Date Published: August 4, 2017
Publisher: Springer Berlin Heidelberg
Author(s): Ali Toolabi, Mohammad Malakootian, Mohammad Taghi Ghaneian, Ali Esrafili, Mohammad Hassan Ehrampoush, Maesome Tabatabaei, Mohsen AskarShahi.
Contamination of water resources by acetamiprid pesticide is considered one of the main environmental problems. The aim of this study was the optimization of acetamiprid removal from aqueous solutions by TiO2/Fe3O4/SiO2 nanocomposite using the response surface methodology (RSM) with toxicity assessment by Pseudomonas aeruginosa BCRC. To obtain the optimum condition for acetamiprid degradation using RSM and central composite design (CCD). The magnetic TiO2/Fe3O4/SiO2 nanocomposite was synthesized using co-precipitation and sol–gel methods. The surface morphology of the nanocomposite and magnetic properties of the as-synthesized Fe3O4 nanoparticles were characterised by scanning electron microscope and vibrating sample magnetometer, respectively. In this study, toxicity assessment tests have been carried out by determining the activity of dehydrogenase enzyme reducing Resazurin (RR) and colony forming unit (CFU) methods. According to CCD, quadratic optimal model with R2 = 0.99 was used. By analysis of variance, the most effective values of each factor were determined in each experiment. According to the results, the most optimal conditions for removal efficiency of acetamiprid (pH = 7.5, contact time = 65 min, and dose of nanoparticle 550 mg/L) was obtained at 76.55%. Effect concentration (EC50) for RR and CFU test were 1.950 and 2.050 mg/L, respectively. Based on the results obtained from the model, predicted response values showed high congruence with actual response values. And, the model was suitable for the experiment’s design conditions.
Due to the ever-increasing growth of population and increased need for agricultural crops, food and fight with pathogenic carriers, use of pesticides has also grown in various sectors. Contamination of water with pesticides is usually caused by agricultural runoffs and the wastewater of toxin-producing industries. The flow of surface water owing to rainfall or irrigation of farmlands carries these materials and introduces them to rivulets and rivers (Samadi et al. 2010; Akhlaghian and Sohrabi 2015; Hossain et al. 2015; Ryberg and Gilliomb 2015; Stehle and Schulz 2015). Today, different pesticides are used for fighting vectors. Acetamiprid is a systemic, contact, and digestive insecticide, belonging to a new class of neonicotinoid insecticides, which is considered one of the most important micro-contaminants. Its solubility in water is 4250 mg/L at 25 °C and has a half-life of 5–15 days in the environment (Fasnabi et al. 2012; Carra et al. 2015). Acetamiprid is widely used in controlling pests of agricultural crops (John et al. 2016). However, most of the time due to unfamiliarity of chemical toxins, consumers are unaware about the damaging effects of these toxins and correct fighting principles. Due to high solubility, stability and presence of some resistant compounds in the structure of acetamiprid, conventional water and wastewater treatment technologies are not effective in its removal (Miguel et al. 2012; Mutsee 2013; Shanping et al. 2014; Sahithya and Das 2015; Jafari et al. 2014).
The Fe3O4/SiO2/TiO2 nanoparticles were successfully synthesized by sol–gel methods. The SEM image clearly indicates that the as-synthesized Fe3O4/SiO2/TiO2 nanoparticles are composed of spheres having uniform features. According to the results in the current study, The ANOVA of the second order quadratic polynomial model for the responses show that the models are significant. The Model F-value of 175.85 implies the model is significant, Table 4. There is only a 0.01% chance that a model F value this large could occur due to noise. Values of Prob > F less than 0.0500 indicate model terms are significant (Lee and Hamid 2015; Dong and Sartaj 2016). In their study, It was observed that maximum removal efficiency was when pH near 6.5 and contact time between 65 and 73 min. Minimum removal efficiency when pH near 9. It was also observed that at lower pH values, the removal of acetamiprid was more than alkaline state. As a result, more hydrolysis of acetamiprid occurred at solutions containing hydrogen. According to the results Fig. 3 contact time was an effective parameter in decomposition of acetamiprid toxin, such that with the increase in contact time from 10 to 65 min, the extent of acetamiprid decomposition grew from 38 to 75%. After this, the removal efficiency saw only minor changes, but at contact time of 70 min, it became constant. This is due to greater electron excitation off the catalyst’s surface, production of more active radicals, and the possibility of greater physical collision of the catalyst’s active agents with acetamiprid, providing enough time for collision and decomposition of acetamiprid.Table 4ANOVA for response surface quadratic model: analysis of variance table (partial sum of squares—Type III)SourceSum of squaresdfMean squareF valuep value Prob > FModel158114112.9175.85<0.0001 SignificantA-pH282.61282.6440.2<0.0001–B-contact time1.56111.5612.4300.1398–C-Concentration of acetamiprid339.21339.2528.2<0.0001–D-dose of N.P236.01236.0367.5<0.0001–AB5.26715.2678.2030.01183–AC0.302510.30250.47110.5030–AD0.00902510.0090250.014060.9072–BC0.705610.70561.0990.3111–BD11.19111.1917.430.06001–CD2.65712.6574.138<0.0001–A2540.51540.5841.8<0.0001–B2228.61228.6356.0<0.0001–C222.30122.3034.73<0.0001–D281.18181.18126.4<0.0001–Residual9.632150.6421–––Lack of fit0.002383100.00023830.00012381.0000 Not significantPure error9.62951.926–––Cor total159029–––– Source: http://doi.org/10.1186/s13568-017-0455-5