Abstract:
Groundwater seems to be the most significant natural source of potable water for
millions of individuals. Fluoride ion pollution in groundwater is a major problem in Sri
Lanka's dry zone areas. Groundwater, particularly in tropical regions such as Sri Lanka,
is a significant source of fluoride ion exposure. In Sri Lanka, well water from the
Eppawala and Anuradhapura regions has been evidenced to contain the highest
concentrations of fluoride ion. Fluoride ion is a useful ion for human health and
fluoride-related health problems can occur due to deficiency or excess intake. Excess
amounts of fluoride cause many diseases: dental fluorosis, skeletal fluorosis, arthritis,
bone damage, osteoporosis, muscular damage, etc. The acceptable fluoride ion
concentration in drinking water according to the Sri Lanka Standard (SLS) is 1.0
mg/dm3 (ppm). This study explores the potential of activated carbon derived from Areca
catechu nut husks as a material for removing fluoride from water. The activated carbon
was produced using a chemical activation process with potassium hydroxide at 500 °C
under a nitrogen atmosphere. Batch adsorption experiments were conducted to evaluate
the influence of contact time, adsorbent dosage, initial fluoride ion concentration,
activation temperature, activation time, potassium hydroxide ratio, and stirring time on
fluoride ion removal efficiency. The percentage removal of fluoride ion by the
adsorbent was ~90% at a contact time of 30 minutes. The maximum fluoride ion
adsorption was observed at 2 ppm of fluoride solution with an adsorbent dose of 40
gm/L, activation time 1 hour, char: KOH ratio 1:3, and stirring time 3 hours. The
adsorption equilibrium data was analyzed using the Langmuir and Freundlich isotherm
models. The Langmuir model fits the experimental data better than the Freundlich
model. The adsorption capacity of the Areca catechu nut husk-activated carbon
composite was found to be 3.5334 mg/g. The composite adsorbent prepared from Areca
catechu nut husk activated carbon could be an efficient adsorbent for the removal of
fluoride ion from water.
