Objectives of thesis: Study on phenol treatment in water by ozonation process combined with catalysts. An empirical kinetic model and one quadratic regression equations were built based on experimental data for destroying phenol by heterogeneous catalytic ozonation process with response variables (initial pH, ozone concentration, catalyst concentration and reaction time). Application of phenol treatment in coking wastewater.
MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY & - NGUYEN THANH THAO STUDY ON PHENOL TREATMENT IN COKING WASTEWATER BY OZONATION PROCESS COMBINED WITH CATALYST Major: Environmental Engineering Code: 9.52.03.20 SUMARY OF DOCTORAL THESIS OF ENVIRONMENTAL ENGINEERING Hanoi, 2019 The work was completed at Graduate University of Science and Technology – Vietnam Academy of Science and Technology Scientific Supervisor 1: PGS.TS Trinh Van Tuyen Scientific Supervisor 2: PGS.TS Lê Truong Giang 1st Reviewer:… 2st Reviewer:… 3st Reviewer:… The thesis will be defended at the Academic Review Board of the Graduate University of Science and Technology - Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Street, Cau Giay District, Hanoi, Vietnam at…hour…date…month…in 2019 The thesis can be found at: - Vietnam National library - Library of the Graduate University of Science and Technology PUBLISHED ARTICLES USED IN THIS THESIS Nguyen Thanh Thao, Trinh Van Tuyen, Le Truong Giang Study on Pre-Treatment of Phenol, COD, Color in the coke wastewater by ozonation Process Journal of Science and Technology, ISSN 2525-2518, 55, (4C) (2017), pages 271-276 Nguyen Thanh Thao, Le Trung Viet, Nguyen Quang Trung Development of method for analysing major phenol derivatives in coke wastewater Jounal of Analytical Sciences, ISSN 0868-3224 (22) (2017), pages 30-36 Nguyen Thanh Thao, Trinh Van Tuyen, Le Truong Giang Evaluating chemical compounds in coke wastewater of Thai Nguyen iron and stell SJC, Thai Nguyen province Jounal of Analytical Sciences, ISSN 0868-3224, (23), number 1/2018, pages 22-29 Thao T Nguyen, Tuyen V Trinh, Dung N Tran, Giang T Le, Giang H Le, Tuan A Vu and Tuong M Nguyen Novel FeMgO/CNT nano composite as efficient catalyst for phenol removal in ozonation process Materials Research Express Volume 5, Number 9, 095603, 2018 Hoang Hai Linh, Nguyen Quang Trung, Nguyen Thanh Thao Removal phenol in coke wastewater by ozone combine with modified laterit Jounal of Analytical Sciences, ISSN 0868-3224, (23), number 4/2018, pages 295-304 Nguyen Thanh Thao, Trinh Van Tuyen, Nguyen Quang Trung Simultaneous determination of hydroquinone, catachol and benzoquinone during phenol ozonation by high-perfomance liquid chromatoghaphy Jounal of Analytical Sciences, ISSN 0868-3224, (21), number 3/2016, pages15-24 Nguyen Thanh Thao, Trinh Van Tuyen, Le Truong Giang Study on the kinetics of phenol degradation in aqueous solution by ozonation process at neutral media Jounal of Analytical Sciences, ISSN 0868-3224 (has been approved for publishment) Thao Nguyen Thanh, Tuyen Trinh Van, Giang Le Truong, Tuan Vu Anh Study on Phenol treatment by Catalytic Ozonization using Modified dolomite Jounal of Analytical Sciences, ISSN 0868-3224 (has been approved for publishment) Nguyen Thanh Thao, Trinh Van Tuyen, Le Truong Giang Study on degradation of phenol in aqueous solution by ozonation combined with FeMgO/CNT Jounal of Analytical Sciences, ISSN 0868-3224 (has been approved for publishment) INTRODUCTION Since the late 20th century, there have been many warnings about the existence of phenol and phenol compounds in the environment, especially the water environment Phenol pollutes the natural water environment due to its presence in many industrial waste streams such as petrochemical, coke, steel [1-3] Although widely used in many industries, science has proved that phenols are toxic to humans and organisms Thus, phenol pollution in water is becoming a serious problem for many countries, including Vietnam Many methods have been applied to treat phenol in water such as adsorption, biology, catalytic wet oxidation However, it is often necessary to combine two or more technologies to completely remove phenol from the waste stream Recently, catalytic Ozonation Process (COP) or catazon has emerged as a new strategy for the treatment of persistent organic substances and has proven very effective in treating wastewater contains phenol compounds This method has many advantages such as no problems related to chemicals, high efficiency of pollutant decomposition, fast processing time, simple equipment, easy to install, no waste sludge and In particular, ozone can be Some solid catalysts have been shown to increase the efficiency of phenol removal in water by catalytic ozonation process such as metal oxides Mn/Al2O3, MgO, ZnFe2O4, metals on carbon materials such as AC/Fe2O4, CNT/Fe2O3, CNF/Fe2O3 or minerals such as perovskite, honeycomb ceramic material [6-10] Carbon nanotubes (CNTS) materials with the advantages of large surface area, unique structure have been becoming a new, promising and advanced class of materials in this field of catalytic synthesis However, the catalysts based on this material are mainly applied to remove phenol in water by catalytic wet oxidation and adsorption method, which is rarely studied to treat phenol by heterogeneous catalytic ozonation process FeMgO/carbon nanotube composite (FeMgO/CNT) and dolomite modified by KOH (M-Dolomit) are the first time to be evaluated for catalytic role for the removal phenol in water by heterogeneous catalytic ozonation process.The thesis with the title "Study on phenol treatment in coking wastewater by ozonation process combined with catalyst” has been conducted to study the treatment of coking wastewater containing toxic phenol compound by ozonationprocess combined with heterogeneous catalysts, using available catalyst materials produced in Vietnam with low cost and environmentally friendly Objectives of thesis: Study on phenol treatment in water by ozonation process combined with catalysts An empirical kinetic model and one quadratic regression equations were built based on experimental data for destroying phenol by heterogeneous catalytic ozonation process with response variables (initial pH, ozone concentration, catalyst concentration and reaction time) Application of phenol treatment in coking wastewater Contents: Overview of phenol pollution status in coking effluent, sources, composition, toxicity and phenol treatment technologies in these kinds of wastewater Study on phenol treatment in water by heterogeneous catalytic ozonation process with two catalytic materials selected: FeMgO/CNT and M-Dolomite From studied results, select one best catalytic material for further phenol treatment Develop the empirical kinetic model and quadratic regression equations for decomposing phenol by O3/FeMgO/CNT process with response variables (initial pH, ozone concentration, catalyst concentration and reaction time) Treatment of coking wastewater of Thai Nguyen Iron and Steel JSC with pilot scale New contributions of the thesis: - The first time, FeMgO/CNT composite and M-Dolomite materials prepared from inexpensive clay minerals have been evaluated catalytic characteristic to decompose phenol in the water by heterogeneous catalytic ozonation process - Development of the empirical kinetic model and the quadratic regression equations for decomposing phenol in water by O3/FeMgO/CNT process with response variables CHAPTER LITERATURE OVERVIEW 1.1.Technology for coke production and source of coking wastewater 1.2 Phenol toxicity and treatment methods for the removal of phenol from coking wastewater 1.3 Ozone-Based Oxidation processes 1.4 Experimental planning and Box-Hunter experimental planning CHAPTER SUBJECTS AND RESEARCH METHODS 2.1 Objects and scope of the thesis Water samples containing phenol prepared from phenol crystals and coke wastewater samples were taken from Thai Nguyen Iron and Steel Joint Stock Company and Formosa Ha Tinh Steel Corporation 2.2 Chemicals and equipments 2.3 Research methods 2.3.1 Experimental methods 2.3.1.1 Experimental description 2.3.1.2 Evaluation on the catalytic activity of materials 2.3.1.3 Study on phenol treatment in water by ozone and heterogeneous catalytic ozonation processes 2.3.1.4 Development of an empirical kinetic model for treatment of phenol by O3/FeMgO/CNT process 2.3.1.5 Development of a quadratic regression equations for treatment of phenol by O3/FeMgO/CNT process 2.3.1.6 Treatment of coke wastewater of Thai Nguyen Iron and Steel Joint Stock Company by O3/FeMgO/CNT process 2.3.2 Field survey and sampling methods 2.3.3 Analysis methods 2.3.4 Data processing methods 2.3.4.1 Efficiency of pollutants removal 2.3.4.2 Method of calculating pseudo first order reaction rate constant 2.3.4.3 Method of developing an empirical kinetic model 2.3.4.4 Method of developing a quadratic regression equation CHAPTER RESULTS AND DISCUSSIONS 3.1 Characteristics of coking waste water The analysis results of 16 samples of coking wastewater were taken from Thai Nguyen Iron and Steel Joint Stock Company and Fomosa Ha Tinh Steel Corporation show that this wastewater has a pungent odor (smell of phenol) and many parameters with high concentration such as color, COD, BOD5, CN-, phenols (phenol and total derivatives), phenol, total nitrogen, NH4-N Other parameters such as heavy metals, total grease, total phosphorus, Cl-, S2-, residual chlorine are quite low The pH of the samples ranged from 6.7 to 9.5 (average at 7.9) For Fomosa samples, the pH ranged from 6.7 to 8.4 (average 7.6) The wastewater is dark brown with average color 673 - 712 Pt/Co TSS parameter is from 132 - 357 mg/L However, the total organic compounds (COD) is high, ranging from 5.014 to 6.350 mg/L (5.794 mg/ L on average) for Thai Nguyen samples, higher than the average 3,871 mg/L in Fomosa samples BOD5 in all samples has a ratio of 3033% compared to COD Phenol and CN- are two parameters with a high concentration in all samples The content of phenols in Thai Nguyen samples has a high content in the range of 850 - 1,052 mg/L (average 949.3 mg/L), higher than 738 mg/L as the average value of Fomosa samples Coking wastewater has a high COD parameter because it is complex wastewater Besides of high levels of phenol, there are many derivatives of phenol as well as other organic substances The average concentration of phenol in Thai Nguyen samples is 665 mg/L, higher than the average of 629 mg/L in Fomosa ones The ratio of derivatives and phenols of all samples varied greatly, accounting for 14.7 - 70% CN- concentration averaged 31.5 mg/L for Thai Nguyen samples and 26.5 mg/L for Fomosa ones 06 samples of coking wastewater collected at Thai Nguyen Iron and Steel Joint Stock Company were analyzed 09 derivatives of phenol commonly found in this kind of water [19, 31, 54] and simultaneously analyzed 943 organic substances by AIQS - DB software by GCMS The results reveal four highly concentrated derivatives, including: 2methylphenol (3.1 - 33.7 mg/L), methylphenol (7.4 - 46.69 m/L), methylphenol (3.1, -16.6 mg/L); 3,5 - dimethylphenol (8.9 - 35.4 mg/L) and 2.5 - dimethylphenol (1.23 - 20.8 mg/L) Other derivatives such as 2,3-dimethylphenol; 3,4-dimethylphenol, 2,4-dimethylphenol; 2,6dimethylphenol are also detected but in small concentrations 3.2 Evaluation of the catalytic activity of materials 3.2.1 Evaluation of adsorption capacity of dissolved O3 on material surfaces Fig 3.1: Dissolved O3 concentration in solution with and without catalyst Fig 3.2: The effects of tert-butanol on the efficiency of phenol decomposition with and without catalyst The results show that the concentration of dissolved O3 in the solution with catalysts were always higher than without catalyst When there is no catalyst, the measured concentration are 2.8; 3.6; 3.2; mg/L at 5; 10; 15; 20 minutes, higher than 2.4; 3.2; 2.7; 2.5 mg/L in the presence of M-Dolomite and 2; 2.8; 2.5; 2.2 mg/L with FeMgO/CNT catalyst (Fig 3.1) That indirectly proves the selected materials have catalytic activities The dissolved O3 produced in the solution has been adsorbed and decomposed on the surfaces of the material to form free radicals OH The analytical results of phenol adsorption capacity on the surface of FeMgO/CNT and M-Dolomite catalyst in 60 minutes show that phenol is not adsorbed on the surface of catalysts 3.2.2 Evaluation of the role of free hydroxyl radicals contribute to phenol treatment by heterogeneous catalytic ozonation process The presence of tert-butanol in solution reduced the efficiency of phenol decomposition in both cases with and without catalyst Fig 3.2 shows the phenol decomposition efficiency are 60.7; 70.9; 76.5; 82.2; 86.2% in ozonation process corresponds to pH values: 3; 5; 7; 9; 11 but reduced to only 50; 53; 54; 55; 52% in ozonation process with tertbutanol The efficiency of phenol decomposition without tert-butanol are 41-78.8%; 50.7-85.5% and 74.1-90.1% corresponding to processes O3; O3/M-Dolomite; O3/FeMgO/CNT processes when pH values increase from to 11 but only reach 37.5 - 55%; 20.1 - 25.2%; 54.3 - 57.2% with scavenger In particular, the O3/M-Dolomite+tert-butanol process is affected highly In alkaline media, the phenol decomposition efficiency decreases much more than the neutral and acidic media Due to in alkaline media, reaction mechanisms by •OH played a key role 3.2.3 Evaluate concentration of metals being released into the solution and contribute to the efficiency of phenol decompose by homogeneous catalytic ozonation process The results showed that the Fe, Mg metals in FeMgO/CNT and Ca, K, Mg in M-Dolomite were dissolved into phenol solution increase to the maximum concentration and then gradually decreased The 11 In the presence of FeMgO/CNT and M-Dolomite catalysts, the efficiency of phenol decomposition increased from 64.2 to 86.3% and 60 - 80.3% respectively when increasing the stirring speed from 150 to 300 rpm Increased phenol decomposition efficiency when accelerating the stirring process is due to the increased ability to diffuse O3 from the gas phase to the liquid phase increases and increases the collision between the substances in the solution to increase the reaction rate Phenol decomposition effects [92, 94, 96] However, the efficiency of decomposing phenol only increases to a maximum value and does not increase further because at this stirring speed the ability to diffuse O from the gas phase to the maximum liquid phase, the concentration of O3 dissolves in the solution saturated k increase from 0.01 to 0.015 (1/min) when increasing the stirring speed from 150 - 300 rpm with O3 process but increases from 0.016 to 0.026 (1/min) with O3/FeMgO/CNT process and 0,018 - 0,032 (1/min) with O3/M-Dolomite process COD removal efficiency increased from 14.6 to 18.1% when the stirring speed increased from 150 - 300 rpm with O3 process but increased to 21.2 - 34.6% with O3/MDolomite process and 27 , - 40% with O3/FeMgO/CNT process Similar to COD, TOC mineralization efficiency increased from 11.2% in O3 process but increased to 15 - 23.2% and 19.1 - 26.4% respectively in O3/M-Dolomite and O3/FeMgO/CNT processes The research results clearly show that the speed of 200 rpm is the optimal stirring speed for O3 and O3/FeMgO/CNT processes and 250 rpm for O3/M-Dolomite process 3.3.4 Influence of temperature on phenol treatment efficiency Figure 3.18 shows that the removal efficiency of phenol after 60 minutes by O3 process is merely 48% and 56% corresponding to the temperature of 10oC and 25oC The removal efficiency increases because at this temperature range, the process of decomposing O3 into 12 • OH and the ability to diffuse the reaction substances prevail But if the temperature continues to increase, the removal efficiency of phenol is reduced to 32.2% at 35oC and 28.6% at 45oC due to the reduction of the concentration of O3 dissolved in the solution The results also show that M/Dolomite catalyst depends on temperature 86% of phenol is decomposed after 60 minutes at 10°C but decreased to only 80.3; 64.2; 60% corresponds to temperature 25; 35; 45oC Fig 3.18: Effect of solution temperature on the removal efficiency of phenol with and without catalyst Fig 3.20: Effect of solution temperature on the apparent reaction rate constant of phenol removal with and without catalyst Figure 3.20 shows the effect of temperature on k with and without the catalyst In O3 process, the value of k increased from 0.011 to 0.015 (1/min) corresponding to the temperature increase of 10 - 25oC but decreases to only 0.006 (1/min) at 35oC and 0.005 (1/min) at 45 °C after 60 minutes of reaction The kcata value of O3/FeMgO/CNT process is quite stable at all investigated temperature In contrast, the O3/MDolomite process depends on temperature The kcata values decrease from 0.03 (1/min) to 0.025 (1/min), correspondingly increasing the solution temperature from 10°C to 45°C The thesis selected phenol solution at 25oC for further studies of phenol decomposition with O3 and catalytic ozonation processes because this temperature is favorable for temperature regulation during the study 3.3.5 Effect of ozone concentration on phenol treatment efficiency 13 The O3 concentration is selected from 0,152 to 1,216 g/L The study results show the removal efficience of phenol, COD, TOC, and apparent reaction rate constants tend to increase when increasing the ozone concentration Fig 3.23: Effect of O3 concentration on the removal efficiency of phenol after 60 minutes with and without catalyst Fig 3.24:The effect of O3 concentration on the apparent reaction rate constants of phenol removal with and without catalyst The results show that 44.6% of phenol is decomposed in 60 minutes at 0.152 g/L O3 concentration without catalyst but only 40 minutes in O3/FeMgO/CNT process or 50 minutes in O3/M- Dolomite process to achieve the same efficiency At O3 concentrations 0.152; 0.304; 0.608; 0.912 g/L efficiency of phenol decomposition after 60 minutes reaches 44.6; 56; 70.8; 85.1% with O3 process but increases 52.7; 80.3; 91.7; 98.1% and 63.2; 86.3; 94.8; 99.6% corresponds to O3/M-Dolomite and O3/FeMgO/CNT processes The removal efficiency of phenol increases when increasing the O3 concentration in all the experiments due to the increase in the concentration of O3 in the gas, increasing the concentration of dissolved O3 in the solution The reaction of O3 with the active components in catalysts such as MgO, Fe2+, Fe+3, CNT occurs faster The more •OH produced increase the rate of reaction while the phenol concentration in the solution is constant In all experiments, no residual O3 is observed even when 100% of phenol is completely decomposed because many intermediate products are generated in reaction and also react with O3 in solution 14 k of phenol decomposition without catalyst increase from 0.0103 (1/min) to 0.05 (1/min) when increasing O3 concentration from 0.152 g/L to 1,216 g/L The presence of catalysts increase these reaction rate constants With the same O3 concentration studied, the kcata values increase from 0.0129 (1/min) to 0.072 (1/min) for O3/M-Dolomite process and increase sharply from 0.0162 (1/min) to 0,1064 (1/min) with O3/FeMgO/CNT process (Fig 24) kcata increased by 1.6 - 2.6 times compared to k achieved in the presence of FeMgO/CNT catalyst but only increase by 1.3 -1.9 times with M-Dolomite catalyst The removal efficiency of COD and TOC tends to increase when O3 concentration increases After 60 minutes, COD removal efficiency by O3 process increased from 14.9 to 32.6% when increasing O3 concentration from 0.152 g/L to 1.216 g/L Efficiency of phenol removal increased from 28.3 to 64.8% with O3/FeMgO/CNT process and 23 - 55.4% for O3/M-Dolomite process The ability of TOC mineralization is only from 7.8 to 15% in O3 process when increasing O3 concentration from 0.152 to 1,216 g/L but increased to 13.5 - 32.5% and 18.4 - 39.5% corresponds to O3/M-Dolomite, O3/FeMgO/CNT processes The thesis selected 0.304 g/L O3 as the concentration of O3 applied for further studies in this thesis because at this concentration, phenol decomposition rate occurs at a moderate speed, convenient for sampling, calculating of kinetic constants with and without catalysts 3.3.4 Effect of phenol concentration on phenol treatment efficiency The study results show the removal efficiency of phenol, COD, TOC and apparent reaction rate constants of phenol decomposition tend to decrease when increasing the initial phenol concentration After 60 minutes of reaction at 0.1 g/L phenol concentration, only 86.4% of phenol was decomposed by O3 process but increased to 100% after 25 minutes of reaction by O3/FeMgO/CNT process or 35 minutes by O3/M-Dolomite process The presence of catalysts increases the removal efficiency of phenol at the same initial 15 phenol concentration After 55 minutes, phenol is completely decomposed at an initial concentration of 0.2 g/L in O3/FeMgO/CNT process but only reached 76.5% and 92.7% corresponding to O3, O3/Mdolomite processes At the investigated phenol concentrations 0.3; 0.4; 0.5; 0.6 g/L, the efficiency of phenol removal after 60 minutes reached 62.7; 56; 46.4; 35.1% with O3 process but increase to 53.6; 60.4; 80.3; 86.8% with O3/M-Dolomite process and 67; 76.4; 86.3; 98.5% with O3/FeMgO/CNT process When increasing the phenol concentration leads to increase the competition O3 between phenol and intermediate products generated during the reaction The concentration of O3 is fed into a fixed reactor, so the amount of •OH are generated by the selfdecomposition process and the reaction with the active components of the catalyst does not increase Therefore, if the phenol concentration in solution continues to increase, the treatment efficiency decreases Fig 3.26: Effect of initial phenol concentration on the efficiency of phenol decomposition by O3/FeMgO/CNT process Fig 3.28: Effect of initial phenol concentration on apparant reaction rate constants of phenol removal with and without catalysis Efficiency of of COD, TOC removal gradually decreases when increasing the phenol concentration in the solution After 60 minutes, 100% COD was removed at the initial phenol concentration of 0.1 g/L and 0.2 g/L in the O3/FeMgO/CNT process Phenol decomposition efficiency decreased from 66.8% to 9% when increasing phenol concentration from 0.2 g/L to 0.6 g/L in O3 process but decreased from 100% to 21.5% with O3/FeMgO/CNT process and from 90% to 17% with O3/M-Dolomite process 16 3.3.5 Influence of NH4+, CN-, HCO3- on phenol treatment efficiency NH4+, CN-, HCO3- are influencing factors selected because they have a high concentration in coking wastewater and reacting with O3 in solution NH4+ 0.5 g/L concentration; CN- 0.03 g/L; HCO3- g/L are chosen because these are the average values detected in 16 wastewater samples in this thesis The results show that the presence of NH4+ in solution does not affect the efficiency of phenol decomposition in both cases with and without catalyst at pH=7 This proves that O3 competition between phenol, NH4+ and intermediate products is produced in the reaction process However, it is possible that the concentration of O3 in the reactor is not high enough so that NH4+ has not been decomposed Studies have shown that NH4+ decomposition efficiency increases when the solution pH increases and this process consumes high amounts of O3 concentration The results of the influence investigation of g/L HCO3- in the solution containing 0.4 g/L phenol show the presence of HCO3- ions without affecting the removal efficiency of phenol The results reveal that the competition for oxidation agents between phenol, HCO3- as well as byproducts in solution Phenol concentration at the time of sampling is similar to the initial phenol concentration Variation of CN- concentration after 60 minutes of reaction in phenol solution with and without catalyst under conditions pH=7; O3 0.304 g/L with the optimal concentration of catalyst determined The results show that O3 competition between phenol and CN- that reduced the removal efficiency of phenol in solution (Table 3.3) The efficiency of CN- decomposition after 60 minutes only reached 8.2% in O3 process but increased to 15.4% and 97.2% corresponding to O3/M-Dolomite and O3/FeMgO/CNT processes The FeMgO/CNT catalyst exhibits the best catalytic activity of degradation of CN- When CN- ion in solution, the efficiency of phenol removal 17 decreases by 43.9% compared to the efficiency achieved without CNwith O3/FeMgO/CNT process 3.3.6 Evaluate the regeneration ability of catalysts The efficiency of phenol removal decreased only 9.7% (from 86.3% to 76.6%) after times using FeMgO/CNT catalyst but decreased by 11.6% after times using M-Dolomite catalyst After times using M-Dolomite catalyst, the catalyst is almost inactivated The efficiency of phenol decomposition increased only 2.3% compared to the efficiency achieved by the O3 process and the loss of activity after times of use M-Dolomite catalyst significantly reduced its activity because of the concentration of K content in the phenol solution with quite high concentration, the alkalinity of the catalytic centers decreased EDX spectra results of catalytic materials after using times also demonstrate the relevance to the research results The EDX spectrum of M-Dolomite material after times of use no longer shows the presence of element K as the EDX image captures M-Dolomite material before processing But the ratio of the main elements in FeMgO/CNT catalyst is not much different from the first time The ratio of major elements in the catalyst is C; O; Mg; Fe corresponding 86; 8; 2.4; 2.7% in the catalytic component after times of use, quite close to the initial ratio of 84.8; 9.79; 2.5; 2.85% when not in use The results of the thesis also open a new research direction using catalysts of natural origin to treat persistent organic substances by heterogeneous catalytic ozonation process 3.4 Establishment of the empirical kinetic mode for phenol treatment in water by O3/FeMgO/CNT process 3.4.1 Effect of catalytic concentration on apparent reaction rate constants of phenol decomposition at pH kcata reaches the values: 0,0109; 0.0175; 0.0210; 0.0490; 0.027; 0.0313 (1/min) corresponds to FeMgO/CNT concentrations: 0; 0.5; 1; 2; 18 3; 3.5 g/L The relationship between the kcata reaction rate constant and the FeMgO/CNT catalytic amount is shown in Figure 3.33 b The line y = 0.0158x + 0.0578 with tagα = 0.0158 and R2 = 0.93 We have: α3 = k2k5 = 0,0158 (L2/g2.min); α2_pH7 = 0,0578 (L/g.min) Fig 3.33: Effect of catalytic concentration on kcata (a); The relationship between α1 and the catalytic concentration (b) at pH=7 3.4.2 Effect of catalytic concentration on apparent reaction rate constants of phenol decomposition at pH 5; 9; 11 Similar to pH = 7, the apparent rate constant for phenol degradation when changing the catalyst concentration at pH = tends to increase when the FeMgO/CNT catalyst concentration increases kcata reaches 0.0109 values; 0.0175; 0.0210; 0.0490; 0.027; 0.0313 (1/min) corresponds to FeMgO/CNT concentration: 0; 0,5; 1; 2; 3; 3.5 g/L (Figure 3.34 b) The line: y = 0.0164 [cata] +0,0453 with R2 = 0.93 We have: α2_pH5 = 0.0453 (L/min) Fig 3.34: The relationship between α1 and catalytic concentration (b) at pH=5 Fig 3.35: The relationship between α1 and catalytic concentration (b) at pH=9 19 Similarly, at pH = 9, the line y = 0.0144 [cata] +0.0732 with R2 = 0.96 We have: α2_pH9 = 0,0732 (L/g.min) At pH=11, the line: y=0,0129 [cata]+0,0891 with R2=0,99 We have: α2_pH11=0,0891 (L/g.min) Fig 3.36: The relationship between α1 and catalytic concentration (b) at pH=11 Fig 3.37: The relationship between α2 when changing the initial pH of the phenol solution The line equation shows the relationship between α2 and the initial pH of the phenol solution with linear form: y = 0.0073 [pH] +0.0081 The higher the pH of the solution, the higher the α2 coefficient We have: k1 = 0,0081 (L/g.min); k2k4 = 0,0073 (L2/g2 min); k2k5 = 0,0158 (L2/g2 min) kcata 0,0081[O3 ] 0,0073[O3 ] pH 0,0158[cata ][O3 ] d [ P] (0,0081[O3 ] 0,0073[O3 ] pH 0,0158[cata ][O3 ])[ P] dt [ P] exp{(0,0081[O3 ] 0,0073[O3 ] pH 0,0158[cata ][O3 ])} t [ Po ] The empirical kinetic mode shows that the process of decomposing phenol in water with O3/FeMgO/CNT process depends on pH, O3 concentration and catalyst concentration Relative error between experimental and predicted phenol concentration by empirical mode at 5.7% 20 3.5 Establishment of the quadratic regression equation for phenol treatment in water by O3/FeMgO/CNT process The results of phenol concentration treated after conducting 31 experiments in the correct order and experimental conditions given by Modde 12.1 software The regression coefficient values for coded variables of the polynomial function is shown in Table 3.11 Table 3.1 Regresstion coefficients values (coded variables) of the polynomial model of responses for phenol treatment Coded variables Y Regression coefficients Variations Student standard (t) bo 153,143 54,907 b1 -21,792 14,458 b2 -19,042 12,634 b3 -74,542 49,457 b4 -43,542 28,889 b11 1,329 0,962* b22 -2,296 1,663* b33 16,204 11,735 b44 8,204 5,941 b12 0,813 0,441* b13 -0,937 0,508* b14 -1,937 1,051* b23 0,812 0,441* b24 -0,937 0,508* b34 -6,937 3,763 * Note: < t (0,95, 6)=2,447 After eliminating the non-significant regresstion coefficients values (