Removal of Ciprofloxacin and Doxycycline Using a Recently Synthesized Triazine-Based Covalent Organic Framework As an Efficient Adsorbent

This study focused on synthesizing TPT-COF as an adsorbent and assessing its effectiveness in capturing two categories of antibiotics: tetracycline and quinolone, specifically targeting doxycycline (DOX) and ciprofloxacin (CIP). X-ray diffraction analysis revealed distinct, sharp peaks in the COF, confirming its high crystallinity. FE-SEM imaging showed that TPT-COF possessed a rod-like morphology, accompanied by filamentous structures that pointed to the presence of a polymeric network. Various parameters influencing antibiotic adsorption were thoroughly investigated, including pH values (spanning from 2 to 10), adsorbent masses (10–90 mg), initial antibiotic concentrations (20–60 mg/L), and contact times (20–100 min). Optimal conditions for the adsorption of DOX and CIP were identified as a pH of 6, an equilibrium time of 60 min, and adsorbent doses of 50 mg for DOX and 70 mg for CIP. Experimental equilibrium data were analyzed using adsorption isotherms based on the Langmuir and the Freundlich models, with the associated parameters calculated. The findings indicated that the adsorption of DOX and CIP antibiotics onto TPT‑COF aligned with the Freundlich isotherm. For both DOX and CIP, the adsorption data demonstrated a stronger correlation with the pseudo-second-order kinetic model (R2 = 0.9945 and 0.9929, respectively) compared to the pseudo-first-order model at pH 6. Additionally, various thermodynamic properties, including Gibbs free energy, enthalpy, and entropy, were assessed. The results confirmed that the process is endothermic and occurs spontaneously. These observations offer valuable insights into water purification technologies and open up avenues for further scientific exploration and practical industrial applications.