RESUMEN
In the present work, composites with non-toxic metal oxides, such as TiO2 and ZnO, and a natural red clay (taua) reach in hematite were used in the photocatalytic degradation of Fenthion. The composite TiO2/Taua (0.5:1â wt. ratio) and pure TiO2 were prepared by sol-gel method while ZnO/Taua (0.5:1â wt. ratio) and pure ZnO were prepared by Pechini method. The materials were characterized by XRD, SEM, EDX, and DRS. The anatase phase was formed in both pure TiO2 and TiO2/Taua, while the hexagonal phase was formed in pure ZnO and ZnO/Taua. The bandgap energies for the two composites were narrowed compared to the respective pure oxides as consequence of the hematite (α-Fe2O3, Eg = 2.1â eV) in the red clay, reaching 2.1â eV for TiO2/Taua and 2.0â eV for ZnO/Taua, while the bandgap energies for pure TiO2 and ZnO were 3.2 and 3.0â eV, respectively. Fenthion was not degraded in the dark, but the concentration droped 20% after 180 min under visible light irradiation without photocatalyst and 60% after 210â min in the presence of the pure red clay. Both TiO2/Taua and ZnO/Taua composites were also photocatalytic active to degrade Fenthion (λ > 420â nm), with degradation of 78% (in 180â min) and 85% (in 210â min) respectively. In the optimized conditions (pH 2, 100â mgâ L-1 of H2O2 and 30â mgâ L-1 of Fenthion), the ZnO/Taua composite was the most efficient, reaching 89% degradation in up to 30â min, with Fenthion sulfoxide as the degradation product.