Technical Journal of Engineering and Applied Sciences Available online at www.tjeas.com 2015 TJEAS Journal-2015-5-2/12-16 ISSN 2051-0853 2015 TJEAS Oxidation of aniline with photo-fenton advanced oxidation process from aqueous solutions in batch reactor Esmaeil Azizi 1, Mehdi Ghayebzadeh 1, Masoumeh Beikmohammadi 2, Kiomars Sharafi 3, Meghdad Pirsaheb 1 * 1. Research Center for Environmental Determinants of Health, Kermanshah University of Medical Sciences, Kermanshah, Iran 2. Department ofenvironmental Health Engineering, school of public health, Semnan University of Medical Sciences, Semnan, Iran 3. Research Center for Environmental Determinants of Health, Kermanshah University of Medical Sciences, Kermanshah, Iran and Phd Student of Environmental Health Engineering Department, Tehran University of Medical Sciences, Tehran, Iran *Correspondence author email: mpirsaheb@yahoo.com ABSTRACT: Fenton-driven oxidation of aniline in water by photo-fenton advanced oxidation process in batch reactor was investigated in this study.the objective of the study was toevaluation of the feasibility of MTBE degradation with photo-fenton advanced oxidation process under optimal conditions.the effectsof different operational parameters such as ph, initial concentration of Fentonreagent and initial aniline concentration on the degradation of aniline have been studied. Results showed that the electro-fentonprocess has a stronger oxidative ability to oxidation of aniline andhighest removal efficiency of aniline (84.14%) achieved when ph value of solution, initial aniline concentration and Fe +2 /H 2 O 2 ratio was 3,0.5 mmol L -1 and 6.66/100 mg/l respectively. The data presented in this paper clearly indicate that Fe +2 /H 2 O 2 /UVhas sufficient capability in order to removal of organic such as aniline from aqueous solutions. Furthermore, the present study showed the potential use of photo-fenton process for aniline containing wastewater treatment. Key words: Aniline, Advanced Oxidation process (AOP S ), photo-fenton INTRODUCTION Aniline is one of the most toxic aromatic pollutants[1]; and is an important compound that widely used as an intermediate or precursor in the manufacture of organic synthesis, such as azo dyes, rubber industries, antioxidants, fuel additives, corrosion inhibitors, pesticides, antiseptic agents, medicines for poultry, pharmaceutical synthesis, etc[2, 3]. Wastewaters from these manufacturers that contaminated with Aniline can pose adverse impacts on water bodes due to its refractory chemical structure and highly toxic properties[4]. Aniline has also been classified by the International Agency for Research on Cancer (IARC) as a group 2B carcinogen, Due to its toxicity, potential carcinogenic and mutagenic effects[5]. As a result appropriate and effective treatment technologies are needed in order to environmental protection and avoid their dangerous environmental accumulation. Photofenton process (Fe +2 /H 2 O 2 /UV) is one of the most used and beneficial advanced oxidation processes (AOP S ) that can provide the destruction of refractory and hazardous organic compounds[4]. Most important factor in these processes is the generation of extremely reactive Hydroxyl radicals that can readily oxidize organic/inorganic pollutants in water and wastewater and convert them into simple, relatively harmless substances[6]. Fenton reaction involves several sequential reaction steps which can be described as equations (Eq. 1-7)[7, 8]: Fe 2+ +H 2 O 2 Fe 3+ + OH + OH k 1 = 76M 1 s 1 (1 Fe 3+ +H 2 O 2 Fe 2+ + OOH + H + k 2 = 0.001 0.1M 1 s 1 (2 Fe 3+ +HO 2 Fe 2+ +H + +O 2 k 3 = 1.2 10 6 M 1 s 1 (3 OH + H 2 O 2 OOH + H 2 O k 4 = (1.2 4.5) 10 7 M 1 s -1 (4 OH + Fe 2+ Fe 3+ +OH k 5 = 4.3 108M 1 s (5
OH + OH H 2 O 2 k 6 = 5.3 109M 1 s 1 (6 OH + OOH O 2 +H 2 O k 7 = 1 10 10 M 1 s 1 (7 Use of Ultraviolet radiation in Fenton process can promote OH generation in oxidation system. Several reports have evaluated the efficiency of Fe +2 /H 2 O 2 /UV for the removal of contaminants in laboratory and surface waters [9-11].The degradation of phenol was recently evaluatedusing a medium pressure UV/Fenton system[12]. In another study the degradation of wastewater containing organic compounds was evaluated in solar reactors (sunlight for UV resource)[13]. Some studies focused on real wastewater treatment such as textile [14], cellulose bleaching[15], olive mill[16] effluents etc. In this study, an experimental design was employed, based on the removal criteria of Aniline from aqueous solution. Regarding the optimum photo- Fenton conditions, the effects of reagent concentrations (H 2 O 2 and Fe 2+ ) and initial ph were also investigated by the photo-fenton process. MATERIALS AND METHODS Oxidation reactor Figure 1 shows a schematic of Fe+2/H2O2/UV reactor.a custom-made reactor made of Plexiglas with 2 liter capacity, included a medium pressure (MP) UV lamp with a 254 nm maximum wavelength and intensity of 50W (0.315 W/cm2) housed inside a quartz box with 6 cm in diameter used for all irradiations. To avoid any energy escape, the reactor was covered with aluminum foil sheet. In order to establish equalized conditions throughout the reactor, a circulating pump was used inside the reactor with Qmax 300 dm3/h and, Hmax 0.6 m. A cooling water flow, surrounding the reactor, was used to control the temperature inside the reactor. Chemicals and Analytical methods Merck analytical quality chemicals such as Hydrogen peroxide %35 (H2O2), Sodium hydroxide (NaOH) and sulfuric acid (H2SO4), were used in preparation of reagents. The ph value of the solutions was measured using by a Jenway 3040 brand ph-meter thatwas calibrated with standard buffers (ph 4.0, 7.0 and 10.0)at 25 C.The concentration of Aniline in water was detected byultraviolet visible spectrophotometry. The UV vis spectra of Aniline were recorded between the ranges of 200 800 nm using a UV vis spectrophotometer (Jenwey 5053) witha 1 cm path length spectrometric quartz cell. The maximum absorbance wavelength (λmax) of Aniline can be found at 282 nmfrom the spectra. Therefore, the concentration of the Aniline inwater at different reaction times was determined by measuringthe absorption intensity at 282 nm and from a calibration curve. Experimental procedure The main objective of this study was to evaluate the performance of photo-fenton process (Fe+2/H2O2/UV) in oxidizing of Aniline from synthetic wastewater. Complex organic compounds can be broke down into simpler compounds by the oxidation process following by adsorption techniques to remove. Laboratory scale experiments involved treating the Aniline by photo-fenton processin a batch system. After turning on the UV lamp, required amount of Fenton injected into the reactor and at intervals of 10 minutes, the sampling was done.samples immediately measured by spectrophotometer and data were recorded. Figure 1. 1- Reactor, 2- Quartz cover, 3- UV lamp, 4- circulator pump, 5- chemicals injection vessel, 6- cooling water, 7- cooling water circulator 13
RESULTS The use of Fenton in conjunction with UV, enhances the degradation of organic compounds due to the contribution of OH radicals generated from the direct photolysis of H 2 O 2, i.e. with a quantum yield of two OH radicals formed per quantum of radiation which are absorbed so as to oxidize and destroyaniline compound. The study of the effect of oxidation conditions such as ph, initial Fen toneconcentration and oxidation time on oxidation performance in Aniline removal revealed the results described in the following chapters. Effect of ph ph is a very effective factor in advanced oxidation processes [17]. Alkaline conditions have been reported unsuitable for advanced oxidation processes [18, 19]. According to the previous studies of advanced oxidation process by Fe+2/H2O2/UV, the proper range of ph for this process was slightly acidic[20, 21]. Generated hydroxyl radical from previous step would hydrolysis to water molecules at very strong acidic condition subsequently. On the other hand, the slight acidic and neutral ph conditions cannot break the H2O2molecules to producehydroxyl radicals. For the study of the effect of ph on the process, ph range (2, 3, 5, 7 and 9) was considered as variable and other parameters as constant. In order to determine optimum range of ph,1mmol L-1Aniline was oxidized in Fenton ratio of 6.66/100 mg/l (Fe+2/H2O2) and 90 min oxidation time. Fig. 2 shows the effects of ph variations on Aniline removal. In general, the Aniline removal increased in acidic condition (low ph values). However, in ph<3, the efficiency reduced sharply. ThereforepH 3 was found the optimum ph for Fe+2/H2O2/UV process with 58.14% Aniline removal.this can be explained that the decreased aniline degradation inthe neutral and alkaline media might result from reduction of OH due to the precipitationof iron (Fe2+ and Fe3+) and consequently less hydroxylradicals are generated due to the presence of less free iron ions[22]. Figure 2.Effect of the initial ph value on the degradation of Aniline ([Aniline] 0= 1mmol L -1, (Fe +2 /H 2O 2)= 6.66/100 mg/l, and 90 min oxidation Effect of Fenton concentration The effect of Fentondosage on the degradation of Aniline in thisprocess was studied and the results were shown in Fig. 3. WhenFentonratio (Fe +2 /H 2 O 2 ) was increased from 3.33/50 to 5/75 mg/l, thedegradation efficiency of 1mmol L -1 Aniline went up from 27.29% to 49.11%within 60 min reaction. Further increase of Fentonconcentrationfrom 5/75 to 6.66/100 mg/lfe +2 /H 2 O 2 resulted in the degradation efficiency ofanilinealso increased but not obvious and efficiency of Aniline removal was reached to 57.11%.Increase of Fenton concentration resultedin increasing production of OH and consequently enhancedthe aniline degradation performance. Results indicated that it is important to control thefenton concentration in photo-fenton process and according to the results optimum dosage for Fenton reagent (Fe +2 /H 2 O 2 ) was 6.66/100 mg/l. 14
Figure 3.Effect of the initial Fenton concentration (3.33/50, 5/75 and 6.66/100 mg/l) on the degradation of Aniline ([Aniline] 0 = 1mmol L -1, ph=3 Effect of initial Aniline concentration The effect of initial Aniline concentration in this process wasstudied and the results were shown in Fig. 4. Three concentration of Aniline (0.5, 1.0. 2.0 mmoll -1 ) were studied and as can be seen in Fig. 4 the degradation of Aniline was inversely proportional to the initialaniline concentration. For example, the degradation efficiencyof Aniline decreased from 84.12% to 56.29% and 31.31% within 60 min ofreaction time as a consequence of increasing Aniline concentrationfrom 0.5 to 1.0 and 2.0mmol L -1 respectively. This is due to that when theinitial concentration of Aniline is increased but the generation of OH is not increased correspondingly, so a relative lower OHconcentration resulted in the decrease of degradation efficiencyof Aniline. Figure 4. Effect of the initial Aniline concentration (0.5, 1.0 and 2.0 mmol L -1 ) on the degradation of Aniline ([Aniline] 0= 1mmol L-1, ph=3 CONCLUSIONS Applicability of Fe +2 /H 2 O 2 /UVadvanced oxidation process for Aniline removal fromaqueous solutions was investigated and suitable ph and oxidant concentration for operation were determined. The variation of ph has a pronounced effect ondegradation rate; acidiccondition promotes the rate considerablybecause of more generation of OH, whereas alkalineenvironment casts a negative effect on degradation. Also the oxidant concentration directly influences the degradationrate of Aniline. ConsequentlypH 3 and Fentonratio6.66/100mg/L was found optimum resulting 84.14% removal of 0.5 mmol L -1 of Aniline concentration. The key success of the study was high removal of the Aniline withphoto-fenton advanced oxidation process operated in suitable condition is suggested as an effective method for the treatment of high polluted water bodies with Aniline. 15
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