Use of Hydroxyapatite Derived from Catfish Bones for Remediating Uranium Contaminated Groundwater
Shyam sundar, Ayalur Chattanathan
Type of Degreethesis
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Hydroxyapatite derived from catfish bones was used for removing uranium from contaminated groundwater. Literature review indicated that apatites from various sources of fish bones can be used for metal remediation. The significance of this study is that apatite prepared from the bones of catfish was used to study uranium removal processes. Since the organic material associated with the fish bones are known to hinder the sorption process, they were systematically removed through mechanical and chemical treatment before using them in the experiments. The catfish bones were further subjected to thermal treatment at 100°C and 300°C. The catfish hydroxyapatite (CFHA) prepared at a lower temperature was found to be the most effective reactant and hence was selected for further studies. Thermally treated catfish bones were characterized using XRD and SEM techniques and the presence of hydroxyapatite was confirmed. Multiple pH edge experiments were performed to understand the variation of uranium removal capacities with changes in pH, and the data showed that the maximum sorption occurred between pH 5 to 8.5. The effect of particle size on uranium adsorption was investigated using three different sizes of CFHA: large (> 2000 µ), medium (2000 µ-300 µ), and small (<300 µ). Batch sorption experiments were completed using these three CFHA particles to understand the role of particle size and surface area on sorption capabilities. The results indicated that the smallest particles exhibited high removal efficiency (of about 18 mg of U/g CFHA). Column experiments were completed using the smallest CFHA particles at different flow rates and breakthrough profiles were obtained. The scalability of the adsorption reaction was tested using different column experiments. First, a column experiment was performed using a fixed amount of sorbent using 1 ppm uranium solution. Later, breakthrough profiles were obtained by doubling both the amount of sorbent in the column and the inlet concentration. The results indicated that both the breakthrough curves followed a similar trend indicating the scalability of adsorption to the sorbent mass. Mass balance closure was verified for both batch and column data. The results indicated that the mass balance error was ~20% and ~10% for batch and column experiments, respectively. The results of this research indicate that CFHA is an effective sorbent and can be potentially used in permeable reactive barriers for treating uranium plumes.