Iodine-doped carbon fibers as an efficient metal-free catalyst to activate peroxymonosulfate for the removal of organic pollutants

Abstract

Developing efficient and metal-free catalytic oxidation systems based on PMS activation has become an increasingly important and challenging objective in the environmental catalysis field. In this study, iodine doped carbon fibers (I-CFs), as a low-cost and environmentally-friendly metal-free catalyst, were used for the activation of peroxymonosulfate (PMS), with the innovative construction of a simple and efficient I-CFs/PMS catalytic system. In this system, I-CFs exhibited extra-high catalytic activity to activate PMS for the removal of Acid Red 1 (AR1) over a wide pH range of 3–10, with a remarkably pH-tolerant performance. Electron paramagnetic resonance (EPR) technology with various spin-trapping agents, such as ascorbic acid, methyl alcohol and L-histidine, was employed to confirm that singlet oxygen (¹O₂) was the key radical species contributing to AR1 removal in the catalytic oxidation system, which is different from the widely reported radical pathway for PMS. Furthermore, the I-CFs/PMS system showed excellent anti-interference performance for the removal of AR1 when dye auxiliaries, such as NaCl, were added into the system, distinct from previous reports where NaCl can capture radicals and severely inhibit the decomposition of organic pollutants. The findings of this study provide a novel catalytic oxidation system for the activation of PMS, which could be potentially applied to environmental remediation.