(Luận văn thạc sĩ) okara derived hydrochar effects of activation on the solid fuel properties and adsorption behaviors of the cationic dye (brilliant green)

VIETNAM NATIONAL UNIVERSITY, HA NOI VIETNAM JAPAN UNIVERSITY NGUYEN THI THU HOA n OKARA-DERIVED HYDROCHAR: EFFECTS OF ACTIVATION ON THE SOLID FUEL PROPERTIES AND ADSORPTION BEHAVIORS OF THE CATIONIC DYE (BRILLIANT GREEN) MASTER’S THESIS VIETNAM NATIONAL UNIVERSITY, HA NOI VIETNAM JAPAN UNIVERSITY NGUYEN THI THU HOA OKARA-DERIVED HYDROCHAR: EFFECTS OF ACTIVATION ON THE SOLID FUEL PROPERTIES AND ADSORPTION BEHAVIORS OF THE CATIONIC DYE (BRILLIANT GREEN) n MAJOR: ENVIRONMENTAL ENGINEERING CODE: 8520320.01 RESEARCH SUPERVISORS: Dr NGUYEN THI AN HANG Dr NGUYEN HONG NAM Hanoi, 2021 ACKNOWLEDGEMENTS First of all, I would like to express my sincere thanks to my principal supervisor Dr Nguyen Thi An Hang, lecturer and director of the Environmental Engineering program at Vietnam Japan University-Vietnam National University, Hanoi for supporting, helping and teaching me in the process of studying and conducting my master's thesis She was always encouraging and ready to help me when I have difficulties, imparting skills and knowledge to help me work in the most effective way This helps me not only improve my professional knowledge but also improve my life skills I would also like to thank Dr Nguyen Hong Nam, lecturer at Vietnam Japan University for his comments, support and creating conditions for me during the process of writing my thesis as well as doing my internship at Viet Phap University I would also like to thank Ms Nguyen Thi Xuyen, the project staff who supported me in conducting experiments as well as analyzing environmental parameters in the master's n thesis I would like to acknowledge the VJU's JICA research fund (2021-2023, Principal Investigator Dr Nguyen Thi An Hang) for providing the financial support I would like to express my sincere thanks and gratitude to my family and friends for facilitating my studies and encouraging me Hanoi, June 14th, 2021 Nguyen Thi Thu Hoa TABLE OF CONTENTS ACKNOWLEDGEMENTS TABLE OF CONTENTS LIST OF TABLES .i LIST OF FIGURES ii LIST OF ABBREVIATIONS iii CHAPTER 1: INTRODUCTION 1.1 Research background 1.2 Research objectives CHAPTER 2: LITERATURE REVIEW .3 2.1 Dye pollution in the world and in Vietnam 2.1.1 Environmental concerns of dyes in the world .3 2.1.2 Dye treatment technologies in the world .3 n 2.2 Potential and challenges of agrowaste 2.2.1 Generation and disposal of agrowaste in Vietnam 2.2.2 Sources, current use and disposal of okara 2.3 Agrowaste thermal conversion technologies 2.3.1 Hydrothermal carbonization (HTC) 2.3.2 Pyrolysis 12 2.3.3 Incineration 13 2.4 Application of agrowaste-derived hydrochars 13 2.4.1 Solid fuels 13 2.4.2 Environmental materials 13 2.4.3 Soil reclamation 14 2.4.4 Carbon sequestration 14 CHAPTER 3: MATERIALS AND METHODS .15 3.1 Materials .15 3.1.1 BG dye 15 3.1.2 Okara 15 3.2 Experiment setup and equipment .15 3.2.1 Hydrochar fabrication 15 3.2.2 Hydrochar modification .15 3.2.3 Hydrochar characterization 16 3.2.4 Fuel properties of raw and activated hydrochars .16 3.2.5 BG dye adsorption by the selected activated hydrochar .16 3.3 Statical analysis 19 CHAPTER 4: RESULTS AND DISCUSSION 20 4.1 Factors influencing the fabrication of okara-derived hydrochars 20 4.1.1 Effect of temperature 20 4.1.2 Effect of contact time 21 4.1.3 The okara/water ratio 22 4.2 Effect of modification on the fuel and adsorption properties of hydrochars .23 4.3 Characterization of hydrochars 25 4.4 The fuel properties of the selected activated hydrochar .28 4.5 BG dye adsorption behaviors of the selected activated hydrochar 28 n 4.5.1 Influential factors .28 4.5.2 Adsorption isotherm 30 4.5.3 Adsorption kinetics 33 CHAPTER 5: CONCLUSION AND RECOMMENDATION 35 5.1 Conclusions 35 5.2 Recommendations 35 REFERENCES 36 APPENDIX 41 LIST OF TABLES Table 4.1 Effects of activation methods on the solid fuel properties of okara-derived hydrochar .24 Table 4.2 Comparing the HHV of AH2 with other materials 25 Table 4.3 Langmuir and Freundlich isotherm parameters for BG adsorption on AH2 .31 Table 4.4 Comparing qmax of AH2 with those of other hydrochars .32 Table 4.5 Pseudo-first-order and pseudo-second-order kinetic parameters for BG adsorption onto AH2 .33 n i LIST OF FIGURES Figure 4.1 Effect of the temperature on okara-derived hydrochar fabrication 20 Figure 4.2 Effect of the contact time on okara-derived hydrochar fabrication 21 Figure 4.3 Effect of the okara: water ratio on okara-derived fabrication 22 Figure 4.4 Effects of activation methods on BG adsorption .23 Figure 4.5 SEM results of RH .26 Figure 4.6 SEM results of AH1 27 Figure 4.7 SEM results of AH2 27 Figure 4.8 FTIR result 28 Figure 4.9 Point of zero charge (pHpzc) for the selected hydrochar (AH2) .29 Figure 4.10 Effect of pH on BG adsorption by AH2 29 Figure 4.11 Effect of AH2 dose on BG adsorption .30 Figure 4.12 Langmuir adsorption isotherm curve for BG adsorption on AH2 31 Figure 4.13 BG adsorption isotherms on AH2 31 Figure 4.14 Freundlich adsorption isotherm curve for BG adsorption on AH2 32 Figure 4.15 Pseudo-first-order and Pseudo-second-order kinetic curves for BG adsorption on AH2 34 n ii LIST OF ABBREVIATIONS BG HTC AOP RH SEM BET FTIR HHV pHzpc COD Brilliant Green Hydrothermal Carbonization Advanced Oxidation Process Raw Hydrochar Scanning electron microscopy Brunauer-Emmett-Teller Fourier transform infared spectroscopy High Heating Value pH zero point charge Chemical oxygen demand n iii CHAPTER 1: INTRODUCTION 1.1 Research background Currently, the increased demand for the use of synthetic dyes is gaining popularity The textile industries use a lot of water, energy as well as emit a large amount of wastewater and many harmful chemicals (Ito et al., 2016) Therefore, the use of dyes has made dye pollution becoming worsen The brilliant green (BG) dye is widely used in many industries such as textiles, plastics and paper printing The BG dye can cause several health risks which include eye burns, skin irritation, coughing and shortness of breath, nausea, vomiting and diarrhea Thus, the treatment of dyestuff wastewaters is necessary (Chequer et al., 2013; Kismir and Aroguz., 2011) There are many treatment techniques being used to eliminate dye compounds from water such as biodegradation, coagulation, reverse osmosis and adsorption Among them, adsorption is considered as the most effective method due to its easy operation and high efficiency However, the large-scale use of activated carbon is limited as the result of its high prices (Mansoout et al., 2020) n Hydrothermal carbonization (HTC) is a promising heat treatment method for converting raw materials into value-added products The two main products of the HTC process are hydrochar and bio-oil, of which hydrochar accounts for 40-70% by volume HTC is usually performed at relatively low temperatures (180-350oC) compared to other heat treatment technologies Since it does not require drying in advance, which is an energyintensive consumption process, HTC is economical Compared with the conventional pyrolysis method, the HTC method has outstanding advantages, such as low energy consumption, high yield and minimal emissions This unique features of HTC have attracted the attention of researchers studying hydrochar as an alternative to fossil fuels used in various processes (Cao et al., 2007) In recent years, the production of activated carbon from agro-waste is being widely studied The use of agrowastes as raw materials for the production of activated carbon will be highly economical because they are abundant, cheap, renewable and sustainable precursor Among agrowastes okara is known as a very potential material Annually, large quantities of okara are produced causing environmental pollution due to its quick decomposition A lot of research has been done to recycle of okara as the additive in snacks Howerver, okara’s usage as a human food is limited by its high fiber content In constrast, as okara contains crude fiber (e.g cellulose, hemicellulose and lignin), it can be useful for dye removal through different mechanisms Based on the principle of waste control by waste, the present work aims at developing a novel adsorbent for removing BG dye from wastewater The use of okara as a low-cost adsorbent will add the economic value to reduce waste disposal costs, and remedy dye pollution Besides the agro-waste disposal discussed above, energy is another important issue The global demand for energy has increased and fossil fuel reserves are depleting at an alarming rate (Change., 2006) Global prediction of the increased fuel use has added to the uncertainty about the balance of fossil fuel supply and demand (Dincer., 2006) Hence, it is urgent to produce energy from cheaper and alternative renewable sources Meanwhile, HTC is known to be capable of producing high energy products from agricultural by-products As a results, the combustion behavior of agrowastederived hydrochar needs to be further investigated in the future 1.2 Research objectives n The overall goal of this study is to (i) prepare hydrochar from okara using HTC technology for the removal of BG dye from aqueous solutions and ii) investigate the fuel properties of the fabricated hydrochar The specific objectives of the study are listed as below: • Optimization of the okara-derived hydrochar fabrication process • Selection of the most effective activation method to enhance the BG dye adsorption of the fabricated okara • Evaluation of the physicochemical and fuel properties of the pristine hydrochar and activated hydrochar • Investigation of the adsorptive removal of BG dye from aqueous solutions using the fabricated hydrochar Figure 4.6 SEM results of AH1 n Figure 4.7 SEM results of AH2 27 Figure 4.8 FTIR result n 4.4 The fuel properties of the selected activated hydrochar HHV is one of the parameters to describe the fuel characteristics of solid materials because it can represent the amount of heat released from a given fuel material during combustion The HHV value of the okara-derived hydrochar increased with greater HTC temperature in the range of 180-260oC The highest HHV of the selected activated okaraderived hydrochar 21,64 MJ/kg was higher than that of the bamboo-derived hydrochar at 260oC (20.3 MJ/kg) The HHV of okara-derived hydrochar was slightly lower than those of some fossil fuels such as peat (22.67 MJ/kg), methanol (22.69 MJ/kg) and Converse School – Sub C Coal (21.67 MJ/kg) (Yang et al., 2016) The results showed that the HHV of hydrochar can be upgraded using appropriate HTC temperature and the activation process 4.5 BG dye adsorption behaviors of the selected activated hydrochar 4.5.1 Influential factors 4.5.1.1 Effect of pH pH is a factor that greatly affects the adsorption process The influence of pH was 28 monitored and expressed via the pHzpc value Fig 4.5.1 represents the pHzpc value of the selected activated hydrochar (AH2) It was observed that the pHzpc value of AH2 was 7.4 Fig 4.5.2 shows that the percentage removal and adsorption capacity of BG by AH2 was increased from pH to 7, and then decreased At pH 7, the BG dye removal efficiency and adsorption capacity were 90.7%, and 70.59 mg/g respectively The lower BG percentage removal obtained at a lower pH value can be explained by the fact that when pH