Synthesis and characterization of Mg–Fe–La trimetal composite as an adsorbent for fluoride removal

• The Mg–Fe–La trimetal composite was prepared by a facile co-precipitation method.
• The as-prepared adsorbents were synthesized at room temperature (25 °C).
• The maximum adsorption capacity for fluoride of the as-prepared material was 112.17 mg/g.
• Langmuir and pseudo-second-order kinetic models were used to fit the adsorption process.

Flaky Mg–Fe–La trimetal composite as an adsorbent for fluoride removal was successfully synthesized by a facile co-precipitation method in this study. Various reaction parameters such as Mg/Fe/La molar ratio, synthesis temperature and calcination temperature were studied. The as-prepared adsorbents were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), energy-dispersive X-ray spectroscopy (EDS) and Brunauer–Emmett–Teller (BET). The experimental results demonstrated that the adsorbent with a Mg/Fe/La molar ratio of 25:1:4, synthesized at room temperature (25 °C) and calcined at 400 °C, obtained the largest adsorption capacity of 112.17 mg/g for fluoride at near neutral pH. The BET surface area and average pore diameter of the adsorbent were 178.55 m2/g and 31.16 nm, respectively. The adsorption process was fitted well with the Langmuir isotherm and pseudo-second-order kinetic model. The adsorption mechanisms for fluoride were adsorption/complexation and ion exchange interaction. Based on the experimental results, the flaky Mg–Fe–La composite can be a very promising material for fluoride removal from aqueous solution.

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