Efficient regeneration of styrene-saturated activated carbon: Dynamic evolution from Co0-CoMn2O4 to a defect-rich mixed interface

In this study, a non-oxidative regeneration strategy based on regeneration-induced dynamic structural reconstruction in a bimetallic Co–Mn-decorated activated carbon system was developed to address the rapid adsorbent deactivation caused by styrene-derived carbonaceous deposits formed during high-temperature regeneration. Co(NO 3 ) 2 and Mn(NO 3 ) 2 were introduced onto activated carbon (AC) via impregnation, where the mild nitrate etching effect facilitated the high dispersion and stable anchoring of metal species. Structural characterization revealed that the initially coexisting metallic Co 0 and spinel CoMn 2 O 4 undergo progressive structural reconstruction and phase evolution during high-temperature cycling, transforming into a defect-rich Co 0 /CoO/MnO mixed interface , while largely preserving the hierarchical pore structure. The optimized 2.5Co-2.5Mn-AC sample exhibited a high adsorption capacity of 630.8 mg/g along with excellent regeneration stability, retaining 76% of its initial capacity after six adsorption-regeneration cycles at 900 °C under a nitrogen atmosphere. Notably, its cycling performance significantly outperformed pristine AC and monometallic counterparts. The regeneration-induced evolution of Co–Mn interfaces is closely correlated with the generation of oxygen vacancies and enhanced cycling durability. Metallic Co 0 and reduced Co–Mn oxide phases promote the catalytic transformation of styrene-derived species, effectively alleviating irreversible pore blockage and suppressing performance attenuation. Overall, this work proposes a non-oxidative regeneration strategy, offering a generalizable design concept for recyclable carbon-based adsorbents.