The function of doping nitrogen on removing fluoride with decomposing La-MOF-NH2: Density functional theory calculation and experiments

Fluoride is an important pollutant in wastewater, and adsorption is an effective way to remove fluoride. Because nitrogen plays an important role in adsorbent materials, computational models were developed to understand the changes in work function resulting from nitrogen doping. La-N-C-800°C, was prepared by pyrolyzing La-MOF-NH2 to verify the influence on the performance of removing fluoride by electrosorption. Material and electrochemical performance tests were performed to characterize La-N-C-800°C. Adsorption kinetics, adsorption thermodynamics, initial concentrations, pH, and ions competition were investigated using La-N-C-800°C for fluoride removal. In addition, density functional theory was applied to evaluate the function of nitrogen. When nitrogen atoms were added, the density of states, partial density of states, populations, and different orbits of charge were calculated to discover deep changes. Nitrogen strengthened the carbon structure and La2O3 structure to remove fluoride. In addition, nitrogen can also act as an adsorption site in the carbon structure. These results provide design ideas for improving the performance of adsorbent materials by doping elements.