Efficient degradation of tetracycline in wastewater by novel biochar-based photocatalytic materials: performance, photocatalytic mechanism and degradation pathways

The rapid increase in antibiotic contaminants such as Tetracycline (TC) in aquatic environments poses significant threats to human health and ecosystems. This study presents a novel Mn-Al layered double hydroxide (LDH) composite with rice husk biochar (RHBC) as a highly efficient visible light photocatalyst for the degradation of TC in wastewater. The Mn-Al-LDH/RHBC composite was synthesized via a simple co-precipitation method and characterized by UV–vis DRS, PL, TRPL, EIS, and TPR tests, confirming its wide visible spectral absorption, low electron–hole recombination rate, and high charge transfer efficiency. Photocatalytic performance tests showed that Mn-Al-LDH/RHBC achieved a 90.10% TC degradation efficiency within 90 min of irradiation. Mechanistic studies using EPR and DFT analysis identified ·OH and ·O₂⁻ as the primary reactive species in TC degradation. Additionally, QSAR analysis demonstrated a reduction in the biotoxicity of TC and its intermediates post-degradation. This work offers a new insight for the utilization of biomass waste and the improvement of Mn-Al-LDH/RHBC photocatalytic performance, and extends the broad potential application of biochar-based photocatalyst in antibiotic-contaminated wastewater treatment applications.