Decontamination of tetracycline from aqueous solution using activated carbon/Fe3O4/ZIF-8 nanocomposite adsorbent

The increase in the amount of antibiotics in water sources, especially after the spread of COVID-19, has caused serious environmental problems. Therefore, finding a suitable adsorbent for these pollutants is a new and serious challenge for researchers. In this study, magnetic activated carbon (AC/Fe3O4) was selected as a novel support to zeolitic imidazolate framework (ZIF-8) to create magnetic separation properties besides promoting its tetracycline (TC) removal efficiency. The successful formation of AC/Fe3O4/ZIF-8 nanocomposite was proved by FTIR, XRD, and SEM-EDX analysis. The surface area of AC/Fe3O4/ZIF-8 nanocomposite was computed at 996.38 m2/g using BET analysis. The maximum removal efficiency was obtained in the optimum condition of adsorption parameters, e.g., pH = 7, dose 1 g/L, initial concentration 20 mg/L, contact time 30 min, and temperature 25 °C. The maximum adsorption capacity (qmax) of AC, AC-H3PO4, AC/Fe3O4, ZIF-8, and AC/Fe3O4/ZIF-8 using Langmuir isotherm was obtained at 25.28, 30.03, 45.45, 51.2, and 57.47 mg/g, respectively revealing the effectiveness of AC/Fe3O4 in improving elimination performance of ZIF-8. Thermodynamically, the removal process of TC using AC/Fe3O4/ZIF-8 nanocomposite happened spontaneously and exothermally due to negative values of ΔG° (-6.94 kJ/mol) and ΔH° (-36.44 kJ/mol). The removal performance of AC/Fe3O4/ZIF-8 nanocomposite after four ad(de)sorption cycles is nearly constant (about 86 %) showing their stability in acidic and water media. Hydrogen bonding, electrostatic interaction, and π-π interactions are main mechanisms in TC removal by AC/Fe3O4/ZIF-8 nanocomposite. The results demonstrate that prepared adsorbents, mainly AC/Fe3O4/ZIF-8 nanocomposite, can be applied as recyclable and efficient adsorbents for TC elimination.