Synergistic effects of sulfur-doped carbon dots/permanganate process for DCF degradation: Mechanism and pathways

Extensive research has explored strategies to enhance permanganate (PM) oxidation capacity, with carbon materials having shown significant promise in treating refractory organic pollutants in water. However, the impacts of carbon quantum dots (CQDs) and heteroatom-doped CQDs on PM oxidation remain unclear, warranting further investigation. In this study, we found that sulfur-doped CQDs (SCQDs) significantly outperformed CQDs, nitrogen-doped CQDs (NCQDs), and boron-doped CQDs (BCQDs) in promoting the oxidation reaction of diclofenac sodium (DCF) by PM. Through quenching experiments, light-shielding tests, and UV-Vis spectroscopy, we revealed that the PM/SCQDs system could rapidly and stably generate Mn(III) and MnO₂, thereby facilitating the removal of DCF. Characterization analysis showed that SCQDs possess a surface enriched with diverse functional groups, and sulfur doping further enhances their electron cloud density. This structural characteristic enhances the ability of SCQDs to donate electrons to permanganate, thereby promoting its reduction to Mn(III) and MnO₂. A comprehensive evaluation of key operational parameters governing the PM/SCQDs system performance was conducted. Additionally, the PM/SCQDs system exhibited substantial resistance to interference from common matrix ions and natural organic matter in water. The study provides a new perspective on enhancing permanganate oxidation by SCQDs and offers a promising pathway for efficient water pollutant degradation.