란탄수산화물과 수산화아파타이트를 이용한 음용수 중 불소제거 특성

Abstract

This research was undertaken to evaluate the feasibility of lanthanum hydroxide and hydroxyapatite(HAp) for fluoride removal from aqueous solutions. A batch sorption experiments were conducted to study the influence of various factors such as pH, presence of competing anions, contact time, initial fluoride concentration and temperature on the sorption of fluoride on lanthanum hydroxide. The optimum fluoride removal was observed in the pHeq≤7.5. The presence of competing anions showed no adverse effect on fluoride removal. The equilibrium data reasonably fitted the Langmuir isotherm model, and the maximum monolayer sorption capacity was found to be 242.2 mg/g at pHeq≤7.5 and 24.8 mg/g at pHeq>10.0. The pseudo-second-order kinetic model described well the kinetic data, and resulted in the activation energy of 53.4-68.8 kJ/mol. It was suggested that the overall rate of fluoride sorption is likely to be controlled by the chemical process. Thermodynamic parameters such as ΔGo, ΔHo and ΔSo indicated that the nature of fluoride sorption is spontaneous and endothermic. The used lanthanum hydroxide could be regenerated by washing with NaOH solution. Results from this study demonstrate the potential usability of lanthanum hydroxide as a good fluoride selective sorbent. A batch sorption experiments were conducted to study the influence of various factors such as pH, presence of competing anions, contact time, initial fluoride concentration and temperature on the defluoridation by HAp. The equilibrium data reasonably fitted Langmuir and Fruendlich isotherm models. The maximum monolayer sorption capacity was found to be 27.93 mg/g at pHeq 6.5-7.0. The defluoridation capacity increased with decreasing pH of solution. The presence of competing anions showed no significant effect on defluoridation except for HCO3-. The pseudo-second-order kinetic model described well the kinetic data. The sorption energy and activation energy for defluoridation by HAp were found to be 13.62 kJ/mol and 8.60 kJ/mol, respectively, indicating that sorption is governed by ion-exchange/ chemisorption mechanism. Thermodynamic parameters such as ΔGo, ΔHo and ΔSo indicated that the nature of fluoride sorption is spontaneous and endothermic. The used HAp could be regenerated by washing with NaOH solution