Degradation of Paracetamol by Electro-Fenton and         Photoelectro-Fenton Processes Using a Double Cathode         Elec...
1987) These techniques transfer the pollutants from one phase to a less harmful phase makingthem more practical than other...
acetaminophen efficiently which only obtained an effiecieny of 16.3%. (Klamerth et al., 2010)Photo-fenton , uses UV light ...
Experimental ApparatusA cylindrical reactor having concentric electrodes were used in this study as shown in figures 1 aan...
requires fewer runs when compared to other RSM designs making its application moreeconomical. Lower and upper limits of th...
to a higher treatment efficiency of the process. On the otherhand, increasing the amount ofapplied current density can res...
Photoelectro-Fenton Process% ACT Degradation = 19.38 +1287.88A – 1.70B+ 76.18C + 72.82AB -1221.21AC - 0.24BC           – 1...
Condition). This was done to investigate the applicability of the model for possible scale-upoperations.  Table 3. Compari...
of the total pollutant. A fast degradation of the target compound was observed in the first 40minutes of the treatment tim...
Figure 3. COD removal for different processes operated at optimum conditions. (Electro-fenton(EF): Fe2+ = 0.087 mM, H2O2 =...
(10)The availble oxygen is the theoretical amount of reactive oxygen in the hydrogen peroxideadded. Other variables includ...
Elmolla, E.S. & Chaudhuri M., 2009a. ‘Degradation of the antibiotics amoxicillin, ampicillin and cloxacillin in    aqueous...
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Degradation of Paracetamol by Electro-Fenton and Photoelectro-Fenton Processes Using a Double Cathode Electrochemical Cell

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prepared by M.C. Lu *, M.L.Veciana**, M.D.G. de Luna*** * Department of Environmental Resources Management, Chia Nan University of Pharmacy and Science, Tainan 717, Taiwan **Environmental Engineering Graduate Program, University of the Philippines, 1011 Diliman, Quezon City, Philippines *** Department of Chemical Engineering, University of the Philippines, 1011 Diliman, Quezon City, Phi for Urban Environments in Asia, 25-28 May 2011, Manila, Philippines. organized by International Water Association (IWA).

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Degradation of Paracetamol by Electro-Fenton and Photoelectro-Fenton Processes Using a Double Cathode Electrochemical Cell

  1. 1. Degradation of Paracetamol by Electro-Fenton and Photoelectro-Fenton Processes Using a Double Cathode Electrochemical Cell M.C. Lu *, M.L.Veciana**, M.D.G. de Luna*** * Department of Environmental Resources Management, Chia Nan University of Pharmacy and Science, Tainan 717, Taiwan **Environmental Engineering Graduate Program, University of the Philippines, 1011 Diliman, Quezon City, Philippines *** Department of Chemical Engineering, University of the Philippines, 1011 Diliman, Quezon City, Philippines Abstract Acetaminophen is a widely used drugs worldwide and is one of the most frequently detected drugs in bodies of water making it a high priority trace pollutant. This study investigated the appliccability of the electro-Fenton and photoelectro-Fenton process using a double cathode electrochemical cell in the treatment of acetaminophen containing wastewater. It used the Box- Behnken design to determine the effects of initial Fe2+ and H2O2 concentrations and applied current density. Results showed that all parameters positively effect the degradation efficieny of acetaminophen with the initial Fe2+ concentration being the most significant parameter for both process. The optimum conditions obtained for maximum removal of acetaminophen were 0.087 mM Fe2+, 16.26 mM H2O2 and 37.67 Amp/m2 for the electro-Fenton process and 0.08 mM Fe2+, 14.81 mM H2O2 and 37.67 Amp/m2 for the photoelectro-Fenton process. The acetaminophen removal efficiences for electro-Fenton was 97.93% and COD removal of 42.72% while a 96.97% acetaminphen removal and 42.26% COD removal was observed for the photoelectro- Fenton method operated at optimum conditions. Therefore, due to a neglible difference between the treatment efficiencies of the two processes, the electro-Fenton method was proven to be more economically advantageous. Also the models obtanied from the study were applcable to a wide range of acetaminophen concentrations and can be used in scale-ups. Keywords Acetaminophen, electro-Fenton process, photoelectro-Fenton processINTRODUCTIONAcetaminophen (ACT) is one of the most frequently used drugs worldwide. It is one of the mostfrequently detected pharmaceutical products in sewage treatment plant effluents, surface waterand drinking water (Kim et al., 2007). It is considered a high priority trace pollutant owing to itshigh detection frequency of 22.38% and adverse environmental effects (Murray et al, 2010).Detection of this compound is greater at highly populated areas such as urban centers where drugusage is expected to reach elevated proportions.The proliferation of new synthetic compounds render conventional wastewater treatmentineffective. Advanced oxidation processes (AOPs) are now preferred to biological treatmentespecially for industrial effluents. AOPs generate powerful non-selective oxidants calledhydroxyl radicals. Hydroxyl radicals can degrade and mineralize a wide variety of pollutants(Masomboon et al., 2010). This is often operated at near ambient and air pressure. (Glaze et al.,
  2. 2. 1987) These techniques transfer the pollutants from one phase to a less harmful phase makingthem more practical than other existing technologies. (Elmolla & Chaudhuri, 2010a )One of the widely used AOP is the Fenton process which uses hydrogen peroxide (H2O2) andferrous ions (Fe2+) in the generation of hydroxyl radicals which can degrade and mineralize awide variety of pollutants. (Masomboon et al., 2010) In this process, hydrogen peroxide iscatalyzed by the ferrous ion to produce the hydroxyl radicals as shown in equation 1. (Ting et al.,2009) Fe2+ + H2O2 → Fe3+ + OH− + •OH k = 53–76M−1 s−1 (1)These hydroxyl radicals then react with the pollutants like organic compounds resulting to itsdegradation and mineralization. (Masomboon et al., 2010) •OH + organics → products (2)Ferrous ions are able to regenerate through the reduction of ferric species (Fe3+) by hydrogenperoxide as shown in equation 3. (Ting et al., 2009) This reaction enables the propagation of theFenton reaction. H2O2 + Fe3+ → Fe2+ + •HO2 + H+ k = 0.01M−1 s−1 (3)One of the major disadvantages of the Fenton process is the large production of ferric hydroxidesludge during the neutralization stage of the process. As can be observed in equations 1 and 3, alarge difference between the rate constants can be seen, which results to the consumption offerrous ions more rapidly rather than its regeneration. Because of this, additional treatment andseparation process is needed before the sludge can be disposed. (Ting et al., 2009)The Electro-Fenton (EF) process was developed to address this disadvantage. In this process,electrical current is applied to induce the reduction of ferric hydrogen sludge to form ferrous ionson the cathode. This does not only reduces the amount of sludge formed but also enhances thedegradation of target compounds. (Masomboon et al., 2010)Another electrochemical process being studied is the Photoelectro-Fenton (PEF) process. It is atype of Fenton technology which uses the same conditions as that of the Electro-Fenton process.The only difference between these two processes is the simultaneous irradiation of UVA light.This accelerates the degradation rate of organic pollutants in the reaction and also increases theregeneration rate of Fe2+. Additional peroxide •OH can also be observed due to the photolysis of[Fe(OH)]2+ and Fe(III) complexes that forms carboxylic acids as shown in equations and .(Brillas et al, 2009) [Fe(OH)]2+ + hV Fe2+ + •OH (4) Fe(OOCR)2+ + hV Fe2+ + CO2 + R• (5)Advanced oxidation methods are being applied to treat acetaminophen containing wastewater.Studies have already been made using Solar Photo Fenton but it was unable to remove
  3. 3. acetaminophen efficiently which only obtained an effiecieny of 16.3%. (Klamerth et al., 2010)Photo-fenton , uses UV light to increase the production of hydroxyl radicals thereby increasingthe efficiency of the treatment process. (Elmolla & Chaudhuri, 2009a ) For the case of solarphoto fenton it uses solar energy as light source.Heterogenous AOP were also applied in the treatment of acetaminophen which includes TiO2Phtocatalysis which gained 95% removal in 80 minutes. (Yang et al., 2008) Photocatalyticmethods includes the illumination of semiconductors such as titanium dioxide (TiO2) with highenergy photons. This process produces hydroxyl radicals which then oxidizes the targetpollutants. (Elmolla & Chaudhuri, 2010a,b,c)Other methods includes photodegradation of ACTin TiO2 suspended solution which was able to remove 95% ACT in 100 minutes (Zhang et al.,2008). The application of membrane bioreactor was also used and was able to remove 100%ACT in 48 hours. (Shariati et al., 2010)In this study the applicability of electrocehmical Fenton processes in the treatment ofacetaminophen containing wastewater was investigated. Unlike the above mentioned processes,electro-fenton and phoelectro-Fenton processes has the ability to treat even high conccentrationsof wastewater making its application possible as a pre-treatment process before the actualtreatment. The effects of important operating parameters were also studied and the system wasoptimized to obtain the maximum removal at the most economical conditions.MATERIALS AND METHODSChemicals and Analytical MethodsAll chemicals used in this study were of analytical grade and were purchased from Merck.Reagents were prepared using de-ionized water from a Millipore system with a resistivity of 18.2M cm. Synthetic wastewater with an initial concentration of 5mM was prepared from ananlytical grade acetaminophen having a 99% purity also supplied by Merck. All experimentswere conducted at room temperature and were run for 2 hours. Samples were taken at identifiedintervals for analyses and were immediately mixed into bottles containing NaOH solution toincrease its pH and stop the reaction. These were then filtered using 0.2µm filters to ensure theremoval of precipitates before analysis. Residual paracetamol concentration was measured usinga high performance liquid chromatography (HPLC) with Spectra SYSTEM model SN4000 pumpand Asahipak ODP-506D column (150mm×6mm×5_m) where the mobile phase was 60%acetonitrile with 40% DI water. Optimization of parameters were done for maximumparacetamol removal using Design Expert 7 software (Stat-Ease, Inc.,Minneapolis, USA.).Closed-reflux titration based from standard methods were used for COD measurement. Sampleswere kept for 12 hours before the analysis to remove the effect of H2O2 on the COD data.The ferrous (Fe2+) ion concentration and remaining hydrogen peroxide (H2O2) in the solutionswere measured using spectrophotometric analysis. The Fe2+ concentration was detected at 510nm after complexation with 1,10 phenanthroline solution while the remaining H2O2 wereanalyzed at 400 nm after complexing with K2TiO4.
  4. 4. Experimental ApparatusA cylindrical reactor having concentric electrodes were used in this study as shown in figures 1 aand b.Two stainless steel cathodes having and inside diameters of 2 and 13 cm respectively and atitanium coated RuO2/IrO2-coated DSA anode witn an inside diamter of 7 cm comprised the 3.5Lelectrochemical-cell reactor (diameter: 13 cm and height: 35 cm). This was operated at constantcurrent mode. For the photoelectro-Fenton process 16 UVA lights emiiting 360 nm at 3 W eachwere used. DSA Anode UVA Light (360 nm) Power Supply Power Supply Power + - + - Cathode Anode 13 7 2 Cathode (a) (b) Figure. 1. Schematic diagram of Reaction System.a. Electro-Fenton b. Photoelectro-FentonElectro-Fenton ProcessSynthetic wastewater having an initial concentration of 5 mM were treated by both processes.Pre-determined amount of FeSo4·7H2O was added into the wastewater solution. The pH wasthen adjusted to 3 before turning on the powersupply at desired current. Samples were takenbefore the addition of H2O2 to get the initial conditions of the system. The time starts after theaddition of the H2O2 to initiaite the reaction. Samples taken at specified time intervals were thenmixed with NaOH solution and then filtered using 0.2µm filters to remove possible precipitates.Photoelectro-Fenton ProcessSame experimental conditions were carried out using the photoelectro-Fenton process. As shownin Figure 1.b, 16 UVA lights were used having a maximum frequency of 360 nm. Each lightssupplies a photoionization energy of 3 W amounting to a total of 48 W.Box-Behnken Experimental DesignThe Box-Behnken Design (BBD) was used to investigate the effects of important operatingparameters in the degradation of acetaminophen and optimize the system. This is a type ofresponse surface method (RSM) which is based on three-level incomplete factorial designs. It
  5. 5. requires fewer runs when compared to other RSM designs making its application moreeconomical. Lower and upper limits of these parameters were as follows: 0.01 - 0.1 mM, 5 - 25mM and 37.67 - 113.01 A/m2 for initial [Fe2+], initial [H2O2] and applied current densityrespectively. The high, middle and low levels were designated with 1,0 and -1 respectively.These range were chosen based from prior experiments. The degradation of ACT was selected asa response factor.RESULTS AND DISCUSSIONThree experimental factors which includes the initial concentration of Fe2+ and H2O2 and currentdensity were varied for this study. These factors were chosen because it greatly affects thetreatment efficiency of the processes being investigated. Based from the results a minimum of48.6 % and 54.6% were observed for the electro-Fenton and photoelectro-Fenton processesrespectively. These were obtained at an initilal Fe2+ and H2O2 concentrations of 0.01 mM and 15mM respectively with an applied current density of 37.67 A/m2 and an intial pH of 3. Themaximum removal on the other hand for both processes were achieved at an initial concentrationof 0.1 mM for Fe2+ and 25 mM for H2O2 and an applied current density of 75.34 A/m2 also at thesame initial pH. A 99.8% removal was observed for the electro-Fenton process and a 100%removal was achieved by the photoelectro-Fenton process after two hours of treatment. Basedfrom these results, the difference between the efficiencies of these two processes decreases as theconcentrations of the Fenton reagents increases. At higher concentrations of Fenton’s reagent, anenough supply of hydroxyl radicals are produced which is enough for the treatment of thepollutant.Effect of Various Parameters in Acetaminophen Degradation EfficiencyTable 1 shows the correlation factors obatined from the BBD model for both electro-Fenton andphotoelectro-Fenton processes. These values can have a value of +1 to -1 where a positivenumber indicates that it has a direct effect on the acetaminophen degradation efficiency and anegative value means that it affects the efficiency in reverse. A higher value would also meanthat it has a greater effect on the response. Table 1. Correlation factors of different operating parameters Parameter Electro-Fenton Photoelectro-Fenton 2+ Initial Fe Conc. 0.662 0.520 Initial H2O2 Conc. 0.318 0.395 Current Density 0.296 0.320All of the factors showed a positive effect on the treatment efficiency of both processes. Anincrease in the initial concentrations of both Fe2+ and H2O2 results in a increase of hydroxylradicals as shown in equations 1. This radicals then react with the organic pollutant to transformit into less harmful products. More radicals means that more pollutant can be degraded resulting
  6. 6. to a higher treatment efficiency of the process. On the otherhand, increasing the amount ofapplied current density can result to faster regeneration of the Fe2+ ions as shown in equations 6and 7, thereby making more Fe2+ ions available for hydroxyl radical production. (Masomboon etal., 2010)On Cathode Side : Fe3+ + e- → Fe2+ (6)On Anode Side : Fe2+ → Fe3+ + e- (7)Based from these factors, the initial Fe2+ concentration was the most significant factor among thethree for both processes. As what was observed, the initial Fe2+ concentration dictates thebehaviour of degradation of acetaminophen. Also, the effect of varying Fe2+ concentration wasmore pronounced in the electro-Fenton process than the photoelectro-Fenton process having acorrelation factor of 0.662 compared to 0.520. In the electro-Fenton process, the Fe3+ ions arecontinuously regenerated in the cathode side. This increases the regeneration rate of Fe2+ ionsthereby increasing the treatment efficiency of the process. However, the photoelectro-Fentonprocess also has the ability of regenerating Fe2+ ions from ferric complexes such as Fe(OH)2+and the like aside from its regeneration in the cathode side as shown in equations 4 and 5 asmentioned by Brillas, et al. In this way, the regeneration efficiency of Fe2+ is higher in thephotoelectro-fenton process than in the electro-Fenton process. This is the reason why higherdegradation efficiencies were obtained for the PEF process even at lower initial Fe2+concentration than the EF process. Thus, the effects of varying Fe2+ concentration is lowerresulting to a lower correlation factor.On the other hand, results also showed that the PEF process has a higher correlation factor forboth the initial H2O2 concentration and the applied current density than the EF process. Due tohigher regeneration efficiency of the Fe2+ ions, the need for more H2O2 to produce morehydroxyl radicals is more pronounce in the PEF than the EF process.Optimum points and validation of the ModelAn empirical correlation between the acetaminophen degradation efficiency and the three factorswere obtained using the Box-Behnken experimental design for both processes. A reduced cubicmodel was fitted for both processes having an r-squared value of 0.9999.Electro-Fenton Process% ACT Degradation = 6.21 + 930.07A + 0.22B+ 68.46C + 75.32AB - 858.29AC - 0.74BC - 5452.29A2 - 5.44x10-003B2 - 7.86C2 - 330.63A2B + 4552.33A2C - 0.87AB2
  7. 7. Photoelectro-Fenton Process% ACT Degradation = 19.38 +1287.88A – 1.70B+ 76.18C + 72.82AB -1221.21AC - 0.24BC – 10315.67A2 + 0.06B2 - 12.24C2 -88.88A2B + 7406.28A2C – 1.80AB2These models can be use to predict the acetaminophen degradation for any values of theparameters with the initial Fe2+ (mM) and H2O2 (mM) concentrations and current (Amp) beingrepresented by A, B and C. These were obtained by correlating the response functions with thevariations in the operating parameters using the Design Expert 7 software.Optimum operating conditions for each processes are shown in table 2. These values wereobtained using the optimization tool incorporated in the Design Expert 7 software. For thisanalysis, the response factor which is the acetaminophen degradation was set at maximum whilethe applied current and initial hydrogen peroxide concentration was set at minimum. This wasdone to ensure that maximum removal can be obtained at the least possible operating cost.However, the initial Fe2+ concentration being the one most significant factor for theacetaminophen removal was set in range. Table 2. Optimum operating conditions for electro-Fenton and photoelctro-Fenton process Parameter Unit Electro-Fenton Photoelectro-Fenton Initial pH 3 3 Initial Fe2+ Conc. mM 0.087 0.08 Initial H2O2 Conc. mM 16.26 14.81 Current Density A/m2 37.67 37.67The electro-Fenton process has a higher requirement for both intial Fe2+ and H2O2 concentrationcompared to the photoelectro-Fenton process. This is mainly because the photoelectro-Fentonprocess has a higher efficiency in the regeneration of Fe2+ ions and hydroxyl radical formationdue to the application of UV lights as shown in equations 4 and 5. On the other hand, the sameamount of current density at 37.67 A/m2 was needed for both processes to obtain 100% removal.But if the amount of energy consumption for UV lights application is to be considered, theelectro-Fenton process proves to be more energy efficient compared to the photoelectro-Fentonprocess.In order to validate the models used, both processes were run at optimum conditions. Table 3shows the ACT degradation for each processes. Another run was done at 50 mM ACT using thesame ratios of parameters at the optimum condition (using the Electro-Fenton process Optimum
  8. 8. Condition). This was done to investigate the applicability of the model for possible scale-upoperations. Table 3. Comparison of predicted and actual acetaminophen degradation for each processes % ACT Degradation Process % Difference Predicted Actual Electro-Fenton 97.93 2.07 Photoelectro-Fenton 100 96.97 3.03 Electro-Fenton (50 mM ACT) 95.34 4.66As can be observed, the difference between the predicted and actual results for both processes issmall. This only proves the reliability of the model used. The usage of the same optimumconditions even at higher concentration yielded a 95.34% ACT removal which differed by 4.66%from the predicted results. The same trend was also obeserved for the COD removal for both lowand high initial ACT concentration resulting to a 42.72% and 41.14% respectively. The modelsobtained from these study are not restricted to the given initial ACT concentration It was proventhat the model can be used to a wide range of ACT concentrations and can be applied for scale-up operations.Process ComparisonTo determine the best process for the removal of acetaminophen containing wastewater, eachprocessses were run at optimum conditions. Two Fenton processes for each set of optimumconditions were also done. The results for ACT, COD and TOC removals are shown in Table 4. Table 4. Comaprison of Acetaminophen, COD and TOC removal efficiencies of each processes at optimum conditions Process %ACT %COD % TOC Removal Removal Removal Electro-Fenton 97.93 42.72 Fenton (EF Optimum) 95.83 27.48 Photoelectro-Fenton 96.97 42.26 Fenton (PEF Optimum) 95.49 29.21The difference between the degradation efficiencies of each process runs at the optimumconditions are negligible for each processes. As can be observed, the Electro-Fenton process wasable to degrade 97.93% while the photoelectro-Fenton process was able to obtain a 96.97%degradation efficiency. Both Fenton processes on the other hand was able to degrade about 95%
  9. 9. of the total pollutant. A fast degradation of the target compound was observed in the first 40minutes of the treatment time as shown in Figure 2.a.Figure 2. Acetaminophen removal for different processes operated at optimum conditions.(Electro-fenton: Fe2+ = 0.087 mM, H2O2 = 16.26 mM, Current Density = 37.67 Amp/m2;Photoelectro-Fenton: : Fe2+ = 0.08 mM, H2O2 = 14.81 mM, Current Density = 37.67 Amp/m2)However, the difference between the COD removal efficiencies between the Fenton andelectrogenerated Fenton processes are evident as shown in Figure 3. The electro-Fenton processws able to remove 42.72% COD while the photoelectro-Fenton process ws able to remove 42.26%. The Fenton processes on the other hand were only able to obtain 27-29% COD even whenoperated at the same conditions.These results shows that the electrochemically operated Fenton processes are superior to theFenton process when it comes to chemical oxygen demand removal. Formation of intermediatesduring the degradation process is one of the reason of low COD removal efficiency in the Fentonprocess. These intermediates are able to form complexes with the reagents making it harder toremove thereby decreasing the COD removal efficiency. Electro-Fenton and photoelectro-Fentonprocesses has the ability to regenerate this complexes back to simple organic acids therebyincreasing the degradation efficiency.
  10. 10. Figure 3. COD removal for different processes operated at optimum conditions. (Electro-fenton(EF): Fe2+ = 0.087 mM, H2O2 = 16.26 mM, Current Density = 37.67 Amp/m2;Photoelectro-Fenton (PEF) : Fe2+ = 0.08 mM, H2O2 = 14.81 mM, Current Density = 37.67Amp/m2)Since the difference between the treatment efficiencies of electro-Fenton and photoelectro-Fenton processes are not concrete, the use of energy-related parameters are utilized in thesestudy as presented in Table 5. These are important parameters for comparison to see the viabilityof each process. Table 5. Comparison of H2O2 efficiency, current efficiency and energy cost for electro-Fenton and photoelectro-Fenton processes Process %H2O2 %Current Energy Cost Efficiency Efficiency (kWh COD-1) Electro-Fenton 134 408 3.53 Photoelectro-Fenton 149 413 3.56The H2O2 efficiency, current efficiency and energy cost for both processes were calculated usingequations 8,9 and 10. (8) (9)
  11. 11. (10)The availble oxygen is the theoretical amount of reactive oxygen in the hydrogen peroxideadded. Other variables included in the equations are (∆COD)t which is the experimental CODdecay (g O2/L) at time t (s), F is the Faradays constant (96487 C/mol), Vs is the volume of thesolution (L), I is the current applied (A) and 8 is the oxygen equivalent mass (g/eq). Ecell on theotherhand is the average cell voltage (V) for the electrolysis time. The H2O2 efficiency can havea value greater than 100 since the COD removal is not only attributed to Fenton reaction alone.This scenario was also observed by Masomboon et al. in their study regarding the degradation ofdimethyaniline. The photoelcetro-Fenton process has a slightly higher H2O2 and currentefficiencies than the electro-Fenton process. But in terms of energy consumption the electro-Fenton process requires lower energy since it does not need additional UVA irradaition fordegradation making the electro-Fenton process more suitable and economical.CONCLUSIONThe electro-Fenton process was proven to be more efficient in the treatment of acetaminophencontaining wastewater than the photoelectro-Fenton method. Although the difference betweenthe removal efficiencies of both processes are negligible, it is more energy efficient than thephotoelectro-Fenton method. All parameters also showed a positive effect on the degradationefficiency with the Fe2+ initial concentration being the most impportant parameter among thethree for both processes. Also the Box-Behnken statistical design was proven to be an effectiveway of optimizing the given process. The optimum conditions obtained for maximum removal ofacetaminophen were 0.087 mM Fe2+, 16.26 mM H2O2 and 37.67 Amp/m2 for the electro-Fentonprocess and 0.08 mM Fe2+, 14.81 mM H2O2 and 37.67 Amp/m2 for the photoelectro-Fentonprocess. The models obtained were also not limited to the specific set of conditions employedduring the study but can be used at a wider range of acetaminophen concentrations.ACKNOWLEDGMENTThis research was finacially supported by the National Science Council, Taiwan (Grant: NSC 96-2628-E-641-001-MY3)REFERENCESAPHA, AWWA, and WPCF, 2000. Standard Methods for the Examination of Water and Wastewater, 20th ed.Brillas, E., Sire´s, I. & Oturan, M.A., 2009. ‘Electro-Fenton Process and Related Electrochemical Technologies Based on Fenton’s Reaction Chemistry’,Elmolla, E.S. & Chaudhuri M., 2010a. ‘Comparison of different advanced oxidation processes for treatment of antibiotic aqueous solution’, Desalination, vol. 256,pp. 43–47Elmolla, E.S. & Chaudhuri M., 2010b. ‘Degradation of amoxicillin, ampicillin and cloxacillin antibiotics in aqueous solution by the UV/ZnO photocatalytic process’, Journal of Hazardous Materials, vol.173, pp. 445–449Elmolla, E.S. & Chaudhuri M., 2010c. ‘Photocatalytic degradation of amoxicillin, ampicillin and cloxacillin antibiotics in aqueous solution using UV/TiO2 and UV/H2O2/TiO2 photocatalysis’, Desalination, vol. 252,pp. 46-52
  12. 12. Elmolla, E.S. & Chaudhuri M., 2009a. ‘Degradation of the antibiotics amoxicillin, ampicillin and cloxacillin in aqueous solution by the photo-Fenton process’, Journal of Hazardous Materials, vol.172, pp. 1476–1481Glaze, W.H., Kang, J.W., & Chapin. D.H., 1987. ‘The Chemistry Of Water Treatment Processes Involving Ozone, Hydrogen Peroxide and Ultraviolet Radiation.’ Ozone Science Engineering, vol.9, pp. 335-352Klamerth N., Rizzo K., Malato S., Maldonado M.I, Aguera A. & Fernandez-Alba A.R., 2010. ‘Degradation of Fifteen emerging contaminants at µg/L-1 initial concentrations by mild solar photo-Fenton in MWTP effluents.’ Water Research , vol.44, pp. 545 – 55Kim Y., Choi K., Jung J., Park S., Kim P-G. And Park J.,2007.” Aquatic Toxicity of Acetaminophen, Carbamazepine,Cimetidine,Diltiazem and Six Major Sulfomides and Their Potential Ecological Risks in Korea”, Environment International, vol.33, pp.370-375Masomboon, N., Ratanatamskul, C. & Lu, M.-C., 2010. ‘Chemical oxidation of 2,6 dimethylaniline by electrochemically generated Fenton’s reagent’, Journal of Hazardous Materials, vol. 176, pp.92–98Murray K.E., Thomas S.M. & Boduor A.A., 2010 “Prioritizing Research for Trace pollutants and Emerging Contaminants in the Fresh water Environment”, Environmental Pollution, vol. 158 pp.3462-3471Ting, W-.P., Lu, M.-C. & Huang, Y.-H., 2008. ‘The reactor design and comparison of Fenton, electro-Fenton and phototelectro-Ffenton processes for mineralization of benzene sulfonic acid’, Journal of Hazardous Materials, vol. 156, pp.421-427Ting, W-.P., Lu, M.-C. & Huang, Y.-H., 2009. ‘Kinetics of 2,6-dimethylaniline degradation by electro-Fenton process’, Journal of Hazardous Materials, vol. 161, pp.1484–1490Yang L., Yu L.E., Ray M.B., 2008. “Degradation of Paracetamol in Aqueous solutions by TiO2photocatalysis’, Water Research, vol. 42, pp.3480-3488Zhang X.., Wu F., Wu X.W., Chen P., Deng N.., 2008. “Photodegradation of Acetaminophen in TiO2 suspended solution’, Journal of Hazardous Materials, vol. 157, pp.300-307

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