Effective adsorption of antimony (V) from contaminated water by a novel composite manganese oxide/oxyhydroxide as an adsorbent.

To obtain an efficient and low-cost adsorbent for the Sb(V) removal in Sb(V)-contaminated water, a novel composite manganese oxide/oxyhydroxide (CMO) was synthesized by a simple hydrothermal synthesis method. The synthesized adsorbent was characterized via scanning electron microscopy, X-ray diffraction, transmission electron microscopy, Brunauer-Emmett-Teller surface area, Fourier transform infrared, and X-ray photoelectron spectroscopy analyses. The results revealed that the as-prepared CMO adsorbent possessed a porous structure consisting of MnO nanoparticles and MnOOH nanorods. Batch experiments showed that the adsorption behaviours were well fitted by the Langmuir isotherm and the pseudo-second-order kinetic model, reaching the maximum adsorption capacity of 119.63 mg/g at 25 °C. The application of CMO adsorbent showed that the Sb(V) removal efficiency in 6.24 L Sb(V)-containing water with a concentration of 3.6 mg/L was more than 90%. The reusability of CMO adsorbent demonstrated that the Sb(V) removal efficiency was still more than 80% even after five times of regeneration. The adsorption mechanism for Sb(V) can be described as ligand exchange between hydroxyl groups on the adsorbent surface and hydroxyl groups in Sb(OH) molecules by forming inner-sphere complexes. Those results suggested that the CMO adsorbent can be considered as a potential adsorbent to remove Sb(V) from contaminated water.