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Weathering of fluoride rich rocks and industrial processes such as electroplating and glass
manufacturing result in accumulation of fluoride in natural w ater bodies. Fluoride is an
essential micro nutrient to humans and animals in many aspects namely, strengthening of
bones, prevention of tooth decay, and regulating the human growth rate. The acceptable level
of fluoride in drinking w ater is 1.5 mg/L as recommended by the World Health Organization.
However, the recommended level of fluoride for tropical countries such as Sri Lanka is 1.0
mg/L. Excess amount of fluoride ions in drinking water causes health risks such as skeletal and
dental fluorosis, cancers, infertility and thyroid disorder. In general, the drinking water sources
in the intermediate and dry zones in Sri Lanka are rich in Fluoride. Therefore, millions of lives
are at the risk of developing fluoride developing diseases. Therefore, removal of fluoride ions
from drinking water has gained much attention of the research community.
A wide variety of novel adsorbents have been developed to remove fluoride ions from aqueous
medium. In this work 1:1:1 ratio of tri-metal composites of Fe-Mg-AI, Fe-Mg-Zn, Al-Mg-Ce and
Fe-Mg-Ce were synthesized using co-precipitation method for the removal of fluoride ions
from aqueous solutions with the efficiency (the amount of fluoride ions adsorbed per unit) of
0.275±0.01, 1.496+0.259, 2.016±1.553 and 2.554±0.0079 mg/g, respectively. As reported
above, the highest amount of fluoride adsorbed per unit of fluoride ions was observed for the
Fe:Mg:Cetri-metallic composite. Therefore, further studies were carried out to improve its
efficiency by varying the solution pH, contact tim e and the molar ratios of metals in the
composite. The adsorption process was highly pH-dependent. The maximum amount of
fluoride adsorbed per unit of the Fe-Mg-Ce tri-metal composite was determined to be 48.31
mg/g at pH 7. Rapid adsorption of fluoride was observed within the first sixty minutes and
equilibrium was established within 5 hours. The fluoride removal efficiencies for Fe:Mg:Ce
composites with molar ratios of 1:1:1, 1:1:2, 1:2:1 and 2:1:1 were 2.550 ± 0.008, 48.310 ± 0
.079,17.230 ± 0.263 and 23.380 ± 0.090 mg/g at pH 7.00 respectively. These composites were
further studied using FT-IR techniques and XRD.
