DFT study on the effect of functional groups of carbonaceous surface on ammonium adsorption from water

Density functional theory (DFT) was used to study the adsorption of ammonium ion on carbon materials. The effects of single and multiple adjacent functional groups of carbon structures on ammonium ion adsorption were emphasized. The electrostatic potential, adsorption energy, charge transfer, molecular orbital, and dipole moment of different configurations were analyzed. Results showed that the carbonyl group was more likely to adsorb ammonium ion than lactone, carboxyl, and hydroxyl. When the carbon material contained multiple adjacent functional groups at the same time, the adsorption of ammonium ion can be promoted or inhibited due to the interaction among functional groups. The effect of functional groups on the adsorption of 7C bond in carbon materials was related to the electronegativity of functional groups, i.e., greater electronegativity led to smaller adsorption energy of 7C bond. Carbon material itself is nonpolar and hydrophobic, so adding oxygen-containing functional groups can increase the dipole moment of carbon material molecules, thereby enhancing its polarity and adsorption capacity.

Automated summary

Results showed that different functional groups on carbon structures have significant effects on the adsorption of ammonium ions, with the carbonyl group being the most favorable for adsorption. Additionally, carbon materials with multiple adjacent functional groups may promote or inhibit the adsorption of ammonium ions due to interactions among functional groups.