Treatment of acetamiprid insecticide from artificially contaminated water by colloidal manganese dioxide in the absence and presence of surfactants

Article abstract of DOI:10.1039/c4ra09685a

Acetamiprid is one of the most important pesticides and is effective against a number of insects. The increasing use of insecticides in the agricultural field is associated with a significant risk to water resources and aquatic systems. Thus the degradation of such compounds, after fulfillment of their insecticidal role, is essential to eliminate or minimize the contamination of water. The degradative treatment of acetamiprid insecticide from artificially contaminated water by water soluble colloidal MnO₂ in acidic medium (HClO₄) has been studied spectrophotometrically in the absence and presence of surfactants. The experiments have been performed under the pseudo-first-order reaction conditions with respect to MnO₂. The degradation kinetics has been observed to be first-order with respect to MnO₂ while fractional-order in both acetamiprid and HClO₄. The anionic surfactant, sodium dodecyl sulfate (SDS) has been observed to be ineffective. On the other hand the reaction in the presence of cationic surfactant, cetyltrimethyl ammonium bromide (CTAB) could not be followed as well because it possesses a positive charge opposite to that of colloidal MnO₂ causing flocculation and therefore could not be studied further. However, the addition of non-ionic surfactant, polyethylene glycol tert-octylphenyl ether (TX-100) accelerates the reaction rate. The catalytic effect of TX-100 has been discussed in the light of the available mathematical model. The kinetic data have been exploited to generate the various activation parameters for the oxidative degradation of acetamiprid by colloidal MnO₂ in the absence and presence of non-ionic surfactant, TX-100.

Full text of DOI:10.1039/c4ra09685a

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PAPER
Treatment of acetamiprid insecticide from
artificially contaminated water by colloidal
manganese dioxide in the absence and presence of
surfactants
Cite this: RSC Adv., 2014, 4, 62844
Qamruzzaman and Abu Nasar*
Acetamiprid is one of the most important pesticides and is effective against a number of insects. The
increasing use of insecticides in the agricultural field is associated with a significant risk to water
resources and aquatic systems. Thus the degradation of such compounds, after fulfillment of their
insecticidal role, is essential to eliminate or minimize the contamination of water. The degradative
treatment of acetamiprid insecticide from artificially contaminated water by water soluble colloidal MnO
in acidic medium (HClO ) has been studied spectrophotometrically in the absence and presence of
surfactants. The experiments have been performed under the pseudo-first-order reaction conditions
with respect to MnO . The degradation kinetics has been observed to be first-order with respect to
MnO while fractional-order in both acetamiprid and HClO . The anionic surfactant, sodium dodecyl
2
4
2
2
4
sulfate (SDS) has been observed to be ineffective. On the other hand the reaction in the presence of
cationic surfactant, cetyltrimethyl ammonium bromide (CTAB) could not be followed as well because it
2
possesses a positive charge opposite to that of colloidal MnO causing flocculation and therefore could
not be studied further. However, the addition of non-ionic surfactant, polyethylene glycol tert-
octylphenyl ether (TX-100) accelerates the reaction rate. The catalytic effect of TX-100 has been
discussed in the light of the available mathematical model. The kinetic data have been exploited to
generate the various activation parameters for the oxidative degradation of acetamiprid by colloidal
Received 3rd September 2014
Accepted 12th November 2014
DOI: 10.1039/c4ra09685a
www.rsc.org/advances
2
MnO in the absence and presence of non-ionic surfactant, TX-100.
human health as well. Hence the treatment of the compound is
essential to eliminate or at least minimize its negative impacts.
The possible treatment of a pesticide is based on the split-
Introduction
0
Acetamiprid, (E)-N-[(6-chloro-3-pyridyl) methyl]-N -cyano-N-
methyl-acetamidine, is a systematic insecticide belonging to the ting of molecules by photochemical, biological and chemical
neonicotinoid group. It shows excellent efficacy against aphids, processes. The photochemical degradation of acetamiprid in
10–13
leaoppers, whiteies, thrips, leaf beetles, leaf miner moths, soil has been studied several investigators.
The degradation
termites, etc. in a wide range of crops such as okra, gram, studies on acetamiprid have also been conducted by different
1
–8
mustard, strawberry, cotton, tea, etc. In spite of advantageous investigators in different regions and locations under varying
14,15
and unavoidable use insecticides oen contaminate the envi- climatic conditions and temperatures.
Although the chem-
ronment and cause public health problems due to their high ical degradation process would be simple and economical for
toxicity and long persistence. Clinical studies have indicated the treatment of waste water contaminated by acetamiprid, a
that the human intake of acetamiprid causes physiological literature survey reveals that so far no systematic efforts have
disturbance resulting in nausea, vomiting, muscle weakness, been made to conduct the study in this direction. It is well
9
hypothermia, convulsions, tachycardia, hypotension, etc.
known that many organic substances undergo chemical
ꢀ
3
ꢁ
Because of high water solubility (4.25 g dm at 25 C) this decomposition in the presence of manganese compounds and
16
th
insecticide has large potential to contaminate the water especially its dioxide (MnO
resources. Thus, agricultural applications of acetamiprid are abundant element in the earth's crust and available in variable
associated with the signicant risk to the environment and amounts depending upon region and location. The MnO
). In fact manganese is 12 most
2
2
particles present in the earth's crust and natural water have
potential for oxidative degradation of humic and organic
Department of Applied Chemistry, Faculty of Engineering and Technology, Aligarh substances including pesticides. However, the oxidizing power
Muslim University, Aligarh – 202 002, India. E-mail: abunasaramu@gmail.com;
of MnO
2
is limited due to its insolubility under ordinary
Fax: +91 0571 2700528; Tel: +91 0571 2700920
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17–19
ꢀ
2ꢀ
+
2ꢀ
+ 2H / 8MnO + 6SO
4
conditions. Fortunately, Perez-Benito and co-workers
in
8MnO4 + 3S O
2
+ H O (1)
3
2
2
their pioneer work have developed a method to prepare a water
soluble form of perfectly transparent colloidal MnO2 by
The required volume of sodium thiosulfate solution (20.0
3
ꢀ2
ꢀ3
employing the redox reaction between potassium permanga- cm , 1.88 ꢂ 10 mol dm ) was slowly added to standard
ꢀ
3
nate and sodium phosphate. The water soluble form of colloidal solution of potassium permanganate (10.0 ml, 0.1 mol dm
)
3
MnO
2
is advantageous over its insoluble form due to the higher and the reaction mixture was then diluted to 1 dm in a stan-
oxidizing power and feasibility of monitoring the reaction by dard ask. In this way the solution prepared to be dark brown
conventional UV-visible spectrophotometry. The water soluble transparent and remained stable for over a month.
colloidal MnO
2
has successfully been used for the oxidative
A method based on Rayleigh's scattering law was used to
degradation studies of a number of pesticides and other organic check the formation of colloidal particles. According to this law
1
8,20
21
22
compounds such as formic acid,
D-fructose, D-glucose,
the absorbance (A) due to scattering of light by a solution of
23
24
25
26
glycyl-glycine, glycolic acid, DL-malic acid, mandelic acid,
colloidal particle is inversely proportional to the fourth power of
27
19,28
29
30
31
metribuzin, oxalic acid,
thiourea and tricyclazole by the wavelength (l). The plot between log A and log l shown in
employing UV-visible spectrophotometric technique. As so far Fig. 1 is linear with a slope of 4.19, which is slightly greater than
the degradation of acetamiprid by colloidal MnO
has not been the theoretical value of 4.0. The fulllment of Rayleigh's law is
2
studied the present investigation has been planned with the indicative of the spectrum due to scattering of light by colloidal
3
2
prime objective to conduct measurements in this direction. In particles instead of absorption of light by non-colloidal species.
the present study the degradation kinetics of acetamiprid
The formation of water soluble colloidal particles of MnO
2
insecticide in articially contaminated water by colloidal MnO2 was also independently conrmed by adding the minimum
in acidic medium (HClO ) has been thoroughly investigated. amount of different electrolytes necessary for their precipita-
4
1
7
HClO
complexing nature of perchlorate ion, ClO
tants are commonly used in pesticide formulation to increase viz., LiCl, NaCl, KCl, NH
the solubility of pesticides and also to enhance their effective- mixed into the solution with constant stirring. Further details of
4
was used as the acidifying agent due to the non- tion. For this purpose appropriate amount of the different
ꢀ
29
4
.
Since surfac- electrolytic salts containing monovalent and divalent cations,
Cl, MgCl , CaCl , SrCl and BaCl were
4
2
2
2
2
30
ness, it was also considered worth to extend the study in the the method have been described elsewhere. With each elec-
presence of three common surfactants such as cetyltrimethyl trolyte, the appearance of brownish precipitate in the reaction
ammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and mixture was observed, which indicated the formation of water
polyethylene glycol tert-octylphenyl ether (TX-100). A selection soluble form of colloidal MnO
2
.
of these surface active agents is based on the criteria of picking
These observations conrm that water soluble form of MnO
2
the one member from each category of cationic, anionic and as prepared from KMnO
non-ionic compounds as chosen in respective order. The kinetic species.
data have been analyzed in the light of Arrhenius and Eyring
4 2 2 3
and Na S O is in the form of colloidal
theories and different activation parameters have also been
determined.
Kinetic measurements
The absorption spectrum of aqueous KMnO
Fig. 2 has a peak (lmax) at 525 nm. With the addition of Na
solution, the band gradually disappeared with the appearance
4
solution shown in
2 2 3
S O
Experimental
Materials
Laboratory reagent grade acetamiprid (Parijat Industries, India),
scintillation grade TX-100 (CDH, India) and analytical reagent
grade each potassium permanganate and sodium thiosulfate
(
(
Qualigens, India), perchloric acid (Merck, Germany), H SO
2 4
Qualigens, India), CTAB and SDS (CDH, India) were used in the
present investigation. Following analytical reagent grade salts:
LiCl, NaCl, KCl, NH Cl, MgCl , CaCl , BaCl (each from SRL,
India) and SrCl (CDH, India) were used for the characterization
of colloidal MnO . The water used was puried by deionization
4
2
2
2
2
2
followed by double distillation. This doubly distilled, deionized
water was used throughout the experimental studies.
Preparation and characterization of colloidal MnO2
The stock solution of colloidal MnO2 was prepared by the
17–20
method described by Perez-Benito and coworkers.
preparation involves the reduction of potassium permanganate
by sodium thiosulfate in dilute H SO medium (pH 4.7),
The
] ¼ 8.0 ꢂ 10ꢀ mol dm ) and
5
ꢀ3
2
4
Fig. 1 Plots of log A versus log l ([MnO
temperature ¼ 30 C.
2
ꢁ
according to the following stoichiometry:
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Fig. 3 Plot of log(absorbance) versus time for the degradation of
Fig. 2 Absorption spectra of KMnO
4
(ꢄ) and colloidal MnO
2
(o) i.e.
acetamiprid by colloidal MnO
2
(reaction conditions: [acetamiprid] ¼
reaction product of KMnO
4
2
and Na S
2
O .
3
ꢀ3
ꢀ3
ꢀ5 ꢀ3
2
5.0 ꢂ 10 mol dm , [MnO ] ¼ 8.0 ꢂ 10 mol dm , [HClO
4
] ¼ 6.0
ꢀ4
ꢀ3
ꢁ
ꢂ 10 mol dm , temperature ¼ 30 C).
of a new single broad band maximum at 360 nm. The new
stabilized spectrum is due to formation of colloidal MnO and
2
2 4
Effect of concentrations of acetamiprid, MnO and HClO on
therefore wavelength of 360 nm was chosen to execute the
kinetic runs. Kinetic experiments were performed by taking a
requisite quantity of aqueous solution of acetamiprid in a
reaction vessel kept in a thermostated water bath. The reaction
vessel was allowed to remain in the water bath for sufficient
the reaction rate
The dependence of the rate of reaction on the concentration of
acetamiprid has been studied by conducting the kinetic
measurements at the varying concentration of acetamiprid
ꢀ
3
ꢀ2
ꢀ3
(
1.0 ꢂ 10 to 1.5 ꢂ 10 mol dm ) keeping the concentrations of
time to attain the desired temperature with an accuracy of
ꢀ5 ꢀ3 ꢀ4 ꢀ3
MnO (8.0 ꢂ 10 mol dm ) and HClO (6.0 ꢂ 10 mol dm
)
ꢃ0.5 ꢁC. The kinetic studies were carried out by adding the
2
4
ꢁ
constant at a typical temperature of 30 C. Under the said
conditions, the values of observed rate constant (kobs) so
obtained are plotted against the concentration of acetamiprid
in Fig. 4. This gure clearly indicates that the variation is
nonlinear and there is a continuous increase in the values of the
rate constant with increasing concentration of acetamiprid up
2 4
calculated volume of colloidal solution of MnO , HClO and
surfactants corresponding to their selected concentrations. The
progress of the reaction was monitored spectrophotometrically.
The absorbance of unreacted MnO in the reaction mixture was
2
taken by UV-visible spectrophotometer (Perkin Elmer, Model-
lambda 25, USA) at an optimized wavelength of 360 nm (i.e.
ꢀ
2
ꢀ3
to 1.0 ꢂ 10 mol dm beyond which the rate constants tend to
l
¼ 360 nm). The fulllment of Beer's law was checked and
max
found to be validated in an experimental concentration range
ꢀ5
ꢀ4
ꢀ3
(
6.0 ꢂ 10 to 1.6 ꢂ 10 mol dm ) of MnO
2
. The measure-
ments were taken under the varying conditions of concentra-
tions (acetamiprid, MnO
temperature (20–50 C).
2
,
HClO
4
and surfactants) and
ꢁ
Results and discussion
General consideration
All the measurements were formulated under the pseudo-rst-
order reaction conditions in which concentrations of acet-
amiprid and HClO were taken in large excess over MnO . The
4 2
pseudo-rst-order rate constants were calculated from the slope
of log A versus time plot. The plot of log A versus time at a typical
ꢀ
3
ꢀ3
ꢀ3

xed concentration of acetamiprid (5.0 ꢂ 10
mol dm ),
ꢀ5
ꢀ3
ꢀ4
MnO
2
(8.0 ꢂ 10 mol dm ) and HClO
4
(6.0 ꢂ 10 mol dm
)
ꢁ
at 30 C shown in Fig. 3 is represented by a straight line with
2
r
¼ 0.989. This indicates that the reaction obeys rst-order
Fig. 4 Effect of [acetamiprid] on kobs for the degradation of acet-
ꢀ
5
kinetics with respect to MnO
conditions.
2
under the adopted reaction
amiprid by colloidal MnO
2
(reaction conditions: [MnO
2
] ¼ 8.0 ꢂ 10
ꢀ3
ꢀ4
ꢀ3
ꢁ
mol dm , [HClO
4
] ¼ 6.0 ꢂ 10 mol dm , temperature ¼ 30 C).
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ꢀ
3
ꢀ3
ꢀ5
acetamiprid (5.0 ꢂ 10 mol dm ) and MnO
2
(8.0 ꢂ 10 mol
ꢀ3
ꢁ
dm ) at a constant temperature of 30 C. The plot of k
vs.
obs
[
HClO ] shown in Fig. 6 clearly indicates that rate constant
4
increases with increase in [HClO ] throughout the entire
4
concentration range. The linear plot (Fig. 6) gives a positive
intercept on kobs axis indicating the existence of acid indepen-
dent and acid dependent paths. The nature of rate constant
with acid concentration has further resolved in a better way by
making a double logarithmic plot between log kobs and log
[
(
HClO ] (Fig. 7). This plot is also linear with a slope of 0.236
4
2
r ¼ 0.988) which is indicative of fractional order dependence
of the degradation of acetamiprid with respect to [HClO ]. On
4
the basis of above observations the rate (n) of degradation of
acetamiprid by colloidal MnO
2 4
in the HClO medium may be
represented by the following experimental rate law equation:
0
.236
n ¼ ꢀd[MnO ]/dt ¼ (k + k [HClO ]
)
Fig. 5 Effect of log[acetamiprid] on log kobs for the degradation of
2
I
D
4
0
.315
acetamiprid by colloidal MnO
2
(reaction conditions: [MnO
2
] ¼ 8.0 ꢂ
[acetamiprid]
[MnO ]
(2)
2
ꢀ5
ꢀ3
ꢀ4
ꢀ3
ꢁ
10
4
mol dm , [HClO ] ¼ 6.0 ꢂ 10 mol dm , temperature ¼ 30 C).
I D
where, k and k are rate constants for the acid independent and
dependent paths, respectively.
remain constant. The plot between log kobs and log[acet-
The acid independent reaction path taking place may
2
amiprid] is linear (Fig. 5) with a slope of 0.315 (r ¼ 0.996) presumably occur by the adsorption of acetamiprid on the
indicating that the reaction is fractional-order (i.e. 0.315) with colloidal particles of MnO followed by reaction between
respect to acetamiprid.
adsorbed acetamiprid molecule and one of the MnO molecules
In this context, it is worth relevant to notice that the oxidative pertaining to the colloidal surface leading to the reaction as
2
2
27
degradation of similar pesticides such as metribuzin and tri- represented by the following plausible mechanism:
30
cyclazole by colloidal MnO
2
has been observed to obey
fast
*
Acetamiprid þ ðMnO
2
Þx )
acetamiprid ꢀ ðMnO
2
Þx
(3)
fractional-order reaction kinetics. These ndings are also in
conformity with the observation of fractional-order reaction
kinetics for the oxidative degradation of a number of other
slow
Þ ƒƒƒƒƒ!
Acetamiprid ꢀ ðMnO
2
x
2
1
23
organic compounds such as D-fructose, glycyl-glycine, gly-
ðMnO
2
Þ
þ MnO þ O-acetamiprid
(4)
xꢀ1
24
29
colic acid and thiourea by colloidal MnO in HClO medium.
2
4
where, (MnO
2
)
x
and O-acetamiprid represent colloidal MnO
2
and
The effect of concentration of HClO (in the range of 2.0 ꢂ
4
ꢀ4
ꢀ3
ꢀ3
intermediate oxidative degrades of acetamiprid, respectively.
On the other hand, the acid dependent path comprises with
the adsorption of two hydrogen ions, in addition to acetamiprid
10
to 1.2 ꢂ 10 mol dm ) was also studied by conducting a
series of kinetic measurements at the xed concentrations of
Fig. 6 Effect of [HClO
4 4
] on kobs for the degradation of acetamiprid Fig. 7 Effect of log[HClO ] on log kobs for the degradation of acet-
ꢀ3
by colloidal MnO
2
(reaction conditions: [acetamiprid] ¼ 5.0 ꢂ 10
amiprid by colloidal MnO
2
(reaction conditions: [acetamiprid] ¼ 5.0 ꢂ
ꢀ
3
ꢀ5
ꢀ3
ꢁ
ꢀ3
ꢀ3
ꢀ5 ꢀ3
ꢁ
mol dm , [MnO
2
] ¼ 8.0 ꢂ 10 mol dm , temperature ¼ 30 C).
10 mol dm , [MnO
2
] ¼ 8.0 ꢂ 10 mol dm , temperature ¼ 30 C).
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ꢀ
3
ꢀ3
molecule, on the colloidal surface of MnO
2
leading to the about 4.0 ꢂ 10 mol dm beyond which it tends to become
degradation of acetamiprid by the following plausible stagnant. Obviously the catalytic effect is more pronounced in
mechanism:
lower concentration range.
While studying the kinetics of the reaction between colloidal
manganese dioxide and formic acid in aqueous perchloric acid
solution, Tuncay et al. have developed an empirical model to
fast
þ
*
Acetamiprid þ ðMnO
2
Þ þ 2H )
x
þ
20
acetamiprid ꢀ ðMnO
2
Þ ꢀ ðH Þ
(5)
x
2
explain the catalytic effect of the surfactant, TX-100. Later on
þ
slow
Þ ꢀ ðH Þ ƒƒƒƒƒ!
this model has successfully been used to describe the role of TX-
Acetamiprid ꢀ ðMnO
2
x
2
1
00 for the oxidative degradation of a number of compounds by
2
þ
ðMnO
2
Þxꢀ1 þ Mn þ H
2
O þ O-acetamiprid (6)
22–27,30
colloidal MnO by different investigators.
According this
2
concept the rate constant (k ) in the presence of the surfactant
J
TX-100 has to obey the following relationship:
Effect of surfactants
1
/(k
J
ꢀ kobs) ¼ a + b/[TX-100]
(7)
In the present investigation commonly used surfactants such as
CTAB (cationic), SDS (anionic) and TX-100 (non-ionic) have
been used to study their role on the degradation kinetics of
acetamiprid. The concentrations of each surfactant were
selected above its critical micelle concentration (cmc). The cmc
values of the chosen surfactants, i.e. CTAB, SDS and TX-100 in
where a and b are empirical constants. Thus, according to the
Tuncay concept a plot of 1/(kJ ꢀ kobs) versus 1/[TX-100] should
be linear, which was also observed in the present case (Fig. 9)
ꢀ
3
2
with a ¼ 512 s and b ¼ 8.034 mol dm s (r ¼ 0.991).
In order to further explain the role of TX-100, an alternative
the presence of HClO
4
under experimental conditions were
20
empirical equation was also suggested by Tuncay et al.
determined by electrical conductivity measurements and found
ꢀ
4
ꢀ3
ꢀ4
ꢀ3
to be 5.2 ꢂ 10 , 4.6 ꢂ 10
and 1.9 ꢂ 10
mol dm ,
log kJ ¼ c log[TX-100] + d
(8)
respectively. The effect of concentrations of surfactants on the
rate constant has been studied at the temperature of 30 C by
keeping the concentrations of MnO
ꢁ
where c and d are empirical constants. The plot between log k
and log[TX-100] (Fig. 10) was linear which resulted the value of
J
ꢀ
5
ꢀ3
2
(8.0 ꢂ 10 mol dm ),
ꢀ3
ꢀ3
ꢀ4
acetamiprid (5.0 ꢂ 10 mol dm ) and HClO
4
(6.0 ꢂ 10 mol
2
c ¼ 0.096 and d ¼ ꢀ2.978 (r ¼ 0.987). The numerical values of
ꢀ3
ꢀ3
dm ) constant. It has been observed that SDS (4.7 ꢂ 10 to
these empirical constants strongly depend on the nature and
concentration ranges of the reactants as well as reaction
conditions.
ꢀ
3
ꢀ3
8
.0 ꢂ 10 mol dm ) has no effect on the value of the rate
constant. This is due to repulsion between anionic micellar
aggregates of SDS (the micelles have a net negative charge due
The validity of eqn (7) and (8) conrms that the oxidative
degradation of acetamiprid by MnO in presence of TX-100
2
obeys Tuncay model. The catalytic effect of TX-100 is presum-
ably due to increasing adsorption of reactants in the presence of
ꢀ
to – OSO3 ) and the negatively charged colloidal MnO . In this
2
context, it is worth relevant to mention here that it has been well
established that the water soluble colloidal MnO
2
in aqueous
media is stabilized by adsorption of anions resulting negative
20
this surfactant. According to Tuncay et al. the driving force for
1
7–19
charge on its particles.
On the other hand the reaction in the
ꢀ4
ꢀ3
ꢀ3
presence of CTAB (5.3 ꢂ 10 to 8.0 ꢂ 10 mol dm ) could
not be followed as well because it possesses the positive charge
opposite to that of colloidal MnO2 causing occulation and
thereby the turbidity of reaction mixture was observed. It is
presumably due to adsorption of cationic CTAB on the surface
2
of negatively charged colloidal particles of MnO resulting in
neutralization of their electrostatic charge and precipitation
occurs. The problem of occulation has also been observed by a
number of earlier investigators for the redox reactions involving
20,23–26
2
colloidal MnO as oxidant in the presence of CTAB.
However, the addition of non-ionic surfactant, TX-100 enhances
the rate of reaction. The plots between log(absorbance) versus
time in the presence of different concentration of TX-100 (2.0 ꢂ
ꢀ4
ꢀ3
ꢀ3
10
to 8.0 ꢂ 10 mol dm ) were also observed to be linear, as
in absence of surfactants, which conrms that the reaction is
also rst-order with respect to MnO in presence of TX-100.
Thus, in other words, the order of reaction with respect to
MnO remains the same as that observed in the absence of
surfactants. The values of the pseudo-rst-order rate constant
kJ) in presence of TX-100 are drawn against [TX-100] in Fig. 8.
There is a continuous increase in the rate constant with
2
2
Fig. 8 Effect of [TX-100] on k
colloidal MnO
J
for the degradation of acetamiprid by
(
ꢀ3
2
(reaction conditions: [acetamiprid] ¼ 5.0 ꢂ 10
ꢀ
3
ꢀ5
ꢀ3
ꢀ4
mol dm , [MnO
2
] ¼ 8.0 ꢂ 10 mol dm , [HClO
4
] ¼ 6.0 ꢂ 10
ꢀ3
ꢁ
increasing concentration of TX-100 up to a concentration of mol dm , temperature ¼ 30 C).
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linear equation which indicates that the system obeys the
Arrhenius relationship:
2
log kobs ¼ ꢀ1114/T + 0.299 (r ¼ 0.995)
(9)
a
The value of the activation energy (E ) as calculated from the
slope of the above equation is listed in Table 1. In order to
realize whether the reaction mechanism is associative or
dissociative, the entropy of activation is necessarily required.
#
The values of entropy of activation (DS ) along with other
thermodynamic activation parameters such as enthalpy of
#
#
activation (DH ) and free energy of activation (DG ) may be
calculated from following Eyring equation:
#
log(kobs/T) ¼ ꢀ(DH /2.3026RT) + log(k /h))
B
#
(DS /2.3026R)
+
(10)
Fig. 9 Plot of 1/(k
J
ꢀ kobs) versus 1/[TX-100] for the degradation of
acetamiprid by colloidal MnO
2
(reaction conditions: [acetamiprid] ¼
ꢀ5 ꢀ3
ꢀ
3
ꢀ3
In the above equation k
and Plank's constants, respectively. The plot of log kobs against
/T has also been observed to follow the following linear
B
, R and h represent Boltzman, gas
5
.0 ꢂ 10 mol dm , [MnO
2
] ¼ 8.0 ꢂ 10 mol dm , [HClO
4
] ¼ 6.0
ꢀ4
ꢀ3
ꢁ
ꢂ 10 mol dm , temperature ¼ 30 C).
1
equation which shows that the degradation process obeys the
Eyring theory:
2
log(kobs/T) ¼ ꢀ980.9/T ꢀ 2.623 (r ¼ 0.994)
(11)
The values of different activation parameters for the degra-
dation of acetamiprid by colloidal MnO , as calculated from the
2
slope and intercept of eqn (11) are given in Table 1. In similar
manner the values of different activation parameters in pres-
ence of surfactant TX-100 have also been calculated and
included in Table 1. This table clearly highlights that the
contribution of entropy factor is much larger than the enthalpy
factor towards the free energy of activation i.e. overall process
controlling parameter. A large negative value of the entropy of
activation points out the formation of highly ordered associa-
tive transition state complex during the degradation process of
acetamiprid by colloidal MnO
2 4
in the presence of HClO .
Therefore the transition state in the region of activated complex
has a more ordered rigid structure than the reactants in the
ground state. Further a lower value of activation energy in the
presence of surfactant is due to a high catalytic effect of
surfactant which provides an alternative path of the lower
activation barrier for the reaction.
Fig. 10 Plot of log[TX-100] versus log k
J
for the degradation of
acetamiprid by colloidal MnO
2
(reaction conditions: [acetamiprid] ¼
ꢀ3
ꢀ3
ꢀ5 ꢀ3
5
2
.0 ꢂ 10 mol dm , [MnO ] ¼ 8.0 ꢂ 10 mol dm , [HClO
4
] ¼ 6.0
ꢀ4
ꢀ3
ꢁ
ꢂ 10 mol dm , temperature ¼ 30 C).
the adsorption of TX-100 is the hydrogen bond formation
between polar ethylene oxide and the surface of MnO particles.
2
Table 1 Activation parameters for the degradation of acetamiprid by
a
colloidal MnO
2
Values
Effect of temperature on rate constant and determination of
activation parameters
Activation parameters
Aqueous
TX-100
17.95
15.40
ꢀ255.42
92.78
A series of kinetic experiments was also performed at different
temperatures in the range of 20–50 C at the xed concentra-
ꢀ
1
ꢁ
E
a
/kJ mol
21.33
18.78
#
ꢀ1
DH /kJ mol
ꢀ
3
ꢀ3
ꢀ3
ꢀ5
tions of acetamiprid (5.0 ꢂ 10 mol dm ), MnO (8.0 ꢂ 10
#
ꢀ1
ꢀ1
2
DS /J K mol
ꢀ247.78
ꢀ
3
ꢀ4
#
ꢀ1
mol dm ) and HClO (6.0 ꢂ 10 mol dm ). The values of the DG /kJ mol
93.85
4
rate constant, so obtained at different temperatures are used to
a
ꢀ3
ꢀ3
Reaction conditions: [acetamiprid] ¼ 5.0 ꢂ 10 mol dm , [MnO ] ¼
2
calculate the activation energy of the process. The variation of
log kobs against 1/T has been observed to obey the following 4.0 ꢂ 10 mol dm
ꢀ5
ꢀ3
ꢀ4
ꢀ3
8
.0 ꢂ 10 mol dm , [HClO
4
] ¼ 6.0 ꢂ 10 mol dm ) and [TX-100] ¼
ꢀ
3
ꢀ3
.
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 62844–62850 | 62849

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RSC Advances
Paper
9
T. Imamura, Y. Yanagawa, K. Nishikawa, N. Matsumoto and
T. Sakamoto, Clin. Toxicol., 2010, 48, 851–853.
Conclusions
The kinetic studies for the oxidative degradation of acetamiprid 10 X. Guohong, L. V. Jianxiao, L. Guoguang, S. Dezhi and
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Biotechnol., 2008, 83, 546–552.
been observed to be fractional order in both acetamiprid and 13 A. Khan, M. M. Haque, N. A. Mir, M. Muneer and C. Boxall,
HClO4 under the pseudo-rst-order reaction condition with
Desalination, 2010, 261, 169–174.
respect to MnO
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with the concentration of reactants, rate law equation was
Bioresour. Technol., 2013, 138, 359–368.
established. Effect of common surfactants, namely, CTAB, SDS 15 H. Yang, X. Wang, J. Zheng, G. Wang, Q. Hong, S. Li, R. Li
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colloidal MnO
has also been studied. It has been observed that 16 T. Sriskandakumar, N. Opembe, C. H. Chen, A. Morey,
2
2
4

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2
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C. Kingondu and S. L. Suib, J. Phys. Chem. A, 2009, 113,
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explained in terms of mathematical models of Tuncay et al. The
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kinetic data as obtained in the present investigation have 18 J. F. Perez-Benito and C. Arias, J. Colloid Interface Sci., 1992,
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149, 92–97.
parameters for the oxidative degradation of acetamiprid by 19 J. F. Perez-Benito, C. Arias and E. Amat, J. Colloid Interface
colloidal MnO
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in acidic medium.
Sci., 1996, 177, 288–297.
2
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0 M. Tuncay, N. Yuce, B. Arlkan and S. Gokturk, Colloids Surf.,
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1 Z. Khan, P. Kumar and Kabir-Ud-Din, Colloids Surf., A, 2004,
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Acknowledgements
The authors are grateful to the Chairman, Department of
Applied Chemistry, Aligarh Muslim University for providing 22 Kabir-Ud-Din, N. H. Zaidi, M. Akram and Z. Khan, Colloid
necessary laboratory facilities. One of the authors (Qamruzza-
Polym. Sci., 2006, 284, 1387–1393.
man) is also thankful to the University Grants Commission, 23 M. Akram, M. Altaf and Kabir-Ud-Din, Colloids Surf., B, 2011,
New Delhi for the award of Maulana Azad National Fellowship.
82, 217–233.
24 Kabir-Ud-Din, S. M. S. Iqubal and Z. Khan, Colloid Polym.
Sci., 2005, 284, 276–283.
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62850 | RSC Adv., 2014, 4, 62844–62850
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