Self-polarized schorl optimizing TiO₂ for photocatalytic persulfate activation and organic pollutants degradation

Photocatalytic activation of persulfate has exhibited tremendous potential in water purification because of its green and environmentally friendly process. However, this process often exhibits low activation efficiencies and difficult recovery of the photocatalyst. Herein, schorl-supported nano-TiO₂ composite photocatalysts (S/TiO₂) were prepared by a mechanical grinding method for efficient activation of potassium monopersulfate (PMS). The anatase TiO₂ nanoparticles with particle size of approximately 30 nm was uniformly loaded on the surface of schorl via forming Si-O-Ti bonds. The S/TiO₂ assisted with PMS (S/TiO₂-PMS) exhibited remarkable degradation performance and stability. In this system (S/TiO₂-PMS), the C/C₀ value of phenol solution (10 ppm) were decreased to 0.070 and 0 after 30 min and 90 min of irradiation, where the degradation extent were 93.0% and 100% respectively. The rate of phenol degradation with S/TiO₂-PMS was 12.6 times that seen with TiO₂-PMS. The oxidation active species were holes and SO₄^•- in S/TiO₂-PMS system subjected to simulated sunlight. It was demonstrated that the polarization electric field of the schorl enhanced the separation efficiency of the photoinduced electrons and holes for improving the performance of the S/TiO₂-PMS. On the other hand, the transformations of Fe³⁺ and Fe²⁺ on the schorl surface further promotes the activation of PMS. This work provides a new choice for designing TiO₂-based photocatalytic persulfate activation system targeting the field of advanced oxidation water treatment.