Evaluation of the ability of ferrihydrite to bind heavy metal ions: Based on formation environment, adsorption reversibility and ageing

Binding ability of heavy metal ions on the surface of environmental minerals may greatly affect the local chemical properties, long-range interactions, surface reactivity, and bioavailability of metal ions in the aquatic environment. In this work, three ferrihydrites (Fh-1, Fh-2 and Fh-3) were prepared by different clearly defined procedures. Among them, the formation condition of Fh-3 is close to that of ferrihydrite in natural environment. The adsorption characteristics of the Cu(II) ions on the three ferrihydrites were investigated. The affinity of three ferrihydrites to Cu(II) ions was evaluated based on pH-sorption edge curves, Langmuir and Freundlich model parameters, adsorption–desorption isotherms and ageing of ferrihydrite adsorbed Cu(II). The results indicate that the maximum adsorption capacity for Cu(II) was found to be 8.74, 13.33 and 14.39 mg g−1 for Fh-1, Fh-2 and Fh-3, respectively. Fh-2 and Fh-3 have stronger affinity than Fh-1 to adsorb Cu(II) ions. The experimental data were well fitted by double layer surface complexation model. The sorption differences of Cu(II) on the three Fhs were investigated by results gained from the simulation.