BaxCo3−xO4 supported on iron-modified coconut shell biochar as a high-efficiency peroxidase-like catalyst for sulfamethoxazole degradation

Abstract

An iron-modified coconut shell biochar (FBC) support was prepared via an iron salt impregnation method, and then the active component of Ba_xCo_3−xO₄ was loaded onto its surface through coprecipitation and reduction processes, constructing a highly active peroxidase-like composite material Ba_xCo_3−xO₄/FBC_0.2-B. Ba_xCo_3−xO₄/FBC_0.2-B has a specific surface area of 133.1 m² g⁻¹, with K_m values of 2.6 mmol L⁻¹ and 3.7 mmol L⁻¹, respectively, and V_max values of 3.22 × 10⁻⁷ M s⁻¹ and 1.4 × 10⁻⁷ M s⁻¹ for TMB and H₂O₂, respectively, demonstrating excellent enzyme-mimetic catalytic properties. In the degradation of sulfamethoxazole (SMX), Ba_xCo_3−xO₄/FBC_0.2-B achieves complete removal within 40 min, with a mineralization rate of 75.89%. It also possesses detection functionality, exhibiting a detection limit of 0.127 µM for SMX. Structural characterization indicates that the biochar support effectively anchors the active sites, with Co and Fe ion leaching rates as low as 0.04% and 0.08%, respectively. The degradation reaction is dominated by a non-radical pathway, with ¹O₂ being the primary reactive species. Ba_xCo_3−xO₄/FBC_0.2-B demonstrates excellent stability, maintaining a degradation efficiency above 85% after five cycles, and its magnetic properties facilitate facile recovery and separation. The reactive sites of the SMX molecule susceptible to oxidative attack were validated via DFT calculations performed on the SMX molecule alone, and four possible degradation pathways of SMX were proposed based on mass spectrometry analysis. Toxicity assessment indicates that the toxicity of the intermediates gradually decreases. This work provides new insights in the development of efficient, stable, and environmentally friendly peroxidase-like materials, demonstrating potential for application in the field of environmental remediation.