Microsoft Word - 2- Dr Dehghani RTL_2_.doc Iran J Arthropod-Borne Dis, 2010, 4(2): 11–18 M Shayeghi et al.: Application of Acoustical … 11 Original Articles Application of Acoustical Processor Reactors for Degradation of Diazinon from Surface Water M Shayeghi1, *MH Dehghani2, AH Mahvi3, K Azam4 1Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran 2Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Center for Environmental Research, Tehran, Iran 3Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran 4Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran (Received 5 Jan 2010; accepted 24 Jul 2010) Abstract Background: Since organophosphorus pesticides are widely used for industry and insect control in agricultural crops, their fate in the environment is very important. Pesticide contamination of surface water has been recog- nized as a major contaminant in world because of their potential toxicity towards human and animals. The objec- tive of this research was to investigate the influence of various parameters including the influence of time, power, and initial concentration on degradation of diazinon pesticide. Methods: The sonochemical degradation of diazinon was investigated using acoustical processor reactor. Acous- tical processor reactor with 130 kHz was used to study the degradation of pesticide solution. Samples were ana- lyzed using HPLC at different time intervals. Effectiveness of APR at different times (20, 40, 60, 80, 100, and 120 min), concentrations (2, 4 and 8 mg/L) and powers (300W, 400W, 500W) were compared. Results: The degradation of the diazinon at lower concentrations was greater in comparison to higher concentra- tions. There was also direct correlation between power and diazinon degradation. In addition, when the power increased, the ability to degraded diazinon increased. Conclusion: The sonodegradation of diazinon pesticide at different concentrations and powers was successfully provided. It has been shown that APR can be used to reduce the concentration of dissolved pesticide using high frequency. Keywords: Diazinon, acoustical processor reactor, initial concentration, power, time Introduction Pesticides are known to be carcino- genic, mutagenic, teratogenic and simulta- neously resistant to destruction in environ- ment. Organophosphorus pesticides are ex- tremely toxic, acting on acetyl choli- nesterase activity (Safi 2002). Diazinon [O, O-diethyl-O- (2-isopropyl-6-methy-4-pyri- midinyl) phosphorothioate] is a commonly used insecticide in the organophosphate che- mical family. Diazinon decomposes above 120° C and is susceptible to oxidation. It is stable at pH 7.0 and can persist in the environment for as long as six months (US EPA 1986, WHO 1998). Many reports for sonochemical treat- ment of water and wastewater plants have been considered (Krueger and Seiber 1984, Norwood 1990, Somich 1990, Benito et al. 2005, Dehghani et al. 2006, 2007a, 2007b, 2008, Asakura et al. 2008). Mahvi et al. *Corresponding author: Dr Mohammad Hadi Dehghani, Email: dehghanihadi@yahoo.com Iran J Arthropod-Borne Dis, 2010, 4(2): 11–18 M Shayeghi et al.: Application of Acoustical … 12 2009). A variety of physical and chemical methods are employed for the removal of aqueous pesticides. Several techniques to eliminate pesticides have been so far con- sidered, like ozonation (Legube 1987, Beni- tez 1995, Asakura 2005,), adsorption by activated coke (Battaglia 1989, Richard 1991, Mason and Lorimer 2002,), ultravio- let irradiation and hydrogen peroxide (Pe- terson et al. 1988, Raha and Das 1990, Bat- tacharya 1994, Baron et al. 1994, Benitez 1995 b, Bellobono et al. 1995, Boisdon and Cacite´ de la 1995, Bourgine et al. 1995, Mansour et al. 1997, Huston and Pignatello 1999, Bachman and Patterson 1999). Acoustical Processor Reactor (APR) has been used to induce or accelerate a va- riety of reactions. These reactors have a board range of industrial applications, in- cluding water and wastewater treatment (Suslick 1994, Suslick and Crum 1997, Suslick and Price 1999, Joyce 2002, Gogate et al. 2003, Dehghani et al. 2008, 2010). Since 1990, there has been increasing inter- est in the sonochemical degradation of aqueous solutions both in water and waste- water decontamination (Laborde and Bouyer 1998, Destaillats et al. 2001,). The chemical effects of APR of aqueous environment are believed to be related with acoustic cavita- tions Ultrasound irradiation enhances che- mical reactivity through cavitation, the for- mation of gas bubbles in a liquid, which rapidly expand and implode. The chemical aspects are realized during and immediately after collapse of a vapor-filled cavitation bubbles. Bubble collapse induced by cavita- tion produces intense local heating, high pressures (Hung and Hoffmann 1999, Beckett and Hua 2001,Wayment and Casadonte 2002, Mason et al. 2004, Hua et al. 2005, Dehghani and Changani 2006, Arrojo and Benito 2008,). These hot spots have tem- peratures of roughly 5000 K, and pressures of about 500 atm as well as the production of free radicals. These conditions provide several possible pathways of degradation, such as free radical attack. (Mason 1991, Hua et al. 1995, Hua and Hoffman 1997, Mason and Lorimer 1998, Crum et al. 1999, Hua and Pfalzer-Thompson 2001, Asakura et al. 2008). The present research deals with the sonochemical degradation of selected di- azinon pesticide in the APR. The objective was to determine the potential of batch re- actor for degradation of diazinon in differ- ent conditions such as power, concentra- tion, and degradation time. Materials and Methods Procedures Sample was prepared by dissolving a measured volume of pesticide with 95% concentration in 1000 ml of distilled water in a volumetric vessel. All organic solvents (acetone, hexane) were of analytical reagent grade, supplied by Merk Company. Ho- mogenized samples were pretreated at 18– 20º C and then were placed in reactor. Re- actor temperature was controlled with the help of condensation water surrounding the reactor. Therefore, temperature did not ex- ceeded 18-20º C in all experiments. Diazi- non pesticide samples were exposed to a fixed frequency of 130 kHz. Characteristics of the reactor and experiment conditions presented in Table 1 and 2 respectively. All sonicated solutions were analyzed for di- azinon and degradation operation by HPLC at different time intervals. Characteristics of the HPLC system were as following (Table 3). All the analyses were performed ac- cording to the procedures outlined in stan- dard methods (APHA 2005). Calculation method The definition of diazinon degradation per- centage (DP) was as follows: DP = (C1 – C2) / C1 × 100 Iran J Arthropod-Borne Dis, 2010, 4(2): 11–18 M Shayeghi et al.: Application of Acoustical … 13 Where DP (%) is the degradation percent- age of the reactor, C1 is the initial concentration of diazinon (mg/l), C2 is the concentration of diazinon (mg/l) after reaction for (t) time Statistical analysis The degradation of diazinon using APR was analyzed statistically by SPSS 11.5 and Excel software. The data were analyzed using one way ANOVA, Post-hoc test and multiple regressions. The variables were degradation time, concentration and power. Degradation was depended variable. Results An aqueous solution of diazinon was sonicated in a batch reactor at different concentrations, powers, fixed frequency, and different times. During the sonochemi- cal degradation, the concentrations of di- azinon were determined and the ultraviolet absorption spectra of the aqueous solution of diazinon were measured. Effect of initial concentration The effect of initial diazinon concentra- tion on the removal percentage is shown Fig.1, 2 and 3. Different initial concentra- tions resulted in different removal percent- age. The removal percentage decreased with increasing initial diazinon concentra- tion in the range of 2 mg/l( Mean= 95.3422 and SD= 3.40735), 4 mg/l (Mean= 91.6033 and SD= 2.84080) and 8 mg/l (Mean= 83. 8294 and SD= 5.89949) under sonication after 120 min. Clearly, the rate of sono- chemical degradation was slow in the pres- ence of high concentration of diazinon. On the other hand, the increase of diazinon concentration in the solutions significantly decreased the rate of diazinon degradation after 120 min. As expected, the degradation percentage is the highest for the lowest concentration. The best status for pesticide degradation was 2 mg/l under sonication after 120 min. One way ANOVA and Post Hoc test indicated that mean difference is significant (P< 0.05). Effect of time The effect of time on the degradation of diazinon was shown in Fig. 1, 2 and 3. The degradation percentage of diazinon was 90.83% (2 mg/l), 86.11% (4 mg/l) and 76.99% (8 mg/l) for 300 W (Fig. 1). In ad- dition, degradation percentage was 96.11 % (2 mg /l), 90.95% (4 mg/l) and 84.54% (8 mg/l) for 400 W (Fig. 2). However, degra- dation percentage was 98.44% (2 mg /l), 94.07% (4 mg/l) and 88.98 % (8 mg/l) after 120 minutes for 500 W (Fig. 3). According to regression analysis using backward method, the mean difference is no signifi- cant. On the other word, degradation time is excluded variables. Effect of pH The results showed that sonolysis had no considerable effect on pH (6.8-7) of pesticide samples, and the minor change occurred were no significant. Effect of temperature In this study, the reaction temperature was controlled with condensation water sur- rounding the reactor bath. Therefore, ex- periments showed that temperature increase of pesticide samples during sonication had no considerable effect on degradation of pesticide. Effect of acoustic power The effect of power on the diazinon degradation was also studied for 300 W (Mean= 85.4694±6.14753), 400 W (Mean= 90.4689±5.61704) and 500 W (Mean= 94.8367±3.41482). One way ANOVA and Post Hoc test showed the mean difference is significant between removal efficiencies at Iran J Arthropod-Borne Dis, 2010, 4(2): 11–18 M Shayeghi et al.: Application of Acoustical … 14 0.05 level, when the power rose from 300 W to 500 W According to statistical analysis, linear relationships equations were as follows: Degradation ratio= 80.495 -1.922 con- centration + 0.047 power In addition, determination coefficient (R square) for above model showed that high- est changes related to degradation efficiency depends upon concentration and power (R square= 0.937). Table 1. Characteristics of acoustical reactor Parameter Characteristics Power 300 W, 400 W, 500 W Frequency 130 kHz Reactor type Basin Flow type Batch Capacity 1.5 L Table 2. Experimental conditions for degradation operations Frequency (kHz) Power (W) Sonication time (min) Initial concentration (mg/L) Sample volume (mL) Temp ( ºC) pH 130 300, 400 , 500 20, 40, 60, 80, 100, 120 2, 4, 8 200 18–20 6.8–7 Table 3. Characteristics of HPLC system Column Inertsil Mobile phase Temperature Detector UV Flow rate ODS – 2 CH3CN/H2O (65:35, V:V) 40 ºC wavelength 210 nm 1mL/min y = -0.0022x + 98.823 R2 = 0.1611 y = -0.0068x + 96.988 R2 = 0.2963 y = 0.0005x + 90.809 R2 = 0.1891 90 91 92 93 94 95 96 97 98 99 100 0 20 40 60 80 100 120 140 Time (min) D eg ra da tio n (% ) 300 w 400 w 500 w Fig. 1. Comparison of degradation percentage at different powers for 2 mg/L Iran J Arthropod-Borne Dis, 2010, 4(2): 11–18 M Shayeghi et al.: Application of Acoustical … 15 y = -0.0083x + 95.464 R2 = 0.1711 y = -0.0212x + 89.852 R2 = 0.5084 y = -0.0007x + 91.606 R2 = 0.003 84 86 88 90 92 94 96 98 0 20 40 60 80 100 120 140 Time (min) D eg ra da tio n (% ) 300 w 400 w 500 w Fig. 2. Comparison of degradation percentage at different powers for 4 mg/L y = 0.0085x + 90.367 R2 = 0.0298 y = 0.0096x + 82.657 R2 = 0.3015 y = 0.0064x + 76.746 R2 = 0.1659 0 10 20 30 40 50 60 70 80 90 100 0 20 40 60 80 100 120 140 Time (min) D eg ra da tio n (% ) 300 w 400 w 500 w Fig. 3. Comparison of degradation percentage at different powers for 8 mg/L Discussion It is possible to degrade efficiently the diazinon pesticide in water by APR. Statis- tical analysis shows that power and initial concentration are effective parameters for degradation of diazinon. Matouq et al. (2008) indicated that per- centage of degradation rate of diazinon varies with initial concentration after ex- posing to irradiation which is basically the steady state phase. Matouq et al. (2008) re- Iran J Arthropod-Borne Dis, 2010, 4(2): 11–18 M Shayeghi et al.: Application of Acoustical … 16 ported that initial concentration decreases with time. Hua et al. 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