Study on the adsorption performance of tetracycline by KMnO4/KOH co-modified cow dung-based biochar

Abstract

Tetracycline (TC) is a broad-spectrum antibiotic whose residues in water systems present a significant risk to both environmental ecosystems and human health. There is an increasing demand for the development of environmentally friendly and efficient adsorbents to effectively remove TC from water. In response to this need, the present study first involved the preparation of cow dung-based biochar through high-temperature pyrolysis. Subsequently, a co-modification process using KMnO₄ and KOH was employed to obtain Mn-K-DMBC, the modified biochar. Microscopic characterization revealed that the introduction of KMnO₄ and KOH significantly altered both the surface morphology and the pore structure of the biochar. Batch adsorption experiments demonstrated that Mn-K-DMBC exhibited a high adsorption capacity for TC, with a value of 142.58 mg/g at 308.15 K. The adsorption behavior was most effectively characterized by the Langmuir isotherm model and the pseudo-second-order kinetic model. Thermodynamic assessments demonstrated that the process was spontaneous and exhibited endothermic properties. Finally, the analysis revealed that the adsorption of TC onto Mn-K-DMBC is primarily driven by mechanisms such as pore filling, hydrogen bonding, metal complexation, and π-π interactions. This study offers valuable insights into the resource utilization of cow dung biomass and presents novel approaches for the preparation and modification of biochar.