Activation of Peroxymonosulfate-Based Advanced Oxidation via Co@Si-A for Tetracycline Degradation: Performance and Mechanism
Cobalt-doped silica aerogel (Co@Si-A) catalysts were synthesized via a one-step sol-gel method and applied for peroxymonosulfate (PMS) activation to degrade tetracycline (TC). The catalyst with 25 wt% cobalt doping (25Co@Si-A) exhibited superior catalytic performance, achieving 98.97% TC degradation within 30 min under specified conditions (TC 10 mg/L, 100 mL). Brunauer-Emmett-Teller (BET) analysis revealed a high specific surface area and well-developed porous architecture with nano-confined spaces. The 25Co@Si-A/PMS system demonstrated outstanding adaptability across a broad pH range (5–9), maintaining >95% degradation efficiency, and showed strong resistance to sulfate and nitrate ions. In real water matrices, degradation efficiency remained around 80%. After five consecutive cycles, the system retained 82.33% degradation efficiency, with cobalt ion leaching of only 23.7 μg/L in the first cycle, indicating excellent stability. Mechanistic studies using electron paramagnetic resonance (EPR), radical quenching, and probe compound tests confirmed a synergistic radical and non-radical pathway. The primary reactive species were sulfate radicals (SO4•−), hydroxyl radicals (•OH), and singlet oxygen (1O2), with contributions of 58.53%, 9.79%, and 31.68%, respectively. Electrochemical tests indicated that 25Co@Si-A exhibited superior charge transfer compared to Co3O4, attributed to the nano-confined effect of the silica aerogel, which enhanced Co(II)/Co(III) redox cycling and PMS activation. This research provides a promising strategy for utilizing silica aerogel-based catalysts in advanced oxidation processes for water treatment.