Authors : K.S. Ndi, G.P. Kofa, G. Tekem, N.P. Ngnie, E.V. Amba and G.J. Kayem
Abstract: Fluoride removal using adsorbents require clarification steps during which the adsorbate is removed from the suspension. In this study, powders of Grewia sp. (Gs) were used as flocculants in the clarification of laterite-fluoride suspensions resulting from the adsorption of fluoride onto laterite. Clarification experiments consisted in adsorption, coagulation, decantation and filtration steps. Experiments were carried out in a settling tank (34.6 cm2) and in a glass column of 0.4 inner diameter, at different pH (5, 7, 9) and Gs concentration (0.25-1 g L-1) with constant laterite concentration (1 g L-1) and adsorption contact time (30 min). Sedimentation was realized for 30 min, prior to sand filtration of the resulted supernatant. Sand beds of granular particle size 400-500 μm and 10 cm high were used for filtration experiments at a fixed flow rate (5 m h-1). Results show that the best removal efficiency was obtained at pH 5 for fluoride and at pH 9 for suspended material. Using Gs extracts alone gave fluoride removal efficiencies greater than what obtained with laterite. The combined process of decantation and filtration was found suitable in the removal of suspended particles and the sedimentation step was the more efficient process under the tested conditions.
K.S. Ndi, G.P. Kofa, G. Tekem, N.P. Ngnie, E.V. Amba and G.J. Kayem, 2013. Clarification of Fluoride Suspensions by Grewia sp. Extracts. Journal of Engineering and Applied Sciences, 8: 104-108.