Selection of Clay Adsorbents and Determination of The Optimum Condition for Defluoridation of Ground Water in Rift Valley Region
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Date
2007-01
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Addis Ababa University
Abstract
People in several regions of the Rift Valley of Ethiopia are suffering
from skeletal and non-skeletal fluorosis as result of consuming water containing
excessive fluoride. Defluoridation of drinking water using variety of material has
been suggested by different researchers. This study assesses the fluoride
adsorption characteristics of clays collected from different areas in Ethiopia.
Bombawoha clay, Combolcha clay and Muger clay 2 were found to have the better
potential as fluoride adsorbents.
The effect of contact time, amount of adsorbent dose, pH, particle size, heat
treatment of adsorbent and initial concentration of fluoride was investigated. The
adsorption was rapid during the first one hour. The adsorption efficiency of
fluoride was increased with adsorbent dosage. The defluoridation capacity was
appreciable with in acidic pH range. Clay adsorbents treated in the range between
400 to 600oC gave better fluoride removal. The fluoride adsorption efficiency
depends directly with initial fluoride concentration. The adsorption data were well
fitted to the Langmuir isotherm model with adsorption capacity of 0.136, 0.168,
and 0.191 for Bombawoha clay, Combolcha clay and Muger clay 2 respectively.
Laboratory scale column were conducted and showed good removal of fluoride.
At breakthrough the three clay samples Bombawoha clay, Combolcha clay and
Muger clay 2 showed 0.1248, 0.235, 0.239 mg/g of adsorption capacity, 1.64, 1.1,
1.02 mg/L of residual fluoride and 300, 500, 500 mL of breakthrough volume
respectively.
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Process Engineering Stream