Enhanced arsenate removal performance of nanostructured goethite with high content of surface hydroxyl groups

Abstract

Goethite (α-FeOOH) with high content of surface hydroxyl groups was synthesized by using a simple sodium dodecyl sulfate (SDS) assisted solution method. The presence of SDS can increase the surface area and the contents of surface hydroxyl groups. The adsorption properties towards arsenate (As(V)) ions were investigated, including adsorption kinetics, adsorption isotherm, influences of pH and coexisting anions, and regeneration of the adsorbent. The maximal adsorption capacity was 60.6mgg−1 at pH 7.0, which is about three times larger than the ones synthesized in pure water, and also is favorable compared to those reported in the literature using other adsorbents. The coexisting of phosphate and carbonate inhibited the As(V) removal especially at high concentrations. The as-prepared α-FeOOH could be readily regenerated using NaOH solution and be repeatedly used in the field of water purification. In addition, the removal mechanism was revealed by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and the zeta potential study. The point of zero charge (pHPZC) of the α-FeOOH is 6.35. At high solution pH, the ion-exchange between the surface hydroxyl groups and As(V) ions dominates in the adsorption of As(V). Around the pHPZC, the hydrogen bonding also contributes to the As(V) removal. When the solution pH is lower than pHPZC, the electrostatic attraction plays key roles in As(V) removal.