Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 42-44). Also available on the World Wide Web.

Ph.D.

Nonylphenol ethoxylates (NPEO) and octylphenol ethoxylates (OPEO), both are alkylphenol ethoxylates (APEO), a type of non-ionic surfactants commonly used in synthetic detergents for household and industrial cleaning purposes. These compounds and their degraded intermediates are xenoestrogens ubiquitously found in runoffs, sewage discharge and sludge. Not only that they persist in our surface waters and sediment, they are also found in the bodies of wildlife and human worldwide. Because of their high volume consumed and their nature as semi-persistent pollutants as well as endocrine disruptors, many developed countries have renounced their use on voluntary basis or through regulatory measure. Hong Kong is situated at the estuary of Pearl River Delta, which is one of the pollution hotspots. It is susceptible to its own water pollutants from municipal sewage (~1,054 million m3/year) and also the discharge (~3.0x109m3/ year) along the river from the industrialized and urbanized Mainland China cities. The local environment and human health are exposed to risks of these chemicals ascribed to rising consumption of detergents and their insufficient removal by sewage treatment, in addition to food intake in particular seafood. However, public awareness about APEO and endocrine disrupting chemicals is low due to no mandatory disclosure and control of these chemicals as well as the uncertainties about their chronic toxicity, based on the survey results of online questionnaires. Several recommendations have been made with reference to overseas regulatory measures and good practices to control and reduce the use of these chemicals. / published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

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A unique penetration instrument has been developed to evaluate the role of surfactants in kraft pulping process. This instrument can screen surfactants which can improve the wood impregnation more effectively and much faster than pilot-plant experiment. The role of surfactants in wood penetration has been explored. Surfactants can improve wood impregnation by dispersing the extractives in the wood structure and optimizing the interfacial properties between wood surface and kraft liquor. The addition of two blends of anionic and nonionic surfactants into kraft pulping process results in a significant reduction of the screen rejects and an increase of screened yield at the same delignification rate. / Six wood species were tested in this study including both non-resinous and resinous wood species. Both sapwood and heartwood of these species were tested. Surfactants were found to have no improvement on sapwood, but a significant improvement on heartwood. The critical micelle concentrations (CMC) of surfactants in kraft liquor were determined. The best dosages of surfactants based on CMC were also determined in this study.

The industrial application of gas-liquid contactors has made effective design and optimisation of these processes a very important topic. In order to sustain a competitive advantage, rate limiting steps must be clearly understood. Hydrodynamics, heat transfer and mass transfer are complicated features of gas-liquid contactors and require a fundamental understanding. The mechanism of mass transfer in the presence of a small concentration of solid micro particles has been the subject of debate. The adsorption of gas by solid particles ("shuttle mechanism") is the traditional explanation. Recent experimental evidence suggests that the introduction of micro particles removes trace surface active impurities from the system and allows the true mass transfer coefficient to be measured. The objective of this study was to confirm the surfactant removal theory. Mass transfer is a field characterised by imprecise empirical relationships and difficult to obtain experimental parameters. This puts into context the significant challenge posed in preparing the careful set of measurements and analyses presented in this study to lend support to the surfactant removal mechanism. The study began with a review of mass transfer models. These models are based on concepts such as surface renewal and idealised turbulence. It is, however, difficult to choose between the models as they predict similar values despite being based on different mechanisms. The overall mass transfer coefficient is composed of the gas-phase coefficient (kGa) and liquid-phase coefficient (kLa). As the values of the coefficients are comparable and the solubility of oxygen or hydrogen is very Iow, the overall mass transfer coefficient is approximately equal to the liquid side coefficient. The relationship of kL with the diffusion coefficient (D) is one of the limited ways of choosing between the models. Mass transfer models predict k j • u:. D" . n is predicted to be % for a rigid surface (contaminated interface region) and Y2 for a mobile surface (clean interface region). If the surfactant removal mechanism applies, the introduction of solid particles will be accompanied by a reduction of n from % to 1/2. The effect of particles on n can be calculated from precise measurement of kL of gases with significantly different diffusion coefficients. A review of experimental methods was made to find precise methods to characterise mass transfer in the presence of solid micro particles. The chemical sulphite, gas-interchange and pressure step methods were identified as appropriate methods. These were implemented in a stirred cell (0.5 !) and an agitated tank (6 I). The chemical sulphite measurements were used to confirm that the enhancement of kLa is due to an enhancement of kL and not the specific interfacial area (a). Flat surface experiments were made using water and 0.8 M sodium sulphate batches. The reduction of n from % to Y2 was confirmed in both apparatuses after the addition of solid particles. The data were very well correlated and the dependence of kr on the energy dissipation rate per unit volume (e) is similar to the theoretically predicted value of 114 for the exponent. Observation of the reduction of n from % to Y2 was extended to agitated dispersions. The stirred cell kLa data were measured by the gas interchange method and are of excellent quality. The agitated tank results were measured by pressure step methods. The pressure dependence of the polarographic probes affected the precision of the results and the effect was within the experimental uncertainty. The effect of particles on n could not, therefore, be conclusively confirmed in the agitated tank. By relating precisely measured mass transfer coefficients to the diffusion coefficients; the surfactant removal theory is confirmed. The result is valid for a flat mass transfer area as well as for agitated dispersion where the nature of the interface region changes with time due to the accumulation of surfactants on an initially clean interface. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2008.

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