The Removal of Aqueous Fluoride Ions through the Implementation of Metal Oxides

Friday, February 12, 2016
Bharat Srirangam, Lexington High School, LEXINGTON, MA
Zahin Ahmed, Lexington High School, LEXINGTON, MA
Pranav Gandham, Lexington High School, LEXINGTON, MA
Water is an essential compound integral to the survival of all organisms; without it, life could not exist. While access to clean water is in abundance to many people, others in developing countries such as India or many different nations in Africa and even some developed countries do not have this luxury. Water in those countries is contaminated by high concentrations of the fluoride ion. Excess fluoride poses a serious threat to the drinkers of this water because it induces a devastating bone condition known as skeletal fluorosis. Over 66 million people  in India have the condition and many more are at risk. In order to reduce the risk of contracting fluorosis, this experiment was conducted to remove fluoride ions from water through the use of metal oxides, namely calcium oxide (CaO). It was hypothesized that CaO would get the most fluoride out of the water (which it did, because it removed the greatest amount of fluoride). CaO, when added to fluoridated water reacts to create CaF2, which has a very low Ksp value meaning that more of it would precipitate out of solution than would stay ionized. Thus fluoride could be separated from the water by removing the precipitated CaF2. A colorimeter-based fluoride kit was used to determine how much fluoride was left in the water post-experimentation. Results showed that CaO had promise as the remaining concentration was 0.4 or a removal of 34.6 ppm. This average is high enough to ensure that post-experimentation water would not cause a buildup of fluoride in food sources or fluorosis, since any concentration under 2 ppm of fluoride is low enough to avoid skeletal fluorosis.