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-TiO 2 composite photocatalysts (S/TiO 2 ) were prepared by a mechanical grinding method for efficient activation of potassium monopersulfate (PMS). The anatase TiO 2 nanoparticles with particle size of approximately 30 nm was uniformly loaded on the surface of schorl via forming Si-O-Ti bonds. The S/TiO 2 assisted with PMS (S/TiO 2 -PMS) exhibited remarkable degradation performance and stability. In this system (S/TiO 2 -PMS), the C/C 0 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/TiO 2 -PMS was 12.6 times that seen with TiO 2 -PMS. The oxidation active species were holes and SO 4 •− in S/TiO 2 -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/TiO 2 -PMS. On the other hand, the transformations of Fe 3+ and Fe 2+ on the schorl surface further promotes the activation of PMS. This work provides a new choice for designing TiO 2 -based photocatalytic persulfate activation system targeting the field of advanced oxidation water treatment.
The flotation separation of scheelite and calcite remains an industrial challenge due to their similar surface properties and active sites, making the development of efficient novel depressants crucial for achieving separation. This study investigates the effect of Fe 3+ -pyrogallol (Fe-PA) complex depressants on the flotation separation of scheelite and calcite, exploring the mechanism by which complex structural stability governs the selective depression of minerals. Flotation results demonstrate that, compared to PA alone, Fe-PA complexes exhibit significant depression of calcite flotation while minimally affecting scheelite flotation; with increasing molar ratio of Fe 3+ to PA in the complexes, the grade and recovery of scheelite initially increase then decrease, reaching optimum values at a Fe 3+ :PA molar ratio of 1:2, thereby enabling effective separation of scheelite from calcite. UV–Vis absorption spectroscopy, automatic potentiometric titration, and DFT calculations collectively reveal that the molar ratio of Fe 3+ to PA critically influences complex stability: at the 1:2 ratio, complex absorbance plateaus, stepwise stability constants maximize, the O-Fe bond order peaks, the HOMO-LUMO energy gap widens maximally, and overall Fe-PA complex stability is highest. This enhanced stability directly impacts flotation separation, evidenced by negative adsorption energies of Fe-PA complexes on calcite versus positive values on scheelite; specifically, the 1:2 complex achieves the most negative adsorption energy on calcite, primarily due to its formation of a hydrophilic surface via an octahedral coordination configuration where two O atoms from surface CO 3 2– groups bond with O-Fe in the complex, thereby depressing calcite.
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