Abstract
Water polluted with heavy metals or dyes that are directly discharged from the mining, paper, textile, carpet, dyeing, and pulp industries cause problems to human beings and the ecosystem. Therefore, the polluted water must be treated before it gets discharged to the environment. Adsorption, photocatalytic degradation of dyes and membrane technology are promising techniques for the removal of these hazardous dyes. Metal organic framework materials have high surface and their functionality assist in trapping metals from water; hence they are defective adsorbents for removal of metals. Also, these porous materials have proven to be good fillers in the fabrication of ultrafiltration membranes with high performance. The thesis focused on the synthesis of various MOF-based materials and their applications in water treatment, specifically as metal adsorbents and filler materials for UF membranes. The metal adsorption studies on both acid mine drainage (AMD) and surface water (river and wastewater) for various metal ions is reported. Firstly, on the removal of Pb(II) from acid mine drainage (AMD) and secondly, on the removal of both As(V) and Cr(VI) from river water and wastewater (raw influent and effluent water samples from Daspoort treatment plant). This led to the production of several MOF materials, namely ZIF-67 (for Pb(II) in AMD and mixed metal ZIF-67/ZIF-8 (for As(V) and Cr(VI) in surface water) and a couple of novel Zr-MOF and Co-MOF bearing a newly synthesised ligand for Cd(II) and Cu(II)). All the MOFs were assessed for metal ion sequestration in water. Various parameters such as pH solution, sonication time, and mass of adsorbent were optimized in the removal of these metals. Multivariate optimization protocol was used in the removal of the three metals whilst the central composite design with 16 experiments was chosen for optimisation. The Pareto chart obtained from the resultant data gave information on the parameters that were significant in the adsorption process...
Ph.D. (Chemistry)