Studies on the oxidation of levofloxacin by N-bromosuccinimide in acidic medium and their mechanistic pathway

Levofloxacin degradation under visible-LED photo-catalyzing by a novel ternary Fe-ZnO/WO3 nanocomposite

As semiconductor photocatalysts showing their efficient redox ability upon illumination, new development of materials to enhance the pollution degradation is gaining popularity, especially on their oxidation ability. In this study, a highly stable ternary Fe-ZnO/WO₃ nanocomposite photocatalyst has been synthesized in order to improve charge transfer of photocatalytic oxidation under 30W LED light (425-470 nm) to efficiency degrade the Levofloxacin (LVF) in the solution. This catalyst was characterized and analyzed by XRD, FE-SEM, HR-TEM, X-ray XPS, UPS, PL, TRPL, LSV, EIS, and Photocurrent. Various important factors for the photodegradation were investigated, including Fe content, initial LVF concentration, catalyst dosage, and solution pH. The optimal conditions were Fe 1.0 wt%, LVF 10 mg L^-1, Fe-ZnO/WO₃ dosage 0.5 g L^-1, and pH 7 for LVF photodegradation up to 96% with a kinetic rate constant of 0.0342 min^-1 and were stable in photodegradation efficiency (90%) after five test cycles. In the visible LED light, the activation bandgap was estimated to be 2.75 eV with high electron-hole pair separation and charge transfer from Fe-ZnO to WO₃ that could enhance the generation of active species of ^•OH. Moreover, the more effective charge separation of Fe-ZnO/WO₃ were confirmed by lower PL intensity and longer charge carrier lifetime. Fe-ZnO/WO₃ also demonstrated the excellent electrochemical properties with high photocurrent and small resistance. For the LVF degradation, 3 possible pathways were proposed with 12 intermediate products. This study demonstrated that the synthesized Fe-ZnO/WO₃ could serve as a reliable visible-light responsive photocatalysts with the potential for degrading antibiotics in solution.

A sustainable ferromanganese biochar adsorbent for effective levofloxacin removal from aqueous medium

This present study reported the synthesis and characterization of a low-cost, environment friendly and high efficient biochar, ferromanganese modified biochar (Fe/Mn-BC) for the removal of levofloxacin (LEV) from aqueous medium. Fe/Mn-BC was synthesized through the facile co-precipitation of Fe, Mn with vinasse wastes and then pyrolysis under controlled conditions. The characterization of Fe/MnBC was analyzed by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction patterns (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman. Some influencing factors (e.g., pH, Fe/Mn-BC dosage, initial LEV concentration, ionic strength, contact time and temperature) were comprehensively investigated. The results manifested that the adsorption process of LEV onto Fe/Mn-BC was high pH dependence and the maximum adsorption capacity was achieved at pH 5. Moreover, the adsorption capacity of LEV was increased with increasing ionic strength. To gain a clearer perspective on the adsorption behavior of LEV onto Fe/Mn-BC, the adsorption kinetics and isotherms were also performed, revealing pseudo-second-order and Freundlich model had a better fitting effect. Reusability experiments indicated that Fe/Mn-BC could maintain a certain adsorption capacity for LEV after 5 recycles. Overall, this work showed that Fe/Mn-BC was an effective and promising adsorbent for eliminating LEV from aqueous medium.

Batch and fixed bed adsorption of levofloxacin on granular activated carbon from date (Phoenix dactylifera L.) stones by KOH chemical activation

Granular activated carbon (KAC) was prepared from abundant Phoenix dactylifera L. stones by microwave- assisted KOH activation. The characteristics of KAC were tested by pore analyses, scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR). The adsorption behavior of levofloxacin (LEV) antibiotic on KAC with surface area of 817m²/g and pore volume of 0.638cm³/g were analyzed using batch and fixed bed systems. The equilibrium data collected by batch experiments were well fitted with Langmuir compared to Freundlich and Temkin isotherms. The effect of flow rate (0.5-1.5ml/min), bed height (15-25cm), and initial LEV concentration (75-225mg/l) on the behavior of breakthrough curves was explained. The fixed bed analysis showed the better correlation of breakthrough data by both Thomas and Yoon-Nelson models. High LEV adsorption capacity of 100.3mg/g was reported on KAC, thus being an efficient adsorbent for antibiotic pollutants to protect ecological systems.