A Molecular Dynamics Study on the Mechanism of Adsorption of Phenol and P-Nitrophenol on Kaolinite Surface

Herein, we investigate the adsorption of two organic pollutants, phenol and p-nitrophenol (PNP) in dilute aqueous solution conditions on kaolinite (001) surface through classical molecular dynamics (MD) simulations. The present investigation addresses both adsorption isotherms and mechanistic issues. MD simulations at different solute concentrations generated density profiles and, thereby, adsorption isotherms. The data generated for phenol adsorption fitted both Langmuir and Freundlich isotherm models equally well. Alternatively, PNP adsorption data on the kaolinite surface followed the Langmuir model better. Overall, phenol exhibits higher adsorption capacity on kaolinite than PNP. These results confirm to the experimental observations made by earlier publications in the literature. Radial distribution functions (RDF) between various atom types on the adsorbent and molecules in the solution phase point towards a hydrogen bond dominated interaction mechanisms for organic pollutants.