TiO2/Schwertmannite nanocomposites as superior co-catalysts in heterogeneous photo-Fenton process

Abstract

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 TiO2 (P25) with Schwertmannite (Sh), a natural iron-oxyhydroxysulfate nanomineral. We expect that the photo-generated electrons from TiO2 could continuously migrate to Sh, which then could enhance the separation of electron-hole pairs on TiO2 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 TiO2 on Sh surface for the nanocomposites (TiO2/Sh). Under simulated sunlight irradiation, the much higher content of Fe(II) was determined on TiO2/Sh than on Sh via a common method in the iron ore, and the consumption of H2O2 and the production of •OH were more significant in the TiO2/Sh system than those in the TiO2 and Sh systems. These results well support our hypothesis that the photo-generated electrons could migrate from TiO2 to Sh on the composites, and can also explain the much higher degradation efficiency of Rhodamine B (RhB) in the TiO2/Sh system. Besides, TiO2/Sh had lower Fe dissolution as compared with Sh, and retained high catalytic stability after four repeated cycles. Above merits of the TiO2/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.