Fluoride and Phosphate Removal Using Ettringite Synthesized from Industrial Wastes
| Autor: | Shih-Han Kao, 高士涵 |
|---|---|
| Rok vydání: | 2016 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 104 The thin-film transistor liquid crystal display (TFT-LCD) industry generates effluents with high concentrations of fluoride and phosphate. The objective of this study was to investigate the removal efficiency of fluoride and phosphate using ettringite synthesized from industrial wastes. The industrial wastes used in this study were basic oxygen furnace (BOF) slag and flue gas desulfurization (FGD) gypsum. Addition of pure aluminum sulfate was also employed in the synthesis reaction. The molar ratio ([Ca]:[Al]:[SO4]) of 3:2:3 under pHeq 11.74 was found to be the optimum synthesis condition for ettringite in this study. The industrial wastes and synthesized ettringite were characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis. Kinetics study indicated that both fluoride and phosphate adsorption obeyed pseudo-second-order rate equation. Experimental results showed that fluoride and phosphate were mainly removed by surface precipitation in combination with adsorption at low equilibrium concentration and by surface precipitation at high concentration. Hydroxyapatite (HAP) and fluorapatite (FAP) were the major precipitates formed in the removal process as analyzed by XRD, which was in good agreement with PHREEQC predictions. The highest removal capacity of fluoride and phosphate with ettringite dose 1.0 g/L at 25°C, pHeq ranged from 10.89 to 12.42 was 186.77 mg/g and 613.33 mg/g, respectively. The results implied that the ettringite could effectively remove fluoride and phosphate. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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