Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

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M.S.

Lack of crystalline order and microstructural features such as grain/grain-boundary in metallic glasses results in a suite of remarkable attributes including very high strength, close to theoretical elasticity, high corrosion and wear resistance, and soft magnetic properties. By altering the morphology and tuning of composition, MGs may be transformed into high-performance catalytic materials. In this study, the catalytic properties of metallic glass powders were demonstrated in dissociating toxic organic chemicals such as AZO dye. BMG powders showed superior performance compared to state of the art crystalline iron because of their high catalytic activity, durability, and reusability. To enhance the catalytic properties, high energy mechanical milling was performed to increase the surface area and defect density. Iron-based bulk metallic glass (BMG) of composition Fe48Cr15Mo14Y2C15B6 was used because of its low cost and ability to make large surface area by high energy ball milling. AZO dye was degraded in less than 20 minutes for the 9 hours milled Fe-BMG. However, subsequent increase in ball milling time resulted in devitrification and loss of catalytic activity as measured using UV-Visible spectroscopy. Aluminum-based bulk metallic glass (Al-BMG) powder of composition Al82Fe3Ni8Y7 was synthesized by arc-melting the constituent elements followed by gas-atomization. The particle size and morphology were similar to Fe-BMG with a fully amorphous structure. A small percentage of transition metal constituents (Fe and Ni) in a mostly aluminum alloy showed high catalytic activity, with no toxic by-products and no change in surface characteristics. Al-alloy particles, being light-weight, were easily dispersed in aqueous medium and accelerated the redox reactions. The mechanism of dye dissociation was studied using Raman and Infrared (IR) spectroscopy. Breaking of -C-H- and - C-N- bonds of AZO dye was found to be the primary mechanism. Mechanical behavior of individual BMG particles was evaluated by in situ pico-indentation in a scanning electron microscope (SEM) to understand the fracture mechanisms. Catastrophic shear banding was found to be the primary fracture mode, which supported the observation of flake formation during high energy ball milling.

Call number: LD2668 .T4 1957 B38 / Master of Science

by Cheung Kit Hing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 175-199). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstracts --- p.ii / Table of Contents --- p.vi / List of Figures --- p.xviii / List of Plates --- p.xxii / List of Tables --- p.xxiii / Abbreviations --- p.xxv / Equations --- p.xxviii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- The chemistry of azo dyes --- p.1 / Chapter 1.2 --- Azo dyes classification --- p.2 / Chapter 1.3 --- Environmental concerns and toxicity --- p.4 / Chapter 1.3.1 --- Toxicity of azo dyes --- p.5 / Chapter 1.3.2 --- Carcinogenicity --- p.5 / Chapter 1.3.3 --- Ecotoxicity --- p.11 / Chapter 1.3.3.1 --- Toxicity to microorganisms --- p.12 / Chapter 1.3.3.2 --- Toxicity towards vertebrates --- p.13 / Chapter 1.4 --- Treatment of azo dyes --- p.13 / Chapter 1.4.1 --- Physical treatment --- p.14 / Chapter 1.4.1.1 --- Adsorption --- p.14 / Chapter 1.4.1.2 --- Membrane technology --- p.15 / Chapter 1.4.2 --- Chemical treatments --- p.15 / Chapter 1.4.2.1 --- Chlorination --- p.16 / Chapter 1.4.2.2 --- Fenton's reaction --- p.16 / Chapter 1.4.2.3 --- Ozonation --- p.16 / Chapter 1.4.2.4 --- Coagulation --- p.17 / Chapter 1.4.3 --- Biological treatments --- p.17 / Chapter 1.4.3.1 --- Activated sludge process --- p.18 / Chapter 1.4.3.2 --- Biodegradation --- p.18 / Chapter 1.4.3.3 --- Biosorption --- p.21 / Chapter 1.4.3.3.1 --- Modeling of sorption --- p.24 / Chapter 1.4.3.3.1.1 --- Langmuir sorption model --- p.24 / Chapter 1.4.3.3.1.2 --- Freundlich sorption model --- p.25 / Chapter 1.4.4 --- Advanced oxidation processes --- p.25 / Chapter 1.4.4.1 --- Photocatalytic oxidation --- p.26 / Chapter 1.4.4.2 --- Titanium dioxide (TiO2) --- p.26 / Chapter 1.4.4.3 --- Mechanism of photocatalytic oxidation using photocatalyst TiO2 --- p.28 / Chapter 1.4.4.4 --- Photocatalytic oxidation of s-triazine containing compounds --- p.30 / Chapter 1.4.4.5 --- Photocatalytic oxidation of Procion Red MX-5B --- p.31 / Chapter 1.4.4.6 --- Cyanuric acid --- p.32 / Chapter 1.4.4.6.1 --- Application --- p.32 / Chapter 1.4.4.6.2 --- Toxicity --- p.32 / Chapter 1.4.4.6.3 --- Photocatalytic oxidation resistance --- p.34 / Chapter 1.4.4.6.4 --- Biodegradation --- p.35 / Chapter 1.4.4.7 --- Enhancement of photocatalytic oxidation by using sorbent immobilized with TiO2 --- p.35 / Chapter 1.4.4.7.1 --- Sorption --- p.35 / Chapter 1.4.4.7.2 --- Immobilization of TiO2 --- p.37 / Chapter 1.4.8 --- Integration of treatment methods --- p.39 / Chapter 2. --- Objectives --- p.41 / Chapter 3. --- Materials and methods --- p.42 / Chapter 3.1. --- Sorption --- p.42 / Chapter 3.1.1 --- Chemical reagents --- p.42 / Chapter 3.1.2 --- Determination of Procion Red MX-5B --- p.42 / Chapter 3.1.3 --- Sampling --- p.44 / Chapter 3.1.4 --- Isolation of Procion Red MX-5B-sorbing bacteria --- p.44 / Chapter 3.1.5 --- Screening of Procion Red MX-5B sorption ability --- p.44 / Chapter 3.1.6 --- Identification of isolated bacterium --- p.46 / Chapter 3.1.7 --- Optimization of cell yield and sorption capacity --- p.47 / Chapter 3.1.7.1 --- Preparation of cell culture of Vibrio sp. --- p.47 / Chapter 3.1.7.2 --- Growth phase --- p.47 / Chapter 3.1.7.2.1 --- Growth curve --- p.47 / Chapter 3.1.7.2.2 --- Dye sorption capacity --- p.47 / Chapter 3.1.7.3 --- Initial pH --- p.48 / Chapter 3.1.7.3.1 --- Growth curve --- p.48 / Chapter 3.1.7.3.2 --- Dye sorption capacity --- p.48 / Chapter 3.1.7.4 --- Temperature --- p.49 / Chapter 3.1.7.4.1 --- Growth curve --- p.49 / Chapter 3.1.7.4.2 --- Dye sorption capacity --- p.49 / Chapter 3.1.7.5 --- Glucose concentrations --- p.49 / Chapter 3.1.7.5.1 --- Growth curve --- p.49 / Chapter 3.1.7.5.2 --- Dye sorption capacity --- p.50 / Chapter 3.1.8 --- Optimization of sorption process --- p.50 / Chapter 3.1.8.1 --- Preparation of sorbent --- p.50 / Chapter 3.1.8.2 --- Dry weight of sorbent --- p.50 / Chapter 3.1.8.3 --- Temperature --- p.50 / Chapter 3.1.8.4 --- Agitation rate --- p.50 / Chapter 3.1.8.5 --- Salinity --- p.51 / Chapter 3.1.8.6 --- Initial pH --- p.51 / Chapter 3.1.8.7 --- Concentration of Procion Red MX-5B --- p.51 / Chapter 3.1.8.8 --- Combination study of salinity and initial pH --- p.51 / Chapter 3.2. --- Photocatalytic oxidation reaction --- p.52 / Chapter 3.2.1 --- Chemical reagents --- p.52 / Chapter 3.2.2 --- Photocatalytic reactor --- p.52 / Chapter 3.2.3 --- Optimization of sorption and photocatalytic oxidation reactions using biomass of Vibrio sp.immobilized in calcium alginate beads --- p.54 / Chapter 3.2.3.1 --- Effect of dry weight of immobilized cells of Vibrio sp. --- p.54 / Chapter 3.2.3.1.1 --- Sorption --- p.55 / Chapter 3.2.3.1.2 --- Photocatalytic oxidation --- p.56 / Chapter 3.2.3.2 --- Effect of UV intensities --- p.57 / Chapter 3.2.3.3 --- Effect of TiO2 concentrations --- p.57 / Chapter 3.2.3.3.1 --- Sorption --- p.57 / Chapter 3.2.3.3.2 --- Photocatalytic oxidation --- p.57 / Chapter 3.2.3.4 --- Effect of H202 concentrations --- p.57 / Chapter 3.2.3.5 --- Effect of the number of beads --- p.58 / Chapter 3.2.3.5.1 --- Sorption --- p.58 / Chapter 3.2.3.5.2 --- Photocatalytic oxidation --- p.58 / Chapter 3.2.3.6 --- Effect of initial pH with and without the addition of H2O2 --- p.58 / Chapter 3.2.3.7 --- Control experiments for photocatalytic oxidation of Procion Red MX-5B --- p.59 / Chapter 3.2.3.8 --- Combinational study of UV intensities and H2O2 concentrations --- p.59 / Chapter 3.2.3.9 --- Photocatalytic oxidation of Procion Red MX-5B under optimal conditions --- p.59 / Chapter 3.2.3.10 --- "Sorption isotherms of calcium alginate beads immobilized with 70 mg Vibrio sp. and 5,000 mg/L TiO2" --- p.59 / Chapter 3.3 --- Biodegradation --- p.60 / Chapter 3.3.1 --- Chemical reagents --- p.60 / Chapter 3.3.2 --- Sampling --- p.60 / Chapter 3.3.3 --- Enrichment --- p.60 / Chapter 3.3.4 --- Isolation of cyanuric acid-utilizing bacteria --- p.61 / Chapter 3.3.5 --- Determination of cyanuric acid --- p.61 / Chapter 3.3.6 --- Screening of Procion Red MX-5B sorption ability --- p.61 / Chapter 3.3.7 --- Screening of cyanuric acid-utilizing ability --- p.61 / Chapter 3.3.8 --- Bacterial identification --- p.63 / Chapter 3.3.9 --- Growth and cyanuric acid removal efficiency of the selected bacterium --- p.63 / Chapter 3.3.10 --- Optimization of reaction conditions --- p.64 / Chapter 3.3.10.1 --- Effect of salinity --- p.64 / Chapter 3.3.10.2 --- Effect of cyanuric acid concentrations --- p.65 / Chapter 3.3.10.3 --- Effect of temperature --- p.65 / Chapter 3.3.10.4 --- Effect of agitation rate --- p.65 / Chapter 3.3.10.5 --- Effect of initial pH --- p.66 / Chapter 3.3.10.6 --- Effect of initial glucose concentration --- p.66 / Chapter 3.3.10.7 --- Combinational study of glucose and cyanuric acid concentrations --- p.66 / Chapter 3.4 --- Detection of cyanuric acid formed in photocatalytic oxidation reaction --- p.66 / Chapter 3.5 --- "Integration of sorption, photocatalytic oxidation and biodegradation" --- p.67 / Chapter 4. --- Results --- p.68 / Chapter 4.1. --- Sorption --- p.68 / Chapter 4.1.1 --- Determination of Procion Red MX-5B --- p.68 / Chapter 4.1.2 --- Isolation of Procion Red MX-5B-sorbing bacteria --- p.68 / Chapter 4.1.3 --- Screening of Procion Red MX-5B sorption ability --- p.68 / Chapter 4.1.4 --- Identification of isolated bacterium --- p.72 / Chapter 4.1.5 --- Optimization of cell yield and sorption capacity --- p.72 / Chapter 4.1.5.1 --- Growth phase --- p.72 / Chapter 4.1.5.1.1 --- Growth curve --- p.72 / Chapter 4.1.5.1.2 --- Dye sorption capacity --- p.72 / Chapter 4.1.5.2 --- Initial pH --- p.75 / Chapter 4.1.5.2.1 --- Growth curve --- p.75 / Chapter 4.1.5.2.2 --- Dye sorption capacity --- p.75 / Chapter 4.1.5.3 --- Temperature --- p.75 / Chapter 4.1.5.3.1 --- Growth curve --- p.75 / Chapter 4.1.5.3.2 --- Dye sorption capacity --- p.79 / Chapter 4.1.5.4 --- Glucose concentrations --- p.79 / Chapter 4.1.5.4.1 --- Growth curve --- p.79 / Chapter 4.1.5.4.2 --- Dye sorption capacity --- p.79 / Chapter 4.1.6 --- Optimization of sorption process --- p.82 / Chapter 4.1.6.1 --- Dry weight of sorbent --- p.82 / Chapter 4.1.6.2 --- Temperature --- p.82 / Chapter 4.1.6.3 --- Agitation rate --- p.86 / Chapter 4.1.6.4 --- Salinity --- p.86 / Chapter 4.1.6.5 --- Initial pH --- p.86 / Chapter 4.1.6.6 --- Concentration of Procion Red MX-5B --- p.90 / Chapter 4.1.6.7 --- Combination study of salinity and initial pH --- p.90 / Chapter 4.2. --- Photocatalytic oxidation reaction --- p.94 / Chapter 4.2.1 --- Effect of dry weight of immobilized cells of Vibrio sp. --- p.94 / Chapter 4.2.1.1 --- Sorption --- p.94 / Chapter 4.2.1.2 --- Photocatalytic oxidation --- p.96 / Chapter 4.2.2 --- Effect of UV intensities --- p.96 / Chapter 4.2.3 --- Effect of TiO2 concentrations --- p.96 / Chapter 4.2.3.1 --- Sorption --- p.96 / Chapter 4.2.3.2 --- Photocatalytic oxidation --- p.101 / Chapter 4.2.4 --- Effect of H2O2 concentrations --- p.101 / Chapter 4.2.5 --- Effect of the number of beads --- p.101 / Chapter 4.2.5.1 --- Sorption --- p.105 / Chapter 4.2.5.2 --- Photocatalytic oxidation --- p.105 / Chapter 4.2.6 --- Effect of initial pH with and without the addition of --- p.105 / Chapter 4.2.7 --- Control experiments for photocatalytic oxidation of Procion Red MX-5B --- p.109 / Chapter 4.2.8 --- Combinational study of UV intensities and H202 concentrations --- p.112 / Chapter 4.2.9 --- Photocatalytic oxidation of Procion Red MX-5B under optimal conditions --- p.112 / Chapter 4.2.10 --- "Sorption isotherms of calcium alginate beads immobilized with 70 mg Vibrio sp. and 5,000 mg/L Ti02" --- p.112 / Chapter 4.3 --- Biodegradation --- p.116 / Chapter 4.3.1 --- Isolation of cyanuric acid-utilizing bacteria --- p.116 / Chapter 4.3.2 --- Determination of cyanuric acid --- p.116 / Chapter 4.3.3 --- Screening of Procion Red MX-5B sorption ability --- p.116 / Chapter 4.3.4 --- Screening of cyanuric acid-utilizing ability --- p.116 / Chapter 4.3.5 --- Bacterial identification --- p.118 / Chapter 4.3.6 --- Growth and cyanuric acid removal efficiency of the selected bacterium --- p.118 / Chapter 4.3.7 --- Optimization of reaction conditions --- p.122 / Chapter 4.3.7.1 --- Effect of salinity --- p.122 / Chapter 4.3.7.2 --- Effect of cyanuric acid concentrations --- p.122 / Chapter 4.3.7.3 --- Effect of temperature --- p.126 / Chapter 4.3.7.4 --- Effect of agitation rate --- p.126 / Chapter 4.3.7.5 --- Effect of initial pH --- p.132 / Chapter 4.3.7.6 --- Effect of initial glucose concentration --- p.132 / Chapter 4.3.7.7 --- Combinational study of glucose and cyanuric acid concentrations --- p.132 / Chapter 4.4 --- Detection of cyanuric acid formed in photocatalytic oxidation reaction --- p.137 / Chapter 4.5 --- "Integration of sorption, photocatalytic oxidation and biodegradation" --- p.137 / Chapter 5. --- Discussion --- p.141 / Chapter 5.1 --- Sorption --- p.141 / Chapter 5.1.1 --- Isolation of Procion Red MX-5B-sorbing bacteria --- p.141 / Chapter 5.1.2 --- Screening of Procion Red MX-5B sorption ability --- p.141 / Chapter 5.1.3 --- Identification of isolated bacterium --- p.141 / Chapter 5.1.4 --- Optimization of cell yield and sorption capacity --- p.142 / Chapter 5.1.4.1 --- Growth phase --- p.142 / Chapter 5.1.4.1.1 --- Growth curve --- p.142 / Chapter 5.1.4.1.2 --- Dye sorption capacity --- p.143 / Chapter 5.1.4.2 --- Initial pH --- p.146 / Chapter 5.1.4.2.1 --- Growth curve --- p.146 / Chapter 5.1.4.2.2 --- Dye sorption capacity --- p.146 / Chapter 5.1.4.3 --- Temperature --- p.146 / Chapter 5.1.4.3.1 --- Growth curve --- p.146 / Chapter 5.1.4.3.2 --- Dye sorption capacity --- p.147 / Chapter 5.1.4.4 --- Glucose concentrations --- p.147 / Chapter 5.1.4.4.1 --- Growth curve --- p.147 / Chapter 5.1.4.4.2 --- Dye sorption capacity --- p.147 / Chapter 5.1.5 --- Optimization of sorption process --- p.148 / Chapter 5.1.5.1 --- Dry weight of sorbent --- p.148 / Chapter 5.1.5.2 --- Temperature --- p.148 / Chapter 5.1.5.3 --- Agitation rate --- p.149 / Chapter 5.1.5.4 --- Salinity --- p.149 / Chapter 5.1.5.5 --- Initial pH --- p.150 / Chapter 5.1.5.6 --- Concentration of Procion Red MX-5B (MX-5B) --- p.152 / Chapter 5.1.5.7 --- Combination study of salinity and initial pH --- p.153 / Chapter 5.2. --- Photocatalytic oxidation reaction --- p.153 / Chapter 5.2.1 --- Effect of immobilized cells of Vibrio sp. --- p.153 / Chapter 5.2.1.1 --- Sorption --- p.153 / Chapter 5.2.1.2 --- Photocatalytic oxidation --- p.154 / Chapter 5.2.2 --- Effect of UV intensities --- p.155 / Chapter 5.2.3 --- Effect of TiO2 concentrations --- p.155 / Chapter 5.2.3.1 --- Sorption --- p.155 / Chapter 5.2.3.2 --- Photocatalytic oxidation --- p.156 / Chapter 5.2.4 --- Effect of H2O2 concentrations --- p.156 / Chapter 5.2.5 --- Effect of the number of beads --- p.157 / Chapter 5.2.5.1 --- Sorption --- p.157 / Chapter 5.2.5.2 --- Photocatalytic oxidation --- p.158 / Chapter 5.2.6 --- Effect of initial pH with and without the addition of --- p.158 / Chapter 5.2.7 --- Control experiments for photocatalytic oxidation of Procion Red MX-5B --- p.160 / Chapter 5.2.8 --- Combinational study of UV intensities and H202 concentrations --- p.161 / Chapter 5.2.9 --- Photocatalytic oxidation of Procion Red MX-5B under optimal conditions --- p.161 / Chapter 5.2.10 --- "Sorption isotherms of calcium alginate beads immobilized with 70 mg Vibrio sp. and 5,000 mg/L Ti02" --- p.161 / Chapter 5.3 --- Biodegradation --- p.162 / Chapter 5.3.1 --- Isolation of cyanuric acid-utilizing bacteria --- p.162 / Chapter 5.3.2 --- Determination of cyanuric acid --- p.163 / Chapter 5.3.3 --- Screening of Procion Red MX-5B sorption ability --- p.163 / Chapter 5.3.4 --- Screening of cyanuric acid-utilizing ability --- p.163 / Chapter 5.3.5 --- Bacterial identification --- p.163 / Chapter 5.3.6 --- Growth and cyanuric acid removal efficiency of the selected bacterium --- p.164 / Chapter 5.3.7 --- Optimization of reaction conditions --- p.165 / Chapter 5.3.7.1 --- Effect of salinity --- p.165 / Chapter 5.3.7.2 --- Effect of cyanuric acid concentration --- p.165 / Chapter 5.3.7.3 --- Effect of temperature --- p.166 / Chapter 5.3.7.4 --- Effect of agitation rate --- p.167 / Chapter 5.3.7.5 --- Effect of initial pH --- p.167 / Chapter 5.3.7.6 --- Effect of initial glucose concentration --- p.167 / Chapter 5.3.7.7 --- Combinational study of glucose and cyanuric acid concentrations --- p.168 / Chapter 5.4 --- Detection of cyanuric acid formed in photocatalytic oxidation reaction --- p.170 / Chapter 5.5 --- "Integration of sorption, photocatalytic oxidation and biodegradation" --- p.171 / Chapter 5.6 --- Recommendations --- p.171 / Chapter 6. --- Conclusions --- p.173 / Chapter 7. --- References --- p.175 / Appendix --- p.200

Ng, Tsz Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 86-98). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / Table of Contents --- p.vii / List of Figures --- p.xiii / List of Plates --- p.XV / List of Tables --- p.xxi / Abbreviations --- p.xxii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- "Pollution, toxicity and environmental impact of azo dye" --- p.1 / Chapter 1.2 --- Common treatment methods for dyeing effluent --- p.2 / Chapter 1.2.1 --- Physicochemical methods --- p.2 / Chapter 1.2.1.1 --- Coagulation/ flocculation --- p.2 / Chapter 1.2.1.2 --- Adsorption --- p.3 / Chapter 1.2.1.3 --- Membrane filtration --- p.4 / Chapter 1.2.1.4 --- Fenton reaction --- p.4 / Chapter 1.2.1.5 --- Ozonation --- p.5 / Chapter 1.2.1.6 --- Photocatalytic oxidation --- p.6 / Chapter 1.2.2 --- Biological treatments --- p.7 / Chapter 1.2.2.1 --- Degradation of azo dyes by bacteria --- p.8 / Chapter 1.2.2.1.1 --- Anaerobic conditions --- p.8 / Chapter 1.2.2.1.2 --- Aerobic conditions --- p.9 / Chapter 1.2.2.1.3 --- Combined anaerobic and aerobic conditions --- p.10 / Chapter 1.2.2.2 --- Decolourization of azo dyes by fungi --- p.11 / Chapter 1.2.2.3 --- Mechanisms of azo dye reduction by microorganisms --- p.12 / Chapter 1.3 --- "Chromium species, toxicity and their impacts on environment" --- p.14 / Chapter 1.4 --- Common treatment methods for chromium --- p.16 / Chapter 1.4.1 --- Chemical and physical methods --- p.16 / Chapter 1.4.2 --- Biological methods --- p.17 / Chapter 1.4.2.1 --- Chromium reduction by aerobic bacteria --- p.17 / Chapter 1.4.2.2 --- Chromium reduction by anaerobic bacteria --- p.18 / Chapter 1.5 --- Studies concerning azo dye and Cr(VI) co-treatment --- p.19 / Chapter 1.6 --- Response surface methodology --- p.21 / Chapter 1.6.1 --- Response surface methodology against one-factor-at-a-time design --- p.22 / Chapter 1.6.2 --- Phases of response surface methodology --- p.25 / Chapter 1.6.3 --- 2 - level factorial design --- p.26 / Chapter 1.6.4 --- Path of steepest ascent --- p.27 / Chapter 1.6.5 --- Central composite design --- p.28 / Chapter 2. --- Objectives --- p.30 / Chapter 3. --- Materials and Methods --- p.31 / Chapter 3.1 --- Isolation of bacterial strains --- p.31 / Chapter 3.1.2 --- Azo dye decolourization --- p.33 / Chapter 3.1.3 --- Chromate reduction --- p.34 / Chapter 3.2 --- Identification of selected bacterial strains --- p.35 / Chapter 3.2.1 --- Gram stain --- p.35 / Chapter 3.2.2 --- Sherlock® Microbial Identification System --- p.35 / Chapter 3.2.3 --- 16S ribosomal RNA sequencing --- p.37 / Chapter 3.3 --- Optimization of dye decolourization and chromate reduction efficiency with response surface methodology --- p.38 / Chapter 3.3.1 --- Minimal-run resolution V design --- p.38 / Chapter 3.3.2 --- Path of steepest ascent --- p.40 / Chapter 3.3.3 --- Central composite design --- p.41 / Chapter 3.3.4 --- Statistical analysis --- p.43 / Chapter 3.3.5 --- Experimental validation of the optimized conditions --- p.43 / Chapter 3.4 --- Determination of the performance of the selected bacterium in different conditions --- p.43 / Chapter 3.5 --- Determination of azoreductase and chromate reductase activities --- p.44 / Chapter 3.5.1 --- Preparation of cell free extract --- p.44 / Chapter 3.5.2 --- Azoreductase and chromate reductase assay --- p.45 / Chapter 3.6 --- Determination and characterization of degradation intermediates --- p.45 / Chapter 3.6.1 --- Isolation and concentration of the purple colour degradation intermediate --- p.45 / Chapter 3.6.2 --- Mass spectrometry analysis --- p.47 / Chapter 3.6.3 --- Atomic absorption spectrometry analysis --- p.48 / Chapter 4. --- Results --- p.49 / Chapter 4.1 --- Azo dye decolourizing and chromate reducing ability of the isolated bacterial strain --- p.49 / Chapter 4.2 --- Identification of selected bacterium --- p.50 / Chapter 4.3 --- Optimization of dye decolourization and chromate reduction efficiency with response surface methodology --- p.50 / Chapter 4.3.1 --- Minimal-run resolution V design --- p.50 / Chapter 4.3.2 --- Path of the steepest ascend --- p.54 / Chapter 4.3.3 --- Central composite design --- p.55 / Chapter 4.3.4 --- Validation of the predicted model --- p.62 / Chapter 4.4 --- Performance of the selected bacterium in different conditions --- p.62 / Chapter 4.4.1 --- Chromate and dichromate --- p.62 / Chapter 4.4.2 --- Initial pH --- p.63 / Chapter 4.4.3 --- Low and high salt concentration --- p.63 / Chapter 4.4.4 --- Initial K2CrO4 concentration --- p.63 / Chapter 4.4.5 --- Initial Acid Orange 7 concentration --- p.63 / Chapter 4.4.6 --- Nutrients limitation --- p.64 / Chapter 4.5 --- Chromate reductase and azoreductase activities --- p.67 / Chapter 4.6 --- Determination of degradation intermediates --- p.67 / Chapter 4.6.1 --- Mass spectrum of the degradation intermediate --- p.68 / Chapter 4.6.2 --- Chromium content of the degradation intermediate --- p.70 / Chapter 5. --- Discussion --- p.71 / Chapter 5.1 --- Characteristic of Brevibacterium linens --- p.71 / Chapter 5.2 --- Optimization of dye decolourization and chromate reduction with response surface methodology --- p.72 / Chapter 5.3 --- Performance of Brevibacterium linens under different culture conditions --- p.75 / Chapter 5.4 --- Postulation of mechanisms --- p.76 / Chapter 5.4.1 --- Possible reasons of unexpected results of the effect of initial Acid Orange 7 and K2CrO4 concentration --- p.76 / Chapter 5.4.2 --- Properties of the purple colour degradation intermediate --- p.78 / Chapter 5.4.3 --- Mechanisms likely responsible for the chromate reduction --- p.80 / Chapter 5.4.4 --- Explanation of the unexpected results --- p.80 / Chapter 6. --- Conclusions --- p.83 / Chapter 7. --- References --- p.86 / Chapter 8. --- Appendices --- p.99 / Chapter 8.1 --- Definition and calculation of different terms in 2-level factorial design --- p.99 / Chapter 8.2 --- Definition and calculation of different terms in ANOVA table --- p.100 / Chapter 8.3 --- Aliases of terms and resolution --- p.103 / Chapter 8.4 --- Moving of factors in path of steepest ascent --- p.105 / Chapter 8.5 --- Estimation of the parameters in linear regression models --- p.106 / Chapter 8.6 --- Definition and calculation of different terms in test of fitness --- p.109

Cai, Qinhong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 142-166). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / Table of contents --- p.viii / List of figures --- p.xv / List of plates --- p.xix / List of tables --- p.xxi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Pollution generated from dyeing industry --- p.1 / Chapter 1.2 --- Occurrence and pollution of chromium azo dyes --- p.2 / Chapter 1.3 --- Common treatment methods for dyeing effluents --- p.7 / Chapter 1.3.1 --- Physicochemical methods --- p.7 / Chapter 1.3.2 --- Chemical methods --- p.9 / Chapter 1.3.2.1 --- Ozonation --- p.10 / Chapter 1.3.2.2 --- Fenton reaction --- p.11 / Chapter 1.3.2.3 --- Sodium hypochlorite (NaOCl) --- p.12 / Chapter 1.3.2.4 --- Photocatalytic oxidation (PCO) --- p.13 / Chapter 1.3.3 --- Physical methods --- p.14 / Chapter 1.3.3.1 --- Adsorption --- p.14 / Chapter 1.3.3.2 --- Membrane filtration --- p.15 / Chapter 1.3.4 --- Biological treatments --- p.16 / Chapter 1.3.4.1 --- Decolorization of azo dyes by bacteria --- p.16 / Chapter 1.3.4.1.1 --- Under anaerobic conditions --- p.18 / Chapter 1.3.4.1.2 --- Under anoxic conditions --- p.19 / Chapter 1.3.4.1.3 --- Under aerobic conditions --- p.21 / Chapter 1.3.4.2 --- Mechanisms of azo dye reduction by bacteria --- p.23 / Chapter 1.3.4.3 --- Decolorization of azo dyes by fungi and algae --- p.27 / Chapter 1.4 --- Chromium species and their impacts on environment --- p.27 / Chapter 1.4.1 --- Chromium toxicology and speciation --- p.28 / Chapter 1.4.2 --- Common treatment methods for chromium --- p.31 / Chapter 1.5 --- Studies concerning treatment of chromium azo dyes --- p.32 / Chapter 1.6 --- Response surface methodology (RSM) --- p.33 / Chapter 1.6.1 --- RSM vs. one factor-at-a-time (OFAT) design --- p.36 / Chapter 1.6.2 --- Phases of RSM --- p.39 / Chapter 1.6.3 --- Two level factorial design --- p.40 / Chapter 1.6.4 --- Path of steepest ascent (PSA) --- p.43 / Chapter 1.6.5 --- Central composite design (CCD) --- p.44 / Chapter 1.6.6 --- Estimation of the parameters in linear regression models --- p.45 / Chapter 1.6.7 --- Test of fitness --- p.47 / Chapter 2. --- Objectives and significance of the project --- p.49 / Chapter 3. --- Materials and methods --- p.50 / Chapter 3.1 --- Chemicals --- p.50 / Chapter 3.1.1 --- Chemicals for preparation of bacterial culture media --- p.50 / Chapter 3.1.2 --- Chemicals for identification of bacteria --- p.50 / Chapter 3.1.3 --- Chemicals for chromium speciation --- p.51 / Chapter 3.1.4 --- Chemicals for immobilization of bacterial cells --- p.52 / Chapter 3.2 --- Sludge samples --- p.53 / Chapter 3.3 --- Characterization of Acid Yellow 99 --- p.54 / Chapter 3.4 --- Monitor of azo dye decolorization --- p.55 / Chapter 3.5 --- "Isolation of bacterial strains, which can degrade Acid Yellow 99" --- p.55 / Chapter 3.6 --- Identification of selected bacterial strains --- p.58 / Chapter 3.6.1 --- Gram stain --- p.58 / Chapter 3.6.2 --- Sherlock® microbial identification system --- p.58 / Chapter 3.6.3 --- Biolog® microstation system --- p.59 / Chapter 3.6.4 --- Selection of the most effective bacterial strains --- p.59 / Chapter 3.6.5 --- 16S ribosomal RNA sequencing --- p.60 / Chapter 3.7 --- Chromium speciation with interferences of chromium organic complexes --- p.60 / Chapter 3.7.1 --- Instrumentation --- p.60 / Chapter 3.7.2 --- Column preparation --- p.61 / Chapter 3.7.3 --- Determination of percentage retained and recovery --- p.62 / Chapter 3.7.4 --- "Speciation of Cr(VI), ionic Cr(III) and chromium azo dye" --- p.63 / Chapter 3.7.4 --- Preparation of Cr(III)-organic complexes --- p.65 / Chapter 3.7.5 --- Preparation of a microbial degraded chromium azo dye sample --- p.65 / Chapter 3.8 --- Chromium distribution in a treated solution --- p.66 / Chapter 3.9 --- Distribution of AY99 in a treated solution --- p.68 / Chapter 3.10 --- Optimization of decolorization process with response surface methodology (RSM) --- p.70 / Chapter 3.10.1 --- Correlation of cell mass and cell density of selected bacteria --- p.70 / Chapter 3.10.2 --- Preliminary investigation of the optimum conditions --- p.70 / Chapter 3.10.3 --- Minimal run resolution V (MR5) design --- p.71 / Chapter 3.10.4 --- Path of steepest ascent (PSA) --- p.74 / Chapter 3.10.5 --- Central composite design (CCD) and RSM --- p.75 / Chapter 3.10.6 --- Statistical analysis --- p.76 / Chapter 3.10.7 --- Experimental validation of the optimized conditions --- p.77 / Chapter 3.11 --- Immobilization of bacterial cells --- p.77 / Chapter 3.11.1 --- Immobilization by polyvinyl alcohol (PVA) gels --- p.77 / Chapter 3.11.2 --- Immobilization by polyacrylamide gels --- p.78 / Chapter 3.11.3 --- Performance of immobilized cells and free cells --- p.79 / Chapter 3.11.5 --- Storage stabilities of immobilized cells and free cells --- p.80 / Chapter 3.12 --- Performance of a laboratory scale bioreactor --- p.80 / Chapter 3.12.1 --- Chromium distribution in the bioreactor --- p.82 / Chapter 3.12.2 --- Distribution of AY99 in the bioreactor --- p.82 / Chapter 3.12.3 --- Fourier transform infrared spectroscopy (FT-IR) analysis of suspended particles in the treated solution --- p.84 / Chapter 4. --- Results --- p.85 / Chapter 4.1 --- Characterization of AY99 --- p.85 / Chapter 4.2 --- Identification of isolated bacterial strains --- p.86 / Chapter 4.3 --- Selection of the most effective bacterial strains --- p.89 / Chapter 4.4 --- Chromium speciation with interferences of chromium organic complexes --- p.91 / Chapter 4.4.1 --- Effect of pH --- p.91 / Chapter 4.4.2 --- Speciation of Cr(VI)，ionic Cr(III) and chromium azo dye --- p.92 / Chapter 4.4.3 --- Effect of other Cr(III)-organic complexes --- p.93 / Chapter 4.4.4 --- Limit of detection --- p.94 / Chapter 4.4.5 --- Capacity of Amberlite XAD-4 resin --- p.94 / Chapter 4.4.6 --- Determination of Cr(VI) in a microbial degraded chromium azo dye solution --- p.95 / Chapter 4.5 --- Chromium distribution in a free cells treated solution --- p.95 / Chapter 4.6 --- Distribution of AY99 in free cells treated solution --- p.96 / Chapter 4.7 --- Optimization of decolorization process with RSM --- p.98 / Chapter 4.7.1 --- Correlation of cell mass and cell density of selected bacteria --- p.98 / Chapter 4.7.2 --- MR5 design --- p.100 / Chapter 4.7.3 --- Path of steepest ascent (PSA) --- p.102 / Chapter 4.7.4 --- Central composite design (CCD) and RSM --- p.103 / Chapter 4.8 --- Immobilization of bacterial cells --- p.106 / Chapter 4.8.1 --- Performance of immobilized cells and free cells --- p.106 / Chapter 4.8.2 --- Storage stabilities of immobilized cells and free cells --- p.108 / Chapter 4.9 --- Performance of the laboratory scale bioreactor --- p.108 / Chapter 4.9.1 --- Treatment efficiencies of the bioreactor --- p.108 / Chapter 4.9.2 --- Performance stability of the bioreactor in 5 consecutive runs --- p.111 / Chapter 4.9.3 --- Chromium distribution in the bioreactor --- p.114 / Chapter 4.9.4 --- Distribution of AY99 in the bioreactor --- p.115 / Chapter 4.9.5 --- FT-IR analysis of suspended particles in the treated solution --- p.115 / Chapter 5. --- Discussion --- p.117 / Chapter 5.1 --- Chromium speciation with interferences of chromium organic complexes --- p.117 / Chapter 5.2 --- Chromium distribution --- p.117 / Chapter 5.3 --- Distribution of AY99 --- p.122 / Chapter 5.4 --- Optimization of decolorization process with RSM --- p.124 / Chapter 5.4.1 --- MR5 design --- p.124 / Chapter 5.4.2 --- Path of steepest ascent (PSA) --- p.125 / Chapter 5.4.3 --- Central composite design (CCD) and RSM --- p.126 / Chapter 5.5 --- Immobilization of bacterial cells --- p.126 / Chapter 5.5.1 --- Performance of immobilized cells and free cells --- p.126 / Chapter 5.5.2 --- Storage stability of immobilized cells and free cells --- p.128 / Chapter 5.6 --- Performance of the laboratory scale bioreactor --- p.130 / Chapter 5.6.1 --- Treatment efficiencies of the bioreactor --- p.130 / Chapter 5.6.2 --- Performance stability of the bioreactor in 5 consecutive runs --- p.131 / Chapter 5.6.3 --- FT-IR analysis of suspended particles in the treated solution --- p.132 / Chapter 5.6.4 --- Post treatments of bioreactor treated effluents / Chapter 6. --- Conclusions --- p.136 / Chapter 7. --- References --- p.142

<p>Decolorization of Azo dyes in synthetic wastewater composition which is similar to real textile wastewater was carried out by microbial process. Experiments were performed in two continuous systems. Experiments were performed under anaerobic conditions in order to break the nitrogen bond of the azo group (-N=N-). A synthetic dye solution which contained 200 mg/L Reactive Black 5, 200 mg/L Procion Red MX-5B and 1 g/L yeast extract was prepared. In this study, living microorganisms were used to degrade the dyes in wastewater. Rice husks which contain bacteria and fungi were used in the reactors of continuous systems. The parameters tested on continuous system were wastewater composition, the number of reactors, the amount of yeast extract in wastewater composition, the wastewater flowrate, washing the system with wood chips solution, addition of yeast extract solution.  Results have shown that increasing the number of reactors, the retention time, the amount of yeast extract and washing the system with wood chips solution had positive effects for degradation of the dyes from wastewater. When the flowrate was increased the retention time has decreased so degradation of dyes has decreased but although the flowrate increased twice, % degradation hasn’t decreased as the same ratio. Therefore this result showed that this process can be worked for faster flowrates. Microbial process is a promising technology which might be used to treat wastewater containing azo dyes with good performance.</p><p> </p>