Experimental investigation and DFT calculation of different amine/ammonium salts adsorption on oxidized coal

To clarify the hydrophobic modification mechanism of AAS (alkyl amine/ammonium salts) on OC (oxidized coal) surface, four different AAS on OC was investigated through experiments and DFT calculations. Adsorption of AAS on OC enhances its surface hydrophobicity and reduces its surface electronegativity, which further promote its aggregation sedimentation, but the overall effect is poor. Polar head groups of AAS adsorb on coal oxygen structural units of OC through hydrogen bonding, while the carbon ring structural units of OC can be adsorbed by both polar head group and non-polar carbon chain of AAS through intermolecular forces, but the adsorption state of AAS on OC particle is not steady in aqueous environment. The main adsorption mechanism of AAS on OC is hydrogen bonding and weak intermolecular forces, with intermolecular forces dominating. Results can provide theoretical support for efficient separation and separation of coal slime water and its pharmaceutical design.