Fabrication of fibrous amidoxime-functionalized mesoporous silica microsphere and its selectively adsorption property for Pb(2+) in aqueous solution.

Fibrous cyano-modified mesoporous SiO2 microspheres with specific surface area of ca. 300 m(2) g(-1) have been successfully fabricated respectively by in-situ synthesis and post-modification methods, based on the hydrolysis of ethyl silicate in the presence of (2-cyanoethyl)triethoxysilane at a certain condition. TEM observations show that the average diameters of the prepared fibrous cyano-modified SiO2 microspheres by these two methods are 68 and 211 nm, respectively. The N2 adsorption-desorption isotherms analysis on the fibrous SiO2 microspheres show sharp peaks in the 10-20 nm range. After the cyano groups transformed to amidoxime groups, the adsorption behavior of the fibrous amidoxime-functionalized mesoporous SiO2 microspheres for Fe(3+), Cu(2+), and Pb(2+) was investigated. The results show that the prepared SiO2 microspheres can selectively adsorb Pb(2+). The maximum equilibrium adsorption capacity for Pb(2+) could reach 284 mg/g. The desorption of Pb(2+) in 2M HNO3 completes within 60 min. The efficiency of the desorption is as high as 96.2%. This work provides the methods to prepare amidoxime-functionalized SiO2 microsphere with high specific surface area and total pore volume, which has the potential to be applied as an efficient adsorbent for specific heavy metal ions.