Catalytic degradation of metronidazole and ciprofloxacin antibiotics using silver-doped magnetic clay nanocomposites and process modeling via the artificial neural network method

In this thesis, bentonite nanoclay and halloysite nanotube clay were doped with Fe3O4 nanoparticles to impart magnetic properties and silver nanoparticles to increase their catalytic activity. Silver and Fe3O4 nanoparticles doped bentonite and halloysite nanocomposites (Ag-FeBNT and Ag-FeHNT) and NaBH4 were used to investigate the removal of metronidazole and ciprofloxacin antibiotics from solution media. In the study, the adsorption capacities of the nanocomposites, the efficiency of the degradation process using only NaBH4 and the efficiency of the catalytic degradation processes using nanocomposites and NaBH4 were compared. The results showed that while limited removal was achieved by adsorption and catalyst-free degradation, the catalytic degradation processes offered significantly higher efficiencies. In order to optimize the steps during nanocomposite synthesis, antibiotic removal experiments were carried out with the produced nanocomposites and silver doped magnetic clay nanocomposites were synthesised with the most efficient results. The nanocomposites obtained under optimum synthesis conditions were investigated by various characterization methods. These methods included Fourier Transform Infrared Spectroscopy, X-Ray Diffraction, Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy, Thermogravimetric Analysis, Vibrating Sample Magnetometer, X-Ray Photoelectron Spectroscopy, Brunauer, Emmett and Teller Surface Area Analysis, Point of Zero Charge pH measurements. Then, the effects of contact time, pH, NaBH4 concentration, nanocomposite dosage, antibiotic concentration and temperature parameters on the removal of antibiotics were evaluated and optimum removal conditions were determined. According to the results obtained, it was found that metronidazole was removed by 90% with Ag-FeBNT and 89% with Ag-FeHNT and ciprofloxacin was removed by 85% with Ag-FeBNT and 82% with Ag-FeHNT in 90 minutes under optimum conditions. Modeling of the removal processes was carried out using artificial neural network method and it was observed that the model successfully represented the processes. In the modeling study, the mean square error values of the overall data sets of the removal experiments with Ag-FeBNT and Ag-FeHNT were found to be 0.0014 and 0.0007 for metronidazole removal and 0.0011 and 0.0007 for ciprofloxacin removal, respectively. These values indicate that the model successfully represented the processes. Finally, the recyclability of nanocomposites in catalytic degradation processes was tested and it was observed that Ag-FeHNT could be used at least 6 times for metronidazole removal and both nanocomposites could be used at least 6 times for ciprofloxacin removal. However, it was determined that Ag-FeBNT lost efficiency after the first use in metronidazole removal. HPLC analysis after catalytic degradation proved that metronidazole and ciprofloxacin were degraded and possible reaction products were reported based on similar studies in the literature.