Novel hierarchically porous allophane/diatomite nanocomposite for benzene adsorption

Abstract

Allophane/diatomite (Allo/Dt) nanocomposite with a hierarchically porous structure was prepared via an in situ hydrothermal method. This hierarchically porous structure consists of i) micropores remaining from the initial stacked coating allophane particles; ii) mesopores formed by the transformation of the macropores of diatom frustules due to the filling of allophane particles in the inner walls, and iii) preserved macropores of diatom frustules. The coating amount of allophane particles in Allo/Dt nanocomposite was 59.1%, leading to a specific surface area of 155.9 m2/g, which was substantially higher than that of diatomite (17.9 m2/g). The benzene adsorption performance and related adsorption mechanisms of Allo/Dt nanocomposite were investigated. The larger benzene dynamic adsorption capacity of 121.6 mg/g, compared to that of the synthetic allophane (105.9 mg/g), resulted from the adequate adsorption space provided by the hierarchically porous structure. Moreover, Allo/Dt nanocomposite displayed a higher efficiency for benzene adsorption in mesopores of the coating allophane particles because of their improved dispersity. These results demonstrated that the fabrication process of Allo/Dt nanocomposite can overcome not only the aggregation of allophane but also diatomite's shortcoming of low specific surface area, making the nanocomposite to be a promising adsorbent for the treatment of volatile organic compounds.