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Degradation of dissolved diazinon pesticide in water using the high frequency of ultrasound wave
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Ultrasonics Sonochemistry 15 (2008) 869–874 www.elsevier.com/locate/ultsonch
Degradation of dissolved diazinon pesticide in water using the high frequency of ultrasound wave Mohammed A. Matouq a,*, Zaid A. Al-Anber a, Tomohiko Tagawa b, Salah Aljbour b, Mohammad Al-Shannag a a
Al-Balqa Applied University, Faculty of Engineering Technology, Chemical Engineering Department, P.O. Box 4486, Amman 11131, Jordan b Department of Chemical Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan Received 9 August 2007; received in revised form 15 October 2007; accepted 24 October 2007 Available online 5 December 2007
Abstract This article aims to apply the ultrasound technique in the field of clean technology to protect environment. The principle of sonochemistry is conducted here to degrade pesticides in simulated industrial wastewater resulted from a factory manufacturing pesticides namely diazinon. Diazinon pesticide selected in this study for degradation under high frequency ultrasound wave. Three different initial concentrations of diazinon (800, 1200, and 1800 ppm), at different solution volumes were investigated in to degrade dissolved diazinon in water. Ultrasound device with 1.7 MHz, and 0.044 cm diameter, was used to study the degradation process. It is found that as the concentration of diazinon increased, the degradation is also increasing, and when the solution volume increases, the ability to degraded pesticides decreases. The experimental results showed an optimum condition achieved for degradation of diazinon at 1200 ppm as initial concentration and 50 ml solution volume. Kinetic modeling applied for the obtained results showed that the degradation of diazinon by high ultrasound frequency wave followed a pseudo-first-order model with apparent rate constant of around of 0.01 s1. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Ultrasound; Sonochemistry; Diazinon; Pesticides; Environmental protection; Wastewater; Reaction kinetics models
1. Introduction The application of power ultrasound to chemical processes is one of number intensification technologies that have undergone serious and wide-ranging development over the past 10–15 years. The driving force for these developments has many aspects, but the increasing requirement for environmentally clean technology that minimizes the production of waste at source is an important factor. Energy input via ultrasound offers possibilities for cleaner production through improved product yields and selectivities, and for enhanced product recovery and quality through application to several processes, other product recovery, and purification processes. *
Corresponding author. Tel.: +962 6 4892345x188; fax: +962 6 4894292. E-mail address: [email protected] (M.A. Matouq). 1350-4177/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.ultsonch.2007.10.012
The usage of pesticides has recently become an integral part of modern agriculture production. Their fate in the environment is of great concern, since most of them as well as their degradation products have been found both in surface water and ground water. Diazinon is the common name of an organo-phosphorus insecticide used to control pest insects in soil, on ornamental plants, and on fruit and vegetable field crops. Diazinon may be found in formulations with a variety of other pesticides such as pyrethrins, lindane, and disulfoton. In agriculture, diazinon is diluted with other chemicals before use. The diazinon that was formerly sold for home and garden use contained 1–5% diazinon in a liquid or as solid granules, but most of the diazinon used is in liquid form. Pesticides are usually classified into toxic substances, which practically do not decompose in nature. Due to this fact they accumulated and increasingly burden the environmental with undesirable chemical and residue. Another
870
M.A. Matouq et al. / Ultrasonics Sonochemistry 15 (2008) 869–874
important and significant impact will be on water resources, especially underground one where farms are located, and pesticides were used in a way not well controlled. Moreover, effluent wastewater from pesticides factories is another source of contamination to our water resources. During the daily activities of such factories there is a big chance for different types of pesticides to escape to wastewater grid either inside or outside the factory, so that the effluent will contain a significant amount of pesticides that should be removed or treated before let it escape to wastewater collection system, and adversely will be flowing to public wastewater grid and to water resources system. The removal of pesticides from such industrial wastewater is an extremely complex problem due to the wide range of pesticides with different chemical structures and properties. There are various processing and technologies used for pesticides removal from industrial wastewater, and while a process is considered to be suitable for a specific application, it may be not suitable for others, but in general still these processes can be classified into physical treatment like adsorption, biodegradation, ozonation (oxidation), ultraviolet degradation process, and advanced oxidation process. Examples on different conventional processes used to treat pesticides in wastewater are: adsorption, oxidation, photocatalytic removal, and using ultrasound techniques. Faurel et al. [1] studied adsorption process for the removal of pesticides, while Qiao et al. [2], studied the biodegradation of pesticides by immobilization of microorganism. Another one is the oxidation of pesticides which was reported by Chiron et al. [3]. In addition to that, the photocatalytic removal of pesticides from water was investigated by McMurray et al. [4], and Bahena and Martinez [5]. The application of the ultrasound power in wastewater treatment and chemical reaction processes is gaining a good attention, due to the increase requirement for environmentally clean technology, product recovery and purification process. Ultrasound techniques have been used for trans-esterification to obtain biodiesel fuel [6]. Lall et al. [7] studied the decolorization of the dye using ultrasound to enhance ozonation. Matouq and Al-Anber [8], studied the removing and the recovery of ammonia from industrial wastewater. Maleki et al. [9] studied phenol degradation by using ultrasound techniques. Chen et al. [10] studied the photo degradation of pesticides at low ultrasound frequency. Yasman et al. [11] studied the detoxification of hydrophilic chloroorganic pollutant in effluent wastewater using combination of ultrasound wave, electrochemistry and Fontons reagent (SEF). This study aimed at applying the high frequency ultrasound technique in the field of industrial wastewater treatment processes, especially for pesticides. The case will represent a real one for industrial wastewater contaminated with diazinon resulting from the daily cleaning process of equipments and vessels used in synthesizing this pesticide by VAPCO factory (one of the main factory to synthesize pesticides in Jordan). According to the recent local envi-
ronmental regulations this kind of wastewater must be treated before sending it to the national sewage grid. Ultrasound technique with high frequency was used in our previous study to remove ammonia from industrial wastewater [8], and here we will apply the same technique to treat wastewater from contaminated pesticide. Thus applying this technique will help: 1. to reduce the pesticides concentration in the industrial wastewater, at source especially for industrial wastewater, i.e., VAPCO company, 2. to introduce the ultrasound waves with high frequency in the field of degradation or removal of pesticides from industrial wastewater, due to its limited use in this field, and 3. to increase the application of high frequency ultrasound wave in the field of environmental protection and clean technology concept. 2. Experimental setup, procedure and materials 2.1. Apparatus The experimental apparatus is demonstrated in Fig. 1, which consists of a cylindrical vessel with 44 mm inside diameter, and 270 mm height. Cover attached to the cylindrical vessel at the upper side, and was kept close in all experimental works, to prevent any mist of pesticides in the form of vapor from leaking to atmosphere. Electrical source with variable voltage supply rages from 0 to 40 V was attached to the apparatus. The electrical supply can also be adjusted to control the electrical current source from 0 to 600 mA. All experiments were conducted at 24 V and 500 mA, according to the specified condition by manufacture for the ultrasound wave device generator.
Reactor ID 0.044 m 0.27 m Height
Cover
Pesticide-water solution
Electrical supply
Ultrasonic vibrator 1.7 MHz
Fig. 1. Experiment setup.
M.A. Matouq et al. / Ultrasonics Sonochemistry 15 (2008) 869–874
2.2. Procedure Sample of pesticide solution was prepared by dissolving a measured volume of diazinon with 95% concentration (as supplied by VAPCO manufacture) in 1000 ml of distilled water. The initial concentration prepared by this method was adjusted to 1200 ppm. This is the same concentration of pesticides found in the effluent industrial wastewater in VAPCO factory. This portion of wastewater is a normal outlet of their effluent due to the daily routine of cleaning process for their equipments after pesticides being synthesized. Sample’s volume for the prepared solution was fixed exactly at 40, 50, and 60 ml, by measuring it in a graduated cylinder before it poured to experimental apparatus. This vessel was used for all experiments works. To study the effect of the initial concentration on the degradation process other samples with initial concentrations of 800 and 1800 ppm were also prepared according to the same procedure. Samples inside the vessel were exposed to a fixed ultrasound wave of 1.7 MHz frequency. The variables which assigned to be investigated here are: diazinon solution’s volume poured inside the vessels, and the pesticides initial concentrations, while time of ultrasound exposing periods was fixed at 600 s for all experimental works. When the solution mixture (contained the pesticides) poured to the vessel with the pre-specified volume and concentration, the power supply switched on. Samples were taken from vessel and analysis using HPLC at different time intervals. Since the volume of sample taken and used for analysis is big and equal to 5 ml (10% of the total volume of the sample inside the vessel), and in order not to have a significant effect on result due to such loss in the initial volume of the mixture inside the vessel, soon after sample was taken the power supply switch off, and the rest portion of the solution was discarded. Another new solution prepared with the same initial volume and concentration was re-exposed again for ultrasound wave until it reached the second assigned time interval, soon 5 ml sample was taken the power supply was switched off again, and the rest portion of the mixture discarded. The same procedure as before was repeated for all experimental works in this study. This procedure was adopted in order to remove any volume reduction effects on the experimental results, and to keep it constant inside the vessel. 2.3. Materials
3. Results and discussion Two variables were investigated in this study, mixture solution volume inside the vessel, the initial concentrations of pesticides, while the ultrasound waves was fixed at 1.7 MHz frequency, and time of exposing to ultrasound waves. The experimental conditions are given in Table 1. Time of exposing was fixed at 600 s in all experimental works. All the experiments were investigated at room temperature. Fig. 2 shows the effect of changing the solution volume on pesticide degradation at constant diazinon concentration, which was fixed at 1200 ppm. The figure shows also the decreasing in concentration profiles with the increasing of irradiation exposing time for the three pesticides solution volumes 40, 50, and 60 ml. It is clear that the concentration decreases with time which means that the rate of degradation is proportional to the time of exposing to ultrasound waves. It is also noticed that as the liquid volume increasing, the ability of ultrasound wave to degrade the pesticide is decreasing when we compare 40 and 60 ml experimental result profiles. This can be attributed to the capacity of transducer producing the ultrasound waves as the liquid volume increases the load of liquid level above the transducer disc will be high preventing the disc from vibrating in easier way compared with lower liquid volume, more explanation will be introduced in the next paragraphs.
Table 1 Experimental conditions Time (s) Ultrasound waves frequency (MHz) Initial concentration of diazinon (ppm)
1600 40 ml 50 ml
1200
60 ml 800
400
0 0
The pesticides diazinon obtained from VAPCO with 95% concentration used in this study without nay further purification.
600 1.7 800 1200 1800 40 50 60
Initial solution mixture volume (ml)
Concentration (ppm)
Ultrasonic vibrator comprised of 20 mm diameter transducer, which contains piezoceramics (sandwich) with titanium end masses leading the face from which the ultrasonic is emitted. It has a frequency of 1.7 MHz and electric input power 9.5 W, and it is supplied by Honda electronics Co., Ltd., of Japan, type HM-2412.
871
100
200
300
400
500
600
Time (sec)
Fig. 2. The concentration profiles for pesticide degradation with time at 1200 ppm initial concentration for different solution volumes of diazinon.
M.A. Matouq et al. / Ultrasonics Sonochemistry 15 (2008) 869–874
Fig. 3 shows the relationship between changing the initial concentration with time at constant solution volume of 50 ml. Three different initial concentrations 800, 1200, and 1800 ppm of pesticides profiles are illustrated in Fig. 3, at 1.7 MHz of ultrasound wave. As is shown in this figure, the initial concentration decreases with time, and as time reached certain period (around 300 s), then the profile become constant and close to straight line meaning that the steady state phase has been achieved. This means that no more degradation will be expected beyond this time. During the experimental work it was noticed that when the initial concentration decreased to 600 ppm (less than 800 ppm), the profile was almost close to straight line, which means that it is not significant compared to 1200 and 800 ppm, hence that the minimum concentration for pesticide to be studied here was fixed at 800 ppm. Here we can propose to introduce a higher ultrasound frequency wave to be used in order to study lower pesticides concentration and below 800 ppm. The diazinon degradation phenomena here can be better explained by the ability of ultrasound waves for the formation the hydroxyl radical. The hydroxyl radical reacts strongly with most organic pesticide, such as diazinon by hydrogen abstraction or electrophilic addition to double bonds. The resulting free radicals further react with dissolved molecular oxygen to give peroxy radicals, initiating fast a sequence of oxidative degradation reactions, for this reason we can see a rapid decrease in concentration profile within the early 300 s as shown in Figs. 2 and 3. However, after that time the diazinon concentration become almost constant, this tangible behavior can be contributed to the fact that since the vapor pressure of the diazinon is high, then the ultrasound wave at high frequency will produce a quiet enough amount of mist rich in diazinon. The closed system we have here will create vapor–liquid equilibrium between the liquid and vapor phase which will give the diazinon to keep its constant profile after certain period of time. Bearing in mind that, the quiet complex degradation mechanism for the diazinon compound which had been studied by others, will make it necessary to investigated the mechanism of this reaction under high ultrasound frequency wave.
800 ppm
1200 ppm
1800 ppm
0.8
C/Co (-)
3.1. Chemical kinetic degradation models This section will deal with finding the suitable chemical degradation model that best describe the experimental kinetic data result. The obtained data were fitted with different kinetics models namely first and pseudo-first-order, 80
0.6
0.4
70
60
50 30
40
50
60
70
liquid volume (ml)
Fig. 4. Pesticides degradation percentage at different solution volume.
80
Percentage of degradation
1
Figs. 4 and 5 show the percentage of degradation rate varies with both volume and initial concentration, respectively, after 600 s exposing to ultrasound wave which is basically the steady state phase. Both figures show that, the best condition for diazinon degradation is 1200 ppm initial concentration and 50 ml liquid volume at maximum point, and as is seen it is 70% degradation rate. At lower volume of mixture solution, the ability of ultrasound device to evaporate the diazinon will be higher compared to 50 and 60 ml, then the chance for the diazinon to exist in the liquid phase will be less, hence the degradation will be lower than in the case of 50 and 60 ml. At the same time as the volume of liquid increased to 60 ml the ability of ultrasound device to evaporate diazinon will be lower compared to 50 ml liquid volume, then a peak value will appear around 50 ml as indicated in both Figs. 4 and 5.
Percentage of degradation
872
70
60
0.2 0
100
200
300
400
500
600
Time (sec)
Fig. 3. The concentration profiles for pesticide degradation with time at different pesticides initial concentrations with fixed solution volume at 50 ml.
50 600
1000
1400
1800
Concentration (ppm)
Fig. 5. Pesticides degradation percentage at different initial concentrations.
M.A. Matouq et al. / Ultrasonics Sonochemistry 15 (2008) 869–874
CðtÞ ¼ C ek1 t
ð1Þ
5.5
ð3Þ
For liner fitting the equation will be rearranged into the following one: ð4Þ
where k is the pseudo-first-order rate constant, and it can be estimated from the slope after plotting ln (Ce Ct) versus t, and Ce is the equilibrium diazinon concentration. Fig. 7 shows the fitting for the experimental data using the pseudo-first-order model. The correlation factors R2 that calculated in this fitting gives higher value than the first-order model, and it reaches 98%. This gives good indication for the consistency with the proposed model, meaning that our experimental data can be modeled by pseudo-first-order. The calculated rate degradation constant from the plotted data is given in Table 2.
7.5
1200 ppm
800 ppm
4.5
3.5 0
50
100
150
200
250
Time (sec)
Fig. 7. The pseudo-first-order model data fitting at 50 ml liquid volume and constant frequency wave length of 1.7 MHz at different diazinon initial concentrations.
Table 2 Degradation rate constant at different initial concentration of diazinon Initial concentration of diazinon (ppm)
k (1/s)
800 1200 1800
0.0075 0.009 0.0104
Second-order kinetics model The proposal of having a second-order kinetic model will be examined here. The change in the degradation concentration can be fitted by using the second-order kinetic equation model described by Eq. (5): r ¼
dC ¼ kC 2 dt
ð5Þ
For liner fitting the equation can be rearranged as: 1 1 ¼ kt þ C C0
ð6Þ
where k is the second-order degradation rate constant and it can be estimated from the slope after plotting 1/C versus t, as demonstrated in Fig. 8, and C0 is the initial diazinon concentration.
1800 ppm
y = -0.0008x + 7.0662 R 2 = 0.6943
7
y = -0.0104x + 6.6766 R2 = 0.9707
5
4
where k1 is the first-order rate constant and it is estimated from the slope by plotting ln C(t) versus time t, as shown in Fig. 6, and C0 is the initial diazinon concentration. The figure indicates clearly that the fitting does not in a good consistency with the proposed model since the correlation factor (R2) cannot reach a value higher than 75%. Pseudo-first-order kinetics The second proposal is to assume a pseudo-first-order kinetic model which described by equation
ln ðCe CtÞ ¼ kt þ ln Ce
y = -0.009x + 6.3862 R2 = 0.8558
6
ð2Þ
dCt ¼ kðCe CtÞ dt
1800 ppm
y = -0.0075x + 6.1503 R2 = 0.9883
6.5
To obtain a liner fitting Eq. (1), rearranged to: ln CðtÞ ¼ ln C kt
1200 ppm
800 ppm
7
ln(Ce - Ct)
second and pseudo-second-order models. The following simulation will demonstrate the best data fitting for the obtained experimental results. First-order kinetics model In this model the experimental data were fitted according to simple first-order rate:
873
0.005
800 ppm
1200 ppm
1800 ppm
0.004 6.5
ln C
y = 8E-06x + 0.0013 R2 = 0.9583
y = -0.0013x + 6.483 R2 = 0.6939
0.003
1/C
6
y = -0.0015x + 6.329
y = 5E-06x + 0.0011 R2 = 0.8687
0.002
R2 = 0.7342
5.5
0.001
5 0
100
200
300
400
500
600
Time (sec)
Fig. 6. The first-order model data fitting at 50 ml liquid volume and constant frequency wave length of 1.7 MHz at different diazinon initial concentrations.
y = 2E-06x + 0.0007 R2 = 0.9298
0 0
50
100
150
200
250
300
Time
Fig. 8. The second-order model data fitting at 50 ml liquid volume and constant frequency wave length of 1.7 MHz at different diazinon initial concentrations.
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M.A. Matouq et al. / Ultrasonics Sonochemistry 15 (2008) 869–874 2.5 2
4. Conclusions
800 ppm y = 0.2842x - 0.467
1200 ppm
2
R = 0.7436
1800 ppm
t/Ct
1.5 y = 0.2196x - 0.3533 2 R = 0.7257
1 0.5
y = 0.0986x - 0.1508 2 R = 0.7689
0 -0.5
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
-0.5 -1
1/Ce
2
Fig. 9. The pseudo-second-order model data fitting (t/Ct versus 1/Ce2) at 50 ml liquid volume and constant frequency wave length of 1.7 MHz at different diazinon initial concentrations.
The experimental result showed that the fitted 1/C versus t, for different initial diazinon concentrations. Although the fitting looks in a good consistency, still the R2, for the pseudo-first-order is higher. Pseudo-second-order kinetics The last proposal model will be pseudo-second-order degradation model and is given by the equation dCt 2 ¼ kðCe CtÞ dt
ð7Þ
The equation can be rearranged to get a liner form equation as: t t 1 ¼ þ Ct Ce kCe2
ð8Þ
where k is the pseudo-second-order rate constant and it can be estimated from the slope after plotting t/Ct versus 1/Ce2, and Ce is the equilibrium diazinon concentration. Fig. 9 shows the fitted experimental data t/Ct versus 1/Ce2 for different initial diazinon concentrations. It is clear that the fitting does not give a good consistency with the data, which indicates the failure of this model to represent the degradation proposal model.
The using of high ultrasound wave frequency techniques to degraded pesticides namely diazinon, was successfully obtained. Three different initial concentrations with three different liquid volumes were selected to study the performance of using ultrasound wave on degradation. Degradation of pesticides using 1.7 MHz wave length of ultrasound can be used to decrease the concentration of pesticides from the solution with different liquid volume and initial concentrations by chemical degradation under ultrasound wave techniques with only 300 s in an average time period. The best condition for pesticides degradation was obtained at 1200 ppm initial concentration and 50 ml liquid volume. As the liquid volume increased, the ability of degradation will be decreased. The degradation process for diazinon was best fitting by a pseudo-first-order reaction model with k equal to about 0.01 (1/s). References [1] C. Faurel, H. Pignon, P. Cloirce, Adsorption 1 (2005) 479–490. [2] L. Qiao, Y. Yan, H. Shanag, X. Zhon, Y. Zhang, Bull. Environ. Contam. Toxicol. 71 (2003) 370–374. [3] S. Chiron, A. Fernandez-Alba, A. Rodriguez, E. Garcia-Calvo, Water Res. 34 (1999) 366–377. [4] T. McMurray, P. Dunlop, J. Byrn, J. Photochem. Photobiol. A: Chem. 182 (1) (2006) 43–51. [5] C. Bhena, S. SilvaMartinez, Int. J. Photoenergy (2006) 1–6. [6] Y. Maeda, S. Carmen, R. Nishimura, M. Vinatoru, Ultrasonic Sonochem. 12 (5) (2005) 367–372. [7] R. Lall, R. Mutharason, Y. Shal, P. Dhurjat, Water Environ. Res. 75 (2003) 171–179. [8] M. Matouq, Z. Al-Anber, Ultrasonic Sonochem. 14 (2007) 393–397. [9] A. Maleki, A.H. Mahvi, F. Vaezi, R. Nabizadeh, Iran. J. Environ. Health, Sci. Eng. 2 (3) (2005) 201–206. [10] Y. Chen, A. Vorontsov, P. Smirniotis, Photochem. Photobiol. Sci. 2 (2003) 694–698. [11] Y. Yasman, V. Bulatov, V. Gridin, S. Agur, N. Galil, R. Armon, I. Schechter, Ultrasonic Sonochem. 11 (2004), 365–372.
Ultrasonics Sonochemistry 15 (2008) 869–874 www.elsevier.com/locate/ultsonch
Degradation of dissolved diazinon pesticide in water using the high frequency of ultrasound wave Mohammed A. Matouq a,*, Zaid A. Al-Anber a, Tomohiko Tagawa b, Salah Aljbour b, Mohammad Al-Shannag a a
Al-Balqa Applied University, Faculty of Engineering Technology, Chemical Engineering Department, P.O. Box 4486, Amman 11131, Jordan b Department of Chemical Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan Received 9 August 2007; received in revised form 15 October 2007; accepted 24 October 2007 Available online 5 December 2007
Abstract This article aims to apply the ultrasound technique in the field of clean technology to protect environment. The principle of sonochemistry is conducted here to degrade pesticides in simulated industrial wastewater resulted from a factory manufacturing pesticides namely diazinon. Diazinon pesticide selected in this study for degradation under high frequency ultrasound wave. Three different initial concentrations of diazinon (800, 1200, and 1800 ppm), at different solution volumes were investigated in to degrade dissolved diazinon in water. Ultrasound device with 1.7 MHz, and 0.044 cm diameter, was used to study the degradation process. It is found that as the concentration of diazinon increased, the degradation is also increasing, and when the solution volume increases, the ability to degraded pesticides decreases. The experimental results showed an optimum condition achieved for degradation of diazinon at 1200 ppm as initial concentration and 50 ml solution volume. Kinetic modeling applied for the obtained results showed that the degradation of diazinon by high ultrasound frequency wave followed a pseudo-first-order model with apparent rate constant of around of 0.01 s1. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Ultrasound; Sonochemistry; Diazinon; Pesticides; Environmental protection; Wastewater; Reaction kinetics models
1. Introduction The application of power ultrasound to chemical processes is one of number intensification technologies that have undergone serious and wide-ranging development over the past 10–15 years. The driving force for these developments has many aspects, but the increasing requirement for environmentally clean technology that minimizes the production of waste at source is an important factor. Energy input via ultrasound offers possibilities for cleaner production through improved product yields and selectivities, and for enhanced product recovery and quality through application to several processes, other product recovery, and purification processes. *
Corresponding author. Tel.: +962 6 4892345x188; fax: +962 6 4894292. E-mail address: [email protected] (M.A. Matouq). 1350-4177/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.ultsonch.2007.10.012
The usage of pesticides has recently become an integral part of modern agriculture production. Their fate in the environment is of great concern, since most of them as well as their degradation products have been found both in surface water and ground water. Diazinon is the common name of an organo-phosphorus insecticide used to control pest insects in soil, on ornamental plants, and on fruit and vegetable field crops. Diazinon may be found in formulations with a variety of other pesticides such as pyrethrins, lindane, and disulfoton. In agriculture, diazinon is diluted with other chemicals before use. The diazinon that was formerly sold for home and garden use contained 1–5% diazinon in a liquid or as solid granules, but most of the diazinon used is in liquid form. Pesticides are usually classified into toxic substances, which practically do not decompose in nature. Due to this fact they accumulated and increasingly burden the environmental with undesirable chemical and residue. Another
870
M.A. Matouq et al. / Ultrasonics Sonochemistry 15 (2008) 869–874
important and significant impact will be on water resources, especially underground one where farms are located, and pesticides were used in a way not well controlled. Moreover, effluent wastewater from pesticides factories is another source of contamination to our water resources. During the daily activities of such factories there is a big chance for different types of pesticides to escape to wastewater grid either inside or outside the factory, so that the effluent will contain a significant amount of pesticides that should be removed or treated before let it escape to wastewater collection system, and adversely will be flowing to public wastewater grid and to water resources system. The removal of pesticides from such industrial wastewater is an extremely complex problem due to the wide range of pesticides with different chemical structures and properties. There are various processing and technologies used for pesticides removal from industrial wastewater, and while a process is considered to be suitable for a specific application, it may be not suitable for others, but in general still these processes can be classified into physical treatment like adsorption, biodegradation, ozonation (oxidation), ultraviolet degradation process, and advanced oxidation process. Examples on different conventional processes used to treat pesticides in wastewater are: adsorption, oxidation, photocatalytic removal, and using ultrasound techniques. Faurel et al. [1] studied adsorption process for the removal of pesticides, while Qiao et al. [2], studied the biodegradation of pesticides by immobilization of microorganism. Another one is the oxidation of pesticides which was reported by Chiron et al. [3]. In addition to that, the photocatalytic removal of pesticides from water was investigated by McMurray et al. [4], and Bahena and Martinez [5]. The application of the ultrasound power in wastewater treatment and chemical reaction processes is gaining a good attention, due to the increase requirement for environmentally clean technology, product recovery and purification process. Ultrasound techniques have been used for trans-esterification to obtain biodiesel fuel [6]. Lall et al. [7] studied the decolorization of the dye using ultrasound to enhance ozonation. Matouq and Al-Anber [8], studied the removing and the recovery of ammonia from industrial wastewater. Maleki et al. [9] studied phenol degradation by using ultrasound techniques. Chen et al. [10] studied the photo degradation of pesticides at low ultrasound frequency. Yasman et al. [11] studied the detoxification of hydrophilic chloroorganic pollutant in effluent wastewater using combination of ultrasound wave, electrochemistry and Fontons reagent (SEF). This study aimed at applying the high frequency ultrasound technique in the field of industrial wastewater treatment processes, especially for pesticides. The case will represent a real one for industrial wastewater contaminated with diazinon resulting from the daily cleaning process of equipments and vessels used in synthesizing this pesticide by VAPCO factory (one of the main factory to synthesize pesticides in Jordan). According to the recent local envi-
ronmental regulations this kind of wastewater must be treated before sending it to the national sewage grid. Ultrasound technique with high frequency was used in our previous study to remove ammonia from industrial wastewater [8], and here we will apply the same technique to treat wastewater from contaminated pesticide. Thus applying this technique will help: 1. to reduce the pesticides concentration in the industrial wastewater, at source especially for industrial wastewater, i.e., VAPCO company, 2. to introduce the ultrasound waves with high frequency in the field of degradation or removal of pesticides from industrial wastewater, due to its limited use in this field, and 3. to increase the application of high frequency ultrasound wave in the field of environmental protection and clean technology concept. 2. Experimental setup, procedure and materials 2.1. Apparatus The experimental apparatus is demonstrated in Fig. 1, which consists of a cylindrical vessel with 44 mm inside diameter, and 270 mm height. Cover attached to the cylindrical vessel at the upper side, and was kept close in all experimental works, to prevent any mist of pesticides in the form of vapor from leaking to atmosphere. Electrical source with variable voltage supply rages from 0 to 40 V was attached to the apparatus. The electrical supply can also be adjusted to control the electrical current source from 0 to 600 mA. All experiments were conducted at 24 V and 500 mA, according to the specified condition by manufacture for the ultrasound wave device generator.
Reactor ID 0.044 m 0.27 m Height
Cover
Pesticide-water solution
Electrical supply
Ultrasonic vibrator 1.7 MHz
Fig. 1. Experiment setup.
M.A. Matouq et al. / Ultrasonics Sonochemistry 15 (2008) 869–874
2.2. Procedure Sample of pesticide solution was prepared by dissolving a measured volume of diazinon with 95% concentration (as supplied by VAPCO manufacture) in 1000 ml of distilled water. The initial concentration prepared by this method was adjusted to 1200 ppm. This is the same concentration of pesticides found in the effluent industrial wastewater in VAPCO factory. This portion of wastewater is a normal outlet of their effluent due to the daily routine of cleaning process for their equipments after pesticides being synthesized. Sample’s volume for the prepared solution was fixed exactly at 40, 50, and 60 ml, by measuring it in a graduated cylinder before it poured to experimental apparatus. This vessel was used for all experiments works. To study the effect of the initial concentration on the degradation process other samples with initial concentrations of 800 and 1800 ppm were also prepared according to the same procedure. Samples inside the vessel were exposed to a fixed ultrasound wave of 1.7 MHz frequency. The variables which assigned to be investigated here are: diazinon solution’s volume poured inside the vessels, and the pesticides initial concentrations, while time of ultrasound exposing periods was fixed at 600 s for all experimental works. When the solution mixture (contained the pesticides) poured to the vessel with the pre-specified volume and concentration, the power supply switched on. Samples were taken from vessel and analysis using HPLC at different time intervals. Since the volume of sample taken and used for analysis is big and equal to 5 ml (10% of the total volume of the sample inside the vessel), and in order not to have a significant effect on result due to such loss in the initial volume of the mixture inside the vessel, soon after sample was taken the power supply switch off, and the rest portion of the solution was discarded. Another new solution prepared with the same initial volume and concentration was re-exposed again for ultrasound wave until it reached the second assigned time interval, soon 5 ml sample was taken the power supply was switched off again, and the rest portion of the mixture discarded. The same procedure as before was repeated for all experimental works in this study. This procedure was adopted in order to remove any volume reduction effects on the experimental results, and to keep it constant inside the vessel. 2.3. Materials
3. Results and discussion Two variables were investigated in this study, mixture solution volume inside the vessel, the initial concentrations of pesticides, while the ultrasound waves was fixed at 1.7 MHz frequency, and time of exposing to ultrasound waves. The experimental conditions are given in Table 1. Time of exposing was fixed at 600 s in all experimental works. All the experiments were investigated at room temperature. Fig. 2 shows the effect of changing the solution volume on pesticide degradation at constant diazinon concentration, which was fixed at 1200 ppm. The figure shows also the decreasing in concentration profiles with the increasing of irradiation exposing time for the three pesticides solution volumes 40, 50, and 60 ml. It is clear that the concentration decreases with time which means that the rate of degradation is proportional to the time of exposing to ultrasound waves. It is also noticed that as the liquid volume increasing, the ability of ultrasound wave to degrade the pesticide is decreasing when we compare 40 and 60 ml experimental result profiles. This can be attributed to the capacity of transducer producing the ultrasound waves as the liquid volume increases the load of liquid level above the transducer disc will be high preventing the disc from vibrating in easier way compared with lower liquid volume, more explanation will be introduced in the next paragraphs.
Table 1 Experimental conditions Time (s) Ultrasound waves frequency (MHz) Initial concentration of diazinon (ppm)
1600 40 ml 50 ml
1200
60 ml 800
400
0 0
The pesticides diazinon obtained from VAPCO with 95% concentration used in this study without nay further purification.
600 1.7 800 1200 1800 40 50 60
Initial solution mixture volume (ml)
Concentration (ppm)
Ultrasonic vibrator comprised of 20 mm diameter transducer, which contains piezoceramics (sandwich) with titanium end masses leading the face from which the ultrasonic is emitted. It has a frequency of 1.7 MHz and electric input power 9.5 W, and it is supplied by Honda electronics Co., Ltd., of Japan, type HM-2412.
871
100
200
300
400
500
600
Time (sec)
Fig. 2. The concentration profiles for pesticide degradation with time at 1200 ppm initial concentration for different solution volumes of diazinon.
M.A. Matouq et al. / Ultrasonics Sonochemistry 15 (2008) 869–874
Fig. 3 shows the relationship between changing the initial concentration with time at constant solution volume of 50 ml. Three different initial concentrations 800, 1200, and 1800 ppm of pesticides profiles are illustrated in Fig. 3, at 1.7 MHz of ultrasound wave. As is shown in this figure, the initial concentration decreases with time, and as time reached certain period (around 300 s), then the profile become constant and close to straight line meaning that the steady state phase has been achieved. This means that no more degradation will be expected beyond this time. During the experimental work it was noticed that when the initial concentration decreased to 600 ppm (less than 800 ppm), the profile was almost close to straight line, which means that it is not significant compared to 1200 and 800 ppm, hence that the minimum concentration for pesticide to be studied here was fixed at 800 ppm. Here we can propose to introduce a higher ultrasound frequency wave to be used in order to study lower pesticides concentration and below 800 ppm. The diazinon degradation phenomena here can be better explained by the ability of ultrasound waves for the formation the hydroxyl radical. The hydroxyl radical reacts strongly with most organic pesticide, such as diazinon by hydrogen abstraction or electrophilic addition to double bonds. The resulting free radicals further react with dissolved molecular oxygen to give peroxy radicals, initiating fast a sequence of oxidative degradation reactions, for this reason we can see a rapid decrease in concentration profile within the early 300 s as shown in Figs. 2 and 3. However, after that time the diazinon concentration become almost constant, this tangible behavior can be contributed to the fact that since the vapor pressure of the diazinon is high, then the ultrasound wave at high frequency will produce a quiet enough amount of mist rich in diazinon. The closed system we have here will create vapor–liquid equilibrium between the liquid and vapor phase which will give the diazinon to keep its constant profile after certain period of time. Bearing in mind that, the quiet complex degradation mechanism for the diazinon compound which had been studied by others, will make it necessary to investigated the mechanism of this reaction under high ultrasound frequency wave.
800 ppm
1200 ppm
1800 ppm
0.8
C/Co (-)
3.1. Chemical kinetic degradation models This section will deal with finding the suitable chemical degradation model that best describe the experimental kinetic data result. The obtained data were fitted with different kinetics models namely first and pseudo-first-order, 80
0.6
0.4
70
60
50 30
40
50
60
70
liquid volume (ml)
Fig. 4. Pesticides degradation percentage at different solution volume.
80
Percentage of degradation
1
Figs. 4 and 5 show the percentage of degradation rate varies with both volume and initial concentration, respectively, after 600 s exposing to ultrasound wave which is basically the steady state phase. Both figures show that, the best condition for diazinon degradation is 1200 ppm initial concentration and 50 ml liquid volume at maximum point, and as is seen it is 70% degradation rate. At lower volume of mixture solution, the ability of ultrasound device to evaporate the diazinon will be higher compared to 50 and 60 ml, then the chance for the diazinon to exist in the liquid phase will be less, hence the degradation will be lower than in the case of 50 and 60 ml. At the same time as the volume of liquid increased to 60 ml the ability of ultrasound device to evaporate diazinon will be lower compared to 50 ml liquid volume, then a peak value will appear around 50 ml as indicated in both Figs. 4 and 5.
Percentage of degradation
872
70
60
0.2 0
100
200
300
400
500
600
Time (sec)
Fig. 3. The concentration profiles for pesticide degradation with time at different pesticides initial concentrations with fixed solution volume at 50 ml.
50 600
1000
1400
1800
Concentration (ppm)
Fig. 5. Pesticides degradation percentage at different initial concentrations.
M.A. Matouq et al. / Ultrasonics Sonochemistry 15 (2008) 869–874
CðtÞ ¼ C ek1 t
ð1Þ
5.5
ð3Þ
For liner fitting the equation will be rearranged into the following one: ð4Þ
where k is the pseudo-first-order rate constant, and it can be estimated from the slope after plotting ln (Ce Ct) versus t, and Ce is the equilibrium diazinon concentration. Fig. 7 shows the fitting for the experimental data using the pseudo-first-order model. The correlation factors R2 that calculated in this fitting gives higher value than the first-order model, and it reaches 98%. This gives good indication for the consistency with the proposed model, meaning that our experimental data can be modeled by pseudo-first-order. The calculated rate degradation constant from the plotted data is given in Table 2.
7.5
1200 ppm
800 ppm
4.5
3.5 0
50
100
150
200
250
Time (sec)
Fig. 7. The pseudo-first-order model data fitting at 50 ml liquid volume and constant frequency wave length of 1.7 MHz at different diazinon initial concentrations.
Table 2 Degradation rate constant at different initial concentration of diazinon Initial concentration of diazinon (ppm)
k (1/s)
800 1200 1800
0.0075 0.009 0.0104
Second-order kinetics model The proposal of having a second-order kinetic model will be examined here. The change in the degradation concentration can be fitted by using the second-order kinetic equation model described by Eq. (5): r ¼
dC ¼ kC 2 dt
ð5Þ
For liner fitting the equation can be rearranged as: 1 1 ¼ kt þ C C0
ð6Þ
where k is the second-order degradation rate constant and it can be estimated from the slope after plotting 1/C versus t, as demonstrated in Fig. 8, and C0 is the initial diazinon concentration.
1800 ppm
y = -0.0008x + 7.0662 R 2 = 0.6943
7
y = -0.0104x + 6.6766 R2 = 0.9707
5
4
where k1 is the first-order rate constant and it is estimated from the slope by plotting ln C(t) versus time t, as shown in Fig. 6, and C0 is the initial diazinon concentration. The figure indicates clearly that the fitting does not in a good consistency with the proposed model since the correlation factor (R2) cannot reach a value higher than 75%. Pseudo-first-order kinetics The second proposal is to assume a pseudo-first-order kinetic model which described by equation
ln ðCe CtÞ ¼ kt þ ln Ce
y = -0.009x + 6.3862 R2 = 0.8558
6
ð2Þ
dCt ¼ kðCe CtÞ dt
1800 ppm
y = -0.0075x + 6.1503 R2 = 0.9883
6.5
To obtain a liner fitting Eq. (1), rearranged to: ln CðtÞ ¼ ln C kt
1200 ppm
800 ppm
7
ln(Ce - Ct)
second and pseudo-second-order models. The following simulation will demonstrate the best data fitting for the obtained experimental results. First-order kinetics model In this model the experimental data were fitted according to simple first-order rate:
873
0.005
800 ppm
1200 ppm
1800 ppm
0.004 6.5
ln C
y = 8E-06x + 0.0013 R2 = 0.9583
y = -0.0013x + 6.483 R2 = 0.6939
0.003
1/C
6
y = -0.0015x + 6.329
y = 5E-06x + 0.0011 R2 = 0.8687
0.002
R2 = 0.7342
5.5
0.001
5 0
100
200
300
400
500
600
Time (sec)
Fig. 6. The first-order model data fitting at 50 ml liquid volume and constant frequency wave length of 1.7 MHz at different diazinon initial concentrations.
y = 2E-06x + 0.0007 R2 = 0.9298
0 0
50
100
150
200
250
300
Time
Fig. 8. The second-order model data fitting at 50 ml liquid volume and constant frequency wave length of 1.7 MHz at different diazinon initial concentrations.
874
M.A. Matouq et al. / Ultrasonics Sonochemistry 15 (2008) 869–874 2.5 2
4. Conclusions
800 ppm y = 0.2842x - 0.467
1200 ppm
2
R = 0.7436
1800 ppm
t/Ct
1.5 y = 0.2196x - 0.3533 2 R = 0.7257
1 0.5
y = 0.0986x - 0.1508 2 R = 0.7689
0 -0.5
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
-0.5 -1
1/Ce
2
Fig. 9. The pseudo-second-order model data fitting (t/Ct versus 1/Ce2) at 50 ml liquid volume and constant frequency wave length of 1.7 MHz at different diazinon initial concentrations.
The experimental result showed that the fitted 1/C versus t, for different initial diazinon concentrations. Although the fitting looks in a good consistency, still the R2, for the pseudo-first-order is higher. Pseudo-second-order kinetics The last proposal model will be pseudo-second-order degradation model and is given by the equation dCt 2 ¼ kðCe CtÞ dt
ð7Þ
The equation can be rearranged to get a liner form equation as: t t 1 ¼ þ Ct Ce kCe2
ð8Þ
where k is the pseudo-second-order rate constant and it can be estimated from the slope after plotting t/Ct versus 1/Ce2, and Ce is the equilibrium diazinon concentration. Fig. 9 shows the fitted experimental data t/Ct versus 1/Ce2 for different initial diazinon concentrations. It is clear that the fitting does not give a good consistency with the data, which indicates the failure of this model to represent the degradation proposal model.
The using of high ultrasound wave frequency techniques to degraded pesticides namely diazinon, was successfully obtained. Three different initial concentrations with three different liquid volumes were selected to study the performance of using ultrasound wave on degradation. Degradation of pesticides using 1.7 MHz wave length of ultrasound can be used to decrease the concentration of pesticides from the solution with different liquid volume and initial concentrations by chemical degradation under ultrasound wave techniques with only 300 s in an average time period. The best condition for pesticides degradation was obtained at 1200 ppm initial concentration and 50 ml liquid volume. As the liquid volume increased, the ability of degradation will be decreased. The degradation process for diazinon was best fitting by a pseudo-first-order reaction model with k equal to about 0.01 (1/s). References [1] C. Faurel, H. Pignon, P. Cloirce, Adsorption 1 (2005) 479–490. [2] L. Qiao, Y. Yan, H. Shanag, X. Zhon, Y. Zhang, Bull. Environ. Contam. Toxicol. 71 (2003) 370–374. [3] S. Chiron, A. Fernandez-Alba, A. Rodriguez, E. Garcia-Calvo, Water Res. 34 (1999) 366–377. [4] T. McMurray, P. Dunlop, J. Byrn, J. Photochem. Photobiol. A: Chem. 182 (1) (2006) 43–51. [5] C. Bhena, S. SilvaMartinez, Int. J. Photoenergy (2006) 1–6. [6] Y. Maeda, S. Carmen, R. Nishimura, M. Vinatoru, Ultrasonic Sonochem. 12 (5) (2005) 367–372. [7] R. Lall, R. Mutharason, Y. Shal, P. Dhurjat, Water Environ. Res. 75 (2003) 171–179. [8] M. Matouq, Z. Al-Anber, Ultrasonic Sonochem. 14 (2007) 393–397. [9] A. Maleki, A.H. Mahvi, F. Vaezi, R. Nabizadeh, Iran. J. Environ. Health, Sci. Eng. 2 (3) (2005) 201–206. [10] Y. Chen, A. Vorontsov, P. Smirniotis, Photochem. Photobiol. Sci. 2 (2003) 694–698. [11] Y. Yasman, V. Bulatov, V. Gridin, S. Agur, N. Galil, R. Armon, I. Schechter, Ultrasonic Sonochem. 11 (2004), 365–372.