A method for representing solid-liquid sorption behavior of solutes by a two step equilibrium is shown to correlate well with observed sorption behavior. By fitting a three term expression to isotherm plots of solute surface concentration vs. the concentration in the bulk solvent the two distribution constants as well as the maximum sorption capacity are determined. Isotherms for hydrocarbon-modified silica are determined for various solvents and solutes. Interpretation of sorption behavior is presented in terms of values determined for sorption capacity and the distribution coefficients. The isotherm model parameters are shown to correlate to the chromatographic retention parameter, k'. Sorption capacity is proposed as a more meaningful representation of the chromatographic phase ratio. Reversed-phase chromatographic retention and efficiency are shown to be affected by ion modifiers as well as the temperature history of a system when a totally aqueous mobile phase is used. The dynamic nature of the octylsilane modified surface is discussed in terms of changes which are induced by cations exchanged on the silica surface and imbibed organic solvent in the bonded hydrocarbon chain previously used to condition the surface. Both polar and non-polar solutes are used and their retention behavior allows interpretation of changes in specific regions of the surface. The development of magnetic Field-Flow Fractionation (Magnetic FFF), a separation technique for small magnetic particles, is described as well as the parameters which affect such separations. The use of a FFF device to characterize small particle suspensions is demonstrated. The change in turbidimetric response of iron oxide particle suspensions in a spectrophotometric device under the influence of a magnetic field is interpreted in terms of the difference in particle shape.

The Hurwitz-Parsons method of analysis is employed utilizing a spreadsheet application on an IBM-AT. It is designed to calculate the extent of specific adsorption of an inorganic anion or neutral organic molecule at a solid electrode without knowledge of the point of zero charge. Up to eight bulk adsorbate concentrations represented by differential capacitance versus potential curves may be input. The curves can contain up to 100 points. Output is in units of moles/cm2 and is provided at 10 potentials for each bulk adsorbate concentration. A detailed overview and a formula list of the application are provided. A brief overview of the theories associated with the electrochemical double layer and a related literature review are included.

Thesis (DTech. degree in Environmental, Water & Earth Sciences)--Tshwane University of Technology, 2009. / The potential of tassel from R52 maize cultivar for the removal of heavy metals from simulated and environmental aqueous samples as well as the physicochemical characteristics of tassel were investigated. Milled tassel powder was employed in metal removal from simulated aqueous sample and thereafter, the developed method was applied to environmental samples. This research has demonstrated the potential of maize tassel to adsorb metal ions from both simulated and environmental samples. Furthermore, metals adsorbed on tassel were easily desorbed suggesting that tassel can be employed in metal recycling.

Abstract The objective of this study was to investigate the possibility of using maize tassel as an alternative adsorbent for the removal of chromium (VI) and cadmium (II) ions from aqueous solutions. The effect of pH, solution temperature, contact time, initial metal ion concentration and adsorbent dose on the adsorption of chromium (VI) and cadmium (II) by tassel was investigated using batch methods. Adsorption for both chromium (VI) and cadmium (II) was found to be highly pH dependent compared to the other parameters investigated. Obtained results gave an adsorption capacity of 79.1 % for chromium (VI) at pH 2, exposure time of 1h at 25 ºC. Maximum capacity of cadmium of 88 % was obtained in the pH range of 5-6 at 25 ºC after exposure time of 1 h. The adsorption capacities of tassel for both chromium (VI) and cadmium (II) were found to be comparable to those of other commercial adsorbents currently in use for the removal of heavy metals from aqueous wastes. These results have demonstrated the immense potential of maize tassel as an alternative adsorbent for toxic metal ions remediation in polluted water and wastewater.

ABSTRACT: The objective of this study was to investigate the possibility of using maize tassel as an alternative adsorbent for the removal of chromium (VI) and cadmium (II) ions from aqueous solutions. The effect of pH, solution temperature, contact time, initial metal ion concentration and adsorbent dose on the adsorption of chromium (VI) and cadmium (II) by tassel was investigated using batch methods. Adsorption for both chromium (VI) and cadmium (II) was found to be highly pH dependent compared to the other parameters investigated. Obtained results gave an adsorption capacity of 79.1 % for chromium (VI) at pH 2, exposure time of 1h at 25 ºC. Maximum capacity of cadmium of 88 % was obtained in the pH range of 5-6 at 25 ºC after exposure time of 1 h. The adsorption capacities of tassel for both chromium (VI) and cadmium (II) were found to be comparable to those of other commercial adsorbents currently in use for the removal of heavy metals from aqueous wastes. These results have demonstrated the immense potential of maize tassel as an alternative adsorbent for toxic metal ions remediation in polluted water and wastewater.

published_or_final_version / Pathology / Doctoral / Doctor of Philosophy

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