In situ preparation of Mn-enriched biochar for catalytic degradation of ciprofloxacin via H2O2 activation

Abstract

Phytoremediation is an effective strategy for removing heavy metals from contaminated soil; however, the subsequent disposal of metal-enriched plants remains a challenge. In this study, manganese-enriched biochar (MEB) was synthesized from Mn-enriched iris and employed as a catalyst to activate hydrogen peroxide (H₂O₂) for the degradation of ciprofloxacin (CIP). Comprehensive characterization using SEM, BET, FT-IR, Raman, XPS, and HRTEM confirmed the successful synthesis of MEB, exhibiting favorable surface properties and catalytic stability. Under optimal conditions, the degradation efficiency of CIP (5 mg/L) reached 66.8 % within 120 min (pH = 6.7), with an observed rate constant (k_obs) of 0.00895 min⁻¹, which was 4.2 times higher than that of Mn-doped biochar (MDB) prepared via an immersion technique. Scavenging experiments and electron paramagnetic resonance (EPR) analysis confirmed that •OH were the dominant reactive oxygen species responsible for CIP degradation. XPS analysis revealed that Mn active sites and sp²-hybridized carbon worked synergistically to enhance H₂O₂ activation, thereby facilitating efficient •OH generation. 8 intermediate products were identified via LC-MS, and potential degradation pathways of CIP were proposed. Furthermore, The MEB/H₂O₂ system exhibited strong anti-interference properties, sustaining high degradation efficiency despite variations in pH, common anions and the presence of humic acid, highlighting its excellent practical applicability. The superior catalytic performance, stability, recyclability, and low metal ion leaching of MEB highlight its significant potential for wastewater treatment applications involving H₂O₂ activation.