Defluoridation of Drinking Water through Adsorption Using Naturally Occurring Zeolites

Excessive fluoride intake can lead to a disease known as fluorosis which is characterized by decaying and weakening of teeth and bones. In certain areas of the world, such as Ethiopia, water sources are naturally at high fluoride levels. The most common methods used to remove fluoride from drinking water are reverse osmosis and activated alumina, both of which require costly resources and electrical power. For a developing nation such as Ethiopia, these processes are impractical. Our research seeks to find a way to use naturally occurring zeolites found in Ethiopia to defluoridate the water. The goal of our project is to determine the operating conditions, zeolite types, and zeolite amounts for fluoride removal in a flow process for applications in defluoridation from drinking water in developing regions of Ethiopia.

In our research, we selected two naturally occurring zeolites to study; analcime and mordenite. In prior research, these two zeolites demonstrated a capability to adsorb fluoride effectively. The mordenite was received calcined in powdered form while the analcime required grinding, sieving, and calcination. We characterized the zeolites using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) in order to understand their structures and morphologies and compare them to what is found in the literature.

Our fluoridated water came from the dilution of 0.1M fluoridated water to concentrations of 100 mg F^- per liter and 20 mg F^- per liter. The fluoride concentrations were measured using an ion-selective electrode. Our fluoridated water received additional treatment with pH adjustment using citric acid. The pH was adjusted to lower the acidity to a range of values for certain experiments. The pH was measured using a pH electrode.

Thus far, we have conducted several batch experiments to test the defluoridation capacities of the zeolites under varying fluoride conditions and pH levels. The pH was found to have a significant effect on the defluoridation capacity, with fluoride removal exceeding 90% under the following conditions: pH of 2.44, initial F^- concentration of 100 mg/L, and adsorbent dose of 100 g/L. Both analcime and mordenite show promise for providing an economically viable option for the removal of fluoride from drinking water in Ethiopia.

Acknowledgment

This research has been funded in part by the UConn Office of Undergraduate Researchâ??s IDEA Grant program.