Study of the aromatic by-products formed from ozonation of anilines in aqueous solution

Article abstract of DOI:10.1016/S0043-1354(02)00003-9

Aniline and p-chloroaniline are frequently detected in many industrial wastewaters. Aqueous solutions of aniline and p-chloroaniline were treated with ozone to study the reaction and oxidation by-products. Aniline solutions were ozonated at low and high p

Full text of DOI:10.1016/S0043-1354(02)00003-9

Water Research 36 (2002) 3035–3044
Study of the aromatic by-products formed from ozonation
of anilines in aqueous solution
Judith Sarasa*, Susana Cort e! s, Pe n* a Ormad, RaquelGracia, Jos e! Luis Ovelleiro
Department of Chemical Engineering and Environmental Technology, University of Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain
Received 14 August 2000; accepted 30 November 2001
Abstract
Aqueous solutions of aniline and p-chloroaniline were treated with ozone in order to study the reaction and oxidation
by-products. Aniline solutions were ozonated at low and high pH, so as to compare both molecular and hydroxyl free
radicalmechanisms, respective yl . The main identified aromatic by-products were nitrobenzene and azobenzene when
the experiment was carried out at acid pH. Formation of nitrobenzene, azobenzene, azoxybenzene and 2-pyridine-
carboxylic was observed when the ozonation was carried out at basic pH. p-Chloroaniline was treated with ozone only
at high pH and the identified by-products were in accordance with those obtained in the ozonation of aniline:
0
p-chloronitrobenzene, 4,4 -dichloroazobenzene and 4-chloro-2-pyridine-carboxylic acid. All the aromatic by-products
found were less toxic than the raw materials. The pseudo-first-order constants in aniline concentration were calculated,
whilst kinetic in p-chloroaniline concentration could not be adjusted to a first-order reaction. r 2002 Elsevier Science
Ltd. All rights reserved.
Keywords: Ozone; Aniline; p-Chloroaniline; Ozonation by-products
1
. Introduction
sives, petroleum refining chemicals, diphenylamine and
phenolics [2–4]. p-Chloroaniline is used as an inter-
mediate for pesticides, pharmaceuticals, pigments and
dyes.
The ozonation of aniline and p-chloroaniline in
aqueous solution is investigated in this study. These
compounds were selected because they are frequently
detected in many industrialwastewaters. An ii ln e is an
In previous works [5–9], we have studied the applica-
tion of ozonation as a chemicaltreatment for industrial
wastewaters. Aniline and p-chloroaniline were identified
as the principalraw materia ls present in effluents derived
from dye manufacturing and manufacturing of rubber
vulcanization accelerators. Aniline is detected in high
concentration in these wastewaters. Although it is not
regulated by legislation, it is highly toxic to aquatic life
and US EnvironmentalProtection Agency (US EPA)
has suggested an ambient limit in water of 262 mg/L,
important raw materialused in the manufacturing of
0
4
,4 -methylene bis(phenyl isocyanate) (MDI) and poly-
MDI, which are intermediates for the production of
urethanes [1]. Other principal applications of aniline
include production of rubber accelerators and antiox-
idants to vulcanize rubber; the manufacture of inter-
mediates for herbicides and other pesticides, especially
fungicides; and the manufacture of dyes and pigments,
especially azo. Aniline is also used to produce medicinals
and pharmaceuticals, resins, varnishes, perfumes, shoe
blacks, photographic chemicals (hydroquinone), explo-
based on health effects [1]. p-Chloroaniline is
a
compound of interest because it is included in List II
of European Union (EU) [10], as a compound which will
be regulated by legislation in the future.
In this investigation, synthetic aqueous solutions of
aniline and p-chloroaniline were treated with ozone
with the aim of studying its application to industrial
*
Corresponding author. Tel.: +34-976761156; fax: +34-
9
76762142.
E-mail address: jsarasa@posta.unizar.es (J. Sarasa).
0043-1354/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 0 4 3 - 1 3 5 4 ( 0 2 ) 0 0 0 0 3 - 9

3036
J. Sarasa et al. / Water Research 36 (2002) 3035–3044
wastewaters containing aniline derivatives. The reaction
of ozone with these compounds was investigated at
different conditions. The aromatic by-products formed
during and after the ozonation reaction were identified.
Ozone reacts with organic compounds in water via two
pathways: directly or indirectly. The molecule of ozone
2.2. Ozonation
A Fischer Model501 Ozonizer was used for the
production of ozone. The ozone stream was continu-
ously introduced in the sample through a porous sparger
as microbubbles at the bottom of the ozone contactor.
The surplus ozone was stored in two bubblers contain-
ing 250 mL of 2% KI solution. According to the
apparatus calibration curve and through the titration
of the solutions in the bubblers using sodium thiosul-
phate and starch as indicator [16], the medium dosage of
ozone consumed was calculated for all the experiments.
Samples of 50 mL were taken at different time steps
during the ozonation reaction for the determination of
the different compounds. Ozonation of aniline was
carried out at two different pH values: pH 2 (by adding
3
can remain as O or it can decompose by a variety of
mechanisms producing the hydroxylfree radical(OH d).
Molecular ozone itself, being a weaker oxidizing agent
than hydroxyl free radical, is a rather selective oxidant
[
11]. Some authors have investigated the by-products
formed from the reaction of ozone with aniline.
Depending on ozonation conditions, the attack of ozone
is directed towards aromatic ring cleavage. Aliphatic
aldehydes, ketones and acids, along with nitrates and
ammonia can be found as finalby-products [12,13].
Chan and Larson [14,15] described the next compounds
as the main by-products formed after ozonation of
anilines: nitrobenzene, nitrosobenzene, azobenzene,
azoxybenzene, 4-amino-diphenylamine, benzidine and
phenazine. Some condensation products, as well as
amino-phenols, have been identified as intermediate by-
products of the ozonation reaction [11].
2 4
6 N H SO ) and pH 8. In the latter case, pH was
controlled with a phosphate buffer and monitored
during the experiment to assure that it was held
approximately constant. The ozonation of p-chloroani-
line solution was carried out at pH 8 with phosphate
buffer. The ozonation conditions are summarized in
Table 1.
Aniline was treated with ozone at low and high pH,
comparing both molecular ozone and hydroxyl free
radicalmechanisms, respectiv ey l.
p-Chloroaniline was
2.3. Analytical methods
treated with ozone only at high pH, due to the best
results obtained from ozonation of aniline at the same
conditions.
The aromatic compounds were determined by means
of a liquid–liquid extraction of the aqueous samples with
methylene chloride and subsequent concentration of the
extracts (US EPA Method 625 [16]).
2
. Materials and methods
A Varian 3300 Gas Chromatograph connected with
an ITD FinniganMAT 800 Mass Spectrometer was used
for identifying the compounds. The chromatographic
conditions were the following: Column: DB-5 (J&W
Scientific); injection volume: 2 mL in splitless (0.8 min.);
injection temperature: 2501C; carrier gas: helium (30 cm/
s) and temperature programme: 60(1)-4-280(15). The
identification of the compounds was carried out by
NationalInstitute of Standards and Techno lo gy (NIST).
Library searching and the main substances were verified
by comparison with reference standards.
2
.1. Preparation of solutions
Aniline and p-chloroaniline solutions were prepared
from pure standards (Merck and Riedel-de-Ha e. n,
s
respectively, 99% of purity) in Milli-Q water, pre-
viously purified by means of methylene chloride extrac-
tion, with the objective of eliminating possible
impurities. The concentration of aniline and p-chloro-
aniline solutions was 1 and 3.5 mM, respectively.
Table 1
Ozonation conditions of the solutions
Conditions
Aniline
p-Chloroaniline
Initialconcentration (mM)
Initial volume of sample (mL)
Final volume of sample (mL)
Ozonation pH
1
1
3.5
1000
750
1000
750
2
1000
750
8 (phosphate buffer)
12
25
8 (phosphate buffer)
Flow rate of ozone (mg/min)
Ozonation time (min)
Medium ozone consumed (mg/L)
12
25
10.4
25
305
6.3
348
7.2
274
1.6
3
Mole O consumed/mole compound

J. Sarasa et al. / Water Research 36 (2002) 3035–3044
3037
A HP5890 Gas Chromatograph equipped with flame
ionization detector (FID) was used for quantifying the
representative substances (aniline, p-chloroaniline, ni-
trobenzene and p-chloronitrobenzene). The chromato-
graphic conditions were the following: Column: DB-
WAX (J&W Scientific); injection volume: 2 mL in
splitless (0.8 min.); injection temperature: 3001C; carrier
gas: helium (30 cm/s); auxiliary gas: nitrogen and
observed in the figure, the elimination of aniline is more
effective at pH 8 than at pH 2, for a similar amount of
ozone consumed (100% and 80% of elimination,
respectively, after 25 min of treatment). It was observed
that the pH value remained constant when ozonation
was carried out at pH 2. The reaction at acid pH is
dominated by the action of molecular ozone whereas at
pH 8, the amino group of aniline enhances the ozone
temperature programme:
60(1)-25-120(3)-4-250(5).
decomposition in hydroxyl radicals by releasing super-
dÀ
Semi-quantitative estimation via GC/MS was used to
quantify some compounds of which no reference
standards were available. Both GC/FID quantification
and semi-quantitative estimation were done taking into
account the variation of volume due to sample collec-
tion.
2
oxide anion radical(O ). In addition, the amino group
of aniline at acid pH remains as its protonated form
(pKa=4.6), which is an electron-withdrawing group. As
a result of this, the electrophilic attack by molecular
d
ozone at acid pH is slower than OH mechanism at basic
pH. From these results, the pseudo-first-order constant
in aniline concentration was calculated for both experi-
0
À4 À1
0
ments:
K
(pH=2)=9.8 Â 10
s
and
. As it was expected, the rate
K
(high
À3 À1
pH)=3.5 Â 10
s
3
. Results and discussion
constant for the hydroxylfree radicalmechanism is
higher than the one corresponding to the molecular
mechanism.
3
.1. Study of the ozonation reaction
In Fig. 1, it can be seen that the decrease in p-
chloroaniline concentration is produced in final steps
of the reaction, and after the complete treatment 60%
of the compound is eliminated. p-Chloroaniline
degradation is produced by an hydroxylradicalmechan-
ism, enhanced by the amino group of the molecule at
pH=8 (pKa=3.98). However, kinetic in p-chloroaniline
concentration cannot be adjusted to a first-order
reaction.
Fig. 1 shows the evolution in aniline and p-chloroani-
line concentration during ozonation reaction. As it is
1
0
0
0
0
0
0
0
0
0
.9
.8
.7
.6
.5
.4
.3
.2
.1
0
3
.2. Study of the by-products formed
The by-products formed after complete ozonation of
0
1
2
3
4
5
6
7
8
aniline in both experiments and p-chloroaniline are
shown in Table 2. The main by-products formed after
ozonation of aniline at low pH were nitrobenzene and
azobenzene, and the evolution of formation of these by-
products is shown in Fig. 2. In the reaction of ozone
with aniline at high pH, in addition to nitrobenzene and
mmol ozone/L consumed
Aniline pH = 2
Aniline pH = 8
p-Chloroaniline
Fig. 1. The evolution of aniline and p-chloroaniline concentra-
tion during ozonation reaction (M0ðanilineÞ ¼ 1 mM and
M0ðp-chloroanilineÞ ¼ 3:5 mM).
Table 2
Finalby-products identified after ozonation of ani il ne and p-chloroaniline solutions
Compound
Identified by-product
Finalconcentration (mM)
pH=2
Finalconcentration (mM)
O
O
3
3
pH=8
À2
À2
Aniline (1 mM)
Nitrobenzene
Azobenzene
Azoxybenzene
1.6 Â 10
8.2 Â 10
n.d.
1.1 Â 10
9.6 Â 10
5.4 Â 10
3.1 Â 10
À5
À4
À4
À3
2
-Pyridine-carboxylic acid
n.d.
À2
À1
À2
À2
p-Chloroaniline (3.5 mM)
p-Chloronitrobenzene
0
F
F
F
F
1.2 Â 10
4.7 Â 10
8.4 Â 10
1.2 Â 10
4
,4 -Dichloro-azobenzene
0
n;n -Dichloro-azobenzene
-Chloro-2-pyridine-carboxylic acid
4
n.d.: not detected.

3038
J. Sarasa et al. / Water Research 36 (2002) 3035–3044
0
.018
.016
.014
.012
0.14
0.12
0.1
0.035
0.03
0.025
0.02
0.015
0.01
0.005
0
0
.00009
0.00008
.00007
0.00006
.00005
.00004
.00003
.00002
0
0
0
0
0
0
0
0
.08
.06
.04
.02
0
0
.01
0
0
0
0
0
0
0
.008
.006
.004
.002
0
0
0.00001
0
0
1
2
3
4
5
6
mmol ozone/L consumed
0
1
2
3
4
5
6
7
4
,4'-Dichloroazobenzene
p-Chloronitrobenzene
mmol ozone/L consumed
Nitrobenzene Azobenzene
n,n'-Dichloroazobenzene
4-Chloro-2-pyrid.carboxylic acid
Fig. 4. The evolution of formation of by-products during
ozonation of p-chloroaniline at basic pH.
Fig. 2. The evolution of formation of by-products during
ozonation of aniline at acid pH.
NH2
NH2
NH OH
OH
0
.012
.01
H
0
OHº
OHº
0
0
0
0
.008
.006
.004
.002
0
X
X
X
Aniline or
p-Chloroaniline
(X = H, Cl)
OHº
N
X
O
NH OH
0
1
2
3
4
5
6
7
8
N
X
OH
OH
C
C
mmol ozone/L consumed
C
O
O
-H O
2
O
C
OH
OH
Nitrobenzene
Azoxybenzene
Azobenzene
OH
*
2-Pyridine-carboxilic acid
active hydrogen
X
Fig. 3. The evolution of formation of by-products during
ozonation of aniline at basic pH.
N
X
COOH
azobenzene, azoxybenzene and 2-pyridine-carboxylic
acid were found (Fig. 3). Nitrobenzene, which was
formed by oxidation of aniline, was the majority by-
product identified in both experiments, and it was
detected in higher concentration at acid conditions.
Mainly azobenzene is formed in final steps of the
reaction at pH 2, while at pH 8, it reaches a maximum of
concentration (mole ozone consumed/mole initial ani-
line=4.1), and then it begins to be eliminated. At basic
pH, OHd radicals are nonselective in their action on
organic matter and can degrade the azobenzene formed.
However, finalconcentration of azobenzene after 25 min
of treatment is much higher when the experiment is
carried out at basic pH. The evolution of the formation
of azoxybenzene is similar to azobenzene, although it is
only detected when the ozonation is carried out at pH 8.
The compounds identified as by-products of aniline
ozonation are in accordance with those reported by
Chan and Larson [14,15], who describe the formation
mechanisms of azobezene and azoxybenzene from the
reaction of ozone with aniline. However, no reference
2-Pyridine-carboxylic acid
Fig. 5. The proposed mechanism for the formation of 2-
pyridine-carboxylic acid from ozonation of anilines.
has been found about the formation of 2-pyridine-
carboxylic acid.
The main by-product formed after ozonation of
0
p-chloroaniline was 4,4 -dichloroazobenzene. Other
0
compounds detected were an isomer of 4,4 -dichloroa-
zobenzene, p-chloronitrobenzene and 4-chloro-2-pyri-
dine-carboxylic acid. These compounds are in
accordance with the results obtained in the ozonation
of aniline in similar conditions, although the corre-
sponding chlorinated azoxybenzene has not been
detected. The evolution of the concentration of by-
products identified during the reaction between p-
chloroaniline and ozone is shown in Fig. 4.
As it can be seen, p-chloronitrobenzene and 4-chloro-
2-pyridine-carboxylic acid are continuously formed

J. Sarasa et al. / Water Research 36 (2002) 3035–3044
3039
during the reaction, whilst azobenzene derivatives are
generated at finalsteps, in accordance with the major
degradation of p-chloroaniline. Although during the first
steps of the reaction, elimination of p-chloroaniline is
rather small in Fig. 1, by-products are being generated in
minor concentration. As in the case of aniline ozonation,
the corresponding chlorinated pyridine-carboxylic acid
is detected as by-product.
of organic chemicals, plastics and synthetic fibers [31].
These effluent limitations are the following: direct
discharge point sources that use end-of-pipe biological
treatment: 68 mg/L (maximum for 1 day) and 27 mg/L
(maximum for monthly average) (EPA 40CFR, Part
414, Subpart I); direct discharge point sources that do
not use end-of-pipe biological treatment: 6402 mg/L
(maximum for 1 day) and 2237 mg/L (maximum for
monthly average) (EPA 40CFR, Part 414, Subpart J);
indirect discharge point sources: 6402 mg/L (maximum
for 1 day) and 2237 mg/L (maximum for monthly
average) (EPA 40CFR, Part 414, Subpart K). Although
nitrobenzene is regulated in some wastewaters by USA
legislation, available information indicates that it is
moderately toxic to aquatic life and less toxic than
aniline. Besides, nitrobenzene is subject to bio- and
photodegradation in water; small amounts also adsorb
to sediment or volatilize from the surface. The half-life
of nitrobenzene in modelwaste stabi il zation ponds was
measured at 3.8 days; 89.5% of the added chemicalwas
degraded, 4.9% volatilized, 2.3% adsorbed to sediment,
2.3% was lost in effluent and 1% remained [19]. The
half-life of nitrobenzene in aquatic environments has
been estimated at 0.3 days [26].
The reaction mechanism proposed for the formation
of the pyridine-carboxylic acid from ozonation of
anilines could be the following: as a first step, the
hydroxylated compound in 2-position is formed.
Although this intermediate has not been detected, the
by-product is generated only at basic conditions, where
the hydroxylfree radica sl are more predominant than
molecular ozone. After the opening of the aromatic ring,
the nitroso- intermediate (–N ¼ O) is formed, as a final
result of the reaction between ozone and the amino
group. The nitroso compound can react with an active
hydrogen of the molecule, yielding an imine (–C ¼ N–)
[
17], which in this case leads to the formation of the
pyridine-carboxylic acid after a rearrangement of the
molecule (Fig. 5).
Although aniline in water is subject to bio- and
photodegradation, it is a toxic substance to aquatic life
and it must be eliminated of wastewaters before being
released to the aquatic environment. Besides, aniline can
be subjected to adsorption to sediment and humic
materials; this fact can extend the persistence of aniline
in the aquatic environment. A half-life for aniline of 2.3
days has been reported in an industrialriver [18,19]. p-
Chloroaniline, being a less toxic compound than aniline,
is highly toxic by ingestion, inhalation and skin contact
The toxicity parameters for p-chloroaniline and its
ozonation by-products are presented in Table 4. No
0
toxicity data have been found for 4,4 -dichloroazoben-
zene and 4-chloro-2-pyridine-carboxylic acid. Although
both p-chloroaniline and p-chloronitrobenzene are
included in List II of UE, comparing LD50 data it can
be concluded that p-chloronitrobenzene is less toxic than
p-chloroaniline.
[
4,20]. The results of this study show that ozonation is
very effective in removing anilines in water. In order to
determine if ozonation is applicable to effluents contain-
ing aniline derivatives, the toxicity of new by-products
and their effect on the environment has been studied.
Some toxicity parameters corresponding to raw materi-
als and final ozonation by-products are shown in Tables
4
. Conclusions
1. Ozonation is very effective in removing aniline and p-
chloroaniline in aqueous solutions. Ozonation reac-
tion of aniline follows a first-order kinetic, with the
0
À4 À1
pseudo-first-order constants K ¼ 9:8 Â 10
s
(high pH). The ozona-
(low
0
À3 À1
3
and 4.
The more representative toxicity parameters for
pH) and K ¼ 3:5 Â 10
s
tion reaction of aqueous solutions of p-chloroaniline
and ozone at basic pH cannot be adjusted to first-
order kinetics in our conditions.
aniline found in published bibliography, are presented
in Table 3. Other authors have reported toxicity
parameters of nitrobenzene (the majority by-product),
however, fewer data have been found about toxicity of
azobenzene and azoxybenzene, and no toxicity data of
2. Nitrobenzene is the majority by-product formed after
ozonation of aniline at acid pH. The selective
reaction of molecular ozone with aniline at acid pH
leads to the oxidation of amino group to nitro group.
Azobenzene is also detected in minor concentration.
3. The indirect reaction of ozone with aniline at basic
pH, in addition to nitrobenzene and azobenzene,
leads to the formation of azoxybenzene and 2-
pyridine-carboxylic acid.
2
-pyridine-carboxylic acid have been published. Com-
paring toxicity data, it can be concluded that ozonation
by-products of aniline are less toxic than the raw
material.
Among the by-products formed, the most interesting
compound is nitrobenzene: it is included in the Priority
Pollutant List [30] and there is an effluent limitation of
US EPA applicable to the process wastewater discharges
containing nitrobenzene resulting from the manufacture
4. It is recommended to ozonize aniline solutions at
basic pH. Although a greater number of aromatic by-
products are generated, nitrobenzene, which is

Table 3
Toxicity parameters for aniline and its ozonation by-products
Aniline
Ozonation by-products
Nitrobenzene Azobenzene
Azoxybenzene
2-Pyridine-carboxylic acid
NO
Chemicalformual
Structuralformual
C
6
H
7
N
C
6
H
5
NO
2
C
12
10
H N
2
C
12
H
10
N
2
O
C
6
H
5
2
NH2
NO2
N
COOH
+
N N
N N
O
-
CAS RN
62-53-3
93.1
98-95-3
123.1
103-33-3
182.2
495-48-7
198.2
98-98-6
123.1
Molecular mass
Acute toxicity parameters
LD50 (orl-rat) (mg/kg)
LD50 (orl-mus) (mg/kg)
LD50 (ipr-rat) (mg/kg)
LD50 (ipr-mus) (mg/kg)
LD50 (skn-rat) (mg/kg)
LD50 (skn-rbt) (mg/kg)
250
464
420
492
1400
820
500
100
1000
200
150
640
n.a.
640
n.a.
2100
n.a.
700
2000
n.a.
150
35
1000
n.a.
n.a.
500
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
620
515
n.a.
n.a.
n.a.
1090
n.a.
n.a.
250
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
LDL
LDL
LDL
LDL
LDL
0
0
0
0
0
(orl-rbt) (mg/kg)
(orl-cat) (mg/kg)
(scu-rbt) (mg/kg)
(ivn-dog) (mg/kg)
(unr-man) (mg/kg)
Toxicity to aquatic organisms
TLm96 (ppm)
100–10
32–53
165
100–10
112.5
20
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
LC50(96) (mg/L) Zebrafish
LC50(48) (mg/L) Medaka
LC50(48) (mg/L) Fathead minnow
LC50(48) (mg/L) Golden orfe
65
61–78
156
60–89

Carcinogenicity
Probable
human
carcinogen
Probable
human
carcinogen
Not classifiable as a human
carcinogen
n.a.
n.a.
n.a.
n.a.
Test of genotoxicity
Positive
262
Negative
n.a.
n.a.
Ambient limit in water (mg/L)
Proposed limit for protection of aquatic life
27,000 (acute
toxicity)
(fresh water) (mg/L)
Proposed limit for protection of aquatic life
salt water) (mg/L)
6680 (acute
toxicity)
(
Proposed limit for protection of human
health (mg/L)
19,800 (toxic
effect)
Compound included in list (water quality)
Priority
pollutant list
(
US EPA)
Sources: Budavari et al. [2]; Clansky [21]; Lewis and Tatken [22]; Sax [23]; Sittig [24]; USEPA [18,25–27] and Verschueren [28].
LD50: lethal dose 50% kill
LDL : lowest published lethal dose
TLm96: threshold limit (96 h)
ipr: intraperitoneal mus: mouse
ivn: intravenous
orl: oral
0
rbt: rabbit
LC50: lethal concentration 50 percent kill scu: subcutaneous n.a.: not available
skn: skin
unr: unregistered

Table 4
Toxicity parameters for p-chloroaniline and its ozonation by-products
p-Chloroaniline
Ozonation by-products
0
p-Chloronitrobenzene
4,4 -Dichloroazobenzene
4-Chloro-2-pyridine carboxylic acid
Chemicalformual
Structuralformual
C
6
H
6
ClN
C
6
H
4
ClNO
2
C
H
12 8
Cl
2
N
2
C
6
H
4
ClNO
2
NH2
NO2
N
COOH
Cl
N
N
Cl
Cl
Cl
Cl
CAS RN
106-47-8
127.57
100-00-5
157.56
1602-00-2
251.1
n.a.
Molecular mass
157.56
Acute toxicity parameters
LD50 (orl-rat) (mg/kg)
LD50 (orl-mus) (mg/kg)
LD50 (ipr-rat) (mg/kg)
LD50 (skn-rat) (mg/kg)
310
100
420
3200
420
650
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
420
16,000
Toxicity to aquatic organisms
TLm96 (ppm)
1000–100
List II (EU)
10
1000–100
List II (EU)
10
n.a.
n.a.
Compound included in list (water quality)
Water quality criteria (mg/L) (EU proposed)
Sources: Budavari et al. [2]; Clansky [21]; Lewis and Tatken [22]; Sax [23]; Sittig [24]; Verschueren, [28] and Bro-Rasmussen [29].
LD50: lethal dose 50% kill ipr: intraperitoneal
TLm96: threshold limit (96 h) orl: oral
n.a.: not available
skn: skin
mus: mouse

J. Sarasa et al. / Water Research 36 (2002) 3035–3044
3043
regulated by US EPA, is detected in minor concen-
tration.
vol. 1. 1993. p. S-7-91–105. Cincinnati, USA: International
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5
. The main by-products identified after complete
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in minor concentration are p-chloronitrobenzene and
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[
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4
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6
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Acknowledgements
We would like to acknowledge the Laboratory of
Confederaci o! n Hidrogr a! fica delEbro staff and Yo al nda
Yag u. e for their help in carrying out this study.
1
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