Removal of 3,4-dichlorobut-1-ene using ozone oxidation

Article abstract of DOI:10.1016/S0043-1354(99)00410-8

The efficiency of ozone oxidation in the removal of 3,4-dichlorobut-1-ene (3,4 DCB), a contaminant often present in the aqueous effluents generated by synthetic rubber processes, was studied. Ozone oxidation removed 3,4 DCB completely from the model solutions with initial concentrations ranging from 4 to 64 mg/l over a maximum ozonation time of 7 min. The complete oxidation of 3,4 DCB was mainly due to the direct reaction with ozone molecules at acidic and neutral pH. At alkaline pH ozone oxidation only reduced the 3,4 DCB concentration by 61% over 15 min of ozonation. Methanol used in preparing the 3,4 DCB solutions did not affect the ozone oxidation rate. Ozone oxidation of a 3,4 DCB/methanol solution with an initial 3,4 DCB concentration of 120 mg/l reduced 95% of the 3,4 DCB concentration but only 4% of the Chemical Oxygen Demand (COD) in the solution. The high COD value in the ozonated solution was probably due to the presence of methanol. Ozone degraded 3,4 DCB and chloroprene (CD) in the effluent samples from a synthetic rubber processing plant and resulted in the maximal reduction of the COD by 45%. The efficiency of ozone oxidation in the removal of 3,4-dichlorobut-1-ene (3,4 DCB), a contaminant often present in the aqueous effluents generated by synthetic rubber processes, was studied. Ozone oxidation removed 3,4 DCB completely from the model solutions with initial concentrations ranging from 4 to 64 mg/l over a maximum ozonation time of 7 min. The complete oxidation of 3,4 DCB was mainly due to the direct reaction with ozone molecules at acidic and neutral pH. At alkaline pH ozone oxidation only reduced the 3,4 DCB concentration by 61% over 15 min of ozonation. Methanol used in preparing the 3,4 DCB solutions did not affect the ozone oxidation rate. Ozone oxidation of a 3,4 DCB/methanol solution with an initial 3,4 DCB concentration of 120 mg/l reduced 95% of the 3,4 DCB concentration but only 4% of the Chemical Oxygen Demand (COD) in the solution. The high COD value in the ozonated solution was probably due to the presence of methanol. Ozone degraded 3,4 DCB and chloroprene (CD) in the effluent samples from a synthetic rubber processing plant and resulted in the maximal reduction of the COD by 45%. Copyright (C) 2000.

Full text of DOI:10.1016/S0043-1354(99)00410-8

Wat. Res. Vol. 34, No. 11, pp. 2963±2970, 2000
2000 Published by Elsevier Science Ltd. All rights reserved
Printed in Great Britain
7
PII: S0043-1354(99)00410-8
0043-1354/00/$ - see front matter
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REMOVAL OF 3,4-DICHLOROBUT-1-ENE USING OZONE
OXIDATION
1
MARYAM ALBORZFAR * , KARINE ESCANDE and STEPHEN J. ALLEN
M
2
1
1
School of Chemical Engineering, The Queen's University of Belfast, David Keir Building, Stranmillis
Road, Belfast BT9 5AG, UK and 3 Square des Roseaux, 77240, Cesson-la-for eà t, France
2
(
First received 1 November 1998; accepted in revised form 1 October 1999)
AbstractÐThe eciency of ozone oxidation in the removal of 3,4-dichlorobut-1-ene (3,4 DCB), a
contaminant often present in the aqueous e‚uents generated by synthetic rubber processes, was
studied. Ozone oxidation removed 3,4 DCB completely from the model solutions with initial
concentrations ranging from 4 to 64 mg/l over a maximum ozonation time of 7 min. The complete
oxidation of 3,4 DCB was mainly due to the direct reaction with ozone molecules at acidic and neutral
pH. At alkaline pH ozone oxidation only reduced the 3,4 DCB concentration by 61% over 15 min of
ozonation. Methanol used in preparing the 3,4 DCB solutions did not a€ect the ozone oxidation rate.
Ozone oxidation of a 3,4 DCB/methanol solution with an initial 3,4 DCB concentration of 120 mg/l
reduced 95% of the 3,4 DCB concentration but only 4% of the Chemical Oxygen Demand (COD) in
the solution. The high COD value in the ozonated solution was probably due to the presence of
methanol. Ozone degraded 3,4 DCB and chloroprene (CD) in the e‚uent samples from a synthetic
rubber processing plant and resulted in the maximal reduction of the COD by 45%. 7 2000 Published
by Elsevier Science Ltd. All rights reserved
Key wordsÐaqueous e‚uent, chlorinated hydrocarbons, synthetic rubber, 3, 4-dichlorobut-1-ene, chlor-
oprene, ozonation
INTRODUCTION
dation in the removal of chlorinated hydrocarbons
from both model solutions and e‚uent samples
taken from a synthetic rubber processing plant.
The treatment of aqueous borne chlorinated hydro-
carbon wastes is very important to a wide range of
industrial processes including the ®bres, plastics and
polymers industries. Chlorinated hydrocarbon com-
OZONATION
pounds are known to be recalcitrant, toxic and in
some cases carcinogenic and discharge of the aqu- Ozone applications
eous wastes can lead to the build up of signi®cant
Ozone oxidation has been widely employed to
amounts of chlorinated hydrocarbons in the en-
disinfect potable water in several European
vironment.
countries (Rice and Netzer, 1984), however, in the
Polychloroprene elastomer belongs to a group of
UK it is primarily used for the removal of pesti-
products known as synthetic rubbers. During the
cides (Aeppli et al., 1997). Ozone oxidation is also
course of its production aqueous e‚uent streams
used for treating waste waters from the electroplat-
are generated which contain derivatives of dichloro-
ing, textile, pulp and paper, and petroleum indus-
butene and chlorobutadiene. The synthetic rubber
tries (Rice, 1997). In recent years ozone oxidation
manufacturers are therefore obliged to ®nd
has been studied for treating rubber additive waste
improved methods for treating their e‚uents to
waters, land®ll leachates and municipal waste
meet the criteria of Integrated Pollution Control,
waters (Rice, 1997).
and in particular to demonstrate that the Best
The advantages of ozone oxidation process are
Available Techniques Not Entailing Excessive Cost
the ability to apply ozone directly in its gaseous
(
BATNEEC) criteria is ful®lled.
This paper discusses the eciency of ozone oxi-
state and a short reaction time between the ozone
and e‚uent. Ozone application neither increases the
volume of e‚uent nor results in formation of
sludge. In addition, ozone reacts preferably with
refractory substances. The disadvantages of ozone
oxidation include the relatively high energy cost of
producing ozone, the pH impact on its oxidation
*
Author to whom all correspondence should be addressed.
Present address: 33 Ferrymoor, Ham, Richmond,
Surrey, TW10 7SD, UK. Tel.: +44-181-940-3907; Fax:
+
44-181-940-3907; e-mail: maryam_at@hotmail.com
2963

2
964
Maryam Alborzfar et al.
potential, insigni®cant TOC reduction and possible reaction of (HOÁ) and M (Masten and Hoigne
Â
,
development of more toxicity in the treated water 1992).
than the unprocessed water (Heinzle et al., 1992;
Parameters in¯uencing oxidation rate
Ga
Schroeder, 1996; Aeppli et al., 1997; Hanmer,
997).
È
hr et al., 1994; Strickland and Perkins, 1995;
The oxidation potential of ozone ranges from
around 2.08 V in acidic solutions to only 1.4 V in
alkaline solutions. The pH therefore in¯uences the
relationship between oxidation potential and de-
1
Ozone reaction with organic compounds
Ozone (O
3
) is an unstable reactive gas which is composition behaviour of Ozone. The oxidising
about 13 times more soluble in water than oxygen agent in acidic solutions is the ozone molecule
at standard temperature and pressure (Hill and whereas in alkaline solutions it is the hydroxyl rad-
È
Rice, 1982). At low pH, saturated ole®ns are essen- ical (Gahr et al., 1994). In oxidising organic sub-
tially unreactive with ozone compared to their stances such as 1,1-dichloro-1-propene and 1,1-
counterparts, the unsaturated ole®ns. Halogens dichloroethylene increasing the pH resulted in an
directly attached to a double bond greatly deacti- increase in the ozone dosage required for the former
vate the rate of ozone oxidation. In competitions and decrease in the ozone dosage required for the
between halogenated and non-halogenated double latter substance (Masten and Hoigne
bonds, ozonolysis appears to occur exclusively at
the latter (Bailey, 1978; Masten and Hoigne, 1992).
Â
, 1992).
Mass transfer of ozone
Â
Mass transfer of ozone into aqueous solutions is
important in both air and water pollution abate-
Kinetics of ozonation
Ozone always reacts in two di€erent mechanisms: ment. The overall mechanism of the gas-liquid reac-
direct reaction of ozone with organic compounds tion system consists of the following steps:
and indirect reaction by free hydroxyl radicals. The
.
.
.
di€usion of ozone into an interface between the
gas and liquid phases;
transport across the interface to the liquid phase
boundary due to a concentration gradient;
transfer into the bulk liquid.
direct reactions are often rather slow but highly
selective. The indirect reactions by free hydroxyl
ions, on the other hand, are highly reactive but less
selective (Aeppli et al., 1997).
3
In the direct reaction, ozone molecule (O ) oxi-
The mass transfer rate is in¯uenced by many fac-
tors, which can be divided into hydrodynamic and
physicochemical e€ects. Hydrodynamic behaviour is
concerned with the movement of the molecules. For
example, bubbles rising slowly to the surface in a
column of liquid have small interfacial areas, and
therefore, mass transfer rates are generally low. If
intense mixing is added, the bubbles are sheared
and mixed thoroughly, increasing both interfacial
area and contact time and therefore higher mass
transfer rate. Physicochemical e€ects include de-
composition reactions of ozone, temperature, press-
ure and chemical composition of the liquid (Kuo
and Yocum, 1982).
dises the dissolved contaminant, M. The rate of the
transformation of M with concentration of [M], by
the ozone molecule is assumed to be ®rst order with
respect to ozone. Masten and Hoigne (1992)
Â
expressed the kinetics of this reaction by the follow-
ing equation:
ꢀ
ꢁ
d‰M Š
dt
�
ˆ kO , M‰O3Š‰M Š
ꢀ1†
3
where t is the reaction time and kO , M is the reac-
3
tion rate constant for the direct reaction of ozone
with the contaminant M. When the concentration
of M is much greater than the ozone concentration
the reaction rate becomes pseudo-®rst order. For
such reactions the following has been formulated by
EXPERIMENTAL PROCEDURES
Hoigne and Bader (1983):
Â
Samples
ꢀ
ꢁ
ꢀ
O3†t
n
0
�
log
ˆ ko ‰M Š t
ꢀ2†
Both model solutions and e‚uent samples from a syn-
thetic rubber processing plant were investigated. The
model solutions were made up using pure 3,4-dichlorobut-
3
ꢀ
O3†0
1
-ene (3,4 DCB) which was dissolved in methanol (1:50 v/
3 0 3 t
where [O ] and [O ] are concentrations of ozone at
v). The 3,4 DCB solutions were prepared by diluting 3,4
DCB/methanol in double distilled water. The aqueous sol-
ution was stirred for one hour using a magnetic stirrer bar
time zero and time t respectively. The rate constant
can then be determined experimentally by measur-
ing ozone concentrations during the reaction time t prior to ozonation. The e‚uent samples were transported
(
Hoigne
In the indirect reaction a part of the decomposed
ozone converts to hydroxyl radical (HOÁ) and the
logarithm of the relative residual concentration of Ozonation
M is a function of the amount of decomposed
ozone and the reaction rate constant for the indirect ozone generator (Ozat , type CF-0B, Ozonia Ltd). Oxy-
Â
and Bader, 1983).
to the laboratory and kept at 58C. Prior to ozonation, the
samples were ®ltered using ®lter papers (Whatman, grade
1) to remove suspended solids.
The ozonation experiments were carried out using an
1

3
,4-Dichlorobut-1-ene removal using ozone oxidation
2965
Table 1. The conditions under which the experiments were run
3
Gas ¯ow (m /h)
Current (A)
Ozone concentration (wt%) (at t = 208C, P = 1.3 bar)
Ozone production (g/h)
0.18
0.8
2
0.18
0.9
3.5
9
0.18
1.0
4.8
0.18
1.1
5.8
5
12
15
gen was used as the feed gas. The ozone reactor, a round
glass vessel with an approximate volume of 6 l, was
equipped with two taps from which aqueous samples were
withdrawn. The ozone bearing gas (inlet gas) was delivered
to the bottom of the vessel through a glass pipe 5 mm in
diameter. The excess gas left the vessel through another
glass pipe situated on top of the vessel. In each experiment
a batch of 5 l of model solution or e‚uent sample was
ozonated continuously in the system mentioned. During
the ozonation the solution/e‚uent sample was stirred by
means of a magnetic stirrer in order to increase the mass
chromatography system (Series 304 Chromatograph, Pye
Unicam Ltd.), with a capillary column (Phase Sep 12 m Â
0
3
.22 mm OV-1) and with electron capture detection. The
,4 DCB samples were extracted from the aqueous phase
to the organic phase using tetrachloroethene in 2,2,4-tri-
methylpentane. The 3,4 DCB standard solutions used for
calibration were treated the same way. The extracts (0.8 ml)
were injected manually. The injection port and the detec-
tor were heated to 2008C whereas the column operated at
358C. The e‚uent samples were extracted using 2,2,4-tri-
transfer rate between the ozone gas and solution. All the methylpentane. The extracts were analysed automatically
experiments were conducted at room temperature; 20 2 by a Hewlett Packard chromatography system (Series II,
2
8C. The experimental conditions are summarised in
Table 1.
The ozone production was calculated using the follow-
ing equation:
5890A GC) on a narrow bore capillary column.
The residual ozone in the ozonated solutions was
measured following the Indigo Method (Method 8311 for
water in the DR/2000 Spectrophotometer Handbook)
using a DR/2000 spectrophotometer (HACH Systems,
USA). Following this method 40 ml of the solution was
brought into contact with an AccuVac Ampoule contain-
ing potassium acid malonate (HACH Systems, USA). The
Indigo reagent when dissolved in ozone free water resulted
in a deep blue colour solution whereas in contact with the
ozonated sample the blue colour faded or disappeared.
The di€erence in absorbency between a blank and a
sample measured at 600 nm presented the residual ozone
in the sample.
1
00 MO3
Vn ˆ
ꢀ3†
r
C
3
where V
feed gas at standard conditions (rOxygen=1.429 kg/m at
8C and 1.013 bar); MO3 is the ozone production in kg/h;
n
is the gas ¯ow in m /h; r is the density of the
3
0
and C is the ozone concentration in wt% corresponding
to the adjusted current supply (Ozonia Operating Instruc-
tions, 1996).
The gas ¯ow rate and the corresponding ozone concen-
trations were taken from the diagrams given in the Ozonia
Operating Instructions, 1996.
The Chemical Oxygen Demand (COD) was measured
following the Reactor Digestion Method (Method 8000
for water, wastewater and sea water in the DR/2000 Spec-
trophotometer Handbook) using the DR/2000 spectropho-
tometer (HACH Systems, USA).
Analytical procedures
3
,4 DCB was analysed using a Pye Unicam gas-liquid
Fig. 1. The e€ect of initial concentration of 3,4 DCB on the oxidation rate at an ozone concentration
of 4.8 wt%.

2
966
Maryam Alborzfar et al.
between 3,4 DCB and ozone could also take place
RESULTS AND DISCUSSION
in the gas phase. Due to the lack of an appropriate
analytical set up, it was not possible to study and
analyse samples from the gas phase. Therefore the
Model solutions
Ozonation was carried out at a ¯ow rate of
3
.18 m /h and a current supply of 1 A. These
lowest ¯ow rate provided by the ozone generator,
3
.18 m /h, was chosen in order to minimise the
0
0
evaporation of 3,4 DCB.
resulted in an ozone concentration of 4.8 wt%
equivalent to an ozone production of 12 g/h in the
inlet gas. Figure 1 shows the reduction in the 3,4
DCB concentration as a function of time for the 3,4
DCB solutions with initial concentrations ranging
from 4-120 mg/l.
To determine the extent of the evaporation of 3,4
DCB during the experiments the following was car-
ried out: a 3,4 DCB solution with an initial concen-
tration of 20 mg/l was purged for 5 min at the
preceding ¯ow rate and a current supply of 0.3 A
The ozonation time required for oxidising 3,4
DCB increased with higher initial concentrations of
(
at this current the inlet gas only contained oxygen).
Under these conditions, the concentration of 3,4
DCB reduced by 12% (Fig. 2). To determine the
e€ect of ozone dosage on the oxidation rate of 3,4
DCB, solutions with initial concentration of 20 mg/
l were ozonated at various ozone concentrations as
shown in Fig. 2. The ozone concentrations
expressed in wt% correspond to ozone productions
of 5, 9, 12 and 15 g/h in the gas phase (equation (3)
3
,4 DCB as shown in Fig. 1. In solutions with low
initial concentrations (4 and 6 mg/l), there was a
rapid linear decrease in 3,4 DCB concentration.
This suggests that the reaction between 3,4 DCB
and ozone was a zero order reaction with respect to
3
equal to the gradient of the line, was 4.10 M/s.
,4 DCB. In this case the reaction rate constant (k )
�
7
For solutions with initial concentrations from 20
to 120 mg/l, the oxidation rate did not appear to be and Table 1).
linear. This suggests that the order of the reaction
The reduction in 3,4 DCB concentration was
between ozone and 3,4 DCB depends on the initial slower at low ozone concentrations. Increasing the
concentration of 3,4 DCB in the solution. More- ozone production three fold from 5 to 15 g/h
over, for the 3,4 DCB solution with an initial con- reduced the ozonation time required for complete
centration of 120 mg/l, 10 min of ozonation oxidation of 3,4 DCB by 50% from 6 to only 3 min.
removed only 95% of 3,4 DCB. After the ozonation At the highest ozone concentration (5.8 wt%), the
was interrupted, the concentration of 3,4 DCB ozone oxidation seemed to be a zero order reaction.
remained constant in the solution. The incomplete
oxidation of 3,4 DCB suggests a rapid decompo- oxidation rate, two 3,4 DCB solutions with initial
sition of ozone molecules in the solution.
concentrations of 120 mg/l were ozonated at an
To determine the e€ect of methanol on the ozone
As 3,4 DCB is highly volatile, the reaction ozone concentration of 4.8 wt% over 10 min. One
Fig. 2. The e€ect of ozone concentration on the oxidation rate of 3,4 DCB in solutions with initial con-
centration of 20 mg/l.

3
,4-Dichlorobut-1-ene removal using ozone oxidation
2967
Fig. 3. The e€ect of methanol on the ozone oxidation rate.
solution was made following the procedure Despite the fact that COD has been used as the key
described in the Experimental Procedures section parameter in the study of the ozone oxidation rate
and one was made up without using methanol. The of organic pollutants in aqueous solutions (Preis et
reduction of 3,4 DCB by 94±95% in both solutions al., 1988), this was not applicable due to the inac-
is illustrated in Fig. 3.
curacy of the COD measurements.
The ozone oxidation rate in both 3,4 DCB sol-
The in¯uence of pH on the oxidation rate of 3,4
utions was the same and not a€ected by the pre- DCB was determined by oxidising alkaline and
sence of methanol. This may be explained by the acidic 3,4 DCB solutions. Prior to ozonation, the
low reaction rate constant (k =0.02 M/s) for the pH values of the solutions were adjusted to 3±4
O
3
ozone and methanol reaction in water (Hoigne
982). The e€ect of methanol on the COD value of comparison between the ozonation time required
the solution was also investigated. The COD of the for these solutions is shown in Fig. 4.
,4 DCB solution made up with methanol was
In the acidic and neutral solutions, 3,4 DCB was
Â
,
using HCl and 9±10 using NaOH, respectively. A
1
3
measured during the ozonation. The COD data oxidised completely after four minutes ozonation
were then compared with the COD values of a 3,4 whereas in the alkaline solution, the relative re-
DCB/water solution and a methanol/water solution sidual concentration of 3,4 DCB was as high as
with an initial concentration of 20 mg/l (Table 2).
39% after 15 min ozonation. The ®nal pH-values of
The COD of the methanol/water solution was all the solutions remained the same as the start
much higher than that of the 3,4 DCB/water sol- values. The residual ozone was measured in the al-
ution (Table 2). Consequently, the high value of kaline and neutral solutions. As expected, there was
COD in the 3,4 DCB solution using methanol no residual ozone detected in the alkaline solution
could be due to the presence of methanol in the sol- whereas the residual ozone was 1.29 mg/l in the
ution. This may be supported by the fact that little neutral solution after 4 min ozonation.
changes were observed in the COD values after
An increase in pH of the solution resulted in a
completing ozonation (10 min) during which 3,4 signi®cant increase in the reaction time required to
DCB concentration was reduced by 95% (Fig. 3). complete oxidation of 3,4 DCB. This suggests that
Table 2. The COD of the samples taken from 3,4 DCB solutions made up with and without methanol
Ozonation
Min
3,4 DCB solution using methanol (120 mg/l)
COD2SD (mg/l)
3,4 DCB/water solution (20 mg/l)
COD2SD (mg/l)
Methanol/water solution (20 mg/l)
COD2SD (mg/l)
0
5083234
4893231
489525
183218
40402259
1
1
2
0
5
0
4840210

2
968
Maryam Alborzfar et al.
Fig. 4. The in¯uence of pH on the oxidation rate of 3,4 DCB in the solutions with initial concentration
of 20 mg/l.
the 3,4 DCB oxidation by ozone molecules is much
Except for the samples taken from the alkaline
faster than the 3,4 DCB oxidation by hydroxyl rad- 3,4 DCB solutions, two main peaks were always
icals formed in the alkaline solution. It is assumed recognised in the GC analysed samples. These
that the reaction between the hydroxyl radicals and included one with a retention time of 0.8 min (elut-
the methanol present in the solution took place at a ing before 3,4 DCB) and one with retention time of
faster rate. Changes in the COD values of the sol- 2.2 min (eluting just before the internal standard).
ution before and after ozonation could have sup- In order to identify the intermediates formed due to
ported this assumption.
ozonation, samples taken prior and following ozo-
Fig. 5. The reduction in the 3,4 DCB concentration in the e‚uent samples DS-1 and DS-2 as a func-
tion of ozonation time.

3
,4-Dichlorobut-1-ene removal using ozone oxidation
2969
Table 3. The COD of the e‚uent samples prior and following ozo-
nation
nation were extracted using hexane, ether and 2,2,4-
trimethylpentane. The extracts were analysed on a
GC-MS using a ¯ame ionisation detector. Unfortu-
nately, none of these attempts gave satisfying
results, as the peaks of the solvents in all the cases
were more dominant than the actual intermediates.
Purge and trap method was used in analysing water
samples withdrawn from a 3,4 DCB solution with
initial concentration of 20 mg/l prior and following
ozonation. A comparison between the spectra of
the intermediates and known organic compounds
suggested formation of 2,3-dichlorobutane due to
Sample
Time after starting ozonation (min)
COD2SD
DS-1
DS-2
1
13772110
759265.5
1394238
1154219
2
0
1
15
chloroprene (CD) and traces of other chlorinated
organic compounds.
Prior to ozonation, the e‚uent samples were ®l-
tered in order to remove the suspended solids. The
ozonation. Formation of
a chlorinated alkane
suggests that ozonation is more reactive towards CD concentration was reduced by 40±45% in the
the C0C double bond than the C0Cl bonds in 3,4 ®ltered samples. The 3,4 DCB concentration was
DCB. Using advanced oxidation processes or cata- reduced by 40% in the ®ltered DS-1 sample but it
lytic ozonation could more likely provide stronger could not be determined for DS-2 due to an error
oxidants for oxidising C0Cl bonds.
in the analytical results. The reduction in the con-
centrations of 3,4 DCB and CD was probably due
to both ®ltration and evaporation.
E‚uent samples
The ®ltered DS-1 and DS-2 samples were ozo-
3
nated at a ¯ow rate of 0.18 m /h and an ozone con-
Preliminary ozone oxidation experiments were
carried out on two samples; DS-1 and DS-2 taken
from the e‚uent generated by a synthetic rubber
plant. Unfortunately, the production plant was shut
down shortly after we obtained the preliminary
results and therefore it was impossible to carry out
further studies on the e‚uent. Since the pH and
composition of the e‚uent generated by the plant
centration of
2
wt% for 20 and 10 min,
respectively. The ozone oxidation was carried out at
the lowest ozone concentration due to the low con-
centration of 3,4 DCB in the samples. The re-
ductions in the 3,4 DCB and CD concentrations are
shown in Figs 5 and 6.
A 20 min ozonation of the DS-1 sample reduced
varied greatly with time, the composition and pH the concentrations of 3,4 DCB and CD by 70 and
of the e‚uent samples were di€erent from those of 63%, respectively. In the DS-2 sample these re-
the model solutions. The e‚uent samples were alka- ductions were 49 and 45% over 10 min ozonation,
line with a pH of 13 and contained low concen- respectively. The higher reductions in DS-1 could
trations
of
derivatives
of
dichlorobutene, be due to the longer ozonation time. Unfortunately,
Fig. 6. The reduction in the CD concentration of the e‚uent samples DS-1 and DS-2 as a function of
ozonation time.

2
970
Maryam Alborzfar et al.
REFERENCES
the reduction of the chlorinated hydrocarbons as a
result of evaporation could not be determined due
to the limited volumes of samples.
The ®nal pH values of both e‚uent samples did
not change due to ozonation. The COD was
measured in both e‚uent samples before and after
ozonation (Table 3).
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and practice of ozone applications in the '90 s in the
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I Ole®nic Compounds. Academic Press Inc (London)
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DS-2 samples by 45 and 17%, respectively. The ac-
curacy of the COD data is, however, not certain as
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hr F., Hermanutz F. and Oppermann W. (1994) Ozo-
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USA.
CONCLUSIONS
.
.
Ozone oxidation degraded 3,4 DCB. The ozona-
tion time required to oxidise 3,4 DCB was longer
for the solutions with higher initial concentration
of 3,4 DCB.
The reaction between ozone and 3,4 DCB was a
zero order reaction with a reaction rate constant
Hoigne J. (1982) Mechanism, rates and selectivities of oxi-
Â
dations of organic compounds initiated by ozonation of
water. In Handbook of Ozone Technology and Appli-
cations, Vol. 1, eds G. R. Rice and A. Netzer, pp. 341±
�
7
of 4 Â 10 M/s with respect to 3,4 DCB in sol-
utions with low initial 3,4 DCB concentrations (4
and 6 mg/l). On the other hand, a zero order
reaction was not observed for the 3,4 DCB sol-
utions with higher initial concentrations from 20
to 120 mg/l.
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,4 DCB was completed after 6 min. Increasing
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Â
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an initial 3,4 DCB concentration of 20 mg/l.
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reduced 95% of the 3,4 DCB but only 4% of the
COD in the solution.
.
.
3,4 DCB was oxidised completely at neutral and
acidic pH after only 4 min ozonation. In the al-
kaline solution, 39% of 3,4 DCB was still in the
solution in spite of 15 min ozonation. Evidently,
the oxidation took place following a direct reac-
tion with ozone molecules in the neutral and
acidic solutions rather than hydroxyl radicals pre-
sent in the alkaline solution.
Preliminary ozone oxidation experiments showed
reduction in the 3,4 DCB and CD concentrations
in the e‚uent samples but did not remove them
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