Palygorskite and SnO2–TiO2 for the photodegradation of phenol

The photocatalytic removal of phenol was studied using palygorskite-SnO2–TiO2 composites (abbreviated as Paly-SnO2–TiO2) under ultraviolet radiation. The photocatalysts were prepared by attachment of SnO2–TiO2 oxides onto the surface of the palygorskite by in situ sol–gel technique. The products were characterized by XRD, TEM and BET measurements. SnO2–TiO2 nanoparticles, with an average diameter of about 10 nm, covered the surface of the palygorskite fibers without obvious aggregation. Compared with palygorskite-titania (Paly-TiO2), palygorskite-tin dioxide (Paly-SnO2), and Degussa P25, Paly-SnO2–TiO2 and SnO2–TiO2 exhibited much higher photocatalytic activity. The photodecomposition of phenol was as high as 99.8% within 1.5 h. The apparent rate constants (kapp) for Paly-SnO2–TiO2, TiO2, and P25 were measured. Paly-SnO2–TiO2 showed the highest rate constant (0.03435 min−1). The chemical oxygen demand (COD) of the phenol solution was reduced from 220.2 mg/L to 0.21 mg/L, indicating the almost complete decomposition of phenol. Reusability of the photocatalyst was proved.