Sorption of 1-hydroxy-2-naphthoic acid to goethite, lepidocrocite and ferrihydrite: batch experiments and infrared study.

The adsorption of naphthoic acids to iron oxides and hydroxides influences strongly their mobility in soils and sediments. Sorption of 1-hydroxy-2-naphthoic acid (HNA) to three iron oxides was examined over a wide range of conditions (pH, ionic strength, sorbate and sorbent concentrations). In the examination of HNA sorption, Tempkin model was performed to fit sorption data of HNA onto all iron oxides. The adsorption in the Henry law range increases in the order: goethite<lepidocrocite<ferrihydrite, while at high sorbate equilibrium concentration, the trend is opposite. Structure of the HNA surface complexes was examined by infrared spectroscopy at different surface coverages and pH conditions. The variation of HNA sorption with solid-to-solution ratio (SSR) in batch experiments exhibited a solid effect for tested oxides except goethite. The role of hydrophobicity in HNA sorption and an eventual formation of solute aggregation on the solid surface have been particularly highlighted on goethite. These results indicate that the mineralogy of the iron oxides and pH value should be considered when predicting HNA sorption in iron oxides and its fate in soil and environment.