Browsing by Author "Von-Kiti, Elizabeth"

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    Synthesis and characterization of zeolites from bauxite and kaolin: application to the removal of heavy metals from mining wastewater
    (2017-01-20) Von-Kiti, Elizabeth
    Different types of zeolites were synthesized from bauxite and kaolin under varying experimental conditions such as aging time, crystallization time, alkaline source concentration and silicon-to-aluminum (Si/Al) ratio and their effects on the type of zeolite produced were investigated. The synthesized zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive xray spectroscopy (EDX) and Fourier transformed infrared spectroscopy (FTIR) analytical techniques. Consequently, the capacity of the zeolites in removing heavy metals such as copper (Cu2+), chromium (Cr6+), iron (Fe2+), lead (Pb2+) and zinc (Zn2+) from simulated and real mine wastewater samples were investigated using a batch system. The results obtained showed that no or short aging ( 0 – 6 hours) of slurries prior to crystallization favored the formation of linde type A (LTA) zeolite whilst aging slurries for twenty four (24) hours resulted in the formation of faujasite (FAU) type zeolites. Aging beyond twenty four hours produced amorphous products. Crystallization times of 3, 5, 24 and 96 hours produced linde type A (LTA), linde type X (LTX), linde type Y (LTY) and analcime (ANA) with traces of sodalite in most cases. Increasing Si/Al ratio of the reactants (1 ≤ Si/Al ≤ 3) produced zeolites LTA, LTX and LTY. Alkalinity of sodium hydroxide (NaOH) mineralizer produced zeolite LTA at lower concentrations and sodalite at higher concentrations. Increasing alkalinity resulted in higher crystallinity with a resulting decrease in crystalline size of the zeolite particles. For simulated mine wastewater sample with single heavy metal cation, the removal efficiency of all zeolites was highest for Pb2+ (99 %) and least for Cr6+ (4 %). The efficiency of zeolites was in the order A< X< Y. Similar trend was observed for simulated mine wastewater samples with mixed metal systems. Removal of Pb2+ was reduced in the mixed metal systems due to counter effect of the other cations. Both zeolite LTX and LTY showed higher removal efficiency than zeolite LTA due to the availability of greater ion exchange sites and their larger pore diameter as compared to zeolite LTA. The results also showed good agreement with zeolites produced from high grade reagents. The results indicated that the zeolites were able to remove the heavy metals to limits below EPA and WHO recommended values. Hence, zeolites produced from bauxite and kaolin provides a cost-effective technology for the treatment of mine wastewaters.
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    Synthesis of Zeolites and their Application to the Desalination of Seawater
    (2012-06-20) Von-Kiti, Elizabeth
    In this study, zeolite X and Y were synthesized hydrothermally in the laboratory at 90˚C and 100˚C respectively. The synthesized zeolites were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infra-red spectroscopy (FTIR), EDX and thermogravimetric analysis. Exchange of Ca, Mg and K for Na ions in seawater were evaluated in Linde type X and Y. The desalination capacity of both zeolite X and Y were evaluated by adding 0.5 g and 1.0 g of each zeolite to 100 ml of seawater on a rotary shaker. The kinetics of desalination was carried by taking analyte samples at 10, 15, 30, 60, 90 and 120 minutes. The results obtained showed that zeolite mass to seawater ratio of 0.5:100 yielded higher removal efficiencies. Ion exchange was carried out at room temperature. Replacement of Na cations by Ca, K and Mg in the zeolite framework was noted. The overall ion exchange selectivity of both X and Y showed preference in the order of Ca > Mg> K > Na. Removal efficiencies obtained when zeolite X was used was Ca 81.5%, Mg 75%, K 59.9% and Na 11.5%. Efficiencies obtained in the case of zeolite Y was Ca 53.9%, Mg 38.5%, K 35.5% and Na 34.5%. Silver nitrate was used to reduce chloride ions and reduce electrical conductivity. It was concluded that zeolites are efficient in the desalination of seawater. The quality of water produced was not suitable for drinking. However, it can be used for irrigation and other industrial purposes. It is suggested that, to effectively desalinate seawater, zeolites without sodium will be appropriate. Also alternate methods like the Column method could be utilized.