Combination of advanced oxidation processes with ultrasonication for removal of orange g

COMBINATION OF ADVANCED OXIDATION PROCESSES WITH ULTRASONICATION FOR REMOVAL OF ORANGE G HU HONGQIANG NATIONAL UNIVERSITY OF SINGAPORE 2004 COMBINATION OF ADVANCED OXIDATION PROCESSES WITH ULTRASONICATION FOR REMOVAL OF ORANGE G HU HONGQIANG A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF ENGINEERING DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2004 Acknowledgements ACKNOWLEDGEMENTS First and foremost, I would like to take this opportunity to express my deepest gratitude to my supervisors, A/Prof. M.B. Ray and Prof. Arun S. Mujumdar. The research would not have been possible without their untiring and continuous guidance throughout the course of this work. They have provided insight and expertise to overcome problems in this research. I am thankful to them for being supportive under all circumstances. I also wish to thank all of the staff and students who provided help kindly and profusely whenever necessary, especially to Mr. Qin Zhen, Mdm. Li Xiang, Mr. Boey, Mr. Ng, and Ms. Sylvia. And special thanks go to Dr Iouri in Biochemical engineering for his precious help in EPR measurement. Financial support from the National University of Singapore in the form of a research scholarship is gratefully acknowledged. And sincere thanks to my friends here at NUS who made my stay a memorable and cherished experience. Importantly, the deepest affection is dedicated to my mother and father! i Table of Contents TABLE OF CONTENTS ACKNOWLEDGEMENTS i TABLE OF CONTENTS ii SUMMARY v NOMENCLATURE vii LIST OF FIGURES ix LIST OF TABLES xi CHAPTER 1 INTRODUCTION 1 CHAPTER 2 LITERATURE REVIEW 7 Sonochemistry 7 2.1.1 Fundamentals of ultrasound 7 2.1.2 Cavitation 8 2.1.3 Reaction zones and pathways 9 2.1 2.1.4 Optimum operating parameters for sonochemical 12 degradation 2.2 Application of sonochemistry in wastewater treatment process 14 2.3 Reactors used in wastewater treatment process and scale-up 17 2.4 Scale-up consideration 19 2.5 Combination of sonochemistry with other technologies in 21 wastewater treatment process 2.5.1 2.6 Combined with photolysis 21 2.5.2 Combined with ozonation 22 2.5.3 23 Combined with biotechnologies EPR and spin trapping 24 EXPERIMENTS 26 3.1 Materials 26 3.2 Experiment set-ups 28 CHAPTER 3 ii Table of Contents 3.3 Experimental procedure 33 3.3.1 Kinetics run 33 3.3.2 Measurement of OH• radical by EPR 34 3.3.3 Measurement of H2O2 36 RESULTS AND DISCUSSION 38 4.1 Hydroxyl radicals and hydrogen peroxide production 38 4.2 Sonochemical degradation of orange G 43 4.3 Photochemical and photosonochemical degradation of orange 47 CHAPTER 4 G 4.4 Ozonation and sonolytic ozonation of orange G 49 4.5 Effect of hydrogen peroxide 51 4.6 Carbon mineralization 54 4.7 Sonophotochemical continuous reactor 56 4.7.1 Hydrogen peroxide evolution 56 4.7.2 Decolorization by ultrasound and photolysis 58 4.7.3 Sonophotocatalysis 63 4.7.3.1 Photocatalytic oxidation 4.7.3.2 Photocatalytic decomposition with ultrasonic 63 66 irradiation 4.7.4 Effect of hydrogen peroxide 68 4.7.5 TOC 72 Energy consumption 74 Conclusions and Recommendations 76 5.1 Conclusions 76 5.2 Recommendations 78 4.8 CHAPTER 5 REFERENCES 82 APPENDIX 95 iii Summary SUMMARY Advanced oxidation processes are defined as processes that generate hydroxyl radicals in sufficient quantities to be able to oxidize majority of the complex chemicals present in effluent water. Hydroxyl radicals are powerful oxidizing reagents with an oxidation potential of 2.33 V and exhibit faster rates of oxidation reactions as compared to the conventional oxidants like hydrogen peroxide or KMnO4. Sonochemistry is the application of ultrasound to enhance or alter chemical reactions, and belongs to advanced oxidation processes (AOPs). Sonochemistry can enhance or promote chemical reactions and mass transfer, resulting in the potential for shorter reaction cycles, cheaper reagents, and less extreme physical conditions, finally leading to less expensive and perhaps smaller plants. In this study, degradation of a dye, orange G, was investigated in order to determine optimum conditions in combined AOP processes involving sonochemistry. The hydroxyl radicals and the subsequent hydrogen peroxide formation in the solution at various conditions were monitored using the spin-trapping method of OH• detection by DMPO and the colorimetric method, respectively. These methods can successfully monitor OH• produced during sonochemical processes, and identify the major reaction sites involving OH• of the three proposed reaction zones: within the cavity, in the bulk solution, and at the gas-liquid interfacial (shell) region. In addition, the efficacy of a sonophotochemical reactor with a maximum volume 2.2 L coupling ultrasonic irradiation with photocatalytic oxidation has been evaluated using iv Summary orange G as the model compound. Results showed that ultrasound may modify the rate of photocatalytic degradation by promoting the de-aggregation of the photocatalyst and by favoring the scission of the photocatalytically and sonolytically produced H2O2, with a consequent increase of oxidizing species in the aqueous phase. v Nomenclature NOMENCLATURE EE/O Electric energy per order of pollutant removal in 1 m3 wastewater, (kWh per m3 per order) k First order rate constant (l/min) T Temperature (K) Pdiss Power dissipated (Watts) P0 Ambient pressure (bar) t Operation time (s) Pv Pressure in the bubble at its maximum size (bar) Tmax Maximum temperature generated inside the bubble (K) tt Treatment time (min) V Volume of the aqueous solutions (l) C0 Initial concentration (mol/l) m Mass of solution (kg) Cf Final concentration (mol/l) cp Specific heat (J/(kg˚C)) P Rated power (kW) r0 Resonant radius of the bubble (m) E Activation energy (J/mol) K Proportionality constant Cg Concentration of organic vapor in the gas phase (mol/m3) D1 Diffusion coefficient (m2/s) f Frequency of the sound waves (kHz) vi Nomenclature I Intensity of sound waves (W/cm2) I0 Intensity at the source (W/cm2) Greek letters γ Specific heat ratio τ Collapse time of the bubbles (s) σ Surface tension (N/m) vii List of Figures LIST OF FIGURES page Figure 2.1 Three reaction zones in the cavitation process 10 Figure 2.2 Schematic representation of sonochemical equipments 18 Figure 2.3 Scale-up consideration 20 Figure 3.1 Chemical structure of orange G 26 Figure 3.2 Setup for the ultrasonic bath experiments 29 Figure 3.3 Experimental set up for ultrasonic probe 31 Figure 3.4 Schematic representation of Sonophotochemical reactor 32 Figure 3.5 Structure of DMPO and its mechanism of formation of adduct 35 Figure 4.1 EPR spectrum of an argon-saturated DMPO-OH adducts 41 Figure 4.2 The production of H2O2 and OH• at different systems 41 Figure 4.3 Changing of the absorption spectra of during ultrasonication 44 (Probe) (initial concentration of orange G =10 mg/l) Figure 4.4 First-order plot of orange G degradation by ultrasonic probe 45 Figure 4.5 Effect of initial concentration on the degradation of orange G in ultrasonic probe 46 Figure 4.6 Effect of frequency on orange G degradation by ultrasonic bath. (20 mg/l, T=20˚C) 46 Figure 4.7a Degradation of orange G by UV and US+UV 48 Figure 4.7b Comparison of color removal of orange G among US, UV, US+UV 48 Figure 4.8a Sonolytic ozonation and ozonation of orange G 50 Figure 4.8b Degradation of orange G by US+O3 and US+UV 51 viii List of Figures Figure 4.9a Effect of H2O2 on the degradation of orange G by US+UV 53 Figure 4.9b Effect of H2O2 on the degradation of orange G by O3 +US 53 Figure 4.10a TOC degradation of orange G by US, UV, US+UV 55 Figure 4.10b TOC degradation of orange G by O3 and O3+US 55 Figure 4.11 H2O2 production by sonolysis of water in the new reactor 57 Figure 4.12 H2O2 production by sonolysis of water 58 Figure 4.13 Sonochemical degradation of orange G at different initial concentrations 60 Figure 4.14 Photochemical degradation of orange G at different initial concentration 60 Figure 4.15 Comparison of orange G degradation by US, UV, and US+UV 61 Figure 4.16 Adsorption equilibrium of orange G for four catalysts 65 Figure 4.17 Photocatalytic degradation of orange G by different catalysts 65 Figure 4.18 Comparison between sonophotocatalysis and photocatalysis for 67 degradation of orange G using TiO2-Montmorillonite Figure 4.19 Control experiment of degradation of orange G using H2O2 70 Figure 4.20 Orange G degradation in presence of H2O2 and US 71 Figure 4.21 Orange G degradation at different conditions using TiO2montmorrilonite 71 Figure 4.22 Mineralization of orange G under various conditions 73 Figure 4.23 TOC degradation of OG by sonophotocatalysis with TiO2ontmorillonite 73 ix List of Tables LIST OF TABLES Page Table 1.1 Application of ultrasound 4 Table 1.2 Some advanced oxidation processes 5 Table 2.1 Various pollutants degraded by ultrasonic irradiation 15 Table 4.1 Measured OH• and H2O2 concentrations (µM) for different systems after 15 minutes of sonication 42 Table 4.2 Comparison of rate constants by ultrasonic irradiation among three reactors (Initial concentration of orange G= 20 mg/l) 61 Table 4.3 Rate constants of orange G degradation at different systems(Initial concentration of orange G = 20 mg/l) 62 Table 4.4 Orange G removal after 120 minute irradiation by UV (365 nm) and US+UV (365 nm) at four different catalysts (Initial concentration of orange G = 20 mg/l) 68 Table 4.5 EE/O values for various AOPs (C0 = 20 mg/l; T = 200C) 75 Table A1 TOC degradation at different systems 95 Table A2 Pseudo-first-order rate constant (kd) for ultrasonication, UV, and US+UV systems, and initial rate constants (kid) for ozonation and sonolytic ozonation 96 Table A3 Rate constants of orange G at different conditions by the sonophotochemical reactor 97 x Chapter 1 Introduction Chapter 1 Introduction Ultrasound occurs at a frequency above 16 kHz, higher than the audible frequency of the human ear, and is typically associated with the frequency range of 20 kHz to 500 MHz. It was first applied to enhance chemical reaction rate in 1927, when Loomis reported the chemical and biological effects of ultrasound for the first time. Since then, the field has been achieving continuous and useful advances. Nowadays, the application of ultrasound covers a wide range of fields, as shown in Table 1.1. The chemical and mechanical effects of ultrasound are mainly result of the implosive collapse of cavitation bubbles, which leads to surprisingly high local temperature and pressure. Locally, the high temperature and pressure may reach up to 5000 K and 1000 atm, respectively (Flint and Suslick, 1991; Suslick, 1990). These rather extreme conditions are very short-lived but have shown to result in the generation of highly reactive species including hydroxyl (OH•), hydrogen (H•) and hydroperoxyl (HO2•) radicals, and hydrogen peroxide (Makino et al., 1982; Misk and Riesz, 1994). These radicals are capable of initiating or promoting many fast reduction-oxidation (REDOX) reactions. Besides the chemical effects, ultrasound may produce other mechanical or physical effects such as increasing the surface area between the reactants, accelerating dissolution, and/or renewing the surface of a solid reactant or catalyst. Ultrasound has proven to be a very useful tool in enhancing the reaction rates in a variety of reacting systems. It has successfully increased conversion, improved yield, changed 1 Chapter 1 Introduction reaction pathways, and/or initiated reactions in biological, chemical, and electrochemical systems. Furthermore, the use of ultrasound may enable operation at milder operating conditions (e.g., lower temperatures and pressures) (Adewuyi, 2001; Gogate, 2002; Gogate and Pandit, 2001; Gonze et al., 1999; Moholkar et al., 1999; Hoffmann et al., 1996; Mason and Lorimer, 2002). For these reasons, use of ultrasound appears to be a promising alternative for high-value chemicals and pharmaceuticals. In addition, research is continually underway to make it a feasible option in the ongoing effort to intensify large-scale processes. Recently a pilot plant, funded by the Electricite de France, uses ultrasound to indirectly oxidize cyclohexanol to cyclohexone (Keil and Swamy, 1999). Hoechst and several other companies worked on a project with Germany’s Clausthal Technical University (Clausthal-Zellerfeld) which used a modular sonochemical reactor to produce up to 4 metric tons of Grignard reagent/year. They found ultrasound to increase the conversion by a factor of 5 and reduce the induction period from 24 h to 50 min (Keil and Swamy, 1999). In addition, its application to the treatment of wastewater containing toxic and complex pollutants (both from industrial and domestic sources) is shown to be among the most attractive field of study. Neppiras (1980) first coined the term sonochemistry, which is the application of ultrasound to enhance or alter chemical reactions, and belongs to advanced oxidation processes (AOPs) (Thompson and Doraiswanmy, 1999). Advanced oxidation processes are defined as processes that generate hydroxyl radicals in sufficient quantities to be able to oxidize majority of the complex chemicals present in effluent water. Hydroxyl radicals are powerful oxidizing reagents with an oxidation potential of 2.33 V and exhibit faster rates of oxidation reactions as compared to the conventional oxidants like hydrogen 2 Chapter 1 Introduction peroxide or KMnO4 (Gogate et al., 2002a). Hydroxyl radicals react with most organic and many inorganic solutes with high rate constants (Glaze et al., 1992; Jiang et al. 2002; Hoigne, 1997). There are several oxidation technologies such as sonochemical oxidation, photocatalytic oxidation, Fenton, chemical oxidation, wet air oxidation, sub-critical, critical and supercritical water oxidation processes. Typical radical reactions of some AOPs are shown in Table 1.2. Among these methods, wet air oxidation, sub-critical, critical and super-critical water oxidation processes need sophisticated instrumentation for high temperature/pressure operation, and they are generally used for highly concentrated effluents (typical COD load > 40,000 ppm) for cost-effective operation. On the other hand, the other processes have the potential to degrade the new toxic chemicals, biorefractory compounds, pesticides, etc. either partially or fully, most importantly under ambient conditions. Hence, the present work puts more emphasis on these processes. A majority of these oxidation technologies, however, fail to degrade complex compounds completely, especially in the case of real wastewaters. Moreover, they cannot be used for processing large volumes of real waste water with the present level of technology of these reactors. Commenges et al. (2000) have shown that ultrasound fails to produce substantial degradation of pollutants in the case of real industrial effluent. Similar results have also been reported by Beltran et al. (1997) for the case of photocatalytic oxidation of distillery and tomato wastewaters. Perhaps, these can be used to degrade the complex residues up to a certain level of toxicity beyond which the conventional biological methods can be successfully used for further degradation (Beltran et al. 1999a, b; Engwall et al., 1999; 3 Chapter 1 Introduction Kitis et al., 1999; Sangave et al., 2004; Scott and Ollis, 1995). It should also be noted that the efficacy of conventional methods would also depend on the level of toxicity reached in the pretreatment stages, using the oxidation techniques. Thus, it is important to select proper pretreatment technique to improve the overall efficiency of the wastewater treatment unit. Table 1.1 Application of ultrasound Chemical and allied industries other air scrubbing atomization cell disruption crystal growth crystallization defoaming degassing depolymerization dispersion of solids dissolution drying emulsification extraction filtration flotation homogenization sonochemistry stimulus for chemical reactions treatment of slurries Abrasion Cleaning Coal-oil mixtures Cutting Degradation of powders Dental descaling Drilling Echo-ranging Erosion Fatigure testing Flaw detection Flow enhancement Imaging Medical inhalers Metal-grain refinement Metal tube drawing Nondestructive testing of metals Physiotherapy Plastic welding Powder production Soldering Sterilization Welding 4 Chapter 1 Introduction Table 1.2 Some Advanced Oxidation Processes Sonolysis H2O → H• + OH• Photocatalysis TiO2 + hv → TiO2 ( hvb+ + e- ) hvb+ + OH- →•OH Ozone-peroxide-UV O3 + -OH → O2 - → •OH 3O3 + UV (US+H2O2>US+UV> US+UV+H2O2>UV>US+O3>UV+H2O2. Although the energy efficiency for the UV+H2O2 system is higher than that of US+O3, the degree of mineralization in case of UV+H2O2 is much lower. Thus ultrasonication in presence of ozone is a viable alternative for the degradation of organic dyes in water. 74 Chapter 4 Results & Discussions Table 4.5 EE/O values for various AOPs (C0 = 20 mg/l; T = 20 ˚C) System Parameters EE/O (kWh per m3 per order) US P = 900 W; f = 28 kHz; 10526 US + H2O2 P = 900 W; f = 28 kHz; 10275-10612 UV P = 16 W; 21.2 UV + H2O2 PUV = 16 W; 12.5-16.43 US + UV PUS = 900 W; PUV = 16 W; 512 US+UV + H2O2 PUS = 900 W; PUV = 16 W; Molar ratio (H2O2/OG) = 160-644 71-83 US (bath) + O3 PUS = 100 W; 　 Pozonator = 400 W; 126 75 Chapter 5 Conclusions & Recommendations Chapter 5 Conclusions and Recommendations 5.1 Conclusions Ultrasonic irradiation shows promise and has the potential for use in environmental remediation. Besides the generation of high concentration of oxidizing species such as hydroxyl radicals and H2O2 in solution which is the common principle for advanced oxidation processes for the degradation of most non-volatile chemicals, ultrasonic cavitation also produces localized transient high temperatures and pressures, which drive some of the chemical reactions by pyrolysis mechanism mainly responsible for the decontamination of volatile pollutants. The magnitudes of temperature, pressure and free radicals can be manipulated by adjusting the operating parameters, such as intensity and frequency of irradiation, temperature, physico-chemical properties of liquid medium and aerated gases. In this work, sonochemical and sonophotochemical degradation of orange G was tested under different conditions in three types of ultrasonic reactors. The production of hydrogen peroxide and hydroxyl radicals was measured in three reactors under different conditions with the objective of identifying the optimal conditions. Experiments of ultrasonic irradiation and its combination with other AOPs were conducted with orange G as a model compound. The effect of hydrogen peroxide addition was also investigated. Furthermore, a new continuous sonophotochemical reactor with a total volume of 2.2 L was constructed to compare the results of batch bath and probe reactors. Experiments 76 Chapter 5 Conclusions & Recommendations with hybrid techniques, sonophotolysis and sonophotocatalysis, were then carried out using this new reactor. Some general conclusions can be drawn: 1. Maximum production of hydroxyl radicals occurs in combined UV and US systems. 2. In bath ultrasonic reactor with three frequencies, 28, 45 and 100 kHz, lower frequency is preferable in generating hydroxyl radicals. 3. The reaction rate is observed to be inversely correlated with the initial concentration of orange G. 4. The addition of optimal amount of H2O2 with UV and US can increase the mineralization rate of orange G which is non-volatile. This indicates that non-volatile solute mainly reacts with oxidizing species at the bubble interfaces or within the bulk solution. 5. The rate of orange G degradation and effects of different process parameter are comparable in three types of reactors of different volume. Enhancement in sonochemical decomposition for orange G was achieved by employing the hybrid system: US/UV, US/photocatalysis and US/O3. This synergism between different hybrid methods is mainly due to the reaction with hydroxyl radicals. Generally, combination of two or more advanced oxidation processes such as UV/ozone, UV/H2O2, US/ozone, sonophotochemical/sonophotocatalytic oxidation etc, leads to an enhanced generation of the hydroxyl radicals, which eventually results in higher oxidation rates. The efficacy of the process and the extent of synergism depend not only on the generation of free radicals but also on the reactor conditions or configuration leading to a 77 Chapter 5 Conclusions & Recommendations better contact of the generated free radicals with the pollutant molecules and also better utilization of the oxidants and catalytic activity. ¾ The kinetic analysis indicates that US/ozone was the fastest in decomposing the orange G. The enhanced turbulence generated by ultrasound decreases the mass transfer resistance which is a major limiting factor for the application of ozone alone. Additionally, ultrasound can promote the dissociation of ozone which results into better utilization and then higher degradation rates. ¾ Use of a catalyst in conjunction with ultrasonication has been found to considerably enhance the rates of the reaction, though the effect is complex as there are multiple factors which are influenced by the presence of the solid particles including detrimental effects such as scattering of sound waves resulting in non-useful utilization of the supplied energy. ¾ In the case of the new sonophotochemical reactor, it is important to have simultaneous irradiation of ultrasound and UV light rather than sequential operation. 5.2 Recommendations for further research Sonochemistry has achieved great improvement over the last 20 years; there are numerous illustrations in the literature where sonochemical reactors have been successfully used for the degradation of variety of compounds at different scales of operation. However, almost all the studies are with model pollutants; hence more investigation about real effluents containing a variety of compounds should be carried out in future work. 78 Chapter 5 Conclusions & Recommendations Further, detailed cost analysis is needed about application of ultrasonic irradiation for the degradation of wastewater process on an industrial scale. The current cost of cleaning of contaminated ground water using acoustic cavitations is an order-of-magnitude, higher than that of the air stripping/active carbon process (Peters, 2001).Thus, it is important to either find an alternative means for generating cavitation energy efficiently or use acoustic cavitation in combination of other AOPs. A hybrid process appears to have the best potential. Future work may be directed to compare all the oxidation technologies on the basis of the operation costs and this should be indeed an excellent work and the need of the present hour. There are still many new frontiers to be explored. Researchers have found that ultrasound chemically enhances reactions which depend on a SET (single electron transfer) process as a key step. Reaction systems which follow an ionic mechanism are enhanced by the mechanical effects of ultrasound. These enhancements are result of increases in the intrinsic mass-transfer coefficient, increase in surface area resulting from particle degradation, and, in some cases, increase in the driving force for dissolution. In some reaction systems, ultrasound changes the reaction pathway from ionic to one which involves a SET step. Several other aspects of sonochemical behavior are unclear. The manner by which free radicals are produced within the cavitation bubble remains elusive, although several researchers have concluded that they are formed during the adiabatic implosion of the cavitation bubble. Ultrasound has been found to enhance the effective diffusivity in a 79 Chapter 5 Conclusions & Recommendations solid-liquid system, increase the intrinsic mass-transfer coefficient, induce supersaturation, and increase the activation energy and frequency factor of various reaction systems. However, the actual mechanisms behind these enhancements have not been discerned. In addition, the amount of available engineering data in the areas of ultrasonic reactor design and scale-up are scanty. It will take the combined work of scientists from all fields to resolve the role of ultrasound in reacting systems and to make it a viable rate enhancement technique for commercial industrial processes. More importantly, majority of the work reported to date is on a laboratory scale and not much information is available at this stage for efficient large-scale of operation. Work needs to be conducted both in terms of the design strategies for scale-up and feasibility of the operation of transducers at higher levels of power dissipation, before successful application of sonochemical reactors is feasible at an industrial scale. It should also be noted that information is required from diverse fields such as chemical engineering (gasliquid hydrodynamics and other reactor operations), material science (for construction of transducers efficiently operating at conditions of high frequency and high power dissipation) and acoustics (for better understanding of the sound field existing in the reactor) for the efficient scale-up of sonochemical reactors. In case of sonophotocatalytic reactors, the major factor controlling the overall efficiency of destruction is the stability of the photocatalyst under the effect of ultrasound. Therefore, efforts are required in terms of new designs which will protect the catalyst but at the same time will give enhanced effects. The development of large-scale reactors 80 Chapter 5 Conclusions & Recommendations could be based on the multiple transducers multiple frequency irradiations for the sonochemical part and achievement of excellent distribution of the incident UV light. It must be said that with ultrasonic irradiation, even its hybrid methods with other AOPs, it is difficult to achieve complete mineralization. Hence it may not be useful in degrading large volumes of effluents cost-effectively. It is recommended for possible use ultrasonic irradiation or its combination with other AOPs to reduce the toxicity of pollutant streams to a certain level beyond which biological oxidation can take care of complete mineralization of the biodegradable products. An optimized pre-treatment stage (in terms of the oxidant dose and the reduction in the toxicity level) will substantially decrease the total treatment time and hence the size of the reactor using the combination technique. 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TOC degradation at different systems by Probe OG-TOC 10 mg/l 20 mg/l 30 mg/l 40 mg/l H2O2 ml/l Degradation % US UV US+UV O3 O3+US 0 18 11 19 41 52 0.25 9 18 23 46 55 1.25 15 25 33 38 51 2.5 15 24 24 28 45 5 17 17 22 27 40 0 5 14 12 53 63 0.25 15 20 37 50 58 1.25 16 28 42 44 53 2.5 13 26 44 39 51 5 11 27 38 38 43 0 7 5 8 58 60 0.25 7 7 13 51 53 1.25 12 8 33 45 47 2.5 7 14 45 38 42 5 11 30 37 32 37 0 2 4 7 47 52 0.25 5 10 20 43 50 1.25 5 15 30 36 47 2.5 3 25 35 36 43 5 4 28 33 32 40 95 Appendix Table A2. Pseudo-first-order rate constant (kd) for ultrasonication, UV, and US+UV systems, and initial rate constants (kid) for ozonation and sonolytic ozonation by probe Orange G 10 mg/l H2O2 ml/l 0 0.25 1.25 2.5 5 20 mg/l 0 0.25 1.25 2.5 5 30 mg/l 0 0.25 1.25 2.5 5 40 mg/l 0 0.25 1.25 2.5 5 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 US 0.0059 0.9795 0.0054 0.9854 0.0053 0.9992 0.0052 0.9857 0.0044 0.9640 0.0042 0.9781 0.0035 0.9841 0.0029 0.9369 0.0019 0.9919 0.0014 0.9824 0.0038 0.9557 0.006 0.9916 0.0033 0.9963 0.0031 0.9489 0.0019 0.9013 0.0028 0.9807 0.0029 0.9796 0.0032 0.9794 0.0027 0.9571 0.0027 0.9749 kd UV 0.0407 0.9939 0.1865 0.9906 0.3582 0.9991 0.315 0.989 0.2332 0.9382 0.0172 0.9978 0.0808 0.9605 0.2356 0.9731 0.2190 0.9706 0.2112 0.9400 0.0085 0.9816 0.0455 0.9890 0.1075 0.9605 0.1400 0.9552 0.1202 0.9917 0.0065 0.9840 0.0220 0.9966 0.0749 0.9840 0.078 0.9858 0.0858 0.9902 US+UV 0.0523 0.9967 0.2579 0.9982 0.426 0.9932 0.3851 0.9982 0.2524 0.9979 0.0259 0.9954 0.1118 0.9886 0.2631 0.9743 0.2935 0.9799 0.2379 0.9272 0.0145 0.9936 0.061 0.9822 0.119 0.9803 0.2454 0.9760 0.1713 0.9757 0.0107 0.9815 0.0411 0.9939 0.0862 0.9949 0.109 0.9836 0.1264 0.9769 O3 4.6925 kid US+O3 5.2739 5.7032 6.3854 2.965 3.5123 1.0259 1.4329 0.931 1.2352 2.0704 2.4042 2.3226 2.6231 1.5732 1.8436 1.0665 1.3653 1.0015 1.2144 1.6979 1.9812 1.5856 1.8994 1.1325 1.2373 0.9086 1.1764 0.835 0.9811 0.9365 1.2421 0.8471 0.9813 0.6969 0.7638 0.6702 0.7254 0.4826 0.6021 96 Appendix Table A3 Rate constants of orange G at different conditions by the sonophotochemical reactor OG 10 mg/l H2O2 ml/l 0 0.25 1.25 2.5 5 20 mg/l 0 0.25 1.25 2.5 5 30 mg/l 0 0.25 1.25 2.5 5 40 mg/l 0 0.25 1.25 2.5 5 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 k R2 US 0.001 0.9886 0.0014 0.938 0.0015 0.9779 0.0014 0.9963 0.0012 0.9959 0.0012 0.9806 0.0013 0.9526 0.0012 0.9586 0.0012 0.9873 0.0011 0.9869 0.0009 0.9687 0.0012 0.9248 0.0012 0.9259 0.0011 0.9546 0.0011 0.9869 0.0007 0.9862 0.0008 0.9245 0.001 0.9172 0.001 0.9519 0.0008 0.9438 kd UV at 254nm 0.036 0.9857 0.2289 0.9998 0.2889 0.9889 0.2469 0.9859 0.2157 0.9983 0.0247 0.9845 0.1917 0.955 0.2442 0.9586 0.2897 0.9973 0.179 0.9946 0.0229 0.9949 0.1832 0.9866 0.2125 0.9889 0.1653 0.99 0.1227 0.9964 0.0215 0.9848 0.1571 0.9839 0.1892 0.9913 0.1508 0.9772 0.1391 0.9979 US+UV(254nm) 0.0416 0.9929 0.2473 0.9995 0.3155 0.994 0.2562 0.9979 0.221 0.9971 0.0295 0.9985 0.1919 0.9934 0.2769 0.9935 0.3083 0.9871 0.2109 0.9505 0.027 0.9855 0.2098 0.9817 0.2688 0.9866 0.2162 0.9961 0.1665 0.9895 0.0238 0.9946 0.1792 0.9852 0.257 0.9866 0.2073 0.9893 0.1603 0.9843 97 Appendix 98 [...]... photocatalysis for 67 degradation of orange G using TiO2-Montmorillonite Figure 4.19 Control experiment of degradation of orange G using H2O2 70 Figure 4.20 Orange G degradation in presence of H2O2 and US 71 Figure 4.21 Orange G degradation at different conditions using TiO2montmorrilonite 71 Figure 4.22 Mineralization of orange G under various conditions 73 Figure 4.23 TOC degradation of OG by sonophotocatalysis... of Figures Figure 4.9a Effect of H2O2 on the degradation of orange G by US+UV 53 Figure 4.9b Effect of H2O2 on the degradation of orange G by O3 +US 53 Figure 4.10a TOC degradation of orange G by US, UV, US+UV 55 Figure 4.10b TOC degradation of orange G by O3 and O3+US 55 Figure 4.11 H2O2 production by sonolysis of water in the new reactor 57 Figure 4.12 H2O2 production by sonolysis of water 58 Figure... 4.13 Sonochemical degradation of orange G at different initial concentrations 60 Figure 4.14 Photochemical degradation of orange G at different initial concentration 60 Figure 4.15 Comparison of orange G degradation by US, UV, and US+UV 61 Figure 4.16 Adsorption equilibrium of orange G for four catalysts 65 Figure 4.17 Photocatalytic degradation of orange G by different catalysts 65 Figure 4.18 Comparison... concentration of orange G= 20 mg/l) 61 Table 4.3 Rate constants of orange G degradation at different systems(Initial concentration of orange G = 20 mg/l) 62 Table 4.4 Orange G removal after 120 minute irradiation by UV (365 nm) and US+UV (365 nm) at four different catalysts (Initial concentration of orange G = 20 mg/l) 68 Table 4.5 EE/O values for various AOPs (C0 = 20 mg/l; T = 200C) 75 Table A1 TOC degradation... defoaming degassing depolymerization dispersion of solids dissolution drying emulsification extraction filtration flotation homogenization sonochemistry stimulus for chemical reactions treatment of slurries Abrasion Cleaning Coal-oil mixtures Cutting Degradation of powders Dental descaling Drilling Echo-ranging Erosion Fatigure testing Flaw detection Flow enhancement Imaging Medical inhalers Metal-grain... (concentration of approx.350 –390 mg/l with other VOC amounting to 80–85 mg/l), reporting that the destruction was complete within 120 min for all the components (at conditions of operating frequency of 361 kHz, calorimetric power dissipation of 16 Chapter 2 Literature Review 260W/m3 W, volume of effluent as 200 ml, operating pH of 6.28 and temperature of 9 ˚C) and also for some of the intermediates formed... is enhanced by using solvents with opposing characteristics (i.e., low vapor pressure, high viscosity, and high surface tension) (Gogate, 2002; Gogate and Pandit, 2001) 4 The rate constant for the sonochemical degradation of the pollutants is higher at lower initial concentration of the pollutant and hence pre-treatment of the waste stream may be done in terms of diluting the stream for enhanced cavitational... cavitationally active volume for multiple transducers (Sivakumar et al., 2002; Gogate et al., 2002b) 2 Greater energy efficiency has been observed for ultrasonic probes with larger irradiating surface, (lower operating intensity of irradiation) which results into uniform dissipation of energy (Gogate and Pandit, 2001) Thus, for the same power density (power input into the system per unit volume of the effluent... potential of 2.33 V and exhibit faster rates of oxidation reactions as compared to the conventional oxidants like hydrogen 2 Chapter 1 Introduction peroxide or KMnO4 (Gogate et al., 2002a) Hydroxyl radicals react with most organic and many inorganic solutes with high rate constants (Glaze et al., 1992; Jiang et al 2002; Hoigne, 1997) There are several oxidation technologies such as sonochemical oxidation, ... plate processor, hexagonal flow cell etc., are available Fig 2.2 gives the schematic representation of the commonly used sonochemical equipment 17 Chapter 2 Literature Review Fig 2.2 Schematic representation of sonochemical equipment (Gogate et al., 2002) Typically, the equipment with higher dissipation area give larger energy efficiency at similar levels of the supplied input energy (Gogate et al., 2001, .. .COMBINATION OF ADVANCED OXIDATION PROCESSES WITH ULTRASONICATION FOR REMOVAL OF ORANGE G HU HONGQIANG A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF ENGINEERING DEPARTMENT OF CHEMICAL... 46 Figure 4.7a Degradation of orange G by UV and US+UV 48 Figure 4.7b Comparison of color removal of orange G among US, UV, US+UV 48 Figure 4.8a Sonolytic ozonation and ozonation of orange G 50... systems 41 Figure 4.3 Changing of the absorption spectra of during ultrasonication 44 (Probe) (initial concentration of orange G =10 mg/l) Figure 4.4 First-order plot of orange G degradation by