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Multifunctional Bismuth Ferrite Nanomaterials As a New‑Generation Catalyst for Water Treatment This document is downloaded from DR‑NTU (https://dr.ntu.edu.sg) Nanyang Technological University, Singapore. Multifunctional bismuth ferrite nanomaterials as a new‑generation catalyst for water treatment Hu, Zhong Ting 2017 Hu, Z. T. (2017). Multifunctional bismuth ferrite nanomaterials as a new‑generation catalyst for water treatment. Doctoral thesis, Nanyang Technological University, Singapore. http://hdl.handle.net/10356/69460 https://doi.org/10.32657/10356/69460 Downloaded on 24 Sep 2021 02:23:24 SGT MULTIFUNCTIONAL BISMUTH FERRITE NANOMATERIALS AS A NEW-GENERATION CATALYST FOR WATER TREATMENT HU ZHONG TING SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING 2017 MULTIFUNCTIONAL BISMUTH FERRITE NANOMATERIALS AS A NEW-GENERATION CATALYST FOR WATER TREATMENT HU ZHONG TING School of Civil and Environmental Engineering A thesis submitted to the Nanyang Technological University in partial fulfillment of the requirement for the degree of Doctor of Philosophy 2017 Acknowledgements First and foremost, I would like to express my sincere gratitude to my respected supervisor, Associate Prof. Lim Teik Thye, for his invaluable advices and patient guidances. He always encourages me to have high aspiration and strive for excellence. I am eternally indebted to my beloved wife (Xu Wen Jin), parents, grandparents, sister/brother-in-law, uncles, and aunts, for their unconditional love, unselfish devotion, and unwavering support. I would like to give very special thanks to my uncle, Prof. Chen Jianfeng, who guides me forward and along the right paths concurrently. I would like to thank many friends for their help and support. My special thanks to the members of Prof. Lim’s group, Dr. Goei Ronn, Dr. Wang Penghua, Wu Weiyi, Oh Wen Da, Zhang Yiqing, Xiao Yongjun, for their support and cooperation given during the experiments. I would like to thank the following staff members in NTU for their kind assistance. They are Mrs. Lim-Tay Chew Wang, Mr. Tan Han Khiang, Mr. Ong Chee Yung, Mrs. Phang-Tay Beng Choo, Mrs. Maria Chong Ai Shing, Miss. Pearlyn See Shen Yen, etc. Last but not least, I am most grateful to Nanyang Technological University for providing the scholarship of my Ph.D program. i Table of contents Acknowledgements ........................................................................................................ i Table of contents ........................................................................................................... ii Abstract ........................................................................................................................ vi List of tables ................................................................................................................. ix List of figures ................................................................................................................ x List of symbols and abbreviations ............................................................................ xvi List of publications .................................................................................................... xix Chapter 1 Introduction ................................................................................................ 1 1.1 Background ...................................................................................................... 1 1.2 Motivation and knowledge gap ........................................................................ 2 1.3 Objectives and scope of work .......................................................................... 4 1.4 Organization of the report ................................................................................ 5 Chapter 2 Literature review ........................................................................................ 6 2.1 Photocatalysis ................................................................................................... 6 2.2 Fenton and photo-Fenton processes ............................................................... 10 2.3 Nanomaterials for removal of heavy metal ions............................................. 14 2.4 Bismuth ferrites .............................................................................................. 15 2.4.1 Crystal structure .......................................................................................... 16 2.4.2 Properties .................................................................................................... 17 2.4.3 Optimization ............................................................................................... 18 Chapter 3 Single Crystals — Single-crystalline Bi2Fe4O9 nanopad synthesized via low-temperature co-precipitation: performance as photo- and Fenton catalysts 24 3.1 Introduction .................................................................................................... 24 3.2 Experimental .................................................................................................. 25 3.2.1 Materials ..................................................................................................... 25 3.2.2 Synthesis ..................................................................................................... 26 3.2.3 Characterization .......................................................................................... 26 3.2.4 Catalytic evaluation .................................................................................... 27 3.3 Results and discussion .................................................................................... 28 3.3.1 Effect of the Bi/Fe molar ratio on crystal growth ....................................... 28 3.3.2 Effect of reaction time on crystal growth ................................................... 29 ii 3.3.3 Phase purity analysis of Bi2Fe4O9 nanopads ............................................... 32 3.3.4 Structure and composition .......................................................................... 33 3.3.5 Surface area and surface property ............................................................... 35 3.3.6 Optical property .......................................................................................... 36 3.3.7 Evaluation of the potential applications ...................................................... 38 3.3.7.1 Visible-light driven photocatalysis ...................................................... 38 3.3.7.2 Fenton-like and photo-assisted Fenton reaction .................................. 39 3.3.7.3 Magnetic property ................................................................................ 40 3.3.8 Proposed mechanism .................................................................................. 40 3.4 Conclusions .................................................................................................... 43 Chapter 4 Nanostructures — Nanostructured hexahedron of Bi2Fe4O9 clusters: development of a delicate synthesis process and efficient multiplex catalyses for pollutant degradation ................................................................................................. 45 4.1 Introduction .................................................................................................... 45 4.2 Experimental .................................................................................................. 46 4.2.1 Materials ..................................................................................................... 46 4.2.2 Synthesis of nanostructured bismuth ferrite clusters .................................. 46 4.2.3 Characterization .......................................................................................... 47 4.2.4 Catalytic evaluation .................................................................................... 48 4.3 Results and discussion .................................................................................... 49 4.3.1 Formation process of nanostructured Bi2F4O9 clusters ............................... 49 4.3.2 Characteristics of nanostructured Bi2Fe4O9 clusters ................................... 51 4.3.3 Performance of nanostructured Bi2Fe4O9 clusters in degradation of MO .. 58 4.3.4 Proposed mechanism .................................................................................. 60 4.4 Conclusions .................................................................................................... 62 Chapter 5 2D Composites — Low-temperature synthesis of graphene/Bi2Fe4O9 NPs composites for synergistic adsorption-photocatalytic degradation of pollutant …………. .................................................................................................... 63 5.1 Introduction .................................................................................................... 63 5.2 Experimental .................................................................................................. 64 5.2.1 Chemicals .................................................................................................... 64 5.2.2 Materials synthesis ...................................................................................... 64 5.2.2.1 Synthesis of GO nanosheets................................................................. 64 5.2.2.2 Synthesis of Bi2Fe4O9 nanoparticles .................................................... 65 iii 5.2.2.3 Synthesis of Bi2Fe4O9/GO composites ................................................ 65 5.2.2.4 Synthesis of Bi2Fe4O9/rGO composites ............................................... 65
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