One-pot synthesis of thiol- and amine-bifunctionalized mesoporous silica and applications in uptake and speciation of arsenic

Abstract

A series of thiol- and amine-bifunctionalized mesoporous silicas were synthesized via one-pot co-condensation of tetraethylorthosilicate, 3-mercaptopropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltriethoxysilane. The mesoporous materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen gas adsorption, infrared spectroscopy, thermogravimetric analysis and elemental analysis. As(V) and As(III) were effectively adsorbed by amine and thiol on the functionalized silica, respectively, through electrostatic interaction and chelation. Adsorption isotherms and kinetic uptake profiles of As(V) and As(III) onto these adsorbents were investigated by batch adsorption experiments. Moreover, this material was employed for the speciation analysis of arsenic using a home-made syringe-based solid phase extraction device. As(V) and As(III) were effectively separated and pre-concentrated in a single run through a sequential elution strategy, in which 0.1 M HNO₃ was first used to selectively elute As(V), and then 1 M HNO₃ with 0.01 M KIO₃ was used to elute As(III). The merits of easy preparation, low cost, high adsorption capacity and selective desorption make the bifunctional mesoporous silica an ideal solid material for the removal and speciation analysis of arsenic in environmental waters.