Structure induced selective adsorption performance of ZIF-8 nanocrystals in water

Inspired by the surface charge and uniform pore size of Zeolitic Imidazolate Framework-8 (ZIF-8), we prepared ZIF-8 nanocrystals and investigated their selective adsorption performance and potential application in water purification by adsorption of Cr(VI), methyl orange (MO) and phenol in aqueous solution. The obtained ZIF-8 nanocrystals have polyhedron morphology, uniform particle size (similar to 25 nm) and high surface area of 1291 m(2) g(-1). The adsorption results indicate that the ZIF-8 adsorption capacity for phenol is less than that for MO and Cr(VI), which exhibits selectivity for anions. Further, the adsorption capacity for Cr(VI) is more than that for MO, exhibiting size selectivity. The adsorption behaviors were investigated to fit well with pseudo-second-order model and Langmuir isotherm model, implying the chemical related adsorption process. Further, the adsorption mechanism was investigated by XPS analysis, which indicating the adsorption was related to electrostatic interaction, hydrogen bonding and chemical reducing process. This work not only gives an insight into the adsorption behavior and adsorption mechanism of ZIF-8, but also provides an excellent adsorbent with selective adsorption performance for the process of water treatment and purification. (C) 2017 Elsevier B.V. All rights reserved.