Heterojunction effect of three-dimensional porous CuFe2O4/CuO for thermal-light excited carriers separation in promoting peroxymonosulfate activation and inhibiting metal ion spillover

Abstract

CuFe2O4/CuO (CC) heterojunctions with three-dimensional porous structures were prepared by polymer-assisted freeze-drying as visible light (Vis)-peroxymonosulfate (PMS) activators given the good light absorption, efficient charge separation, and high-quality mass transfer characteristics. The heterojunction had Z-scheme interface contact and presented composition-dependent behaviors in enhancing tetracycline hydrochloride (TCH) degradation (∼91.1 % within 36 min for the best ratio) and inhibiting the Cu (155 μg/L) and Fe (5 μg/L) ions spillover. The comparisons of the catalyst/Vis/PMS, catalyst/Vis, and catalyst/PMS systems demonstrated that the heterojunction could separate the light excited electron-hole pairs and thermally generated intrinsic carriers simultaneously. Then, the thermal-light excited carriers could directly participate in the PMS activation process and promote the charge separation and transfer in turn, resulting a higher synergy index of the heterojunction in the CC/Vis/PMS system (7.3) than in the CC/Vis system (4.8). Because visible light has much stronger excitation power than thermal excitation at room temperature, the synergy index of the heterojunction in the CC/Vis/PMS system is also higher than the CC/PMS system (1.9). The PMS activation from thermal-light excited carriers also inhibited the leaching-related surface reactions contributing for the extremely small metal ions spillover. In addition, the porous structure provided a high specific surface area for surface reactions and interconnected channels for mass transfer, while the self-supporting structure can be directly separated from aqueous system for recycling in water treatment process. The new insights on the carriers’ behavior in PMS activation could provide some new ideas for developing high efficient catalyst/Vis/PMS system for wastewater treatment in future.