Ciprofloxacin adsorption via compressed wood activated carbon with ZnCl<sub>2</sub> activating agent from simulated wastewater: Mechanism studying

The current study objective is to synthesize activated carbon (AC) from compressed wood using the ZnCl2 activating agent and to assess the ciprofloxacin (CIP) elimination efficiency in simulated wastewater. The produced AC was characterized using multiple techniques, including SEM, BET, FTIR, AFM, and XRD. The adsorbent demonstrates high adsorption performance, achieving 91% removal of CIP within 5 hours at an initial pollutant concentration of 100 mg/L with an AC dose of 2 g/L. Experimental data correspond to the Freundlich isotherm model (R² = 0.995) as well as the Langmuir competitive fitting (R² = 0.99), while the root mean square error (RMSE) equation best fits the Langmuir model. Moreover, the pseudo-second-order model (R² = 0.999) was used to describe the kinetic data. The adsorption thermodynamics indicate spontaneous adsorption with exothermic behavior (ΔG◦<0, ΔH◦<0, ΔS◦<0). A combination of mechanisms contributed to the CIP adsorption process (π-π interaction, hydrophobic interaction, bulk diffusion, hydrogen bonds, in addition to physical and chemical adsorption mechanisms). Pyrolysis recoverability shows a good result after three cycles (qe = 101.08 mg/g, compared to 170.13 mg/g in the first cycle). In conclusion, compressed wood AC offers a sustainable, low-cost adsorbent for treating wastewater and presents a prospect for addressing ecosystem contamination challenges.