Fabrication of fibrous amidoxime-functionalized mesoporous silica microsphere and its selectively adsorption property for Pb2+ in aqueous solution

Abstract

Fibrous cyano-modified mesoporous SiO2 microspheres with specific surface area of ca. 300m2g−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 211nm, respectively. The N2 adsorption–desorption isotherms analysis on the fibrous SiO2 microspheres show sharp peaks in the 10–20nm range. After the cyano groups transformed to amidoxime groups, the adsorption behavior of the fibrous amidoxime-functionalized mesoporous SiO2 microspheres for Fe3+, Cu2+, and Pb2+ was investigated. The results show that the prepared SiO2 microspheres can selectively adsorb Pb2+. The maximum equilibrium adsorption capacity for Pb2+ could reach 284mg/g. The desorption of Pb2+ in 2M HNO3 completes within 60min. 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.