Flower-shaped nanoscale Na2Mg(CO3)2: a promising adsorbent for fluoride removal from drinking water

In this paper, flower-shaped Na2Mg(CO3)2 nanoparticles were synthesized by a simple hydrothermal method for defluoridation in water. The effects of the initial concentration of fluoride, pH value, and coexisting ions on the removal of fluoride were investigated. Na2Mg(CO3)2 nanoparticles were characterized by using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and energy disperse analysis of X-rays. The experimental results show that the adsorption isotherm is consistent with the Freundlich model at pH = 7 and 35°C. When the initial concentration is 200 mg/L, the maximum adsorption capacity calculated by the Langmuir model is up to 113.64 mg/g. The adsorption kinetics is consistent with the pseudo-second-order model, and the adsorption equilibrium can be achieved within 100 min. There is little effect on Na2Mg(CO3)2 nanoparticles in the wide range of pH values (3–10). The fluoride removal rate reaches up to 92.26% at pH = 7 for the initial fluoride concentration of 5 mg/L, along with the adsorbent dose of 1 g/L. Except for PO4, SO4, and HCO3–, other anions don’t affect the fluoride adsorption. The experiment results also demonstrate that the prepared adsorbents can be reused for at least six times. Finally, the mechanism for fluoride adsorption by Na2Mg(CO3)2 nanoparticles is discussed.