TiO/Schwertmannite nanocomposites as superior co-catalysts in heterogeneous photo-Fenton process.

The heterogeneous photo-Fenton reaction is an effective technique in combating organic contaminants for both soil and water remediation, and extensive studies have focused on enhancing its efficiency and reducing its costs. In this work, we developed novel photo-Fenton catalysts by simply milling commercially available TiO (P25) with Schwertmannite (Sh), a natural iron-oxyhydroxysulfate nanomineral. We expect that the photo-generated electrons from TiO could continuously migrate to Sh, which then could enhance the separation of electron-hole pairs on TiO and accelerate the reduction of Fe(III) to Fe(II) on Sh, leading to high degradation efficiency of the target organic contaminants. SEM and TEM results showed the distribution of TiO on Sh surface for the nanocomposites (TiO/Sh). Under simulated sunlight irradiation, the much higher content of Fe(II) was determined on TiO/Sh than on Sh via a common method in the iron ore, and the consumption of HO and the production of •OH were more significant in the TiO/Sh system than those in the TiO and Sh systems. These results well support our hypothesis that the photo-generated electrons could migrate from TiO to Sh on the composites, and can also explain the much higher degradation efficiency of Rhodamine B (RhB) in the TiO/Sh system. Besides, TiO/Sh had lower Fe dissolution as compared with Sh, and retained high catalytic stability after four repeated cycles. Above merits of the TiO/Sh composites, in combining with their simple synthesis method and low-cost property, indicated that they should have promising applications as heterogeneous photo-Fenton catalysts.