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A mechanism for the mass transfer of anthraquinone (AQ) into wood during alkaline pulping has been developed. Although the chemistry of action of AQ is well-developed, there has not been much work conducted on its diffusion properties. The discrepancies between different experiments with AQ indicate that something other than the chemistry is at work. Because most of the differences arise from differences in pulping conditions, it is likely that mass transfer is the source of these discrepancies. A model system was therefore developed to explore the mass transfer properties of AQ. It was shown that AQ must be reduced to anthrahydroquinone (AHQ) at the membrane surface before any permeation of a membrane can occur. It was also shown that increasing surface coverage of the membrane through AQ particle size reduction could improve the rate of membrane permeation. The mechanism described by the model system was then tested against pulping data. It was shown that the addition of surfactants increases the pulping efficiency of AQ. This is probably through better dispersion of AQ particles to cover more chip surface area. Bulk reduction effects were also tested, and it was shown that bulk phase reducing agents decrease the efficacy of AQ in pulping. This led to the development of the mechanism for AQ diffusion in alkaline pulping.

Call number: LD2668 .T4 1959 Y36

Call number: LD2668 .T4 1962 A35

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Air pollution became a major concern in South Africa in the late 1980’s and regulatory requirements for the chemical process industries to reduce hazardous emissions have increased ever since. Volatile organic compounds (VOCs) contribute significantly to the formation of ozone and photochemical oxidants and their associated impact on human health has become a major issue worldwide. Volatilisation is a significant process in determining the fate of organic compounds in the environment. In this study, volatilisation rate of VOCs (specifically benzene, toluene, ethylbenzene, and xylene) from a wastewater collection basin, also called the oily sewer basin (OSB) was measured using a flux chamber method and the VOCs were characterised. Theoretical models that can be used to estimate volatilisation rate were also studied. Meteorological data was collected to evaluate the effect of temperature, humidity and wind speed on volatilisation rate. This study showed that toluene and ethylbenzene have the highest volatilisation rate compared to benzene and o-xylene. It was found that system conditions and physicochemical properties of a compound have a significant effect on volatilisation. It was also identified that the measured concentrations of VOCs escaping from the OSB do comply with Occupational Health and Safety Act and Regulations 85 of 1993 standards. It was recommended that surfactants be used to inhibit volatilisation of VOCs

Thesis. 1978. M.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographies. / M.S.

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No description available.

No description available.