1. XRD pattern(a), FT-IR spectrum(b), particle size distribution (c) and SEM image (d) of synthetic fluorapatite powder

2. (a) Distribution of uranium (VI) species in the solution with different pH (C₀=100 mg/L, T= 308 K); (b) Adsorption capacity and removal rate of uranium (VI) by fluorapatite in the solution with different pH; (c) Zeta potential of fluorapatite in the solution with different pH; (d) Effect of solid-liquid ratio on adsorption of uranium (VI) by fluorapatite (pH3); (e) Change of the adsorption of uranium (VI) by fluorapatite with adsorption time (pH3, solid-liquid ratio at 0.12 g/L); (f) Effect of initial uranium (VI) concentration on adsorption of uranium (VI) by fluorapatite (pH3, solid-liquid ratio at 0.12 g/L, adsorption time=120 min)

3. Solubility of fluorapatite (a) and fluorapatite adsorbed with uranium (VI) (b) in the solutions with different pH

4. (a) Adsorption capacity and removal rate of uranium (VI) by fluorapatite in the temperature range of 303-323 K; (b) Linear fitting of thermodynamic model for adsorption process; (c) Nonlinear fitting of pesudo-first-order kinetic model; (d) Nonlinear fitting of pesudo-second-order kinetic model; (e) Nonlinear fitting of Langmuir isotherm adsorption model; (f) Nonlinear fitting of Freundlich isotherm adsorption model

5. SEM images of fluorapatite before (a) and after (b) adsorption of uranium (VI), and element mappings (c-g) of the surface of fluorapatite after adsorption of uranium (VI)

6. (a) XPS spectra of fluorapatite before and after adsorption of uranium (VI) and (b) U4f on the fluorapatite after adsorption of uranium (VI) (b), and XPS spectra of Ca2p(c), O1s(d), P2p(e) and F1s(f) on the fluorapatite before and after adsorption of uranium (VI)

7. (a) XRD pattern and (b) FT-IR spectra of fluorapatite before and after adsorption of uranium (VI)

Table 1. Fitting parameters of thermodynamic model for adsorption

Table 2. Fitting parameters of pesudo-first-order and pesudo-second-order kinetic models

Table 3. Fitting parameters of Langmuir and Freundlich isothermal adsorption models