Removal of danofloxacin and ofloxacin as different generations of fluoroquinolones from aqueous solutions through the adsorption process using granular activated carbon: A comparative study, mechanism elucidation, and applicability investigation

Antibiotics are often found in wastewater, but they are rarely removed by conventional treatment methods. In this study, granular activated carbon manufactured from coconut shell char-coal was used as an adsorbent to remove two fluoroquinolone antibiotics-danofloxacin and oflox-acin-from synthetic wastewater. The solution was studied at various initial pH values (5.0, 7.0, and 9.0). Equilibrium studies were conducted at the optimal pH using different doses of adsorbate (10, 30, 50, and 70 mg/L), and kinetic analyses were performed at different time intervals (10, 30, 90, 120, 150, 180, 240, 300, 360, 1,400, and 4,320 min). Thermodynamic experiments were conducted at different temperatures (10, 25, and 40 degrees C), and desorption studies were conducted at different hydrochloric acid concentrations (0.2, 0.4, 0.6, and 0.8 M). The adsorbent's average surface area was 583.444 m2/g, determined using the Brunauer-Emmett-Teller method. The maximum removal efficiencies were 85 % and 88 % at adsorbent doses of 2,500 mg/50 mL, a pH of 5, and initial con-centrations of 30 mg/L for danofloxacin and ofloxacin. The experimental data was represented by the Temkin isotherm, and the adsorption mechanism was fitted to a pseudo-second-order kinetic model. The adsorption of danofloxacin and ofloxacin was found to be spontaneous and endother-mic. Moreover, 0.8 M HCl regenerated the granular activated carbon to 93.38 % and 93.95 % for 70 mg/L of danofloxacin and ofloxacin, respectively. (c) 2023 The Authors. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).