Removal of ciprofloxacin from aqueous solution by a three-dimensional electrocoagulation process using Fe3O4@AC nanocomposite as a particle electrode in combination with persulfate: nonlinear fitting of isotherms and kinetic models

Abstract

In the present study, the removal of ciprofloxacin (CIP) from aqueous solutions was performed using the magnetic Fe3O4@AC (MAC) nanocomposite as a particle electrode in three-dimensional electrocoagulation (EC) system, as well as using persulfate (PS) to increase the removal efficiency. First, the MAC nanocomposite was synthesized and then characterized by X-ray diffraction, vibrating-sample magnetometer and field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, Mapping and Fourier-transform infrared spectroscopy analyses. Each process was evaluated separately and the appropriate process was selected. The results confirmed the spherical structure of the MAC nanocomposite, with the smallest amount of clogging, uniform distribution of the elements on the nanoparticle surface and the creation of suitable magnetic properties. The CIP removal values for each of PS, EC, MAC, EC-MAC and EC-MAC-PS processes were 0, 0, 70, 94.2 and 98.9, respectively. However, since significant amounts of non-recoverable sludge were formed in the EC-MAC-PS process, no sludge was produced in the EC-MAC process, and only recoverable nanoparticles existed, PS was excluded from the tests. Finally, optimal conditions for the EC-MAC process were determined. Under the optimum conditions: CIP (10 mg/L), MAC (0.9 g/L), pH (7), current density (0.3 mA/cm(2)) and contact time (35 min) the CIP removal efficiency was 98.21. The results revealed that the Avrami fractionary and pseudo-second-order kinetic models fitted better the experimental results and Q(max) of MAC nanocomposite obtained from the Langmuir isotherm model was 97.39 mg/g. Based on the results, the EC-MAC process has a good efficiency in removing the CIP antibiotic and can be considered as an economical process.