One-pot synthesis of novel hierarchically porous and hydrophobic Si/SiOx composite from natural palygorskite for benzene adsorption

A low-cost and scalable strategy for the synthesis of the hierarchically porous and hydrophobic adsorbent for volatile organic compounds removal remains a challenge. In this work, a novel silicon/silicon oxide (Si/SiO x ) composite with hierarchical porosity and hydrophobicity was successfully designed from natural palygorskite via a one-pot synthesis strategy, which could be promising in the scalable production due to the cost-effective precursor and simple procedure. The insufficient reduction of palygorskite during the molten salt-assisted magnesiothermic reaction led to the formation of hydrophobic crystalline silicon and the maintenance of amorphous silica framework. The results showed that the Si/SiO x composite possessed the large specific surface area (~307 m 2  g −1 ) and hierarchically porous structure ( i.e. , micro-, meso-, and macropores). As adsorbent for benzene molecules, the Si/SiO x composite exhibited much better static and dynamic benzene adsorption capacities (585.7 and 316.2 mg g −1 , respectively) than raw palygorskite (265.7 and 166.1 mg g −1 , respectively). The excellent benzene adsorption performance of the Si/SiO x composite could be attributed to the large specific area (offering ample adsorption sites) and hierarchical porosity (facilitating the diffusion/mass transfer process). Moreover, the Si/SiO x composite maintained a high adsorption capactiy for benzene under humidity condition (238.7 mg g −1 , with the adsorption efficiency of 76%). Our work provided a universal one-pot method from clay mineral to the hierarchically porous and hydrophobic Si/SiO x composite, and this novel product could be used as an attractive adsorbent for the practical removal of volatile organic compounds.