Synthesis and characterization of cotton-like Ca–Al–La composite as an adsorbent for fluoride removal

• The cotton-like Ca–Al–La composite was prepared by a simple one-step method.
• The composite exhibited high fluoride removal rate in a wide pH range from 3 to 11.
• The maximum adsorption capacity of the as-prepared samples is 26.17 mg/g.
• The composite still showed high adsorption capacity after four reuse cycles.

Cotton-like Ca–Al–La composite as an adsorbent for fluoride removal was successfully synthesized by an easy one-step hydrothermal process. The as-prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that the samples have uniform and cotton-like morphology. Batch sorption experiments were conducted to study the influence of various factors such as pH, initial fluoride concentration, equilibrium contact time, co-existing anions on the sorption of fluoride. The fluoride adsorption over the Ca–Al–La composite follows the Langmuir model. The maximum adsorption capacity of the adsorbent is 29.30 mg/g. The fluoride adsorption kinetics over the adsorbent can be well described by the pseudo-second-order kinetic model. In addition, the cotton-like Ca–Al–La composite showed high fluoride removal efficiency over a wide range of pH (3–11).

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