No description available.

No description available.

A variety of iron precipitates formed in the electrolytic zinc industry were studied to estimate the possibility of magnetic filtration to augment conventional thickening/filtering systems. The precipitates included K,NH(,4),Na jarosites, (alpha) and (beta) goethite, (alpha) hematite and an industrially produced NH(,4) jarosite. The wet Frantz Isodynamic Separator was used to generate magnetic susceptibility data. Susceptibilities ranged from (kappa) = 6.9 x 10('-5) (--->) 15.5 x 10('-5) emu/cm('3)0e. Particle size of the precipitates ranged from 25 (mu)m to < 1 (mu)m. Magnetic filtration breakthrough curves were produced using a high gradient magnetic filtration technique. The role of fluid viscosity and velocity as well as magnetic field was studied. / All the precipitates proved filterable. A comparison was made of a physical and an empirical model of the breakthrough curves in the sizing of the magnetic filters required to treat thickener overflow at the CEZ Valleyfield plant. / For a volumetric flow of 100m('3)/hr electrolyte, containing 15g/L NH(,4) jarosite, 2 magnets of 2.6m diameter and 0.35m bed depth are required to lower solids contents to the present operating level of 3g/L.

Thesis (Ph. D.)--Victoria University (Melbourne, Vic.), 2007. / Includes bibliographical references.

M.Ing. / Scaling problems in a heating or cooling system can be recognised by one or more of the following symptoms. Reduction in heat transfer rate, in which the formation of an insulating deposit on a heat transfer surface significantly reduces the cooling or heating efficiency of the equipment. Reduced water flow, which results from a partial or complete blockage of pipelines, condenser tubes, or other openings. Even a small build-up of scale on a heat exchange surface reduces water flow. Scale may continue to build up in boilers until heat transfer is so low that the metal overheats, permitting the tubes to rapture under the operating pressure. Scale is usually found in water-handling equipment in which water is heated, i.e. hot-water storage tanks, boilers, etc. The magnitude of this problem may be appreciated by considering that scaling can cause degradation, or complete failure in thermal and hydraulic performance which increases initial and operating costs (Chan and Ghassemi, 1991). A fairly low-pressure boiler, with only 0.6 mm of calcium sulphate scale on the tubes results in a 180°C temperature drop. The cost involved due to heat transfer inefficiency and the removal of scale, in Britain alone, is estimated at £1 billion per annum (Darvill, 1993). Poor conductivity of a 25 mm thick CaC03 scale layer can decrease the heat transfer by 95% (Glater eta/., 1980), whereas a Si02 scale layer 0.5 mm thick results in a 90% decrease in heat transfer (Grutsch and McClintock, 1984).

No description available.

No description available.

Magnetic particles with active functional groups offer numerous advantages for use in μ-TAS (Micro Total Analytical Systems). The functional site allows chemical binding of the particle with the target species in the fluid sample. Selection of the functional group establishes the target molecule and vice versa under assumptions of highly specific biding. The particles hence act as mobile reaction substrates with high surface to volume ratios owing to their small size. The concept of action at a distance allows their use as agents for separation in microchannels based on relatively simple design. It is possible to manipulate magnetic particles and bound target species using an externally applied magnetic field. Hence, the particles can be effectively separated from the flow of a carrier fluid. Magnetic fields create dipolar interactions causing the particles to form interesting structures and aggregates. Depending upon the applied field, the microstructure evolution of the aggregate is interesting in its own right, e.g. related to improvements in material properties and bottom-up self assembly. The shape of the aggregates can be determined a priori if the interaction between the particles is well characterized. The dominant competing forces that influence magnetic particle dynamics in a flow are magnetic and viscous. There are a number of physical parameters such as viscosity, magnetic susceptibility, fluid velocity, etc. which are varied to study their individual effects. Initially dilute suspensions are studied experimentally and numerically using a particle based dynamics approach. Once established, a force model for particle interaction is investigated for concentrated suspensions. A Lagrangian particle tracking algorithm that returns positions of the particles is used for this work that focuses on studying the dynamics of these particles. A mathematical model is proposed and investigated for functionalization between magnetic and non-magnetic particles. Having characterized the collection of magnetic particles, the effect of relative concentrations is investigated on the collection of the non-magnetic species. / Ph. D.

Nanoparticles produced with surfaces functionalised by highly specific molecular tags are able to target aberrant cells and detect or eliminate them without causing damage to surrounding healthy tissues. Single-stranded DNA (ssDNA) and RNA which fold to form secondary or tertiary structures, termed aptamers, represent a new class of such molecular tags. The nanoparticles, in turn, may carry therapeutic payload or luminescent entities which enable elimination or visualisation of targeted cells respectively. This project presents fabrication and isolation of a surface-functionalised nanoparticle construct, namely aptamer-tagged silica nanoparticles. DNA aptamers were chosen with the intention to make them useful for clinical or diagnostic applications of targeting neoplastic cells. Indeed, the ssDNA applied here is known to bind mucin-1 which in turn is a biomarker found on the surface of metastatic breast cancer cells. The separation of the construct was made possible by the inclusion of oligonucleotide-bound superparamagnetic particles in the construct; these enabled separation by magnetic capture. This project investigates two approaches to fabrication of the construct. In the first approach, aptamers, oligonucleotides and magnetic particles are mixed in solution. In the second, silica nanoparticles are functionalised with aptamers, oligonucleotides are bound to magnetic particles and the resulting two parts are hybridised together. The first approach gives higher yields. This may suggest that binding of silica nanoparticles to aptamers may hinder aptamer hybridisation to oligonucleotide fragments, thus resulting in lower construct synthesis yields. However, it is not known yet how the yield changes upon addition of silica nanoparticles into the solution. Therefore, the second experimental approach provides a starting point for fabrication and purification of an anti-cancer drug targeting platform in a simple bench-top setting. In addition, this thesis discusses the fabrication of silica nanoparticles which were intended to constitute an element of the construct. The work on nanoparticle fabrication aimed to develop a quick and repeatable synthesis method which would result in monodisperse entities. Despite trying various experimental approaches, suitable particles could not be reproducibly obtained. Agglomeration was identified as a major obstacle in the silica nanoparticle production process. Finally, this project assesses whether the chosen aptamers bind to the metastatic breast cancer cells, which would be necessary if they were to be used for diagnosis or therapy. FACS analysis indeed indicate that ssDNA aptamers attach to the MCF7 cell line, but the optimum conditions for that attachment remain to be determined.

Master of Science / Department of Civil Engineering / Alexander P. Mathews / Nanoscale magnetite is being examined for possible uses as an adsorbent of heavy metals and for the enhancement of water treatment processes such as stripping of trichloroethylene (TCE) from contaminated water supplies and wastewaters. Methods for recovering nanoscale magnetite must be developed before the particles can be used in water treatment processes. This is necessary because expelling high amounts of particles into the environment will be unacceptable and costly; if captured they can be reused; additionally, they could potentially cause environmental impacts due to their stability in an aqueous environment and possible toxicity. Nanoscale magnetite is superparamagnetic, so it has a high magnetic susceptibility, and hence it is very attracted to magnetized materials. Utilizing the magnetic properties of magnetite may be one possible means of separating the particles from a treatment process. High Gradient Magnetic Separation (HGMS) has been studied for the separation of micron and even tenths of a micron size particles, but there is little experimental data for HGMS of nanoscale magnetite. This research looks to filter nanoscale magnetite through a HGMS and determine the capture efficiency of the filter. Subsequently, the filter was backwashed to determine particle recover efficiencies. The flow rate was adjusted to determine the dependency of particle capture efficiency on cross sectional velocity through the filter. Additionally, particle loading was changed to better understand the correlation of particle loading with capture efficiency. Filtrations for nanoscale magnetite dispersed with sodium tripolyphosphate were also completed as well as filtrations of nanoscale magnetite coated with silica and magnetite silica composites. Experimental data in this research indicates that magnetite nanoparticles can be captured at 99.8% efficiency or higher in a well-designed filtration system. Capture efficiencies around 99.8% have been found for magnetite. The silica coated magnetite and magnetite silica composites were captured at efficiencies as high as 96.7% and 97.9%, respectively. The capture efficiency of the dispersed magnetite is lower than non-dispersed magnetite and most promising at relatively low fluid flow velocities and particle loadings. The maximum capture efficiency for dispersed magnetite particles was 90.3%. Both magnetite and dispersed magnetite were successfully recovered using backwash at pH of 10 to 11.