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Degradation of Ethanolamine by Fluidized-bed Fenton         Process         J. Anotai*,**, C.M. Chen***, L. Bellotindos***...
considered to be slow or non-biodegradable due to its low BOD/COD ratio(Park et al. 2001).Moreover, the organic stream com...
Chemicals                                                                           ‧Monoethanolamine, ammonia solution, f...
procedure was used but without using carriers in the reactor.Chemical Precipitation Experiments                           ...
Table 3. Design of experimental runs for the BOX-Behnken statistical design of fluidized-bedFenton process with 5 mM MEA. ...
Design-Expert?Software                       Monoethanolamine removal                         98.9                        ...
Design-Expert?Software                      COD removal                        64.7                        3.4            ...
Design-Expert?Software                      Total iron                         67.4                         7.4           ...
From the Box-Behnken design experiment, using Fenton process experiments, the best conditions at5 mM of MEA are pH = 3, [F...
The COD removal efficiency from Fenton and fluidized-bed Fenton processes were 57.3 % and 64.7%, respectively.            ...
Table 4. Effect of conditions for ammonia nitrogen removal    Effect of initial pH                    Effect of added rati...
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Degradation of Ethanolamine by Fluidized-bed Fenton Process

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prepared by J. Anotai*,**, C.M. Chen***, L. Bellotindos**** and M.C. Lu*** Department of Environmental Engineering, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, Bangkok 10140, Thailand (E-mail: jin.ano@kmutt.ac.th) ** National Center of Excellence for Environmental and Hazardous Waste Management (NCE-EHWM), Chulalongkorn University, Bangkok, Thailand *** Department of Environmental Resources Management, Chia-Nan Univer for Urban Environments in Asia, 25-28 May 2011, Manila, Philippines. organized by International Water Association (IWA).

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Degradation of Ethanolamine by Fluidized-bed Fenton Process

  1. 1. Degradation of Ethanolamine by Fluidized-bed Fenton Process J. Anotai*,**, C.M. Chen***, L. Bellotindos**** and M.C. Lu*** * Department of Environmental Engineering, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, Bangkok 10140, Thailand (E-mail: jin.ano@kmutt.ac.th) ** National Center of Excellence for Environmental and Hazardous Waste Management (NCE-EHWM), Chulalongkorn University, Bangkok, Thailand *** Department of Environmental Resources Management, Chia-Nan University of Pharmacy and Sciences, Tainan 717, Taiwan (E-mail: mmclu@mail.chna.edu.tw) **** Office of Research and Extension, Universidad de Zamboanga, Zamboanga City, Philippines (E-mail: bingb@uz.edu.ph) Abstract The mass production value of thin film transistor liquid crystal display (TFT-LCD) in Taiwan, which is second in the world next to Korea, will reach one trillion NT dollars yearly in the near future. However, the resulting wastewater will also increase to approximately 200,000 m3/day. The main component of this wastewater is ethanolamine (MEA). Advanced oxidation processes (AOPs) are efficient methods for degrading toxic chemicals. One of these processes, the Fluidized-bed Fenton process, was used for the treatment of the TFT-LCD wastewater to remove the monoethanolamine. In the design of experiment, the Box-Behnken design was used to optimize the operating conditions. As a result of the degradation of this wastewater by Fluidized-bed Fenton process, the treated wastewater contained a large amount of ammonia which can be removed using magnesium chloride and sodium hydrogen phosphate as the precipitating agents. A removal efficiency of 98.9% for 5mM MEA was achieved after 2 hours under optimal conditions of pH = 3, [Fe+2] = 5mM and [H2O2] = 60mM. A removal efficiency of 99.8% for ammonia nitrogen was achieved under optimal conditions of pH = 3 and molar ratio of Mg+2 :NH4+ :PO4-3 at 1.4:1:1.1. The objective of this study is to determine the optimal conditions for the degradation of ethanolamine by Fluidized-bed Fenton process and removal of ammonia from TFT-LCD wastewater. For this study, the use of Fluidized-bed Fenton process proves to be effective for the treatment of TFT-LCD wastewater from an industry with increasing demand. Since the process can result in reduced sludge production, it can be used for wastewater reuse applications. Keywords: TFT-LCD; Monoethanolamine; Fluidized-bed Fenton processINTRODUCTIONThin film transistor liquid crystal display (TFT-LCD) is one of the most popular displays used allover the world. It can be applied in computers, televisions, and even on cellular phones. Taiwan,being one of the largest TFT-LCD producing countries in the world, is experiencing problemsregarding the treatment of wastewater generated from these industries. The total amount ofwastewater from TFT-LCD manufacturing plants alone is expected to exceed 200,000 m3/day in thenear future. The amount of pollutants produced during manufacturing processes of TFT-LCDsubstantially increases due to an increasing production of the opto-electronic industry. Therefore,finding an effective and economical way to treat this wastewater is an essential work for TaiwaneseTFT-LCD industry.Most of the wastewater produced from these processes contain an organic stream, which is mostlycomposed of dimethylsulfoxide (DMSO, (CH3)2SO), monoethanolamine (MEA, H2NC2H4OH),tetramethylammonium hydroxide (TMAH, (CH3)4NOH) and isopropanol (IPA, C3H7OH). Theseare high strength nitrogen and sulfur containing wastewater. This kind of organic wastewater is 1
  2. 2. considered to be slow or non-biodegradable due to its low BOD/COD ratio(Park et al. 2001).Moreover, the organic stream comprises more than 33% of the total wastewater makingconventional treatment processes ineffective.Advanced oxidation processes (AOPs) show potential as one of the technologies for treatingrefractory compounds in waters and wastewater (Chou et al. 1999). The combination of hydrogenperoxide and ferrous salt is referred to as “ Fenton’s reagent ”. The primary oxidant in Fenton’sreagent is the hydroxyl radical (·OH) generated by the reaction of hydrogen peroxide with ferrousion (Fe2+) as shown in equation 1.H2O2 + Fe2+ → OH ‧ + OH- + Fe3+ (1)Fenton’s reagent is an effective and simple oxidant for various types of organic contaminants.The drawback of Fentons reaction is the production of substantial amount of Fe(OH)3 precipitate.To solve this problem, the application of iron oxides as catalysts in oxidizing organic contaminantshas been studied extensively (Chou. 1990; LinR. 1997; Valentine. 1998; Al-Hayek. in press). Majordisadvantage of Fenton reaction is the production of a substantial amount of ferric precipitation. Toovercome this problem, the fluidized-bed reactor (FBR) is one of the possible alternatives. In FBR,several important processes occur simultaneously including: homogeneous chemical (H2O2/Fe2+),heterogeneous chemical oxidation (H2O2/iron oxide), fluidized-bed crystallization, and reductivedissolution of iron oxides. The ferric hydrolysis product of Fenton reaction can crystallize and growon the surface of the carriers; hence, decreasing the precipitation in puffy ferric hydroxide from( Khunikakorn).In this study, it was found out that after the degradation of MEA, large amount of ammonia nitrogencould be produced, therefore, the ammonia nitrogen removal was also investigated. The presence ofammonium nitrogen in excess on bodies of water can lead to water eutrophication. Conventionalbiological and physicochemical treatment methods are the widely used treatment processes forammonium nitrogen removal. The biological process is economical for wastewater treatment, but isoften not effective for high concentration of ammonium nitrogen due to shortage of carbon sourcesfor denitrification. Various methods of physico-chemical processes can be applied to treat highconcentrations of ammonium nitrogen, such as air stripping, ion exchange, membrane separation,and chemical precipitation. Chemical precipitation of ammonium nitrogen removal by addingmagnesium salt and phosphate to form magnesium ammonium phosphate hexahydrate (MAP) is auseful method. MAP is a white crystal substance consisting of equal molar concentrations ofmagnesium, ammonium and phosphorus. The chemical reaction is expressed in Eq. (2):Mg2+ + NH4+ + PO43- + 6H2O → MgNH4PO4·6H2O (2)The method of chemical precipitation has been studied widely for the treatment of high strengthammonium nitrogen wastewater. In the present research, the chemical precipitation technology forammonium nitrogen removal from wastewater (Zhang et al. 2009) was examined.In this study, MEA degradation by fluidized-bed Fenton and Fenton process was investigated. Theeffects of varying pH values, the initial concentration of Fe2+ concentration and H2O2 dosage onMEA removal efficiency, by fluidized-bed Fenton and Fenton process were explored in greaterdetail. The removal of ammonia nitrogen by chemical precipitation was determined and theperformance of Fenton process and fluidized-bed Fenton were compared.MATERIALS AND METHODS 2
  3. 3. Chemicals ‧Monoethanolamine, ammonia solution, ferrous sulfate heptahydrate(FeSO4 7H2O), 35% hydrogen ‧peroxide(H2O2), magnesium chloride (MgCl2 6H2O) and disodium hydrogen phosphate ‧(Na2HPO4 12H2O) were purchased from Merck Company. The rest of the reagents used were atleast of reagent grade. Silica dioxide (SiO2) having an average particle diameter of 0.42-0.50 mmwas used as the main carrier in the fluidized-bed Fenton process. A 1.45 L reactor was used in allthe experiments. The fluidized-bed reactor was a cylindrical glass vessel consisting of outlet, inletand re-circulating sections, as shown in the Figure. 1. Figure. 1. The schematic diagram of fluidized-bed reactor (FBR).Analytical MethodSamples were taken at selected time intervals and were immediately injected into the tubescontaining NaOH solution to stop further reaction by increasing the pH to 11. The samples werethen filtered with 0.45 µm syringe micro-filters to separate precipitated iron from the solutions.Samples were analyzed for residual H2O2, Fe2+, and MEA. The residual MEA and ammonianitrogen were analyzed using the DX-120 (Dionex, USA) ion chromatography having theCG-12A (guard) and CS-12A (analytical) column. The suppressor type was CSRS Ultra 4-mm(Cation Self Regenerated Suppressor) and auto-regenerated with 50mA current. Eluent used was10mM methanesulfonic acid (CH3SO3H) at 1.00 ml/min. The volume of the sample loop was 25µl.The Fe2+ was determined by light absorbance measurement at 510 nm after complexing with1,10-phenanthroline using a UV-Vis spectrophotometer. Residual H2O2 was analyzed by titaniumoxalate method.Fluidized-bed Fenton processSynthetic MEA wastewater was prepared using de-ionized water. The initial pH was adjusted withthe addition of 1.0 M H2SO4. Calculated amount of ferrous sulfate was added in the volumetricflask containing the synthetic wastewater. The solution was then added into the reactor followed bythe carriers. The re-circulation pump was turned on to suspend the carriers and to mix the solution.Hydrogen peroxide was finally added to the solution and the reaction was started. Samples weretaken at selected time intervals. The Fentons reaction was stopped instantly by adding NaOH to thereaction mixture after sampling. The samples were then filtrated on cellulose acetate membraneswith 0.45 um pore size to remove the precipitates. For the conventional Fenton process, the same 3
  4. 4. procedure was used but without using carriers in the reactor.Chemical Precipitation Experiments ‧Magnesium chloride (MgCl2 6H2O) and disodium hydrogen phosphate (Na2HPO4 12H2O) were ‧added to the ammonium wastewater (1 L) at NH4+:Mg2+:PO43- molar ratios of 1 : 1.4 : 1.1. Thereaction solution was agitated by magnetic stirrers for 15 min at pH 10.1. Then it was allowed tosettle in the reaction solution for 15 min. The reaction solution was filtered through a 0.45 mmmembrane filter for analysis.Design of ExperimentsMost of studies have only focused on the basic single-factor-at-a-time approach, studying the effectof each experimental parameter on the process performance while keeping all other conditionsconstant. However, this strategy does not consider cross-effects from the factors which can result inpoor optimization. To overcome this problem, the use of statistical design experiments has provento be advantageous, allowing the use of the minimum number of experiments while simultaneouslychanging several variables. Moreover, statistical design experiments can be used for optimizationprocess in multivariable system.The Design-Expert software version 7.0(Stat-Ease, Inc., Minneapolis, USA) was used to determinethe number of experiments to be performed, calculate the experimental data and evaluate theexperimental results. In order to investigate the effects of significant factors and to obtain theoptimum condition, in this study, the Box-Behnken statistical design was used.The optimization procedure involves studying the response of statistically designed combination,estimating the coefficients by fitting experimental data to the response functions and predicting theresponse of fit model.RESULT AND DISCUSSIONThree important factors affecting the fluidized-bed Fenton process consisting of the initial pH,initial Fe2+ and H2O2 concentrations were selected as factors in the Box-Behnken statistical design.MEA, chemical oxygen demand (COD) and total iron removal efficiencies were used as theresponse functions. Table 1 shows the range of values of the factors used on the Box-Behnkenstatistical design.Table 2. The levels of variables in Box-Behnken statistical design. Variable level Variables Symbol Low ( -1 ) Center ( 0 ) High ( +1 ) -1 0 +1 pH A 2 3 4 2+ Fe (mM) B 0.5 1.75 3 H2O2 (mM) C 5 27.5 50The low, center and high levels for each variable are designated as -1, 0, and +1, respectively. Atotal of 17 experimental runs with three variables and three levels in Box-Behnken design,including five replications at the center point (0,0,0,0,0) were done. The result are shown in Table 2.Results from the experiment revealed that the maximum removal of MEA was > 98.9% while theminimum removal was 21%. The removal of COD and total iron were between 3.4 and 64.7% and7.4 - 67.4%, respectively. 4
  5. 5. Table 3. Design of experimental runs for the BOX-Behnken statistical design of fluidized-bedFenton process with 5 mM MEA. Monoethanolamine COD T-Fe Run Fe2+ H2O2 pH Removal Removal Removal No. (mM) (mM) % % % 1 4.00 0.50 27.50 21 3.4 67.3 2 3.00 1.75 27.50 56 22 41.3 3 2.00 1.75 5.00 56.7 16.8 46.1 4 3.00 0.50 50.00 30.1 9.3 27.6 5 3.00 1.75 27.50 55.8 21.3 41.6 6 2.00 1.75 50.00 60.4 19.2 16.3 7 4.00 3.00 27.50 48.8 10.5 28.7 8 4.00 1.75 5.00 38.7 16.5 43.6 9 3.00 1.75 27.50 54.9 21.5 40.8 10 3.00 0.50 5.00 39.6 21.56 14.2 11 4.00 1.75 50.00 33.4 22.57 36 12 2.00 3.00 27.50 77.1 28.4 12.7 13 3.00 3.00 50.00 98.9 64.7 43.5 14 3.00 1.75 27.50 55.7 21.7 41.7 15 3.00 3.00 5.00 47.6 11.5 7.4 16 2.00 0.50 27.50 63.1 23.4 11.5 17 3.00 1.75 27.50 55.2 22.4 41.1Correlation of Each Parameter on Monoethanolamine Removal EfficiencyFigure 2 shows the effect of the parameters to MEA removal efficiency. Using an initialconcentration of 5 mM of H2O2 and 0.5 mM of Fe2+ resulted to a 40% MEA removal efficiency.However, increasing the H2O2 concentration to 50 mM while maintaining the other two factorsconstant resulted only to a 30% removal efficiency. 5
  6. 6. Design-Expert?Software Monoethanolamine removal 98.9 21 Monoethanolamine removal ( % ) X1 = B: Fe2+ 99 X2 = C: H2O2 81.5 Actual Factor A: pH = 3.00 64 46.5 29 50.00 3.00 38.75 2.38 27.50 1.75 16.25 1.13 C: H2O2 C: H2O2 B: Fe2+2+ (mM) 5.00 0.50 B: Fe (mM)Figure 2. Three-dimensional representation of the response surface plot of the effect of initialconcentration of Fe2+ and H2O2 on removal efficiency of MEA at pH 3, ([MEA]=5×10-3M;[Fe2+]=3×10-3M; [H2O2]=50×10-3M; [SiO2]=100g).On the other hand, increasing Fe2+ concentration from 0.5 to 3 mM at 3 mM of H2O2 resulted to a98.9% removal efficiency. At low Fe2+ concentration, the amount of catalyst is insufficient tocatalyze H2O2 to produce enough hydroxyl radical which resulted to a decrease in the removal ofMEA. However, too much ferrous iron and H2O2 also compete with MEA for hydroxyl radicalscavenging under certain conditions according to Eqs. 3 and 4.Fe3+ + H2O2 → Fe-HOO2+ + H+ (3)Fe-HOO2+ + H+ → Fe2+ + HO2 ‧ (4)Based from the results, the best set of conditions for this system is an initial pH of 3, with an initialferrous iron concentration of 3mM and 50mM of H2O2 operating at 100g carrier by fluidized-bedFenton process.Correlation of Each Parameter on COD removal EfficiencyAs shown in Figure. 3, the maximum COD removal of 64.7% was achieved at the best conditionswith an initial concentration of 50 mM H2O2 and 3 mM Fe2+. 6
  7. 7. Design-Expert?Software COD removal 64.7 3.4 X1 = B: Fe2+ X2 = C: H2O2 65 COD removal ( % ) Actual Factor 51 A: pH = 3.00 37 23 9 50.00 3.00 38.75 2.38 27.50 1.75 1.13 B: Fe2+ (mM) 16.25 C: H2O2 (mM) C: H2O2 B: Fe2+ 5.00 0.50Figure 3. Three-dimensional representation of the response surface plot of the effect of initialconcentration of Fe2+ and H2O2 on removal efficiency of COD at pH 3, ([MEA]=5×10-3M;[Fe2+]=3×10-3M; [H2O2]=50×10-3M; [SiO2]=100g).At low ferrous iron concentration, the hydroxyl radical production rate is very slow, therefore,hindering the COD degradation. Increasing the concentration of H2O2 however, also increases CODremoval efficiency But with excessive dosage of H2O2, scavenging reactions with hydroxyl radicaloccurs as shown in Eq. 5 resulting to a decrease in COD removal. When H2O2 concentrationreached a certain level, hydroxyl radical production rate will not increase.‧ OH + H2O2 → H2O + HO2 ‧ (5)Correlation of Each Parameter on Total Iron Removal EfficiencyThe correlation of total iron removal with pH, ferrous iron, H2O2 concentration and amount ofcarriers all yielded a positive effect. The result shows that total iron removal increased when pH andamount of carriers increased. On the other hand, increasing ferrous iron and H2O2 concentrationscould decrease the total iron removal. As can be seen from Figure 4, increasing pH value enhancesthe total iron removal efficiency. The precipitation of iron hydroxide at higher pH resulted in thedecrease of dissolve iron. 7
  8. 8. Design-Expert?Software Total iron 67.4 7.4 X1 = A: pH 68 Total iron removal ( % ) X2 = B: Fe2+ Actual Factor 53.75 C: H2O2 = 27.50 39.5 25.25 11 3.00 4.00 2.38 3.50 1.75 3.00 1.13 2.50 B: Fe2+ B: Fe2+ (mM) A: pH A: pH 0.50 2.00Figure 4. Three-dimensional representation of the response surface plot of the effect of initialconcentration of Fe2+ and H2O2 on removal efficiency of total iron at pH 3, ([MEA]=5×10-3M;[Fe2+]=3×10-3M; [H2O2]=50×10-3M; [SiO2]=100g).Fe2+ concentration also played an important role in total iron removal. Increasing Fe2+ concentrationwould slightly decrease the total iron removal due to the amount of Fe3+ generated from Fentonreaction which could crystallize on the surface of carrier.The application of Box-Behnken design offers an empirical relationship between the responsefunction and variables. The equation for the removal of MEA by fluidized-bed Fenton process interms of coded factors are shown below:Monoethanolamine removal = 55.52 – 14.42A + 14.82 B + 5.03C +3.45AB – 2.25AC + 15.20BC – 4.89A2 + 1.87B2 - 3.34C2Where A, B and C are pH, initial Fe2+ concentration and initial H2O2 concentration, respectively.Optimization ProcessThe main objective of the optimization process was to determine the optimum condition for removalof MEA, COD and total iron in fluidized Fenton process from the experimental data. Theoptimization module in Design-Expert searches for combination of factor levels that simultaneouslysatisfy the requirements placed on each of the responses (I et al. 2009). The optimum conditions forthe removal of MEA by fluidized-bed Fenton process are pH = 2.01, 100g of carriers, [Fe2+] = 3 mMand [H2O2] = 50 mM. But the predicted result is only 97.4% MEA removal. Based from the actualexperiments, at the same Fe2+ and H2O2 concentrations with pH = 3, MEA removal is 98.9%.Therefore, these conditions were chosen as the optimum for the comparison between fluidized-bedFenton and Fenton processes since at pH = 3, less amount of acid is needed as compared to pH = 2.The removal efficiencies of MEA, COD and total iron at the best conditions were predicted to be 89.1,56.49 and 26.81 %, respectively. The actual removal efficiencies were 98.9 % for MEA, 64.7 % forCOD and 43.5 % for total iron. It can be summarized that the experimental results obtained underoptimized concentration were close to the predicted resulted in terms of MEA, COD removal andtotal iron removal, evidencing the reliability of the methodology used within the range ofconcentration investigated.Comparison between the Fluidized-bed Fenton and Fenton process at the optimum condition 8
  9. 9. From the Box-Behnken design experiment, using Fenton process experiments, the best conditions at5 mM of MEA are pH = 3, [Fe2+] = 5 mM and [H2O2] = 60 mM. However, the MEA removal wasonly 96.4% as illustrated in Figure. 5. Fenton prpcess Fluidized-bed Fenton process 1.0 0.9 Monoethanolamine remaining ( C/C0 ) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 20 40 60 80 100 120 time (min)Figure 5. Comparison of MEA remaining between Fenton and Fluidized-bed Fenton process withcondition of [MEA=5×10-3M]; [Fe2+=5×10-3M (Fenton); 3×10-3M (FB-Fenton)]; [H2O2=60×10-3M(Fenton); 50×10-3M (FB-Fenton)]; [SiO2=100g].As found in the fluidized-bed Fenton process, with a lesser amount of Fenton reagent, the MEAremoval efficiency can still reach 98.9%. This indicated that the carriers with iron oxide coating mayhave catalytic reaction with H2O2.It can be seen from Figure 5, the removal efficiency of MEA in fluidized-bed Fenton and Fentonprocess shows the same trend. 1.0 Fenton process Fluidized-bed Fenton process 0.9 0.8 CDO remaining ( C/C0 ) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 20 40 60 80 100 120 time (min)Figure 6. Comparison of COD remaining between Fenton and Fluidized-bed Fenton process withcondition of [MEA=5×10-3M]; [Fe2+=5×10-3M (Fenton); 3×10-3M (FB-Fenton)]; [H2O2=60×10-3M(Fenton); 50×10-3M (FB-Fenton)]; [SiO2=100g]. 9
  10. 10. The COD removal efficiency from Fenton and fluidized-bed Fenton processes were 57.3 % and 64.7%, respectively. 2+ Fenton Fe detection dosage 2+ 5 FB-Fenton Fe detection dosage 2+ Fenton Fe addition dosage 2+ FB-Fenton Fe addition dosage 4 Total iron remaining ( mM ) 3 2 1 0 0 20 40 60 80 100 120 time (min)Figure 7. Comparison of total iron remaining between Fenton and Fluidized-bed Fenton process withcondition of [MEA=5×10-3M]; [Fe2+=5×10-3M (Fenton); 3×10-3M (FB-Fenton)]; [H2O2=60×10-3M(Fenton); 50×10-3M (FB-Fenton)]; [SiO2=100g].Continuous dosing of iron was used in this study. The iron remaining in the solution fromfluidized-bed Fenton and Fenton processes are illustrated in Figure 7. A 25 % removal from Fentonprocess and a 43.5 % removal in fluidized-bed Fenton process of total iron were observed. This showsthat 43.5 % of iron was crystallized on the surface of the carrier and were left on the adsorbent of thefluidized-bed reactor. This amounts to a 43.5% reduction of the amount of sludge in fluidized-bedFenton process. A decrease in the amount of sludge was considered as an advantage of fluidized-bedFenton process which also reduces the separation and disposal costs as well (Muangthai et al. 2010).Ammonia nitrogen removal by Chemical PrecipitationIn this study, it was found out that after the degradation of MEA, large amount of ammonia nitrogencould be produced, causing interference in the analysis Furthermore, ammonia nitrogen is anessential nutrient that can lead to water eutrophication when present in excess. . Because of this, astudy on ammonia removal was also done.In the chemical precipitation process, 5 mM of ammonia nitrogen was used. The effects of initial pH,ratio of Mg2+ : NH4+ : PO43- and stirring times to ammonia nitrogen removal solution with initial pHof 9.0, 10.0 and 11.0 were investigated and the results are presented in Table 4. 10
  11. 11. Table 4. Effect of conditions for ammonia nitrogen removal Effect of initial pH Effect of added ratio Effect of stirring time 2+ 4+Initial of Removal Mg : NH : Removal Stirring Removal pH efficiency % PO43- efficiency % time efficiency % 9.0 84.3 1:1:1 73.5 5 88.7 10.0 99.6 1.2 : 1 : 1 81.7 10 92.4 11.0 78.7 1.4 : 1 : 1.1 99.6 15 99.6The results showed that the best ammonia nitrogen removal efficiency (99.6%) was observed at pH =10.0, with Mg2+ : NH4+ : PO43- ratio of 1.4 : 1 : 1.1, at 15 min stirring time.CONCLUSIONSThe fluidized-bed Fenton process was found to be an efficient method for treating syntheticwastewater containing MEA. Box-Behnken design was used to determine the optimum conditionsin the removal of MEA, including the prediction of the interaction between process variables. Thefluidized-bed Fenton process was proven to be more effective on MEA degradation than theconventional Fenton process. This process is also superior in terms of total iron removal byreducing the iron sludge via crystallization process. Chemical precipitation method was found to bean effective way on removing ammonia nitrogen in water.ACKNOWLEDGMENTSThis work was financially supported by the National Science Council of Taiwan under Contract No.NSC 99-2221-E-041-012-MY3.REFERENCEA. A. I., G. Tureli., O. Hanci. Treatment of azo dye production wastewaters using Photo-Fenton-like advanced oxidation process: Optimization by response surface methodology. J. Photochem. Photobio. A-Chem. 202(2-3), 142-153 (2009).Chou, S., Huang, C. Application of a supported iron oxydroxide catalyst in oxidation of benzoic acid by hydrogen peroxide. Chemosphere,38, 2719-2731 (1999).I. Muangthai., C. Ratanatamsakul., M. C. Lu. Removal of 2,4-dichlorophenol by fluidized-bed Fenton process. Sustain. Environ. Res. 20(5), 325-331 (2010).L. Khunikakorn, J. Anotai, M. C. Lu. Competitive oxidation of nitrobenzene and aniline in fluidized-bed Fenton process.N. Al-Hayek., M. Dore. Oxidation of phenols in water by hudrogen peroxide on alumina supported ion. Water Res. 24, 973-982 (1990).Park, S. J., Yoon, T. I., Bae, J. H., Seo, H. J., Park, H. J. Biological treatment of wastewater containing dimethyl sulphoxide from the semi-conductor industry. Process Biochemistry 36:579–589 (2001).R. L. Valentine., H. C. A. Wang. Iron oxide surface catalyzed oxidation of quinoline by hydrogen peroxide. J. Environ. Eng. 124, 31-38 (1998).S. S. Lin. Interaction of H2O2 with iron oxide for oxidation of organic compounds in water. (Ph. D. Thesis.), Drexel Univ., Philadelphia (1997).S. Chou., C. Huang. Application of a supported iron oxydroxide catalyst in oxidation of benzoic acid by hydrogen peroxide. Chemosphere (in press).T. Zhang., L. Ding., H. Ren., X. Xiong. Ammonium nitrogen removal from coking wastewater by chemical precipitation recycle technology. Water Research. 43, 5209-5212 (2009) 11

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