Atmosphere regulation: unraveling effective strategies for creating high-performance iron ore/biochar composite nanomaterials in ball milling processes

Abstract Ball milling technology has become an important method for material modification due to its high efficiency, environmental protection and economy. However, previous studies mainly focused on the adjustment of ball milling parameters and lacked an in-depth understanding of the effect of ball milling atmosphere on material properties. To this end, siderite/biochar composites (BM-SD/BCs) were prepared by ball milling technique and the effects of different ball milling atmospheres (air, nitrogen, vacuum) on the physicochemical properties of the composites and their catalytic performance were systematically investigated. The results showed that the N/BM-SD/BC prepared under nitrogen atmosphere exhibited excellent catalytic performance in phenol removal efficiency of 90.3%, which was significantly higher than that of the A/BM-SD/BC prepared under air atmosphere (73.8%) and the V/BM-SD/BC prepared under vacuum atmosphere (81.3%). Characterization analysis revealed that the ball milling treatment markedly altered the surface morphology and structural properties of the composites. Specifically, the composites ball-milled under nitrogen atmosphere exhibited smaller particle sizes, larger specific surface area (ascending from 27.0 to 187.6 m2 g−1), and richer distribution of surface functional groups and Fe(II) species. All these characteristics significantly enhanced their redox activities. This structural optimization not only increased the active sites of the composites, but also effectively enhanced their activation of persulfate (PS), which was capable of generating a variety of reactive radicals (such as SO4 −·, ·OH, and ·O2 −) for the efficient degradation of phenol, in which ·OH and ·O2 − contributed 50.7% and 25.3% of phenol removal, respectively. In addition, the N/BM-SD/BC/PS system demonstrated its capability to degrade phenol across a broad pH spectrum (especially in the pH range of actual wastewater), showing good adaptability and potential for practical application. This study reveals the key role of ball milling atmosphere in the modulation of material physicochemical properties and reactivity, which provides theoretical support for the future application of ball milling in the engineering of nanomaterials. Graphical Abstract