| Popis: |
Dolomite and charred dolomite have been evaluated for use in the removal of dissolved arsenic anions (arsenate and arsenite) from wastewaters. Experimental equilibrium isotherm investigations, kinetic experiments and fixed-bed column experiments have been used to assess the uptake from a wide range of aqueous arsenic solutions, employing both dolomite and thermally processed (charred) dolomite. Scanning electron microscopy, X-ray diffraction, FTIR analysis, Zetasizer (size analysis), mercury porosimetry and inductively coupled plasma atomic emission spectrometry (ICP-AES) have been utilized to aid in the evaluation of the dolomitic materials as adsorbents. Equilibrium experimental data have been analyzed using Langmuir, Freundlich, Henry and Redlich-Peterson isotherm models. Kinetic data have also been analyzed using elementary first and second reaction models and an intra particle diffusion model. The data from the models have been used to help determine the mechanism of arsenic removal. Dolomite and its thermally activated dolomites have shown potential as a cost effective material for use in the removal of arsenic from drinking water. Modifying the surface of the dolomite by charring, helped to overcome obstacles encountered with the adsorption of arsenic onto raw dolomite. The charred dolomite shows significant potential in removing As (III) from aqueous solutions and has been shown to operate effectively under a wide pH range. The thesis provides evidence for ion exchange, adsorption and precipitation mechanisms, to account for the removal of arsenic from aqueous solutions using dolomite and charred dolomite. |
