Porous biochar encapsulating highly dispersed Co3O4 as peroxymonosulfate activator for the enhanced tetracycline removal

Abstract

A cobalt-based composite porous biochar (Co₃O₄@KWS) was fabricated by co-precipitation and calcination treatment. The porous biochar could effectively anchor the Co₃O₄, preventing the agglomeration and maintaining the active reaction sites of Co₃O₄, and thereby boosting its peroxymonosulfate (PMS) activation ability. Co₃O₄@KWS exhibited dual functionality with both adsorption and catalysis, achieving 97.4 % tetracycline (TC) removal efficiency within 1 h in a broad pH range of 3 −11 via a PMS-based Fenton-like reaction. Co₃O₄@KWS exhibited a 24-fold increase in specific surface area (991.3 m²∙g⁻¹), a higher degree of graphitization, and improved ability to charge transfer performance than that of Co₃O₄. Contribution calculations of reactive species revealed that ¹O₂ was the predominant species of Co₃O₄@KWS/PMS, followed by ^•OH, SO₄^•−, and O₂^•−. Structure-activity relationship analysis showed that Co(II), CO, C−O−C, and sp²−C functioned as the active sites, furthermore, a synergistic effect, induced by the interaction among these active sites, enhanced PMS activation performance significantly. Additionally, the possible degradation pathways for TC were proposed. The subsequent toxicity assessments confirmed the ecological safety of the system. This study proposed a suggestive strategy for developing cobalt-anchored biochar as an eco-friendly and high-performance PMS activator for contaminant water purification.