Copper-functionalized hydrochar from swine manure with complexation sites for selective adsorption of tetracycline antibiotics

Emerging antibiotic pollutants pose a growing environmental challenge due to their complexity and widespread use. Swine manure (SM)-derived hydrothermal carbon adsorbents offer the potential for waste mitigation in livestock farming but are limited by low efficiency and poor pollutant recognition. Herein, a copper-decorated hydrochar with high selective adsorption capacity for antibiotics was engineered by incorporating Cu(II) into SM via a low-temperature hydrothermal carbonization. Characterizations revealed that copper, mainly in the form of CuO at lower hydrothermal temperatures, significantly enhanced tetracycline (TC) adsorption, achieving an uptake capacity of 291.2 mg·g −1 at 298 K, which surpassed that of most reported adsorbents on carbon materials. The adsorption performance was largely unaffected by various coexisting substances (anions and cations), except for H 2 PO 4 − and CO 3 2− . It remained effective across a wide pH range (4–10), exhibited exceptional selectivity for tetracycline-family antibiotics (TCs) in single and mixed systems, and was significantly superior to the pure CuO system. This selectivity was attributed to the formation of surface complexation between Cu(II) and the enol-carboxyl groups in TCs, as confirmed by XPS analysis and theoretical calculations. Fixed-bed column tests validated its efficiency in TC removal from real effluent, with a breakthrough point of 253 min for 10 % of the initial adsorbate concentration. This study not only supports the high-value utilization of SM resources but also provides valuable insights into the efficient and selective adsorption of antibiotics from wastewater.