Adsorption mechanism of phenol, p-chlorophenol, and p-nitrophenol on magnetite surface: A molecular dynamics study

Industrial wastewater organic pollutants like phenol can either be treated by a catalytic oxidation process or by adsorption on active surfaces. In this context, the understanding of the mechanism of adsorption on easily recoverable magnetic adsorbents is an important requirement for further progress in this area. The present study employs canonical ensemble molecular dynamics simulations to gain a better understanding of the adsorption mechanism of the organic pollutants phenol (Ph), p-chlorophenol (PCP) and p-nitrophenol (PNP) present in water on (111) magnetite surface. Systems with varying concentrations of these molecules in water were considered. Simulations generated equilibrium density profiles of adsorbed molecules on the (111) magnetite surface. The density profiles at various adsorbate concentrations were used to generate adsorption isotherms. It was found that data generated for all three organic molecules fitted best the non-linear Freundlich isotherm. Adsorption constant for PCP is found to be greater than those of PNP and Ph. The order of adsorption energies is in agreement with this. Functional groups involved in absorbate-adsorbent interaction have been identified by radial distribution function analysis. (C) 2019 Elsevier B.V. All rights reserved.