenimine
side chain allows for nanoparticle surfaces to become polar owing to the presence of a
substantial number of -NH 2 groups on the polymer chain. The result is typically a ~5-fold
increase in the partition coeficient for most dissolved polar organics. For example, the
extraction of aliphatic organic acids from low TDS water improves signiicantly with poly-
ethylenimine modiication of the surface (Figure 8.7). Binding of organic acids is likely
enhanced by hydrogen bond formation between the amine groups of the polyethyleni-
mine and the organic solutes. Phenol has relatively low afinity for standard hydrophobic
Osorb ( k = 100) owing to the molecule's hydrogen-bonding interaction with water. Addition
of hydrogen-bonding groups to the Osorb surface through the use of polyethylenimine
increases the partition coeficient to k = 1400. These types of improvements demonstrate
4.0
NH +
H
NH +
H
N
N
N
N
N
H +
3.5
N
n
NH +
+ H 3 N
3.0
2.5
2.0
1.5
1.0
2
3
4
5
6
7
8
Aliphatic acid (no. of carbons)
FIGURE 8.7
Comparison of partition coeficients for aliphatic organic acids (C3-C7) of Osorb (⚫) vs. polyethylenimine mod-
iied Osorb (⚪). Inset: chemical structure polyethylenimine.
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