Ciprofloxacin adsorption using magnetic and ZnO nanoparticles supported activated carbon derived from Azolla filiculoides biomass

Contaminationwith pharmaceutical compounds, especially antibiotics, has become the focus of pollution control studies because of their high toxicity and difficulty in removing from aqueous media. In this study, activated carbon was prepared from Azolla filiculoides (ACAF) and magnetized using Fe₃O₄; finally, its further stabilization was done using ZnO nanoparticles (ACAF/Fe₃O₄/ZnO). The prepared adsorbent was used to remove ciprofloxacin (CIP) antibiotic from an aqueous solution. The adsorption–desorption process was performed in six consecutive runs, and only an 8% reduction was observed in the efficiency. Various parameters such as temperature, contact time, initial CIP concentration, nanocomposite concentration, and pH were examined. The results showed that removal of 100% was obtained at 75 min contact time for a CIP concentration of 10 mg/L at the optimum pH of 5 and temperature of 30 °C. The surface area and size of the nanocomposite were studied, which were equal to 1401 m² g⁻¹ and 2.26 nm, respectively. Also, the nanocomposite had a saturated magnetic property equal to 21.5 emu g⁻¹. Equilibrium data were analyzed using four isothermal models and four kinetic models, and four error coefficient models were used to ensure. Due to the high regression coefficient and lower error coefficient, the Langmuir isotherm and pseudo-second-order (PSO) kinetic model were more consistent with equilibrium data. Moreover, the adsorption capacity of the adsorbent according to the Langmuir model was equal to 147.7, 153.3, 165.6, and 178.8 mg/g at temperatures of 20, 30, 40, and 50 °C. Examination of thermodynamic quantities shows that ΔG° is negative and ΔH° is positive. Therefore, the adsorption occurs optimally and spontaneously and has endothermic nature. Finally, this study shows a sustainable and commercially viable route for the use of environmentally friendly compounds.