An N-doped porous carbon/alumina composite from spent aluminum ash for efficient peroxymonosulfate activation and tetracycline degradation

Direct conversion of hazardous spent aluminum ash into an N-doped porous carbon/alumina composite (NPC-2). • NPC-2 activates peroxymonosulfate via both radical and non-radical pathways for rapid tetracycline degradation. • Radical ( HO . ${\mathrm{HO}}^{\mathbf{.}}$ , SO 4 . – ${\mathrm{SO}}_4^{\mathbf{.}–}$ ) and non-radical ( 1 O 2 , electron-transfer) processes cooperate to enhance performance. • The porous structure ensures robust redox cycling and maintained activity over multiple runs. • Toxicity of degradation intermediates is significantly reduced, confirming environmental safety. Spent aluminum ash (SAA), a hazardous industrial solid waste, is conventionally landfilled or downcycled into low-value materials, presenting environmental risks and resource underutilization. Meanwhile, the removal of refractory antibiotics like tetracycline hydrochloride (TCH) often relies on advanced oxidation processes that face challenges related to cost, efficiency, and catalyst stability. To address these dual issues, we developed a novel method to convert inert SAA into a high-performance N-doped porous carbon/alumina composite catalyst (NPC-2) via an integrated alkali-activation and pyrolysis strategy. The resulting NPC-2 acts as a highly effective peroxymonosulfate (PMS) activator, achieving complete TCH degradation within 100 min with 69.2% COD removal and retained 82% removal efficiency throughout 30 cycles of continuous-flow operation, owing to the redox-active platform induced by its porous architecture. Mechanistic investigations reveal that the porous architecture creates a redox-active platform, while nitrogen doping modulates the electronic structure to facilitate electron transfer. This combination drives PMS activation through potential coupled radical ( HO . ${\mathrm{HO}}^{\mathbf{.}}$ / SO 4 . – ${\mathrm{SO}}_4^{\mathbf{.}–}$ ) and non-radical ( 1 O 2 /electron transfer) pathways. This work demonstrates the sustainable conversion of solid waste into a green and highly effective detoxification material, presenting a dual-purpose strategy for environmental remediation and value-added waste utilization. Download: Download high-res image (200KB) Download: Download full-size image