Polydopamine/β-cyclodextrin/coal fly ash composite for the highly efficient extraction of uranium from water environment

To obtain a green, low-cost and efficient adsorbent, polydopamine (PDA) and β-cyclodextrin (β-CD) were adopted to modify coal fly ash (CFA) to prepare polydopamine/β-cyclodextrin/coal fly ash composite (PDA/β-CD/CFA). The successful introduction of PDA and β-CD was proved by FT-IR, XRD and XPS. The uranium extraction efficiency on PDA/β-CD/CFA reached 95.6% (pH = 5.0, T = 298 K, C0 = 10 mg/L and m/V = 0.2 g/L) and the whole adsorption process was perfectly fitted by the Pseudo-second-order model (R2 = 0.999), illustrating that uranium was extracted via chemisorption. The correlation coefficient R2 of Langmuir model was 0.999, which was higher than other models, meaning that uranium extraction behavior on PDA/β-CD/CFA was uniform monolayer adsorption. The maximum extraction capacity of uranium on PDA/β-CD/CFA calculated by Langmuir model was 537.6 mg/g, which was larger than most of reported adsorbents, indicating that PDA/β-CD/CFA was a potential candidate for uranium extraction from water environment. Moreover, PDA/β-CD/CFA performed excellent uranium extraction properties with the existence of coexisting ions and the desorption efficiency of uranium by PDA/β-CD/CFA was higher to 95.8% at the fifth cycles, fully suggesting that PDA/β-CD/CFA possessed good selectivity and cycle stability. Characterization results demonstrated that uranium was immobilized on PDA/β-CD/CFA through chelation, complexing action, electrostatic interaction and hydrogen bonding.