| Abstrakt: |
Fluoride pollution in groundwater is mainly from natural factors, which will harm those who use groundwater as drinking water. Herein, an iron-lanthanum watermelon rind biochar composite was prepared by a coprecipitation method and used to remove fluoride from the aqueous solution by a static adsorption method. The effects of adsorbent composition, aging time, calcination temperature, pH, adsorption time, adsorbent dosage, adsorption temperature, initial concentration of fluoride, and coexisting anions on the removal of fluoride were evaluated. When the amount of adsorbent was 0.05 g/50 mL, the removal efficiency of the fluoride with an initial concentration of 10 mg/L reached 98.29%. The best conditions for the static adsorption process of 10 mg/L fluoride were: pH was in the range 2-9, the amount of adsorbent was 0.05 g/50 mL, and the reaction time was 5 h. Scanning electron microscopy-energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Brunauer--Emmett--Teller of the adsorbent were tested. Experimental results showed that electrostatic attraction, metal complexation, and ion exchange were the main adsorption mechanisms. The calculated value of k2 varies from 0.2943 to 0.0071 g/mg·min with the decrease of the fluoride concentration. The kinetics and isotherm showed that chemical adsorption was the main control step in the fluoride adsorption of Fe-La-WBC-300. The value of the Freundlich constant (n) in the range 0-1 showed that Fe-La-WBC-300 had the best performance for fluoride removal. The fluoride adsorption process consisted of single-layer adsorption and multilayer adsorption. Thermodynamic studies showed that the adsorption of fluoride was a process of spontaneous endothermic reaction. Fe-La-WBC-300 showed a good application prospect to remove fluoride in groundwater. [ABSTRACT FROM AUTHOR] |
