>Magister Scientiae - MSc / Studies involving the use of natural clays such as bentonite, montmorillonite and natural zeolite clinoptilolite in water treatment have been reported. Researchers suggested cost effective processes, such as ion-exchange and adsorption for the removal of heavy metals from waste waters by using naturally occurring and synthetic materials. The current study investigated application of natural adsorbents in brine treatment. Brines are hypersaline waters generated in power stations and mining industries rich in Mg2+, K+, Ca2+,Na+, so,': cr and traces of heavy metals, thus there is a need for these brines to be treated to recover potable water and remove problematic elements. Natural adsorbents have been successfully used in waste water treatment because of their high surface area and high adsorptive properties when they are conditioned with acid or base. The natural adsorbents used in this study were obtained from Ecca Holdings company (Cape bentonite mine) Western Cape in South Africa, comprising bentonite clay and natural zeolite (clinoptilolite) and another clinoptilolite sample was obtained from Turkey. These adsorbents were investigated in their natural and pretreated form for removal of toxic elements in brine water. The pretreatment was aimed at removing Na+, K+, Ca2+, Mg2+ from the clinoptilolite as well as the bentonite and replacing these cations with the H+ cation to activate the materials. The cation exchange capacity (CEC) of natural zeolite from South Africa was found
to be 2.14 meq/ g, Turkish Clinoptilolite was 2.98 meq/ g while South African bentonite was 1.73 meq/g. at 25°C using ammonium acetate (pH 8.2) method. Characterization of these natural adsorbents was done prior to pretreatment and after the treatment. ICP-AES analysis was used for determination of toxic elements in brines before and after sorption. The morphology of clays was characterized by X-ray
diffraction (XRD), Brunauer Emmett Teller (N2-BET) and Scanning electron microscopy (SEM) for confirmatory purposes and X-ray Fluorescent spectroscopy (XRF) was used for the composition analysis of the natural adsorbent. The results from batch experiments prior to pretreatment of the natural adsorbents showed that these natural adsorbents contained Mg2+, K+, Ca2+, Na+ in their structures as charge
balancing cations, thus needed pretreatment to remove the cations. The natural adsorbents were pre-treated with 0.02M HCI. After the pretreatment of natural adsorbents it was possible to enhance the percentage removal of the major cations from brine, and the Na+ and Mg2+ removal achieved (86 % and 85% respectively) from brine was more than C02+ (70% ) the SC was the adsorbent one that gave
highest removal of cations in the brines. Trace elements removal was high with Cu2+and Zn2+ being the highest of toxic elements in brine. The optimum contact for the toxic element removal was found to be 30 min for the Turkish clinoptilolite and 1 hr for the South African clinoptilolite and South African bentonite clay. Leaching of Ae+ and Si4+ during adsorption was also investigated and it was found that less than 1 ppm of A13+ and Si4+ were leached into the solution during adsorption experiments indicating that these materials were stable. The investigation of pH showed that natural adsorbents did not perform well at low pH of 4 and 6. The adsorbents were able to work efficiently at the natural pH of 8.52 of the brine solution. These results show that natural adsorbents hold great potential to remove cationic major
components and selected heavy metal species from industrial brine wastewater. Heterogeneity of natural adsorbents samples, even when they have the same origin, could be a problem when wastewater treatment systems utilizing natural clinoptilolite and bentonite are planned to be developed. Therefore, it is very important to characterize the reserves fully in order to make them attractive in developing treatment technologies.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uwc/oai:etd.uwc.ac.za:11394/8769 |
| Date | January 2011 |
| Creators | Mabovu, Bonelwa |
| Contributors | Petrik, Leslie F. |
| Publisher | University of the Western Cape |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Rights | University of the Western Cape |
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