Adsorption effect for removing fluoride with species of nitrogen by using La-BDC-NH2/C3N4: Experiments and mechanism.

Fluoride contamination has emerged as a significant global environmental concern, with prolonged consumption of fluoride-rich groundwater being a primary contributor to fluorosis. Nitrogen sites play an important role in the process of fluoride removal, but the influence of different nitrogen species on fluoride adsorption has not been clearly clarified. In this study, a lanthanide organic framework adsorbent La-MOF-NH 2 was prepared by solvothermal method, and a new adsorbent La-MOF-NH 2 @g-C 3 N 4 was synthesized by adding g-C 3 N 4 rich in various nitrogen sources. The effects of adsorbent dosage, pH, temperature and co-existing anions on the adsorption of fluorine were systematically studied. Optimal conditions were identified at a dosage of 2 g/L and a pH of 3, achieving theoretical maximum adsorption capacities of 219.4406 mg/g and 63.1401 mg/g, respectively. The results of five regeneration experiments shown that La-MOF-NH 2 and La-MOF-NH 2 @g-C 3 N 4 have strong recovery capacity. According to the adsorption isotherm and kinetic model, the adsorption mechanism of fluoride ions is mainly hydrogen bonding and chemisorption. In addition, through the experimental characterization and mechanism study, it was proved that amino group > pyridinic nitrogen > graphitic nitrogen. It provides a good guide for designing adsorbents containing nitrogen sites. [Display omitted] • After five cycles of regenerations, the adsorption capacity remained at 60 %. • The adsorption capacities of La-MOF-NH 2 and La-MOF-NH 2 @g-C 3 N 4 were up to 219.44 mg/g and 63.14 mg/g. • The effects of different nitrogen species on fluoride adsorption were investigated. • The adsorption mechanism of fluoride ion was mainly hydrogen binding and chemisorption. [ABSTRACT FROM AUTHOR]