Polyvinylpyrrolidone in the one-step synthesis of carbon quantum dots anchored hollow microsphere Bi2WO6 enhances the simultaneous photocatalytic removal of tetracycline and Cr (VI)

The development of visible-light-responsive catalysts that are capable of simultaneous photo-oxidation and photo-reduction has been a major focus of research. In this study, carbon quantum dots anchored hollow microsphere Bi2WO6 (CQDs/HBWO) photocatalyst was successfully prepared via a one-step polyvinylpyrrolidone (PVP)-assisted hydrothermal method. PVP had a dual function: controlling hollow microsphere morphologies as well as serving as a precursor of carbon quantum dots. The as-prepared CQDs/HBWO-18 had the highest catalytic activity for the photocatalytic degradation of TCH (0.02768 h −1), which was approximately 2.1 and 1.23 times higher than that for the hollow microsphere Bi2WO6 without CQDs and the nanosheet Bi2WO6, respectively. Only CQDs/HBWO-18 was effective for the photoreduction of Cr (VI) in the system without pH adjustment or scavenger addition. The photoreduction efficiency of Cr (VI) increased 83% and 58% in the bi-pollutant system with 5 mg/L and 10 mg/L of Cr (VI) containing 20 mg/L TCH compared with Cr (VI) alone. The improved photoreduction activity of Cr (VI) could be attributed to TCH acting as a photogenerated hole scavenger. The results of the scavenging test and electron spin resonance confirmed that h+, O2− and OH were the main reactive species. Eventually, the possible degradation pathway of TCH was proposed.