Bismuth-Based Composite Photocatalyst Activating Persulfate For Visible-Light Photodegradation Of Organic Micropollutants

In this study,carbon quantum dots（CDs）modification and oxygen vacancy defects were used to modify Bi OCl semiconductor catalysts,and two nanocomposite photocatalysts,CDs-BOC and CDs-BO_1-xC,were synthesized.Using XRD,FT-IR,SEM,TEM,UV-vis DRS,PL and other physiochemical characterization methods,the microstructure,morphology,electronic and photocatalytic properties of the samples were explored.The results showed that CDs were successfully bonded to Bi OCl surface,the light absorption boundary of the composite material was significantly broadened to the visible-light region,with excellent visible-light absorption.Moreover,due to the electron transfer characteristics of CDs,the photo-induced electron-hole pairs of the nanocomposite were effectively separated,which highly improved the photocatalytic performance.In order to explore the photocatalytic degradation performance of the prepared photocatalysts,acetamidophenol（AAP）and bisphenol A（BPA）were used as target micropollutants.The two visible-light photocatalytic systems,CDs-BOC/PS and CDs-BO_1-xC/PS,effectively removed pollutants under different reaction conditions.The results showed that the higher the CDs doping concentration in a certain range（﹤10%）,the better the photocatalytic effect;when the photocatalyst concentration was 1.0 g/L,the AAP concentration was 5 mg/L and the PS addition amount was 2 mmol/L,7%CDs-BOC/PS system showed the best photodegradation performance,and AAP was completely removed within 20 min;when the catalyst concentration was 0.3 g/L,the BPA concentration was 10 mg/L and the PS addition amount was 2 mmol/L,the catalytic performance of 5%CDs-BO_1-xC/PS system was the best,BPA was completely removed within 15 min,and the mineralization efficiency reached 67.4%.The chemical quenching experiments and EPR detection,confirmed that the main reactive oxidizing species（ROS）in the two visible-light photocatalytic systems were·OH,·SO₄^-,·O₂^-and h⁺,among which·O₂^-and h⁺were the dominant ROS.Four major intermediate products during BPA photodegradation were identified by TOF-MS,and the degradation pathways were deduced.Finally,the mechanisms of photodegrading reactions via CDs-BOC/PS and CDs-BO_1-xC/PS visible-light photocatalytic systems were proposed.