Sequestration of Arsenic by Moringa Oleifera Seeds and Bauxite

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The ability of Moringa oleifera seeds and bauxite to sequester arsenic was studied individually and in combination. The study was in relation to how the bauxite, Moringa oleifera seeds and the Moringa-bauxite mixture could reduce the concentration of arsenic in aqueous solution. Matured Moringa oleifera seeds were dried and processed into powder and the bauxite pulverised. Both sorbents were sieved using 500 um copper sieves. Fifty millilitres each of arsenic solution with concentrations 1, 5, 10, 25, 50 and 100 mg/L were prepared into Erlenmeyer flasks and sorbed with 2g of Moringa oleifera seeds. The procedure was repeated with bauxite and Moringa-bauxite mixture. The duration of sorption was one and half hours. Both Moringa oleifera seeds and the bauxite were good sorbents over the concentration range of arsenic solutions prepared. Moringa oleifera recorded a mean sorption of 90.94% at 25 mg/L and bauxite a sorption of 98.60% at 1 mg/L. A combination of the two sorbents recorded a percentage sorption of 85.20% at 1 mg/L. There was also a significant sorption of 82.00% at 25 mg/L when Moringa oleifera seeds were combined with bauxite. The results were modelled along the Langmuir and Freundlich sorption isotherms with the latter providing a mathematical evidence that sorption were high for all the sorbents. This piece of work provides a competitive option for the removal of arsenic from aqueous solution particularly for the gold mining companies that process sulphidic gold ores and can be extended to areas of arsenic contamination in general.
Thesis Submitted to the Department of Environmental Science in Partial fulfillment of the Requirements for the award of Master of Science Degree in Environmental Science.2012