Understanding the potential of coal gangue as photocatalyst for antibiotic degradation: The role of abundant oxygen vacancies and electron-hole pairs

Coal gangue (CG) offers promising potential as a cost-effective photocatalyst for antibiotic degradation. However, current approaches do not emphasize the origin of its photocatalytic activity. This study investigates the photocatalytic activity of CG through a comparative analysis with one-pot aerobic/anaerobic calcinated CG. The potential application of CG as a photocatalyst for tetracycline (TC) decontamination in water was evaluated under dark and light. Characterization results identified anatase and kaolinite as the critical photosensitive minerals in CG. Batch removal experiments indicated that CG achieved up to 98 % TC removal at 1 g/L dosage, with most biotoxic intermediates reduced to below 0.9 mg L⁻¹ Lethal Concentration 50 (LC50) of Fathead minnow (Pimephales promelas). Degradation pathways identified by density functional theory (DFT) and quantitative structure-activity relationship (QSAR) indicated that superoxide anion (^⁎O₂⁻) and electron-hole (e⁻-h⁺) pairs were predominant contributors to TC photodegradation. Theoretical calculations suggest that the oxygen vacancies on the CG surface can accelerate the production of ^⁎O₂⁻, while fast electron transport channels within surface hydroxyl groups facilitate e⁻ and h⁺ separation. The findings of this research elucidate the origin of CG's photocatalytic activity and highlight the potential to serve as a photocatalyst for low-cost antibiotic removal, offering a promising solution for coal waste management and utilization.