Fe-Zn bimetallic oxide functionalized biochar for enhanced adsorption of enrofloxacin in water

This study employed an iron/zinc bimetallic oxide co-precipitation method to prepare magnetic areca nut husk biochar under nitrogen conditions at 650 °C and investigated its adsorption performance towards enrofloxacin (ENR). Characterization analysis indicates that the specific surface area (1475.35 m2·g−1) and total pore volume (0.71 cm3·g−1) of areca nut husk biochar modified by iron/zinc bimetallic oxide (ZFBC) are significantly greater than those of unmodified areca nut husk biochar (BC). Batch adsorption experiments demonstrated that ZFBC displayed strong removal capabilities for ENR over a broad pH range (3−11), with a maximum adsorption capacity of 198.13 mg·g−1 at 303 K and pH=9, which is nine times higher than BC. In the presence of various competing ions within the concentration range of 0–100 mmol·L−1, the removal efficiency of ENR exceeded 80%. In addition, in adsorption experiments with pig wastewater synthesized in different matrices, ZFBC exhibited an adsorption capacity for ENR (at a concentration of 100 mg·g−1) exceeding 89 mg·g−1. Adsorption behavior conformed to a pseudo-second-order kinetic model and Freundlich isotherm model. In addition, the change in enthalpy (ΔH) of the adsorption was 43.313 kJ·mol−1, indicating primarily physical adsorption. The adsorption mechanisms of ENR on ZFBC encompassed pore filling, π-π conjugation, electrostatic interactions, hydrogen bonding, and functional group complexation. This study demonstrates the potential of areca nut husk as a promising biochar source for the removal of ENR.