Environmental Engineering Reference
In-Depth Information
Cationic surfactant
CH
3
CH
3
(CH
2
)
n-1
COOH
CH
3
N
(CH
2
)
n
CH
3
CH
3
(CH
2
)
n-1
CHO
CH
3
(CH
3
)
3
N
CH
3
CH
3
CH
3
N
(CH
2
)
n
COOH
CH
3
N
(CH
2
)
n
CH
2
OH
CH
3
CH
3
Anionic surfactant
CH
3
(CH
2
)
n
CH
2
OH
CH
3
(CH
2
)
n
COOH
CH
3
(CH
2
)
n
CH
2
OSO
3
SO
4
O
3
S
(CH
2
)
n
COOH
O
3
S
(CH
2
)
n
CH
2
OH
O
3
S
(CH
2
)
n
CH
3
Nonionic surfactant
C
m
H
2m+1
O(CH
2
CH
2
O)
n
CH
2
COOH
C
m
H
2m+1
O(CH
2
CH
2
O)
n
CH
2
CH
2
OH
C
m
H
2m+1
OCH
2
CH
2
OH
C
m
H
2m+1
O(CH
2
CH
2
O)
n
H
C
m
H
2m+1
OH
C
m
H
2m+1
OCH
2
COOH
CH
3
(CH
2
)
m
CH
2
O(CH
2
CH
2
O)
n
H
CH
3
(CH
2
)
m
CH
2
O(CH
2
CH
2
O)
n-1
H
HO(CH
2
CH
2
O)
n
H
CH
3
(CH
2
)
m
COOH +
HOOC(CH
2
)
m
CH
2
O(CH
2
CH
2
O)
n
H
Fig. 6
Primary biodegradation pathways of typical surfactants
Furthermore, many of them are transparent in a UV-visible region from their
structures and, hence, direct photolysis initiated by absorbing sunlight is unlikely
except for the surfactants having an aromatic moiety such as alkylphenoxy ethoxy-
lates. By using several photosensitizing agents in aqueous photolysis, Tanaka et al.
(1991) estimated the triplet energy (E
T
) of monodisperse
p
-(1,1,3,3-tetramethyl-
butyl)phenoxy nonaethoxylate to be 53-54 kcal/mol. This surfactant can act as a
photosensitizer for some herbicides but mostly protects photodegradation of
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