Synthesis and characterization of pine cones biochar for the removal of an antibiotic (Metronidazole) from aqueous solutions

Abstract

This study aimed to develop a potential biochar derived from pine cones for the removal of metronidazole from water. Biochars were prepared at three different pyrolysis temperatures (500, 700, and 900 °C) in order to select the best biochar with the highest metronidazole removal efficiency. The findings showed that the specific surface area increased with increasing pyrolysis temperature: 64.77 m2/g for 500 °C, 353.97 m2/g for 700 °C, and 597.97 m2/g for 900 °C, as well as the micropore volume, which increased by 89.18% when the temperature increased from 500 to 900 °C. This improvement favors the pore-filling mechanism. The structural aromatic carbon is formed when the hydrogen, oxygen, and volatile carbon are removed. Thus, the π-π interaction mechanism is included in metronidazole adsorption since it is an organic pollutant with an aromatic structure. The adsorption kinetics results highlighted that metronidazole was effectively removed (98.57%) when using PCB-900 °C. The kinetic adsorption was described by the pseudo-second-order model. The adsorption capacity of the Langmuir isotherm was 138.94 mg/g. It also appeared that the pH medium did not have a considerable effect on metronidazole adsorption, indicating that electrostatic interactions did not have a significant effect on the process. According to the thermodynamic study, the adsorption of metronidazole was spontaneous and endothermic. The reuse of PCB-900 °C was tested in 8 cycles with an efficiency decreasing from 98.57% to 37.89%. Thus, it can be concluded that the PCB-900 °C constitutes a promising adsorbent for metronidazole removal from aqueous solutions.