Adsorption of ciprofloxacin on co-pyrolyzed biochar from fish scale and pine needle

The biochar (FS-PNBC) is prepared by pyrolyzing mixed biomass of fish scale and pine needle in varied proportions in a tube furnace. The biochar was characterized by a specific surface area analyzer (BET), scanning electron microscope (SEM), Fourier infrared spectrometer (FTIR), and X-ray diffractometer (XRD). In a solution with an initial concentration of 60 mg/L, the adsorption of ciprofloxacin (CIP) by a 1:1 ratio of fish scale and pine needle co-pyrolyzed biochar (FS-PNBC1) reached 27.97 mg/g. The adsorption properties such as thermodynamics, kinetics, isothermal adsorption, and adsorption factors were investigated by batch experiments. The results indicate that FS-PNBC exhibits a significantly large specific surface area, abundant pore structure, and a high level of porosity. After approximately 180 minutes, adsorption equilibration was achieved in a pH=4 solution. The kinetic data was well-matched with a quasi-second-order model, suggesting that chemisorption plays a role in the adsorption process. Isothermal adsorption and thermodynamic results indicate that the adsorption of CIP by biochar is more consistent with the Freundlich model, which suggests multilayered non-homogeneous phase adsorption and an exothermic entropy-increasing reaction capable of proceeding spontaneously. FS-PNBC contains oxygen-containing functional groups, and through FTIR analysis, it was observed that hydrogen bonding, π-π bonding, and electrostatic interaction are closely linked to adsorption. This study demonstrates that biochar produced through the co-pyrolysis of fish scale and pine needle has the potential to serve as an efficacious adsorbent for extracting ciprofloxacin from wastewater.