Synthesis of FE3O4-MWCNT structure and investigating of use its in antibiotic removal from aqueous solutions

In this study, the removal of sulfamethoxazole (SMZ) and oxytetracycline (OTC) antibiotics, which are frequently used in human and veterinary medical applications, from aqueous solutions using magnetic multi-walled carbon nanotubes (Fe3O4-MWCNT) was investigated. Synthesis of Fe3O4-MWCNT was carried out by chemical co-precipitation method and all experiments were modeled using the Response Surface Method (RSM). In the modeling study, parameters effective on percentage of antibiotic removal selected as the response variable were selected as the initial pH of solution, the concentration of antibiotic, the concentration of Fe3O4-MWCNT and the contact time. As a result of variance analysis (ANOVA), high regression coefficients were obtained for SMZ and OTC removals. In order to examine the effect of temperature on removal of SMZ and OTC antibiotics from aqueous solutions using Fe3O4-MWCNT, experiments were carried out depending on time at different constant temperatures (20, 30, 40 and 50 °C). These data were applied to pseudo-first order and pseudo-second order adsorption kinetic models, and the processes were found to better fit the pseudo-second order kinetic model. As a result of the isotherm studies, it was determined that SMZ adsorption is better compatible with Langmuir and Redlich Peterson isotherm and OTC adsorption is better fit Freundlich and Redlich Peterson isotherm. Thermodynamic parameters (ΔH°, ΔG°, ΔS°) were evaluated for the adsorption processes. ΔH° values were calculated as -16.08 and -17.44 kJ/mol for SMZ and OTC removals, respectively. The results were showed that adsorption processes are exothermic. ΔG° values were found to be negative at all temperatures where SMZ and OTC adsorption experiments were performed. This situation was showed that the processes occur spontaneously at the specified temperatures. The positive ΔS° values obtained were showed that SMZ and OTC molecules were adsorbed randomly to the Fe3O4-MWCNT surface. In addition, SEM, FT-IR, BET surface area and pHzpc analyzes were performed for the characterization of the synthesized Fe3O4-MWCTs. The surface and functional properties of both the synthesized Fe3O4-MWCNT and the post-adsorption Fe3O4-MWCNT have been revealed by characterization studies.