Cobalt-based silica nanospheres for enhanced peracetic acid activation: the efficiency and mechanism to degrade tetracycline hydrochloride

Abstract

Peracetic acid (PAA)-based advanced oxidation processes (AOPs) have emerged as a prominent research focus in the field of water treatment due to their high efficiency and environmental friendliness in degrading organic pollutants. Herein, cobalt-based silica nanosphere catalysts (Co@SiO₂) were synthesized by loading the transition metal cobalt onto the surface of hollow silica nanospheres using a wetness impregnation method to activate PAA for tetracycline hydrochloride (TCH) degradation. The Co@SiO₂/PAA system exhibited significantly superior TCH degradation performance within 10 minutes, with a reaction rate (rate constant: 0.1751 min⁻¹) 4.5 times higher than that of Co@SiO₂. The optimal operating parameters for the degradation of 10 mg L⁻¹ TCH were identified as 0.5 mM PAA, 200 mg L⁻¹ Co@SiO₂ and a neutral pH. The effects of Cl⁻, NO₃⁻ and SO₄²⁻ on this catalytic system were negligible, whereas humic acid exhibited a significant inhibitory effect. Characterization results revealed that hollow silica nanospheres suppressed cobalt ion agglomeration, with Co leaching concentration reaching 0.137 mg L⁻¹ after four cycles. Mechanistic studies indicated that the contributions of CH₃C(O)OO·, ·OH, and ¹O₂ to TCH degradation were 40.55%, 21.83% and 37.62%, respectively. Furthermore, the degradation products of TCH were identified by liquid chromatography-mass spectrometry, which further elucidated the potential degradation pathways. Catalyst recycling experiments and various aquatic environment tests demonstrated that Co@SiO₂ exhibited excellent reusability and catalytic stability. This study demonstrates that the Co@SiO₂/PAA process may be a viable approach, advancing the development of AOPs for wastewater treatment.