Alumina nanofibers grafted with functional groups: A new design in efficient sorbents for removal of toxic contaminants from water

A new design in efficient sorbents for the removal of trace pollutants from water was proposed: grafting the external surface of γ-alumina (γ-Al2O3) nanofibers with functional groups that have a strong affinity to the contaminants. This new grafting strategy greatly improves the accessibility of these sorption sites to adsorbates and thus efficiency of the fibrous sorbents. The product sorbents could capture the pollutants selectively even when the concentration of the contaminants is extremely low. Two types of γ-Al2O3 nanofibers with different size were prepared via facile hydrothermal methods. Thiol groups were then grafted on the γ-Al2O3 fibers by refluxing the toluene solution of 3-mercaptopropyltrimethoxysilane (MPTMS). The thiol group modified fibers not only can efficiently remove heavy metal ions (Pb2+ and Cd2+) from water at a high flux, but also display high sorption capacity under sorption equilibrium conditions. Similar result was obtained from the nanofibers grafted with octyl groups which are employed to selectively adsorb highly diluted hydrophobic 4-nonylphenol molecules from water. This study demonstrates that grafting nanofibers is a new and effective strategy for developing efficient sorbents.