M.Sc. / The addition of lignocellulosic fibres to thermoplastic polymers is known to increase the toughness of the polymers but it compromises the tensile strength. On the other hand, inorganic fillers like TiO2 are known to improve the tensile strength of polymers. These plant fibres have been used as adsorbents of metal pollutants in water. Best results were obtained when such materials were ground to fine powder but due to low density, the fibres float and form aggregates in water. Being highly biodegradable in nature makes plant fibres unsuitable for water treatment over lengthy periods of time. They cannot be used as standalone materials. Mixing these adsorbents with polymers, which cannot only act as support for the adsorbents but also disperse the fibres within it thus preventing leaching, is a cause for concern. This study was aimed at fabricating plant fibre-polymer composites that will have improved mechanical and thermal properties. These composites were to be tested for their ability to be used as metal ion adsorbents. The composites were fabricated using a melt-mix compounding method. Two thermoplastic polymers, EVA and PCL were each mixed with either lignin or SCB and TiO2 in different ratios. A rheomex mixer coupled with a single screw extruder which was attached to a sheet die was used to synthesise the composites. TGA and DSC were used for thermal propagation while the mechanical properties were investigated using an instron. Metal ion adsorption measurements were analysed using an atomic absorption spectrometer (AAS). These adsorbents were used to remove Cr(VI), Cr(III) and Pb(II), varying different environmental parameters like pH, concentration, time and adsorbent at constant temperature. The reinforcing effect of both lignin and SCB resulted to poor thermal and mechanical properties. This was shown by a decrease in onset degradation temperature and the tensile and toughness of the composites compared to the neat polymers. The incorporation of TiO2 on SCB-EVA composites, however, improved the mechanical strength and resulted in a thermally stable composite compared to counterpart composites without TiO2. This observation was surpassed at high filler loading as the addition of TiO2 resulted in a decrease of the properties. For the tensile strength, neat EVA recorded 11.35 MPa while 2% TiO2-EVA registered 12.49 MPa for example. For the same composite, the onset degradation temperature for EVA was 353 oC but shifted to 368 oC after the addition of TiO2. At higher filler loading, no effect was observed when adding TiO2.

Lead's uptake on magnetite has been quantitatively evaluated in the present study at a temperature of 200°C and pH of 8.5 with lead concentrations ranging from 5 ppm to175 ppm by equilibrium adsorption isotherms. The pH independent sorption behavior suggested lead sorption due to pH independent permanent charge through weak electrostatic, non-specific attraction where cations are sorbed on the cation exchange sites. The permanent negative charge could be a consequence of lead substitution which is supported by increase in the lattice parameter values from the X-ray diffraction (XRD) results. Differential scanning calorimetry (DSC/TGA) results showed an increase of exothermic (magnetite to maghemite transformation) peak indicating substitution of lead ions due to which there is retardation in the phase transformation. Presence of outer sphere complexes and physical sorption is further supported by Fourier transformed infrared spectroscopy (FTIR). None of the results suggested chemisorption of lead on magnetite.

The measurement of fluorine penetration into archeological flint artifacts using Nuclear Reaction Analysis (NRA) has been reported to be a potential dating method. However, the mechanism of how fluorine is incorporated into the flint surface, and finally transported into the bulk is not well understood. This research focuses on the study of the fluorine uptake phenomenon of flint mineral in aqueous fluoride solutions. Both theoretical and experimental approaches have been carried out. In a theoretical approach, a pipe-diffusion model was used to simulate the complicated fluorine transportation problem in flint, in which several diffusion mechanisms may be involved.

Recent work indicates that microorganisms present in soils can remove carbon monoxide from the atmosphere and as such constitutes a major sink. B.E.T. adsorption studies were carried out on representative soils from the Willamette Valley River Basin in order to determine their adsorptive characteristics for carbon monoxide and other gases. Attempts were made to isolate, through a non-soildestructive sterilization, the adsorptive characteristics of the soil microorganisms as well as of the test soil. The carbon monoxide studies show physical adsorption equivalent to the coverage of a few per cent of the surface area at 25.0° and 76 cm-Hg. Adsorption studies also shows that the soil rather then the microorganisms adsorbs most of the carbon monoxide. On sterilized soil, chemical sorption of oxygen was present and was probably caused by the oxidation of dead or damaged soil microorganisms. Hysteresis effects were present in all adsorption studies at 25.0° and appears to be a characteristic of the constituents of the soil and represents a new and as yet unexplained phenomenon.

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