Abstract:
The problem of high fluoride in water sources in Africa and the rest of the developing
world has exacerbated in the latest past due to increasing shortage of water. More
people are being exposed to high water fluoride resulting in elevated levels of fluorosis
in the societies. Fluoride (F) adsorption from solutions using a siliceous mineral from
Kenya (M1) was studied on batch basis and results verified on high fluoride water using
fixed-bed column experiments. About 100% batch F adsorption was achieved at 200 mg/L
F concentration, 0.5 g/mL adsorbent dosage, 303–333 K, and pH 3.4 0.2. Based on
Giles classifications, F adsorption isotherm was found to be an H3 type isotherm. The
equilibrium data was correlated to Freundlich and Langmuir models and the maximum
Langmuir adsorption capacity was found to be 12.4 mg/g. Column experiments were
conducted for different fluoride concentrations, bed depths, and flow rates. The F
breakthrough curves were analyzed using the Thomas model and efficient F adsorption
was found to occur at low flow rates and low influent concentrations. The Thomas F
adsorption capacity (11.7 mg/g) was consistent with the Langmuir isotherm capacity
showing that M1 could be applied as an inexpensive medium for water defluoridation.
