The copolymerization of L-methyl styrene and methyl methacrylate at high pressures

Imperial Users onl

Photocatalytic Affinity Membranes for The treatment of Dyes Contaminated Wastewater. Fabrication of the photocatalytic affinity membranes, using chemical and electrohydrodynamic processes; electrospinning, and electrospraying, for the efficient removal and degradation of the dyes that are present in the contaminated water

Electrospinning and electrospraying are electrohydrodynamic processes used for the fabrication of nano- and microfiber membranes and the deposition of particles on the membrane. Despite the numerous research papers found in the literature on electrospun polymers and their application in water treatment, not much is reported on the functionalization of electrospun nano- or microfibers and the deposition of ceramic nanoparticles on their surface by electrospraying. The use of these two processes may increase the efficiency of membranes in removing contaminants. In the present research, the processes of electrospinning and electrospraying are described and the factors affecting electrospinning are investigated. All parameters affecting the production of smooth NFs and NPs are discussed. A literature review of the recent advances in electrospinning and electrospray applications, as well as the application of NFs membranes in water treatment, has been described. This research has been designed based on the knowledge gaps identified in the literature. Detailed experiments were carried out on the preparation of PAN_P and Cs_P NFs membranes by electrospinning technique, the NFs membranes were then functionalized with different functional groups. The membranes were used for removal (Chapter 3) and degradation (Chapters 4 and 5) of dyes synthetic solutions. In the case of degradation, the membranes were electrosprayed with TiO2 NPs. All membranes were characterized by standard spectroscopic, microscopic, surface analytical, and thermal methods. Adsorption of MB, RB, and ST from a synthetic aqueous solution on the membranes PAN and EA-g-PAN NFs decreased in the order PAN<EA-g-PAN. The adsorption isotherm for the dyes fitted well with the models of Langmuir and Freundlich. The values of the correlation coefficient (r2) for Langmuir varied from 0.940 to 0.995 and for Freundlich from 0.941 to 0.998. The slightly increased values of the correlation coefficient in the case of Freundlich indicate that condensation (physical adsorption) of dyes on the NFs membranes also occurred in addition to the formation of monolayers. PAN_P NFs membranes prepared by electrospinning were functionalized with DETA to produce a functionalized PAN _F NFs membrane. TiO2 NPs synthesized in the laboratory were anchored to the surface of the PAN_F NFs membrane by electrospray to prepare PAN _Coa. A second PAN_Co was prepared by embedding TiO2 NPs into the PAN_P NFs by electrospinning. A similar strategy was also used for the Cs and TiO2 NPs system. The PAN_Coa NFs membrane was used for the degradation of MO while the Cs_Coa NFs membrane was used for the degradation of MB. The higher photocatalytic activity of PAN _Coa NFs membranes (92%, 20 ppm, and 99.5%, 10 ppm) compared to PAN_Co NFs membranes (41.64%) was due to the smaller band gap, high surface roughness, and large surface area. Also, the higher photocatalytic activity of the Cs_Coa NFs membrane (89%) compared to TiO2/Cs composite (Cs_Co) NFs membranes (40%) was due to a balance between the band gap, high surface roughness, and lower surface area. BET showed that the isotherms and hysteresis were similar for all NFs membranes, and they were classified as isotherm type IV and hysteresis H3 (IUPAC), corresponding to mesopores and slit-shaped pores

Catalytic enhancement of hydration of CO₂ using nickel nanoparticles for carbon capture and storage

PhD ThesisThe capture and storage of atmospheric CO2 as mineral carbonates, is one of the safest ways to combat global warming. The slow CO2 hydration rate is one limitation of the mineralization process. The current study presents the discovery of nickel nanoparticles (NiNPs) as a catalyst for enhancing the rate of CO2 hydration for mineralization carbon capture and storage. The NiNPs at an optimum concentration of 30 ppm, increased the saturation concentration by three folds as compared with deionized water alone. The mechanism of the reaction on NiNPs surface is also proposed. The kinetics of catalysis of CO2 hydration was additionally studied using stopped flow spectrophotometery and pH changes in buffer solution upon addition of saturated CO2 solution. To distinguish between physical gas-liquid transfer and catalysis, other inorganic nanoparticles (NiO and Fe2O3) have been studied. The effect of CO2 partial pressure on NiNPs catalysis was studied. Nickel nanowires (NiNWs) were synthesised and tested for catalysis of CO2 hydration. The photocatalytic activity of NiNPs was evaluated under artificial solar irradiation compared with that in the dark. The results suggest that the surface plasmonic resonance (SPR) of NiNPs enhances the rate of water dissociation on the NiNPs surface leading to higher rate of CO2 hydration under solar irradiation. The effect of temperature on the catalytic activity of NiNPs is evaluated. Optimum activity was observed at room temperature (20-30 °C). Application of NiNPs catalysis was investigated for CaCO3 precipitation and the rate of CO2 absorption in 50 wt% carbonate solutions. Vapour-liquid equilibrium studies of CO2-H2O in presence of nanoparticles (Ni, Fe2O3 and NiO) found that ii the presence of nanoparticles decreases the surface tension of DI water, responsible for the increase in CO2 saturation concentration. Additionally a novel method for mineralization of CO2 using gypsum and sodium chloride was developed including design of a customized reactor

Ninth annual V.M. Goldschmidt Conference : August 22-27, 1999, Harvard University, Cambridge, Massachusetts

The meeting is a forum for presenting and discussing new chemical and isotopic measurements, experimental and theoretical results, and discoveries in geochemistry and cosmochemistry.sponsored by Geochemical Society ... [and others]hosted by Department of Earth and Planetary Sciences, Harvard University ; compiled by Lunar and Planetary Institute.PARTIAL CONTENTS: Bacteria-promoted Dissolution of a Common Soil Silicate / S.L. Brantley, L.I. Liermann, and B.E. Kalinowski--Evolution of Temperature Control on Alkenone Biosynthesis / S.C. Brassell--Chemical Composition of Silurian Seawater: Preliminary Results from Environmental Scanning Electron Microscopy-Energy Dispersive Spectroscopy Analyses of Fluid Inclusions in Marine Halites / S.T. Brennan, T. Lowenstein, M.N. Timofeeff, and L.A. Hardi

An investigation of spray-freezing and spray-freeze-dryings

Drying is an important process for a variety of industries such as pharmaceuticals, food, and chemicals, and produce products with low bulk density, good shelf stability, economical storage and transport, and in some cases unique structural qualities. Of the various drying methods available, freeze-drying is the most beneficial for heat sensitive products that susceptible to thermal degradation. Freezedrying also confers a porous structure on the material result from the voids left after subliming the ice crystals. Freeze-drying however is used mainly for high value products due to the high capital and operational costs. The cycle time of such a drier may take several hours. The spray-freeze-drying process has evolved in an attempt to shorten the freezedrying process time. The process atomises a liquid feed to increase the heat and mass transfer surface area. The spray is then frozen in a very cold gas or a cryogenic liquid to form solid particles, which are then freeze-dried. Some processes incorporate a - fluidised bed freeze-drier to reduce the drying time by forced convection heat and mass transfer. This project aim to develop the Spray Freeze- Drying process and examine the effect of the process on the drying entities and resulting product quality, followed by modelling of the spray freezing operation in an attempt to optimise the operation. This thesis is divided into two main areas of investigations; Spray freezing investigation as an influential on the resulting product size and structure. The experiments performed using Phase Doppler Anemometry technique to measure the particle size distributions and velocities in a specially constructed spray freezing chamber with incorporated windows. A spray freeze-drying chamber was constructed composed of three parts co-current spray freezing, gas - particle separation, and fluidisation freeze-drying unites. Successfully spray characterisation measurement was carried in both ambient and sub-ambient temperatures, producing data of the drop size distribution and velocities from refractive scattered laser PDA measurement. The technique produced valuable information about the spray size distribution and velocity, the application of this technique appear was a novel approach in the spray freezing process measurement. The result were used in the established spray freezing model derived from Pham (1984) freezing model incorporating with a recalescence stage from the Hindmarsh (2003) spray freezing model. The current model predicted the droplet freezing time, which is influenced by the droplet diameter, velocity and freezing gas temperature. The results also shows an agreement between the freezing time predicted and the PDA recognition of bursts rejected due to their possible phase change. The spray-freezing-drying chamber was operated in vacuum conditions to produce freeze-dried whey protein powder. The powder characteristic results shows an physical properties such as density, solubility and particle sizes in comparison to spray drying and cryo-spray freeze-drying. The morphology of the spray freeze-dried whey powder is substantially different to that produced by spray drying and displays a porous microstructure. The operation of the freeze-drying unites requires an further investigation for temperature, pressure, and flow control to maintain the freezedrying.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Uranium isotope separation in the UK during World War II

This thesis investigates the practical, rather than theoretical, aspects of the uranium isotope separation technology developed in the United Kingdom during the Second World War. The overall scientific control of the bomb project was initially under G.P. Thomson but later devolved to Chadwick. Simon, at the University of Oxford, oversaw the practical aspects of isotope separation while Peierls, at Birmingham, was largely responsible for the theory, although many other leading scientists were involved in both the choice of a separation method and the associated measurement techniques required for its application. Frisch, the joint proposer of fission, was working on uranium isotope separation prior to the end of 1939. Frisch and Peierls produced a memorandum, in March 1940, which set the u.K. project in motion and eventually triggered the Americans into action. The Frisch-Peierls Memorandum led to the formation of the M.A.U.D. Committee which produced its report in July of 1941 that confirmed the scientific feasibility of such a weapon. A new and larger organisation, Tube Alloys, was then formed to complete the project. Virtually all methods of isotope separation were investigated before the choice of gas diffusion through a porous membrane was made. Most of the other methods became viable in the post war period or were applied to elements other than uranium. Two main problems had to be solved in the gas diffusion system: the design of a gas compressor system capable of operating at low absolute pressure, and the manufacture of a suitable diffusion membrane. A whole variety of membranes were investigated and a number taken to pilot production stage by small commercial firms. Experimental machines were designed and a pilot production plant constructed. The separation properties of both membranes and the diffusion machine were demonstrated. The transfer of core members of the team to America prevented completion of this work during the wartime period. The Americans, with their strong economy, wider range of scientific facilities, and enormous manufacturing capability, gradually assumed a leading role in the atomic work. The realisation that both the construction of both the separation plant and the manufacture of a bomb was beyond the financial and production capability of the U.K. led to the transfer of the leading members of the British team to America to pursue the project

1986-1987 Bulletin

Volume LXXXXVII, Number 1 Scanned from the copy held in the Registrar\u27s Office.https://ecommons.udayton.edu/bulletin_grad/1023/thumbnail.jp