Nano-nebula superstructure decorated wood-derived biochar for efficient and rapid antibiotic degradation

Abstract

Fe-based biochar catalysts are widely recognized as promising materials for activating peroxymonosulfate (PMS) to degrade antibiotics in wastewater, owing to their high catalytic activity, notable environmental compatibility, and cost-effectiveness. In this study, wood-derived biochar was first obtained via the pyrolysis of natural wood, and subsequently utilized as a substrate for the strategic assembly of a Fe-based biochar catalyst (referred to as BCNNSP), which possesses a nano-nebula superstructure (NNSP) derived from consecutive hydrothermal and co-precipitation processes. This unique NNSP architecture is characterized as a hierarchical assembly in which the MoS2 nanoflowers, self-assembled from monolayer nanosheets, and the highly dispersed Fe3O4 NPs surface-anchored onto them are referred to as the clouds and stars, respectively. The resulting BCNNSP served as a high-performance catalytic platform to trigger PMS activation, thereby achieving the rapid degradation of tetracycline (TC). Experimental results indicated that under optimal conditions, the BCNNSP/PMS system achieved a superior TC removal efficiency of 94% (initial [TC] = 20 mg/L) within 60 min. Additionally, BCNNSP demonstrated remarkable catalytic persistence and interference resistance, sustaining excellent removal efficiency across a wide pH range and in diverse real-water backgrounds. Moreover, BCNNSP demonstrated excellent reusability, maintaining a TC removal efficiency over 91.2% after six consecutive cycles. Quenching experiments and electron paramagnetic resonance (EPR) analyses identified singlet oxygen (1O2) as the predominant reactive oxygen species (ROS) driving the TC degradation process in the BCNNSP/PMS system. Moreover, X-ray photoelectron spectroscopy (XPS) analysis further elucidated that MoS2 promoted the Fe2+/Fe3+ redox cycle and interfacial electron transport, which consequently improved PMS activation performance. Additionally, the wood-derived biochar exhibits intrinsic electrical conductivity, which facilitates interfacial charge transport during the catalytic process. This work provides an innovative strategy for the rational design of high-performance Fe-based biochar catalysts for practical antibiotic wastewater treatment.