Hong, Wei = 膠體玻璃化相變的實驗及理論研究 / 洪偉. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 89-91). / Abstracts in English and Chinese. / Hong, Wei = Jiao ti bo li hua xiang bian de shi yan ji li lun yan jiu / Hong Wei. / Abstract --- p.i / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Experimental background --- p.2 / Chapter 1.1.1 --- What is a colloidal system? --- p.2 / Chapter 1.1.2 --- Single particle diffusion --- p.5 / Chapter 1.1.3 --- Inter-particle interaction --- p.9 / Chapter 1.1.4 --- Colloidal phase transition --- p.14 / Chapter 1.2 --- Glass transition --- p.16 / Chapter 1.2.1 --- Vibrational modes --- p.18 / Chapter 1.2.2 --- Dynamics --- p.21 / Chapter 2 --- Experimental setup and methods --- p.29 / Chapter 2.1 --- Sample and setup --- p.29 / Chapter 2.1.1 --- Sample preparation --- p.29 / Chapter 2.1.2 --- Setup --- p.32 / Chapter 2.2 --- Resolution enhancement --- p.36 / Chapter 2.2.1 --- Alignment --- p.36 / Chapter 2.2.2 --- Lens resolution --- p.37 / Chapter 2.2.3 --- Lens combination --- p.38 / Chapter 2.2.4 --- LED light source and filter --- p.39 / Chapter 2.3 --- Image preprocessing --- p.42 / Chapter 2.3.1 --- Background subtraction --- p.42 / Chapter 2.3.2 --- Noise filter --- p.43 / Chapter 2.3.3 --- Particle recognition and tracking --- p.45 / Chapter 2.3.4 --- Dedrift --- p.47 / Chapter 3 --- Measurement --- p.50 / Chapter 3.1 --- Dynamical characteristics --- p.50 / Chapter 3.1.1 --- Mean squared displacement --- p.50 / Chapter 3.1.2 --- Diffusion coefficient versus area fraction --- p.56 / Chapter 3.2 --- Structural characteristics --- p.58 / Chapter 3.2.1 --- Pair correlation function --- p.58 / Chapter 3.2.2 --- Cluster statistics --- p.62 / Chapter 4 --- Dynamical heterogeneity and structural properties --- p.67 / Chapter 4.1 --- Dynamical heterogeneity --- p.67 / Chapter 4.2 --- Structural properties --- p.71 / Chapter 4.2.1 --- The general picture --- p.71 / Chapter 4.2.2 --- Identification of the slow particles --- p.72 / Chapter 4.2.3 --- Growing clusters of slow particles --- p.80 / Chapter 5 --- Discussion --- p.81 / Chapter 5.1 --- Percolation model --- p.81 / Chapter 6 --- Summary and conclusion --- p.87 / Bibliography --- p.89

Solid-liquid separation is an important unit operation in many industrial processes. Research on the process optimisation and technical advancement of this operation is crucial to ensure a reliable and economical process. Work include developments in filtration theory and understanding of suspension behaviour are constantly investigated to ensure the process reaches the target. / In this work, enhancement in dewatering was quantified with the use of shear. Shear, in this context, is a mechanism used to deform a suspension network such as the action of raking in thickeners. In order to understand the inter-play between shear and dewatering for colloidal networked suspension, the relationship between shear and compression rheology was investigated. / The effect of shear was investigated in two situations, which are the presence of shear during and before dewatering. The former was achieved by applying an electric field to a suspension during (in-situ to) dewatering and the latter was achieved through varying shear condition for flocculated suspensions prior to dewatering. The analysis of dewatering properties was then performed by applying the consolidation theory of Landman and White (Landman et al. 1995; Landman and White 1997). / The materials used in the study were two types of colloidal metal oxide particles namely AKP-30 alumina and Ajax kaolin. They were chosen due to their physical differences such as particle size and shape. The dispersion state of these suspensions from coagulated to dispersed, was fully controlled by manipulation of the particle surface chemistry. This changed the suspension micro-structure. Flocculated suspensions were prepared by the addition of a non-ionic, high molecular weight polyacrylamide to the coagulated AKP-30 alumina suspension. / The study on shear rheology was investigated by employing steady shear and small amplitude oscillatory shear (SAOS) measurements. The use of these two methods allowed quantitative interpretation of a network deformation of a suspension which involved the transition between solid-like behaviour (before yielding) and liquid-like behaviour (after yielding). The network deformation can be characterised as either being of a brittle or ductile type. The use of Lissajous figures also aided the understanding of the deformation. / The shear rheology of the metal oxide suspensions was found to depend critically on the extent of the inter-particle interactions. Both dispersed and coagulated suspensions show different rheological properties. In the case for coagulated suspensions, rheological parameters such as the shear and compressive yield stresses, and elastic modulus plateau value, all scaled, which indicate that these parameters arise from particle interaction. This is in contrast to the understanding of shear rheology on freshly flocculated suspension which is still limited, particularly for concentrations at close the gel point. The shear rheology of flocculated suspension was then compared to that of coagulated suspensions. Various degrees of flocculation conditions were investigated. Network deformation was found to show an identical pattern to that of coagulated suspensions but the network strength was found to increase with shear rate. / The dewatering properties of dispersed and coagulated AKP-30 alumina and Ajax kaolin suspensions were compared. It was found that dispersed suspensions have lower compressibility (i.e. produce a higher final solids concentration at the same applied pressure) and permeability compared to coagulated suspensions. Comparison between the two model suspensions shows that AKP-30 alumina suspensions have better dewatering qualities compared to kaolin suspensions. The effect of flocculation conditions for AKP-30 alumina suspension was found to dramatically affect the settling rate but had only a small effect on dewatering at higher solids. / A combination of dewatering methods was used and they gave excellent results for the prediction of the dewatering characteristics of suspensions for a wide range of solids concentration from close the gel point up to close to the maximum close packed concentration. Finally, electrically enhanced dewatering (EED) for Ajax kaolin suspension was compared to that of normal dewatering. Results showed significant dewaterability enhancement at pressures below 10 kPa. The application of EED was also investigated for an industrial sample of water treatment sludge. Similar results were noted as for Ajax kaolin, with an increase of equilibrium solids concentration and permeability with EED at a given pressure. In this context, EED delivered promising results in improving the dewatering properties of difficult-to-dewater suspensions.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Eric M. Furst, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (Ph. D.)--Washington State University, December 2007. / Includes bibliographical references (p. 127-140).

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Eric M. Furst, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (Ph. D.)--Drexel University, 2007. / Includes abstract and vita. Includes bibliographical references (leaves 188-217).

The contamination of groundwater and soils has been a big issue of great interest and importance to human health. When organic compounds from leaking underground storage tanks or accidental spills on the surface infiltrate into the subsurface environment, they migrate downward through the unsaturated zone. These contaminants are dissolved into groundwater and move with groundwater flow. Thus, there is a need for remediation technologies. Air sparging is relatively cost-effective, as well as an efficient and safe technique for recovering organic contaminants in the subsurface. This technique introduces air into the subsurface system to enhance the volatilization and bioremediation of the contaminant in the groundwater system. In this operating system, the movement of air phase can take place either as a continuous air phase or as discrete air bubbles. However, the present research focused on continuous air phase assumption and mass balance equations of individual phases rather than taking into account the movement of air bubbles and colloidal particle capture on discrete air-water interface. Generally colloidal particles are treated as suspended particles in the water, so the hypothesis is that the rising air bubble can collect the particles and transport them up to the water table where the pump extracts the dirty bubbles from the groundwater system to the processing unit on the ground surface. This dissertation developed a pore-scale study to model the migration of discrete air phase in the presence of colloidal particles captured on the air-water interface. The model was based on the pore-scale balance equation for forces acting on a bubble rising in a porous medium in the presence of colloids. A dimensional analysis of the phenomenon was also conducted to provide a more generalized methodology to evaluate the effect of individual forces acting on an air bubble. The results indicate that the proposed model can predict the terminal velocity of a rising bubble without or with colloidal particles and provide the effect of numbers of colloidal particles, properties of colloidal particles, and solid grain size. The results showed that the terminal velocity of a discrete bubble was affected by the attachment of particles on a bubble, and then the volatile organic compound (VOC) removal rate was changed by the various radii of a bubble and the number of colloidal particles on a bubble.

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