Adsorption of Low-Concentrated U(VI) on a Preferable Crystalline Boehmite (γ-AlOOH) in Alkaline Conditions

Contamination of uranyl ions is a severe environmental problem, and the development of a new removal method is essential for removing uranyl ions, especially in alkaline solutions of the rare earth production process. The boehmite (γ-AlOOH) adsorbent with a large specific surface area was prepared from aluminum-containing residues. The U(VI) adsorption behavior and mechanism of γ-AlOOH were investigated by inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS), ζ-potential, and so on. It could be found that in an alkaline solution with up to 20 mg/L U(VI), more than 94.18% U(VI) could be removed and the U(VI) in an alkaline solution could be decreased to as low as 1.16 mg/L, at 60 °C, 1 h with the γ-AlOOH dosage of 20 g/L. Thermodynamic and kinetic studies showed that U(VI) adsorbed onto γ-AlOOH was consistent with the pseudo-second-order model (R2 = 0.999). The γ-AlOOH adsorption of U(VI) conformed to chemisorption. The adsorption mechanism showed that UO2(OH)42– exchanged with −OH of γ-AlOOH. The desorption and recyclability results revealed that about 94% of U(VI) was desorbed. After five adsorption/desorption experiments, the U(VI) removal yield by γ-AlOOH was reduced by only 17.2%. This work provided a potential to remove U(VI) by γ-AlOOH adsorbents in an alkaline solution.