Sulfate radical-assisted photocatalytic degradation of quinoline with WO3/ CuFe2O4/Cu Z-scheme system: Comparison of persulfate and sulfite activation

In this work, we systematically investigated the performance and degradation mechanism of quinoline using a persulfate (PS) or sulfite (S(IV)) assisted WO3/CuFe2O4/Cu (10WCC) photocatalysis. The experimental results showed the degradation efficiency of quinoline were the best in the PS-photocatalysis system with the catalyst dosage of 3 g/L, the PS dosage of 4 mmol/L and pH of 7, and that were the best in the S(IV)-photocatalysis system with the catalyst dosage of 2 g/L, the S(IV) dosage of 5 mmol/L and pH of 7. In addition, the S(IV)-photocatalysis system (77.2%, 1.43 h-1) had lower degradation efficiency than the PS-photocatalysis system (100%, 11.04 h-1) under visible light irradiation. The main active species in the 10WCC/VIS/PS system were h+ and center dot OH, while in the 10WCC/VIS/S(IV) system they were h+, center dot O2- and SO4 center dot-. This was likely because the electrons of 10WCC could not be captured by S(IV), and more electrons were captured by O2 to form center dot O2- . Some h+ oxidized S(IV), resulting in a small amount of center dot OH. Thus, center dot O2 - and SO4 center dot- played key roles in presence of S(IV). Moreover, h+ was most important in both systems, indicating photocatalytic degradation dominated quinoline removal reaction. This study provides some reference for SO4 center dot- coordinated photocatalysis technology.