Thesis (PhD)--Macquarie University, Division of Environmental and Life Sciences, Department of Chemistry, 2002. / Bibliography: leaves 234-240.

published_or_final_version / Endodontics / Master / Master of Dental Surgery

Ultrasonic instruments are used with the aid of an irrigant such as NaOCl in endodontic treatments to remove dentin debris and calculus from infected root canals. This cleaning process may be assisted by various factors, such as acoustic streaming, and the production of radicals and microjets from the collapse of transient cavitation bubbles. The aim of this project is to understand the principal factors affecting the performance of a number of different endosonic files in order to correlate to their cleaning efficiencies. Characterisation includes detecting transient cavitation activity, mapping the areas of cavitation, assessing the file vibration movements and the streaming effects produced by the files. Experiments to assess the cleaning efficiencies of the files include: emulsification, dye removal with a dental irrigant, ink and hydroxyapatite paste removal from model systems designed to mimic the structure of a tooth. The results show that there is a correlation between the sonochemical output and the cleaning efficiencies, and this brings in further study on the possible factors that may affect the production of transient cavitation and the vibration profiles of the endosonic files. Lastly, a series of computational simulation of the acoustic pressure fields from different endosonic files were performed. Correlations of the simulated and experimental results showed the difference in ultrasonic output of the endosonic files is strongly related to their design. This work provides the basis and techniques necessary to perform a comprehensive study on the design of the endosonic files in order to enhance and optimise their cleaning efficiencies during clinical use and to inform future endodontic practice.

Trifluorovinylsulfur pentafluoride dimerizes to (SF5CFCF2)2 in the presence of cesium fluoride. Two derivatives of trifluorovinylsulfur pentafluoride, SF5CF(CF3)C(O)F and SF5CF(CF3)C(O)NH2, were used to prepare the new compounds, SF5CF(CF3)CO2H and SF5CF(CF3)CN, respectively. The first was prepared by reacting the SF5-acid fluoride with water, while the second involved the abstraction of water from the SF5-amide using P4O10. The attempted preparation of a bis-pentafluorosulfur ketone and a pentafluorosulfur containing acid anhydride were unsuccessful. Selected transition and post transition metal chlorides and elements undergo oxidative displacement and oxidative addition reactions with F-(tert-butyl) hypochlorite, (CF3)3COCl, to form new F-(tert-butoxides). Preliminary studies with selected aromatic systems were also carried out.

No description available.

This study armed to develop a chemical scrubbing process to eliminate odorous VOCs (volatile organic compounds) in gases emitted from hot-melted coal tar used in bamboo antiseptic processing. Major VOCs are mono-aromatic hydrocarbons (MAHs), polycyclic aromatic hydrocarbons (PAHs), phenol and ammonia. A pilot scrubber with a recycling scrubbing liquid tank and with an acrylic column of 0.10 m in length, 0.10 m in width, and 0.58 m in height, packed with 1¡¦¡¦ diameter plastic packings to a height of 0.38 m will be used for the scrubbing test of the emitted gas. Aqueous solutions of sodium hypochlorite (NaOCl), hydrogen peroxide (H2O2), detergent, and the Fenton¡¦s reagent (hydrogen peroxide with ferrous chloride) will be used as oxidants for the VOCs. Results indicated that with operation conditions of VOCs 20-30 ppm (as methane), an empty bed retention time (EBRT) of around 28.5 s in the packed section, and a sodium hypochlorite concentration of 450 mg Cl2/L with pH of 6, around 45.3-50.3% of the VOCs in the influent gas could be removed at a L/G (liquid to gas flow rate ratio) of 0.295 m3/m3. A test indicated that the overall odor(expressed as the dilution to threshold D/T value) removal was around 97.6% and the D/T were 1303 and 30.9, respectively, for the influent, and scrubber effluent. Using double packed towers to deal with coal tar odorous, result from the test indicated that 70-75 and 94.4% of VOCs and odorous intensity in the influent gas could be removed, respectively, with the operation of an initial sodium hypochlorite concentration of 450 mg Cl2/L with pH of 6, combined with a hydrogen peroxide concentration of 4000 mg/L with pH of 9 , VOCs (methane equivalent) concentrations of 20-30 ppm, gas flow rate of 8 NL/min, and a liquid/gas rate ratio of 0.295 m3/m3. At running 300 minutes can smell much odor than beginning. Baesd on the results from the pilot study, a full-scale plant with waste gas flow rate 200 m3/min was proposed. It was estimated that the cost is around NT$ 20.9 and 52.2 for treating 1,000 m3 of the emitted gases, respectively, for sodium hypochlorite, and sodium hypochlorite combined with hydrogen peroxide. Efforts should be made by decreasing the cost by other alternative technologies.

Almost all dyestuffs used for textile processing impose heavy colors on effluents such that they can¡¦t meet effluent regulations. Sodium hypochlorite (NaOCl) has long been used for effluent decoloration by most textile plants. However, despite by the operators¡¦ experience, there is still no scientific method for controlling the dosing rate of sodium hypochlorite. An insufficient dosage may result in an aesthetically and legally unacceptable effluent. Whereas an excessive one may lead to the formation of chlorine-containing organic compounds which are harmful to the aquatic life and may limit the water utilization. It is necessary to develop a control technique for chlorination decoloration of textile wastewaters. In this study, secondary effluent samples from a textile wastewater plant and synthetic wastewater samples prepared by two azo-type dyestuffs were used for chlorination decoloration tests in a batch reactor with a residual chlorine indicator. Experimental results indicate that the most economic and effective reaction conditions for decoloration of the test wastewaters were pH = 4 and residual chlorine = 14 mg/L. In the conditions, wastewaters with true color intensity = 1,200 ADMI could be reduced to values less than 400 ADMI within 60 min. Results also confirm that on-line monitoring of residual chlorine concentration in the reacting liquid can be used to achieve a better control of chlorine addition. Experimental data also indicate that the color removal rate (-dC/dt) was linearly proportional to the color intensity (C) and free hypochlorous acid (HOCl) concentration.

This study armed at the development of an adequate process for the odor control of a gas vented from a plant for treating olefin-resin manufacturing wastewater.The gas contains various aromatic and olefin compounds, such as toluene, £\-methyl styrene, vinyl toluene, styrene, naphthalene, dicyclopentadiene, and indene.Primary tests showed that these odorous compounds could not be effectively eliminated by a biotrickling filter packed with fern chips.Instead, these compounds can easily be removed or eliminated by using sodium hypochlorite as an oxidant and followed by sodium thiosulfate as a reductant for removing the residual chlorine odor. Results indicate that by scrubbing the gas with sodium hypochlorite solution with an effective residual chlorine of 40-60 mg/L, pH of 7.9-9.8, and oxidation-reduction potential (ORP) of 500-760 mV, concentration of volatile organic compounds (VOCs) in the test gas could be removed from 250 ppm (expressed as methane) to 23 ppm.Trace olefin and chlorine odors in the oxidized gas could further be removed by scrubbing it with an aqueous solution of 270 mg/L Na2S2O3.The overall VOC removal was around 92%.

The long term degradation of polyethersulfone (PES) based ultrafiltration membranes used in the dairy industry has been investigated. The main aim of the study was to identify characterisation techniques which could give an indication of the condition and performance of ultrafiltration membranes after long term exposure to sodium hypochlorite solution. Membranes were degraded using sodium hypochlorite solution at pH 9, 10, 11 and 12, and with 5000 ppm-days to 25,000 ppm-days of exposure at 55°C. The degraded membranes were studied using the following characterisation techniques: dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), tensile testing, field emission scanning electron microscopy with energy dispersive x-ray spectroscopy (FESEM-EDS), Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR), contact angle, drop absorption, zeta potential, liquid-liquid displacement porosimetery (LLDP), protein separation, and colour measurement. The protein separation test included membrane throughput measurements (using casein-whey as feed), with size exclusion chromatography and gel electrophoresis to analyse the feed, permeate and retentate. Also a membrane disinfection experiment was performed to study the effect of sodium hypochlorite pH on disinfection of mixed dairy culture.

Thesis (PhD)--Macquarie University, Division of Environmental and Life Sciences, Department of Chemistry, 2002. / Bibliography: leaves 234-240. / Introduction, theoretical descriptions of spontaneous combustion phenomena and aims of this thesis -- Laboratory measurements of the self-heating phenomenology of bagasse -- Field experiments investigating the self-heating behaviour of large scale stockpiles of low symmetry -- Self-heating and thermal ignition of calcium hypochlorite -- Experimental methods and procedures used for the critical ambient temperature of HCH -- Results of critical ambient temperature measurements upon single containers of hydrated high strength HCH -- Experiments on the interaction of self-heating drums -- Conclusions. / The hazard of spontaneous combustion is a problem that confronts any industry that transports or stores a reactive material. Bagasse is a reactive material that presents an expensive spontaneous combustion hazard for the sugar industry since this material is the principal fuel used at sugar mills. Calcium Hypochlorite is another such material presenting a significant industrial spontaneous combustion hazard for the transport and insurance industry as it has been linked to a number of expensive maritime conflagrations. The investigation of fundamental self-heating phenomenon is critical for the understanding, control and prevention of spontaneous ignition with these materials. -- By way of isothermal calorimetry techniques and fundamental thermal ignition measurements, this study has provided improved understanding into the oxidative self-heating phenomenology of bagasse and thermal ignition phenomenology of calcium hypochlorite. Both substances have been shown to possess unusual and previously unknown self-heating behaviour at temperatures below 100°C, with water being a principal component of each mechanism. -- The outcomes of this study have provided a platform which has enabled current mathematical models to predict large scale self-heating phenomena for industrially stored quantities of these materials. / Mode of access: World Wide Web. / 240 leaves, bound ill