Performance of Mg and Al mixed Oxides Derived From Hydrotalcite For Removal of Fluoride from A Solution
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Date
2015-10
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Addis Ababa University
Abstract
Exploiting efficient and affordable treatment technology for fluoride removal via adsorption is
highly desirable.
In this study, calcinedhydrotalcites with different Mg/Al molar ratios were prepared. Layered
double hydroxides calcined at 450 have been shown to recover their original layered structure
in the presence of appropriate anions which may enhance its adsorption capacity. Uptake of
fluoride ion from aqueous solution by CHT was investigated by batch experiments. The response
surface methodology was applied to optimize the adsorption capacity by employing a
factorial design. The optimal pH, initial fluoride concentration and Mg/Al molar ratio in CHT
were found to be 6.0, 5mg/L and 2 respectively for the maximum percentage adsorption of
94.4%.The equilibrium isotherm showed that the uptake of fluoride ion by CHT was consistent
with the Langmuir and Freundlich equations and that the Langmuir model gave a better fit to the
experimental data than the Freundlich model. The maximum uptake capacity of CHT for fluoride
ion by the Langmuir isotherm model was estimated to be 0.4762 mg/g. The influence of varying
pH of solution, initial fluoride concentration and Mg/Al molar ratio in the structure of CHT on
the kinetics of fluoride removal has also been explored. Kinetic models were used to fit the
experimental data, and it was found that the pseudo-second-order kinetics model could be used
to describe the uptake process satisfactorily. The present work demonstrates that
calcinedhydrotalcites may be promising adsorbents for effective removal of fluorine from water
resources.
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Keywords
Mg, Al, hydrotalcite, Mg and Al mixed oxides