Excellent fluoride removal performance by CeO2–ZrO2 nanocages in water environment

• CeO2–ZrO2 nanocages with high capacity and affinity for fluoride were prepared.
• The adsorbent kept good adsorption capacity for fluoride around pH 3.0–7.0.
• The adsorption mechanisms involved anion exchange and electrostatic interaction.

CeO2–ZrO2 nanocages were prepared by Kirkendall effect, and their fluoride removal performance was investigated in batch studies. The obtained CeO2–ZrO2 adsorbent presented a good adsorption capacity in the pH range of 3.0–7.0, and the optimum pH range was 3.5–4.5. The adsorption isotherm could be better described by the Langmuir model than the Freundlich model. The Langmuir maximum capacity of the CeO2–ZrO2 adsorbent was calculated to be 175 mg/g at pH 4.0, which was much higher than that of other adsorbents reported previously. The effect of co-existing anions, such as sulfate, chloride, arsenate, and bicarbonate, on fluoride adsorption was systematically studied. Furthermore, the as-prepared adsorbent showed an excellent fluoride removal properties in real underground water. The adsorption mechanism was investigated by zeta potential measurement, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis. Anion exchange and electrostatic interaction play key roles in fluoride removal.