Fluoride Removal using Modified Spent Diatomaceous Earth Adsorbents
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Date
2017-10
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Addis Ababa University
Abstract
Elevated concentrations of fluoride in drinking water are a serious health concern. Dental and
skeletal fluorosis being the most commonly reported fluoride-related diseases in Ethiopian rift
valley. Various naturally occurring materials have been explored as adsorbents for the removal
of fluoride from water .This study investigate the fluoride removal capacity of spent
diatomaceous earth from aqueous solution. The spent diatomaceous earth was collected, washed
and dried in an oven at 110 0C for 24 hrs. The dried 10 gram of spent diatomaceous earth was
reacted in 100 ml of 0.1M HCl and dried in an oven at 110 0C .The dried spent diatomaceous are
powdered, sieved and preserved. The effect of processing conditions (pH, initial fluoride
concentration, adsorbent dose and contact time) was investigated using batch adsorption
experiments. The adsorption efficiency was increased with increasing contact time and adsorbent
dose and decreased with increasing pH and initial fluoride concentration. At low pH (2)
maximum amount of fluoride was adsorbed by acid treated spent diatomaceous earth (58.48).
Response surface methodology (RSM) involving Box–Behnken design was used to optimize the
adsorption process of fluoride ions. The second order mathematical model was developed by
regression analysis of the experimental data obtained from 29 batch runs. The optimum pH,
initial fluoride concentration, adsorbent dose and contact time were found by desirability
function to be 2.02,24.04mg/l, 18.83g and 2.95 hr respectively. Fluoride removal was 43.19% at
the optimum combination of process parameters. The results of validation experiments
conducted at optimum conditions for the removal of fluoride ions (42.94%) indicate that the
predicted values are in good agreement with the experimental result. The adsorption data were
well fitted to the Langmuir and Freundlich isotherm model. The adsorption capacity was 0.321
mg/g. Acid treated spent diatomaceous earth could be used as adsorbent for fluoride ion
containing aqueous solution
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Keywords
Diatomaceous Earth Adsorbents