Oxidation of volatile organic vapours in air by solid potassium permanganate

Abstract

Volatile organic compounds (VOCs) may frequently contaminate groundwater and pose threat to human health when migrating into the unsaturated soil zone and upward to the indoor air. The kinetic of chemical oxidation has been investigated widely for dissolved VOCs in the saturated zone. But, so far there have been few studies on the use of in situ chemical oxidation (ISCO) of vapour phase contaminants. In this study, batch experiments were carried out to evaluate the oxidation of trichloroethylene (TCE), ethanol, and toluene vapours by solid potassium permanganate. Results revealed that solid potassium permanganate is able to transform the vapour of these compounds into harmless oxidation products. The degradation rates for TCE and ethanol were higher than for toluene. The degradation process was modelled using a kinetic model, linear in the gas concentration of VOC [ML(-3)] and relative surface area of potassium permanganate grains (surface area of potassium permanganate divided by gas volume) [L(-1)]. The second-order reaction rate constants for TCE, ethanol, and toluene were found to be equal to 2.0×10(-6)cms(-1), 1.7×10(-7)cms(-1), and 7.0×10(-8)cms(-1), respectively.

Full text

Oxidation of volatile organic vapours in air by solid potassium
permanganate
Mojtaba Ghareh Mahmoodlu
a,
⇑
, Niels Hartog
b,c
, S. Majid Hassanizadeh
a,b
, Amir Raoof
a
a
Utrecht University, Department of Earth Sciences, The Netherlands
b
Soil and Groundwater Systems, Deltares, Utrecht, The Netherlands
c
KWR Watercycle Research Institute, Nieuwegein, The Netherlands
highlights
"
Oxidation of chlorinated and non-chlorinated hydrocarbon vapours by solid potassium permanganate was investigated.
"
A linear kinetic oxidation model effectively predicted the degradation rate of TCE, ethanol, and toluene.
"
The reaction rate constants for TCE, ethanol, and toluene in gas phase by solid pot assium permanganate were calculated.
article info
Article history:
Received 31 July 2012
Received in revised form 12 December 2012
Accepted 15 December 2012
Available online 26 January 2013
Keywords:
Solid potassium permanganate
VOC vapour
Kinetic parameters
Chemical oxidation
abstract
Volatile organic compounds (VOCs) may frequently contaminate groundwater and pose threat to human
health when migrating into the unsaturated soil zone and upward to the indoor air. The kinetic of chem-
ical oxidation has been investigated widely for dissolved VOCs in the saturated zone. But, so far there
have been few studies on the use of in situ chemical oxidatio n (ISCO) of vapour phase contaminants.
In this study, batch experiments were carried out to evaluate the oxidation of trichloroethylene (TCE),
ethanol, and toluene vapours by solid potassium permanganate. Results revealed that solid potassium
permangan ate is able to transform the vapour of these compounds into harmless oxidatio n products.
The degradation rates for TCE and ethanol were higher than for toluene. The degradation process was
modelled using a kinetic model, linear in the gas concentration of VOC [ML
3
] and relative surface area
of potassium permangan ate grains (surface area of potassium permanganate divided by gas volume)
[L
1
]. The second-order reaction rate constants for TCE, ethanol, and toluene were found to be equal to
2.0 10
6
cm s
1
, 1.7 10
7
cm s
1
, and 7.0 10
8
cm s
1
, respectively.
Ó2013 Elsevier Ltd. All rights reserved.
1. Introduction
Volatile organic compound s (VOCs) are defined as organic com-
pounds with boiling points (at 1 amt) below 260 °C(De Nevers,
2000). VOCs have high vapour pressures under normal conditions,
so they can easily vapourize into the atmosphere or form vapour
plumes in the soil (Kim et al., 2007 ). VOCs are present in some
household products and automobile liquids (Berscheid et al.,
2010). Releases of VOCs to the environment have occurred through
surface spills, leaking underground storage tanks, and inadequate
disposal practices (Berscheid et al., 2010 ).
Small quantities of VOCs may contaminat e large volumes of
water. When released as free product, VOCs may migrate down-
ward to significant depths through the soil. In addition, VOC va-
pours can migrate upwards to the surface through diffusion and
produce elevated concentratio ns within indoor air spaces (Bersc-
heid et al., 2010 ). Exposure to some VOCs might affect central ner-
vous system and internal organs, and might cause symptoms such
as headache , respiratory tract irritation, dizziness and nausea,
known as the Sick Building Syndrome (SBS) (Yu and Lee, 2007 ).
We have chosen TCE, ethanol, and toluene, as model VOCs (tar-
get compound s) for chlorinat ed solvents, biofuel, and mineral oil,
respectivel y, for the reasons explained below.
TCE is one of the most common man-made chemicals found in
soil (Albergaria et al., 2012 ). It has been widely used as a dry clean-
ing solvent, degreasing agent, and chemical extraction agent. Since
TCE is carcinogenic, its movement from contaminated groundwa-
ter and soil into the indoor air of overlying buildings is of serious
concern (EPA, 2011 ).
Ethanol is being increasingly used in (renewable) fuel alterna-
tives and as replacemen t for methyl tertiary-b utyl ether (MTBE),
which, despite helping to accomplis h Clean Air Act goals, has
caused widespread water contaminat ion problems (Johnson
et al., 2000; Capiro et al., 2007 ). Ethanol can reduce the biodegra -
0045-6535/$ - see front matter Ó2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.chemosphere.2012.12.035
⇑
Corresponding author.
E-mail address: mahmodlu@geo.uu.nl (M.G. Mahmoodlu).
Chemosphere 91 (2013) 1534–1538
Contents lists available at SciVerse ScienceDi rect
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journal homepage: www.elsevier.com/locate/chemosphere

dation rate of light non-aqueous phase liquid (LNAPL) such as ben-
zene, toluene, ethylbenzene, and xylene isomers (BTEX) in ground-
water and soil (Mackay et al., 2007; Freitas et al., 2010 ).
Toluene is found frequently in indoor environments. Toluene is
mainly used as an additive to improve the octane number of gaso-
line (Yu and Lee, 2007 ).
One of most common treatment techniques for unsaturated
zone polluted with VOCs is soil vapour extraction (SVE). This is a
long-term operation and does not convert a contaminan t to less
toxic compounds . A promising alternative is in situ oxidation of
VOC that can lead to favourab le results in less time. Oxidation of
VOCs may convert hazardous contaminan ts to harmless com-
pounds. The oxidizing agents most commonl y used for the treat-
ment of hazardous contaminants are potassium permanganate ,
ultraviolet radiation, ozone, chlorine dioxide, hydrogen peroxide,
sodium persulfate, and Fenton’s reagent (H
2
O
2
oxidation in the
presence of ferrous iron, Fe
2+
).
Among these oxidants, potassium permanganate has been
receiving increased attention for the treatment of liquids, slurry
soils, and sludges polluted with VOCs (Kao et al., 2008 ). Early lab-
oratory studies have indicated that dissolved potassium perman-
ganate can remediate a variety of organic compounds ,
chlorinated alkanes (Waldeme r and Tratnyek, 2006 ), chlorinated
ethylenes (Huang et al., 1999; Hood et al., 2000; Yan and Schwartz ,
2000; Waldeme r and Tratnyek , 2006; Kao et al., 2008; Urynowicz,
2008), oxygenates (Jaky et al., 2000; Damm et al., 2002; Waldemer
and Tratnyek, 2006 ), BTEX (Gardner, 1996; Rudakov and Lobachev,
2000; Waldeme r and Tratnyek, 2006 ), substituted phenols (Jin
et al., 2003; Waldemer and Tratnyek, 2006 ) and PAHs (Forsey,
2004), in aqueous phase. However, the potential of solid potassium
permanganate to oxidize VOC vapours in unsaturated zone is cur-
rently unknown .
In this study, we demonst rate the ability of solid potassium per-
manganate to oxidize VOC vapours.
Currently, the literature lacks data on the reaction between so-
lid oxidants such as permanganate and vapour phase of contami-
nants. Therefore, we planned a series of batch experiments with
two objectives: (1) to evaluate the ability of solid potassium per-
manganate to fully oxidize vapour phase contaminants, (2) to
determine kinetic parameters for TCE, ethanol, and toluene oxida-
tion by solid potassium permang anate.
2. Materials and methods
2.1. Materials
We used 4.8 10
6
, 3.5 10
6
, 2.3 10
6
mole of TCE, etha-
nol, and toluene vapours, respectively. These values were calcu-
lated based on 1.5 mL of gas samples (under normal condition s)
which were obtained from the headspace of their highly pure li-
quid phases. Solid potassium permanganate of 99% purity was ob-
tained from Sigma–Aldrich. The required potassium permanganate
for complete oxidation of VOCs was calculated based on the fol-
lowing reactions for TCE, ethanol, and toluene, respectively:
C
2
HCl
3ðgÞ
þ2KMnO
4ðsÞ
!2K
þ
þ3Cl

þ2MnO
2ðsÞ
þH
þ
þ2CO
2ðgÞ
ð1Þ
C
2
H
5
OH
ðgÞ
þ4KM nO
4ðsÞ
þ4H
þ
!4K
þ
þ4MnO
2ðsÞ
þ2CO
2ðgÞ
þ5H
2
Oð2Þ
C
6
H
5
CH
3ðgÞ
þ12KMnO
4ðsÞ
þ12H
þ
!12K
þ
þ12MnO
2ðsÞ
þ10H
2
Oþ7CO
2ðgÞ
ð3Þ
The required amount of potassiu m permangana te for oxidizin g
4.8 10
6
mole of TCE, 3.5 10
6
mole of ethanol, and 2.3 10
6
-
mole of toluene were estimated to be 1.25, 2.22, and 4.44 mg,
respective ly. These were calculated based on reactions in aqueou s
environm ent, assuming a full dissolution of crystals. In dissolved
form, potassium permangana te may be fully available for oxidation.
But, in the solid form only the surface of potassium permangana te
grains is in contact with the gas phase. Accordingly , more potas-
sium perman ganate is needed to avoid limitation in the degrada tion
rate. Hence, excess amount of potassium permangana te (2.703 g)
was used for each batch.
Potassium permanganate grains were put inside12- mL trans-
parent glass vials, which were capped with a hard septum to pre-
vent any leakage. VOC vapour was injected using a gas tight
syringe (2.5 mL Hamilton, SGE) and 16 mm disposab le needles
(£0.5 mm, Terumo).
In order to get kinetic parameters, three batch experiments at
three different initial amounts of vapour and potassium permanga-
nate were performed for all compounds (Table 1). All experiments
were carried out in duplicate. For each experiment, we prepared
several identical batches and each batch was allocated to a given
sampling time.
A control experiment was also performed in duplicate for each
compound to ensure that the loss of target compound due to leak-
age was negligible over the course of the experiments . To prepare a
control batch, a 12-mL transparent glass vial was capped with a
hard septum. Then VOC vapour was injected into the vial.
All experiments were carried out in a vertical rotary shaker, at
room temperat ure, 20 ± 2 °C, and air humidity of 37 ± 2%, which
is also the initial humidity inside the vials.
2.2. Sampling and measurem ents
Reaction and control batches were periodically sampled using a
gas tight syringe until no detectable concentr ation was found in
the reaction vial. To eliminate the effect of pressure drop due to
sampling , each vial was used only once.
The concentratio ns of target compounds , TCE, ethanol, and tol-
uene were measure d by a gas chromatograp h (GC). Gas samples of
Table 1
Initial experim ental conditions for each compound.
Compound Experiment n(mol) M
KMnO4
(g) A(cm
2
)V(cm
3
)S
0
(cm
1
)
TCE 1 4.8 10
6
2.703 2703 10.5 257.43
2 2.4 10
6
2.703 2703 10.5 257.43
3 4.8 10
6
1.351 1351.5 11.25 120.13
Ethanol 1 3.5 10
6
2.703 2703 10.5 257.43
2 1.75 10
6
2.703 2703 10.5 257.43
3 3.5 10
6
1.351 1351.5 11.25 120.13
Toluene 1 2.3 10
6
2.703 2703 10.5 257.43
2 1.15 10
6
2.703 2703 10.5 257.43
3 2.3 10
6
1.351 1351.5 11.25 120.13
n= Initial number of VOC moles. M
KMnO4
= mass of solid potassium permanganate. A= surface area of potassium permanganate, V= volume of the gas phase. S
0
= initial
relative surface area.
M.G. Mahmoodlu et al. / Chemosphere 91 (2013) 1534–1538 1535

2 mL were taken using the headspace syringe of the GC from each
vial. Then, samples were injected into the GC. The GC (Agilent
Technologie s 6850) equipped with a capillary column
(0.25 mm 60 m), a flame ionization detector, and a purge and
trap.
Specific surface area of potassium permang anate was measured
using 10-point Brunauer–Emmett–Teller (BET) method by a Nova
3000 from Quantachrome . Performa nce of this machine was con-
trolled using reference 173 from Community Bureau of Reference.
Samples were degassed at 120 °C overnight before measureme nts.
The relative surface area was calculated as the surface area per vol-
ume of gas (Table 1).
To calculate the amount of the potassium permanganate con-
sumption, at end of experiment potassium permanganate grains
were dissolved in deionized (DI) water and its concentr ation was
measured using a UV-spectrop hotometer (UV-1800, Shimadzu) at
a wavelength of 525 nm.
3. Results and discussion
3.1. Oxidation study
Fig. 1 depicts the normalized concentr ation (C/C
0
) of the target
compounds as a function of time, where Cdenotes the observed
concentratio n of the target compound for a given time and C
0
is
the initial concentratio n of the target compound . Degradat ion of
target compound s shows an exponential trend, as indicated by
the fitted formula in the graph (Fig. 1). These results also show that
solid potassium permang anate was able to rapidly oxidize the va-
pour phase of TCE and ethanol. Toluene was also degraded but less
rapidly.
No VOC intermedi ates or by-products were found in vapour
samples. During the experiment, potassium permang anate crystals
turned into dark colour, which is the colour of a coating layer of
produced manganese dioxide (MnO
2
).
3.2. Kinetics analysis of data
Since the degradat ion of three reactants showed an exponential
trend, we assumed that the kinetics followed a first-order reaction
rate. We also assumed that only surface of solid potassium per-
manganate reacts with compounds . So, to a proper calculation of
the reaction rate coefficient, we should have an equation that in-
volves the physical properties of potassium permanganate , such
as the surface area and mass of potassium permanganate . Such
an equation may be written as:
dC
dt ¼kCS ð4Þ
where kdenotes the reaction rate constant, Cis the vapour concen-
tration of compound [ML
3
], tis time [T], and Sis the relative sur-
face area of solid potassiu m permangana te [L
1
], which is defined
as:
S¼A
Vð5Þ
where Ais the surface area of the potassium permangana te [L
2
] and
Vis the volume of the gas phase [L
3
].
First, we assumed the relative surface area not to alter signifi-
cantly during the course of the reaction. To validate this assump-
tion, we determined the amount of potassium permanganate that
was consumed, at the end of the experime nt. This was done by dis-
solving potassium permanganate grains which were used in the
experiments in DI water and then using a spectrophot ometer to
determine its mass. We compared this to the initial mass and the
result showed that there was no significant consump tion of solid
potassium permanganate during our experiments .
With Sset equal to S
0
Eq. (4) can be solved to obtain:
1
S
0
Ln C
C
0
¼kt ð6Þ
where S
0
denotes the initial relative surface area of potassium per-
mangan ate [L
1
].
According to Eq. (6), plot of 1/ S
0
Ln C/C
0
vs. time should yields a
straight line. Then, the reaction rate constant kcan be obtained
from the slope of this line.
We used all data from Experiments 1, 2, and 3 to estimate kfor
each compound. Fig. 2 shows that the plots of 1/ S
0
Ln C/C
0
vs. time
for all compounds . The square of linear correlation coefficients (R
2
)
obtained for TCE, ethanol, and toluene were 9.6 10
1
, 9.9 10
1
,
and 9.9 10
1
, respectively . Results suggest that the degradation
of the target compound s can be modelled by Eq. (6) as long as suf-
ficient relative surface area of potassium permanganate is avail-
able. These results also show the accuracy of reaction rate
constant s which are given in Table 2.
Fig. 1. Degradation of TCE, ethanol, and toluene vs. time using experiment 1 (exp.
x–y:xdenotes number of experiment and yis the experiment repetition).
1536 M.G. Mahmoodlu et al. / Chemosphere 91 (2013) 1534–1538

We compared results of our experiments with the oxidation of
VOCs in aqueous phase reported in the literature (Waldemer and
Tratnyek, 2006 ). We found that the oxidation process in both
phases follows a first-order model. This comparison also revealed
that the oxidation rates for VOCs in vapour phase are much smaller
than for aqueous phase. However, in both phases, the reaction rate
for TCE is higher than for ethanol and toluene.
As mentioned above, as a result of oxidation, MnO
2
is produced
and coats the grains. This may affect the efficiency of oxidation
process. To analyze the effect of surface coating, we accounted
for the reduction of the relative surface area during the experi-
ment. This was done by supplem enting Eq. (4) with an equation
relating the relative surface area to the MnO
2
concentr ation. This
resulted in the following equation:
dC
dt ¼kC S
0

x
c
ðC
0
CÞ
 ð7Þ
where
x
is the number of moles of MnO
2
produced per mole of tar-
get compound (based on stoichiom etry reaction) and
c
is the coat-
ing factor (number of moles of produce d MnO
2
per area of
potassiu m permangana te grains) [ML
2
].
The numerical solution of Eq. (7) was fitted to the TCE experi-
mental data. Results showed a maximum reduction of around 4%
in the relative surface area. This confirms the validity of our
assumpti on that there is a negligible change in the relative surface
area of potassium permang anate during our TCE experiments.
Although the largest amount of MnO
2
was produced during
degradat ion of ethanol and toluene (based on stoichiomet ry reac-
tion), there was still a large excess of the relative surface area dur-
ing the ethanol and toluene experime nt (based on the amount of
potassium permanganate we used). Moreover, we calculated the
amount of used potassium permanganate for all three compounds.
On all cases, this was found to be small fraction of initial amount
(around 4%).
4. Conclusion s
In this study, we investiga ted the kinetic paramete rs of both
chlorinat ed and non-chlorin ated hydrocarbo n vapours by solid
potassium permanganate under room temperature and humidity
condition s. Results showed that potassium permanganate is able
to oxidize the vapour of TCE and ethanol, and toluene. We also
found that TCE and ethanol in vapour phase can be rapidly oxi-
dized by solid potassium permanganate . However, toluene was de-
graded slower. A linear kinetic oxidation model, based on the
concentr ation of VOC in gas and a constant relative surface area,
effectively predicted the rate of TCE, ethanol, and toluene degrada-
tion. Results revealed that the reaction rate constant s for TCE, eth-
anol, and toluene are 2.0 10
6
cm s
1
, 1.7 10
7
cm s
1
, and
7.0 10
8
cm s
1
, respectivel y. Results also showed that the
amount of used potassium permanganate for all three compounds
was small fraction of initial amount (around 4%).
These findings will be helpful in designing a horizontal perme-
able reactive barrier with solid potassium permang anate in unsat-
urated zone for vapour intrusion. The performance of such
methodol ogy may be affected by moisture content, pH, and tem-
perature of the soil matrix. Also, one has to consider the health ef-
fects of by-product gases such as ethane (Pant and Pant, 2010 ) and
methane (Freitas et al., 2010 ) that can be produced under anaero-
bic biodegradat ion of TCE and ethanol, respectively .
Acknowled gments
The authors would like to thank Jan Kubiak (Wageningen Uni-
versity), Pieter J. Kleingeld (Utrecht University) and Pieter Van Rij-
wijk (NIOO-CEME) for their technical assistance, Dr. Kotai Laszlo
(Hungarian Academy of Sciences) and Dr. Hamid Nick (Utrecht
Universit y) for providing critical comments throughout the course
of this research and Tom Bosma (Utrecht University) for his
thoughtful review of this manuscript. Through review comments
by two anonymous referees helped to improve the manuscr ipt.
This work was supported by Ministry of Science, Research and
Technolo gy of Iran.
References
Albergaria, J.T., Alvim-Ferraz, M.dc.M, Delerue-Matos, C., 2012. Remediation of
sandy soils contaminated with hydrocarbons and halogenated hydrocarbons by
soil vapour extraction. Environ. Manage. 104, 195–201.
Berscheid, M., Burger, K., Hutchison, N., Muniz-Ghazi, H., Renzi, B., Ruttan, P.,
Sterling, S., 2010. Proven Technologies and Remedies Guidance. Remediation of
Fig. 2. Plot of 1/ S
0
Ln C/C
0
(denoted by y) vs. time (denoted by x) for evaluating k
following Eq. (6).
Table 2
Reaction rate constants for oxidat ion of TCE, ethanol, and toluene in vapour phase at
20 °C.
Compound K(cm s
1
)R
2
TCE 2.0 10
6
9.6 10
1
Ethanol 1.7 10
7
9.8 10
1
Toluene 7.0 10
8
9.9 10
1
R
2
= the square of the correlation coefficient.
M.G. Mahmoodlu et al. / Chemosphere 91 (2013) 1534–1538 1537

Chlorinated Volatile Organic Compounds in Vadose Zone Soil. California
Department of Toxic Substances Control. 154 pp.
Capiro, N.L., Stafford, B.P., Rixey, W.G., Bedient, P.B., Alvarez, P.J.J., 2007. Fuel-grade
ethanol transport and impacts to groundwater in a pilot-scale aquifer tank.
Water Res. 41, 656–664.
Damm, J.H., Hardacre, C., Kalin, R.M., Walsh, K.P., 2002. Kinetics of the oxidation of
methyl tert-butyl ether (MTBE) by potassium permanganate. Water Res. 36,
3638–3646.
De Nevers, N., 2000. Air Pollution Control Engineering, second ed. McGraw-Hill
International, Boston.
EPA, 2011. Toxicological Review of Trichloroethylene. CAS No. 79-01-6.
Forsey, S.P., 2004. In Situ Chemical Oxidation of Creosote/Coal Tar Residuals:
Experimental and Numerical Investigation. PhD. thesis, University of Waterloo.
Freitas, J.G., Fletcher, B., Aravena, R., Baker, J.F., 2010. Methane production and
isotopic fingering in ethanol fuel contaminated sites. Groundwater 48, 844–
857.
Gardner, K.A., 1996. Permanganate Oxidations of Aromatic Hydrocarbons in
Aqueous and Organic Solution. PhD thesis, University of Washington.
Hood, E.D., Thomson, N.R., Grossi, D., Farquhar, G.J., 2000. Experimental
determination of the kinetic rate law for the oxidation of perchloroethylene
by potassium permanganate. Chemosphere 40, 1383–1388.
Huang, K.C., Hoag, G.E., Chheda, P., Woody, B.A., Dobbs, G.M., 1999. Kinetic study of
oxidation of trichloroethylene by potassium permanganate. Environ. Eng. Sci.
16, 265–274.
Jaky, M., Szammer, J., Simon-Trompler, E., 2000. Kinetics and mechanism of the
oxidation of ketones with permanganate ions. J. Chem. Soc. Perkin Trans. 2,
1597–1602.
Jin, Z., Gui-bai, L., Jun, M., 2003. Effects of chlorine content and position of
chlorinated phenols on their oxidation kinetics by potassium permanganate.
Environ. Sci. 15, 342–345.
Johnson, R., Pankow, D., Bender, C.P., Zogorski, J., 2000. Target compounds-to what
extent will past releases contaminate community water supply wells? Environ.
Sci. Technol. 34, 210A–217A.
Kao, C.M., Huang, K.D., Wang, J.Y., Chen, T.Y., Chien, H.Y., 2008. Application of
potassium permanganate as an oxidant for in situ oxidation of
trichloroethylene-contaminated groundwater: a laboratory and kinetics study.
Hazard. Mater. 153, 919–927.
Kim, H.H., Ogata, A., Futamura, S., 2007. Complete oxidation of volatile organic
compounds (VOCs) using plasma-driven catalysis and oxygen plasma. Int. J.
Plasma Environ. Sci. Technol. 1, 46–51.
Mackay, D., De Sieyes, N., Einarson, M., Feris, K., Pappas, A., Wood, I., Jacobson, L.,
Justice, L., Noske, M., Wilson, J., Adair, C., Scow, K., 2007. Impact of ethanol on
the natural attenuation of MTBE in a normally sulfate-reducing aquifer. Environ.
Sci. Technol. 41, 2015–2021.
Pant, P., Pant, S., 2010. A review: advances in microbial remediation of
trichloroethylene (TCE). Environ. Sci. 22, 116–126.
Rudakov, E.S., Lobachev, V.L., 2000. The first step of oxidation of alkylbenzenes by
permanganates in acidic aqueous solutions. Russ. Chem. Bull. 49, 761–777.
Urynowicz, M.A., 2008. In-situ chemical oxidation with permanganate: assessing
the competitive interactions between target and nontarget compounds. Soil
Sedim. Contam. 17, 53–62.
Waldemer, R.H., Tratnyek, P.G., 2006. Kinetics of contaminant degradation by
permanganate. Environ. Sci. Technol. 40, 1055–1061.
Yan, Y.E., Schwartz, F.W., 2000. Kinetics and mechanisms for TCE oxidation by
permanganate. Environ. Sci. Technol. 34, 2535–2541.
Yu, K.P., Lee, G.W.M., 2007. Decomposition of gas-phase toluene by the combination
of ozone and photocatalytic oxidation process (TiO
2
/UV, TiO
2
/UV/O
3
, and UV/
O
3
). Appl. Catal. B: Environ. 75, 29–38.
1538 M.G. Mahmoodlu et al. / Chemosphere 91 (2013) 1534–1538