Insights into Heteroatom Doping on Iron-Based Catalyst Supported on Asphalt-Derived Carbon for Peroxymonosulfate Activation in Tetracycline Degradation

Abstract

To investigate the role of heteroatoms (N, B, S, and P) doping in activating peroxymonosulfate (PMS) for the degradation of tetracycline (TC) using iron-based catalysts, 10 different Fe-based catalysts supported on asphalt-derived carbon were synthesized. Activity tests showed that doping with B, N, and S enhanced PMS activation for TC degradation, with B and N exhibiting the highest degradation efficiency. In contrast, P doping impaired the catalyst’s ability to activate PMS, resulting in a marked decrease in TC degradation performance. To further explore the inhibitory effect of P doping, three representative catalysts─Fe@C, Fe@C–N–B, and Fe@C–N–B-P─were characterized using various techniques. These included TEM, HAADF-STEM, XRD, XPS, BET, FTIR, and ICP-MS. The results revealed that P doping significantly altered the structural properties of the catalyst, which, in turn, impaired the adsorption behavior of TC. Further investigation using electron paramagnetic resonance and reactive oxygen species scavenging experiments showed that P doping notably suppressed the generation and contribution of key radicals, •OH and SO₄•^–, which are primarily responsible for TC degradation, thereby hindering the catalytic process. Electrochemical performance also demonstrated that P doping obstructed electron transfer between the catalyst and PMS, further diminishing catalytic efficiency. Additionally, experiments were conducted to examine the effects of various parameters on TC degradation, as well as the recyclability and practical applicability of Fe@C–N–B. The toxicity of TC degradation products was also assessed. These findings offer valuable insights into the substantial impact of heteroatom doping on the catalytic performance in PMS activation for the degradation of TC.