Study on the adsorption of Ciprofloxacin antibiotic in water using biochar synthesized from pine bark via microwave pyrolysis

The presence of antibiotic residues in aquatic environments—particularly ciprofloxacin—poses serious risks to ecosystems and public health due to their persistence and ability to promote antimicrobial resistance. This study aimed to synthesize biochar from Pinus kesiya bark using microwave-assisted pyrolysis and to evaluate its effectiveness in removing ciprofloxacin from aqueous solutions. The physicochemical characteristics of the biochar were investigated using FT-IR, SEM, EDX, and BET analyses. The optimal pyrolysis condition was determined to be 800 W for 10 minutes, producing a material with a high specific surface area (592.32 m²/g) and pore volume (0.197 cm³/g), indicating a well-developed porous structure—favorable for adsorption. Adsorption experiments revealed that the maximum ciprofloxacin removal efficiency (90.97%) was achieved at pH 6, with an initial concentration of 20 mg·L-1 and an equilibrium time of 180 minutes. Kinetic data were well-fitted to the pseudo-second-order model (R2 = 0.9945), suggesting the possibility of chemical interactions between the biochar surface and ciprofloxacin molecules. Additionally, the adsorption process was best described by the Langmuir isotherm model, with a maximum monolayer adsorption capacity (qmax) of 26.51 mg/g. These findings demonstrate that biochar derived from pine bark is a promising, sustainable, and low-cost adsorbent for the treatment of antibiotic-contaminated water. The biochar synthesized via microwave pyrolysis not only exhibits high efficiency in ciprofloxacin removal but is also environmentally friendly, making it a viable material for wastewater treatment systems, especially those dealing with antibiotic residues from medical and agricultural sources.