Calcium carbonate nanoparticles fabricated by a facile method based on the colloidal gas aphrons for removal of fluoride ions from aqueous solutions

In this study, calcium carbonate nanoparticles were proposed as a potential material for fluoride ion removal from aqueous solution. For this purpose, a new method based on the colloidal gas aphrons was applied for the preparation of the calcium carbonate nanoparticles. The synthesized nanoparticles were characterized by SEM, XRD, and FTIR analyses. Factors affecting the sedimentary reaction including the initial concentration of fluoride ion, pH, time, and temperature were individually investigated. The morphology of the successfully synthesized nanoparticles was quasi-spherical vaterite structure without important aggregation. The maximum fluoride ion removal capacity was obtained about 460 mg/g at 298 K. Also, the effect of temperature displayed that temperature change has a significant effect on the removal rate. The removal rate was highly dependent on the pH and by decreasing the pH, the removal rate decreased. Kinetic results indicated that the removal kinetics is in perfect agreement with the first-order model. The experiments showed that although the synthesized sample has a better performance than the industrial one, the purity and the low cost of calcium carbonate particles produced in the water softening process make them a great candidate for the removal of fluoride from aqueous solutions.