Valorizing copper-contaminated manure into biochar for tetracycline adsorption: Dynamics and interactions of tetracycline adsorption and copper leaching

Valorizing animal manure into biochar for antibiotic removal from farm wastewater represents a “waste-to-waste” recycling approach for farms. The novelty of this study lies in systematically elucidating the dynamics and interactions of tetracycline adsorption and copper leaching under a laboratory-simulated scenario of treating tetracycline (TC)-contaminated farm wastewater treatment using heavy metal-contaminated biochar. In this study, the biochar was produced from cow manure through pyrolysis at 800 °C, with varying amounts of CuCl₂ to simulate heavy metal-contaminated cow manure. A series of lab physiochemical measurements, including isothermal, kinetic, and thermodynamic experiments, were conducted to characterize the patterns of TC adsorption, Cu leaching, and their interactions. The results showed that Cu improved TC adsorption capacity by facilitating the diffusion of TC into the interior of the biochar. The observed phenomena of rapid absorption and desorption of TC in the first hour of adsorption dynamics could be caused by interactive surface site competition. The molecular dynamic simulation results using Materials Studio indicated that exogenous Cu decreased the average interaction energy between TC and biochar from −2.07 eV to −1.57 eV, further supporting the aforementioned findings. The revealed complex interaction mechanism between Cu and TC advances our understanding of the removal of organic pollutants from farm wastewater using biochar derived from animal manure.