9 ,  1 0 ­ D
i h
9 ,  1 0 ­ D
i h
9 ,  1 0 ­ D
i h
9 ,  1 0 ­ D
i h
2 ­ M
e t h
C
C
C
C y c l o p
C y c l o p
C y c l o p
e n z o t h i o p h e n e
u i n o l i n e
q u i n o l i n e
y l q u i n o l i n e
e r i d i n e
y d r o p y r a n
y d r o p y r a n
c u m
a r a n
e n z o t h i o p h e n e
9 ,  1 0 ­ D
i h y d r o a c r i d i n e
y d r o a n t h r a c e n e
y d r o a n t h r a c e n e
y d r o a n t h r a c e n e
y d r o a n t h r a c e n e
P h e n a n t h r e n e
F l u o r e n e
F l u o r e n e
F l u o r e n e
N
a p h t h a l e n e
N
a p h t h a l e n e
y l n a p h t h a l e n e
y c l o h e x a n e
y c l o h e x a n e
y c l o h e x a n e
I n d a n e
I n d a n e
I n d a n e
I n d e n e
I n d e n e
I n d e n e
e n t a d i e n e
e n t a d i e n e
e n t a d i e n e
A c r i d i n e  
A
n t h r a c e n e
X a n t h e n e
Th
i o x a n t h e n e
D
i b e n z o d i o x i n
P h e n a n t h r i d i n e
C a r b a z o l
D
i b e n z o f u r a n
D
i b
Q
I s o
2 ­ M
e t h
P i p
T e t r a h
Th
i o t e t r a h
I n d o l i n e
C u m
a r a n
Th
i o
I n d o l e B e n z o f u r a n
B
P y r r o l e F u r a n
Th
i o p h e n e
He tero cy cl es
Aromatics and P AH
S
S
O
O
O
O
S
N
N
N
N
N
O
O
O
N
S
S
N
C H 3
S
O
10
N
H
N
H
N
H
N
H
7
10
6
10
5
10
4
10
3
10
2
10
1
10
0
10
–1
–1
Water solubility/mgL
10
–2
217
Remediation of PAHs and NSO-Heterocycles
heterogeneous spectrum of compounds typically present in contaminated
groundwater. In addition, pK a -values of many N-HETs and especially
hydroxylated N-HETs in the range of 3 < pK a < 7 suggest pH-dependent
properties. This is an important factor that needs to be taken into account
in designing analytical methods and adsorption experiments. Due to pHdependent adsorption parameters, the adsorption equilibrium could be
different for cations (e.g., N-HETs at pH ≪ pK a ) and anions (e.g., phenols or
carboxylated compounds at pH ≫ pK a ) compared to the neutral molecules
[11–15]. Therefore, pH-values at the surface of activated carbons (for PRBs the
pH of the corresponding groundwater is assumed), and pK a -values of the
adsorbents are important to assess the efficiencies of PRBs. A comparison
of the solubilities of NSO-heterocycles and their parent hydrocarbons and
PAHs is shown in Figure 11.1.
FIGURE 11.1
A comparison of water solubilities of representative NSO-heterocycles (neutral molecules)
and their corresponding parent aromatic compounds. (Experimental data from EPI-Suite U.S.
Environmental Protection Agency. 2012. Estimation Programs Interface Suite ™ for Microsoft ®
Windows, v 4.11.)