Dynamic adsorption process of phthalate at goethite/aqueous interface: An ATR-FTIR study

Insights into the molecular-level behaviors of phthalate at the goethite/aqueous interface can further our understanding of the fate and transport of natural organic matter analogs in the environment. The motivation of this work is to explore the interfacial configuration and dynamic adsorption process of phthalate on goethite at the molecular scale. The flow-cell ATR-FTIR measurement, curve-fitting analysis, and pseudo-second-order kinetic simulation were used to investigate the adsorption mechanisms. The results showed that phthalate formed one electrostatic outer-sphere complex and two inner-sphere configurations in mononuclear bidentate and binuclear bidentate structures. The contribution of outer-sphere complex to the overall phthalate adsorption was suppressed with increasing ionic strength and decreasing pH values. The ratio of adsorption capacity between these two inner-sphere configurations was slightly affected under different experimental conditions. Furthermore, the dynamic adsorption process of these three interfacial configurations followed the pseudo-second-order kinetics model, and reached equilibrium rapidly within 60 min.