Engineering and optimization of nano- and mesoporous silica fibers using sol-gel and electrospinning techniques for sorption of heavy metal ions.

In this paper, we report on a novel design strategy of an efficient sorbent for removal of trace contaminants from water. This kind of sorbent is composed of a nonporous core of SiO(2) nanofiber and a mesoporous shell (denoted as nSiO(2)@mSiO(2) ("n" means "nonporous" and "m" means "mesoporous")). The nSiO(2)@mSiO(2) fiber possesses a continuously long fibrous shape and mesoporous micromorphology, thus, showing both high sorption capacity and separability. The flexible nonporous SiO(2) nanofiber was prepared with electrospinning first, followed by covering a mesoporous SiO(2) shell based on a modified Stöber method using CTAB (cetyltrimethylammonium bromide) as the directing agent for formation of the mesopores. Also, functional thiol groups were grafted on the nSiO(2)@mSiO(2) to enhance its performance. With a large specific surface area and long fibrous morphology, the nSiO(2)@mSiO(2) fiber and its thiol-functionalized counterpart exhibit impressive performance on removal of Pb(2+) and Cd(2+) from water. Furthermore, the flexible texture and fibrous morphology of the nSiO(2)@mSiO(2) fiber also made the removal of metal ions and the separation process more convenient and efficient, implying that the nSiO(2)@mSiO(2) fiber could have great potential for industrial applications.