Network capture effect-driven enhanced activation of peroxymonosulfate by iron-doped carbon quantum dots derived from ferrous gluconate for efficient ciprofloxacin degradation: DFT calculations and mechanism analysis

Abstract

Carbon quantum dots (CQDs) have gained extensive application in advanced oxidation processes (AOPs) due to the advantages of their unique carbon network structure. However, CQDs still face issues such as uneven electron distribution and low utilization of active sites during application, which have limited their further use in peroxymonosulfate (PMS)-based AOPs. In this study, ferrous gluconate derived iron-doped CQDs (Fe-CQDs) with a unique structure of Fe doping sites were synthesized by a one-step method to activate PMS. The degradation of ciprofloxacin in the Fe-CQDs/PMS system reached 98.19% within 30 minutes, surpassing that in the CQDs/PMS system (30.39%) and PMS system (25.30%), with approximately 10.74 times and 12.92 times higher reaction rates, respectively. Mechanistic studies have revealed that the Fe³⁺ sites on Fe-CQDs can optimize the electronic structure of CQDs and enhance the utilization of active sites within the carbon network structure, improving the electron transfer ability from Fe-CQDs to PMS. This optimization strengthens the contact and activation of PMS by Fe-CQDs through the network capture effect. Simultaneously, the carbon network on Fe-CQDs provides abundant reactive sites for PMS activation and pollutant degradation reactions. DFT calculations were utilized to explore the correlation between pollutants and active species by computing their corresponding Fukui functions. This work presents novel insights into the network capture effect on the Fe-CQD-based PMS activation system.