Dual metal ions/BNQDs boost PMS activation over copper tungstate photocatalyst for antibiotic removal: Intermediate, toxicity assessment and mechanism

In the metal-based peroxymonosulfate (PMS) activation process, the sluggish surface redox cycle of metal ions generally hampered the efficiency of PMS activation for pollutant removal. Herein, Co-doped CuWO4/BN quantum dots (CW/Co/BNQDs) photocatalysts were developed to realize Cu2+/Cu+ and Co2+/Co3+ dual ions redox cycles for PMS activation, which would facilitate the tetracycline (TC) removal. CW/4Co/2BNQDs could degrade 94.8% TC within 30 min in PMS/Vis system, and the apparent rate constant of CW/4Co/2BNQDs was 2.7 times and 1.2 times higher than those of CW and CW/4Co, respectively. The improved TC degradation performance could be attributed to the synergetic effect between BNQDs and dual redox cycles. X-ray photoelectron spectroscopy (XPS) spectra of samples before and after the reaction demonstrated that BNQDs were beneficial for accelerating the Cu2+/Cu+ and Co2+/Co3+ redox cycles in CW/4Co/2BNQDs, further boosting the activation of PMS in TC degradation. Experiments of different radical scavengers revealed that the SO4·−/·OH/h+/1O2 reactive species participated in the PMS activation for the TC degradation process. The possible TC degradation pathway and intermediate toxicity were detailed investigated. In addition, CW/4Co/2BNQDs exhibited outstanding photocatalytic activity over five consecutive cycles, which illustrated that it was supposed to be a reliable PMS activator over antibiotic elimination for practical application. And this work shed new light on constructing dual redox cycles for efficient PMS activation.