Article
Enhanced Photo-Fenton Degradation of Antibiotics through Internal Electric Field Formation at the Interface of Mixed-Phase FeS₂
Hongyan Liu 1,2, Yunhang Shao 1,2, Shuai Dou 1,2 and Chengsi Pan 1,2,*
1 Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, China
2 International Joint Research Center for Photoresponsive Molecules and Materials, Jiangnan University, Wuxi 214122, China
* Correspondence: cspan@jiangnan.edu.cn
Received: 9 September 2024; Revised: 9 October 2024; Accepted: 13 November 2024; Published: 15 November 2024
Abstract: Iron sulfide (FeS₂) is a rich mineral resource widely used as an efficient Fenton and photo-Fenton reagent due to its non-toxicity and low synthesis cost. However, the mechanism underlying its photo-Fenton degradation activity related to the two crystal phases—pyrite (P-FeS₂) and marcasite (M-FeS₂)—is still not well understood. In this study, P-FeS₂, M-FeS₂, and their mixed phase (P/M-FeS₂) were prepared through hydrothermal reactions. The results showed that P/M-FeS₂ exhibited the highest photo-Fenton degradation activity, achieving a removal rate of approximately 99% for 50 ppm of ciprofloxacin (CIP) within 3 minutes, outperforming other photo-Fenton catalysts in pollutant degradation. The study revealed that an internal electric field (IEF) is generated at the interface of M-FeS₂ and P-FeS₂ due to their differing work functions. This IEF accelerates the regeneration of the active sites (Fe²⁺ in S₂²⁻-P-FeS₂ and M-FeS₂) required for the Fenton reaction, thereby explaining the superior activity of the P/M-FeS₂ mixed phase. This study introduces the IEF theory for the first time to explain the mechanism of mixed-phase catalysts in the photo-Fenton reaction. The formation of IEF can enhance the regeneration of the active sites involved in the Fenton reaction, thereby improving both reaction activity and stability. This work highlights the significance of regulating crystal phases in the degradation of pollutants during heterogeneous Fenton reactions and offers insights for developing highly efficient Fenton catalysts.
