Browsing by Author "Beksissa, Regassa"

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    Investigation of the Adsorption Performance of Acid Treated Lignite Coal for Cr(Vi) Removal From Aqueous Solution
    (Addis Ababa University, 2016-07) Beksissa, Regassa; Tekola, Beteley(PhD)
    The presence of heavy metals in aqueous streams arising from the discharge of industrial effluents into water bodies is one of the most important environmental issues because of their toxic nature and its removal is highly essential. This paper deals with the adsorption studies for the removal of hexavalent chromium ions from aqueous solutions using acid treated lignite coal as adsorbent. The collected samples were stage crushed and sieved to a wide particle size range of (250-500μm) and washed using hydrochloric acidic solution to remove any inorganic ash material for production of adsorbent. Preliminary investigation of proximate analyses for raw lignite coal and acid treated was done. The adsorption study was evaluated as the function of initial chromium(VI) concentration, adsorbent dosage and pH. Batch experiments were conducted using artificial wastewater containing Cr(VI). The effects of independent variables on various initial Cr(VI) concentrations between 20 mg/l and 100 mg/l were evaluated. A Cr(VI) removal efficiency of 98 % was achieved at pH 1 with 3.5 g of acid treated lignite in 200mL of solution at 4 hours contact time using initial Cr(VI) concentration of 20 mg/l. Adsorption of Cr(VI) ions was highly pH-dependent and the results showed that the optimum pH for the removal was found to be pH 1. The equilibrium adsorption isotherm (Langmuir and Frendlich) and adsorption kinetic models (first and second order) were evaluated using experimental data. Frendlich isotherm model and second order kinetic model were better for the description of acid treated lignite coal for the adsorption of Cr(VI). Keywords: Cr(VI) Adsorption, Acid treated Lignite Coal, Equilibrium Isotherms, Kinetics.