published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

by Yuk-Lin Chan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 78-83). / Abstracts in English and Chinese. / Abstract (English version) --- p.i / Abstract (Chinese version) --- p.ii / Acknowledgments --- p.iii / Table of Contents --- p.iv / List of Figures --- p.vi / List of Tables --- p.vii / Chapter 1. --- Introduction / Chapter 1.1 --- Indoor Air Pollution --- p.1 / Chapter 1.2 --- Typical Treatment of Air Pollutant --- p.6 / Chapter 1.3 --- Photocatalytic Degradation over Titanium Dioxide --- p.7 / Chapter 1.4 --- Advantages of Titanium Dioxide as a Photocatalyst --- p.12 / Chapter 1.5 --- Applications of Photocatalytic Degradation in Pollution Control --- p.14 / Chapter 1.5.1 --- Aqueous Phase Decontamination --- p.15 / Chapter 1.5.2 --- Gas Phase Decontamination --- p.15 / Chapter 1.6 --- Development of the Photocatalytic Degradation Technique --- p.16 / Chapter 1.6.1 --- Pure Ti02 --- p.17 / Chapter 1.6.2 --- Design of the Reactors --- p.18 / Chapter 1.6.3 --- Metal Ion Dopants --- p.21 / Chapter 1.6.4 --- Mixture with Supports --- p.21 / Chapter 1.7 --- Adsorbent-Supported Titanium Dioxide --- p.22 / Chapter 1.7.1 --- Use of Adsorbents other than Zeolites --- p.22 / Chapter 1.7.2 --- Use of Zeolites --- p.25 / Chapter 1.8 --- Molecular Sieves --- p.29 / Chapter 2. --- Experimental / Chapter 2.1 --- Block diagram of the Reaction Setup --- p.31 / Chapter 2.2 --- Fixed Volume Batch Reactor --- p.32 / Chapter 2.3 --- Reagents --- p.34 / Chapter 2.3.1 --- Degussa P25 Ti02 powder --- p.34 / Chapter 2.3.2 --- Aldrich Molecular Sieves (Organophilic) --- p.35 / Chapter 2.3.3 --- Other Adsorbents Used for Comparison --- p.35 / Chapter 2.4 --- Instrumental Analysis --- p.36 / Chapter 2.4.1 --- Photoacoustic Multi-gas Monitor --- p.36 / Chapter 2.4.2 --- X-Ray Diffraction Analysis --- p.42 / Chapter 2.4.3 --- Scanning Electron Microscopy --- p.42 / Chapter 2.4.4 --- UV-vis Diffuse Reflectance Spectroscopy --- p.42 / Chapter 2.4.5 --- Iso-electron Point Measurements --- p.43 / Chapter 2.5 --- Photocatalytic Degradation of Simple Alkanes by P25 Titanium Dioxide --- p.45 / Chapter 2.6 --- Photocatalytic Degradation of Gaseous Acetone over Organophilic Molecular Sieves-Supported Titanium Dioxide --- p.49 / Chapter 3. --- Results and Discussion / Chapter 3.1 --- Photocatalytic Degradation of Simple Alkanes by P25 Titanium Dioxide --- p.52 / Chapter 3.1.1 --- Rate of Photocatalytic Degradation of Simple Alkanes --- p.52 / Chapter 3.1.2 --- Summary of Rate of Photocatalytic Degradation of Simple Alkanes --- p.57 / Chapter 3.2 --- Photocatalytic Degradation of Gaseous Acetone over Organophilic Molecular Sieves-Supported Titanium Dioxide --- p.58 / Chapter 3.2.1 --- The Adsorption Ability of Various Adsorbents --- p.58 / Chapter 3.2.2 --- XRD Pattern Measurement --- p.60 / Chapter 3.2.3 --- Scanning Electron Microscopy --- p.64 / Chapter 3.2.4 --- UV-vis Diffuse Reflectance Spectroscopy --- p.65 / Chapter 3.2.5 --- Iso-electron Point Measurements --- p.67 / Chapter 3.2.6 --- Photocatalytic Activity of Various Catalysts --- p.69 / Chapter 4. --- Conclusion --- p.76 / Bibliography --- p.78 / Appendix / "A Demonstration of Photocatalytic Degradation by Gaseous Organic Pollutant, Dichloromethane " --- p.83

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Several factors which affect the transport of pyridine, quinoline and acridine (aza-arenes) in saturated porous media were investigated in laboratory experiments in order to provide data for input into coupled models that may be applied to predicting the fate of these compounds in groundwater. The effect of pH and ligand type and concentration on acridine solubility was studied in a series of batch and pH-stat experiments. There was a decrease in acridine solubility below the compound's pKₐ due to acridine/ligand precipitate formation. The reaction stoichiometry and solute/sorbent interactions of aza-arene adsorbed to porous silica were determined from batch adsorption and Raman spectroscopy experiments. The neutral aza-arene was hydrogen bonded to surface sites above the compound's pKₐ and there was a cation/ClO₄⁻ complex interacting with surface sites through dipole-dipole interactions below the pKₐ of the compound. The effect of pH, temperature, ligand type, average linear velocity and initial aqueous phase solute concentration on the adsorption of aza-arenes to porous silica was investigated in a series of column experiments. The extent of adsorption followed the trend pyridine < quinoline < acridine due to greater overlap of the molecule with adsorption sites as the number of rings increases. The extent of adsorption was greater below the compound's pKₐ than above because the complex was able to optimize its orientation with the surface. The extent of adsorption of neutral acridine was enhanced when carbonate was used as a buffer relative to phosphate due to carbonate's more exothermic hydration enthalpy. The isotherms were non-linear above and below the pKₐ of acridine. The enthalpy of the adsorption reaction was less exothermic below the compound's pKₐ than above due to the stronger hydrogen bonds formed between the surface and the neutral molecule compared to the dipole-dipole interactions that bond the complex to the surface below the pKₐ. Non-equilibrium effects on the adsorption reaction were minor. Adsorption-desorption was on the order of seconds to minutes. Kinetic effects became more important as temperature decreased.

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M.Tech. (Chemical Engineering) / Increasing pressure on industry from national and international communities for more environmentally friendly operations has generated a drive towards the use of ‘green’ absorbents in the removal of volatile organic compounds from contaminated air streams. The objective of this work was to investigate the use of ester solvents, especially biodiesel esters, as suitable ‘green’ scrubbing solvents for the absorption of volatile organic compounds (VOCs) from gaseous waste streams. The objective was accomplished by investigating the nature of molecular interactions between ester solvents and various families of VOC solvents, and by studying the effect of temperature on absorption, through the analysis of infinite dilution activity coefficients. Activity coefficients were computed with a Microsoft Excel generated spread sheet using Modified UNIFAC Dortmund (1987) as a thermodynamic predictive model. Results show that non-polar solutes are more soluble in long chain ester solvents whilst polar solutes absorb easier in short chain ester solvents. The solubility of non-polar solutes decreases with increasing ester solvent unsaturation, whilst the opposite is true for polar solutes in esters. Short chain length non-polar solutes are more soluble than long chain length non-polar solutes in ester solvents, whilst the opposite trend occurs for polar solutes in ester solvents. An increase in branching of polar solutes results in the solute behaving more like a non-polar solute. Unfortunately UNIFAC models fail to account for functional group proximity effects, which may result in inaccurate results for systems involving highly branched solutes. However given that the purpose of this study was only to establish trends for generating an understanding of molecular interactions between the solutes and the solvent, it was acceptable to assume that these inaccuracies would be minor for the intended purpose. It was found that activity coefficients of ester/ solute interactions generally tend towards ideality with increasing temperature with the exception of alkanes and the nitrogen based VOCs, as well as tetrahydrofuran and tetrahydropyran, methacrolein and organic acid/ unsaturated ester interactions. In the case of the alkanes, tetrahydrofuran and tetrahydropyran, high-temperature absorption is preferred whilst for methacrolein lower temperature absorption is preferred. It was concluded that ester solvents ,especially biodiesel esters, are well suited for the removal of non-polar to moderately polar VOC solutes from waste gas streams due to the favourably low activity coefficients obtained for these ester/ solute interactions. The results presented in this report are comprehensive and can assist in making informed decisions in using biodiesel as a scrubbing solvent.

published_or_final_version / abstract / Botany / Master / Master of Philosophy

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