Ofloxacin degradation by Fe3O4-CeO2/AC Fenton-like system: Optimization, kinetics, and degradation pathways

Photo-transformation of ofloxacin in natural aquatic conditions: Impact of indirect photolysis on the product profile and transformation mechanism

The natural phototransformation of organic pollutants in the environment depends on several water constituents, including inorganic ions, humic substances, and pH. However, the literature information concerning the influence of various water components on the amount of phototransformation and their impact on the development of various transformation products (TPs) is minimal. This study investigated the phototransformation of ofloxacin (OFL), a fluoroquinolone antibiotic, in the presence of various water components such as cations (K+, Na+, Ca2+, NH4+, Mg2+), anions (NO3-, SO42-, HCO3-, CO32-, PO43-), pH, and humic substances when exposed to natural sunlight. The study reveals that neutral pH levels (0.39374 min⁻1) enhance the phototransformation of OFL in aquatic environments. Carbonate, among anions, shows the highest rate constant (2.89966 min⁻1), significantly influencing OFL phototransformation, while all anions exhibit a notable impact. In aquatic environments, indirect phototransformation of OFL, driven by increased reactive oxygen species, expedites light-induced reactions, potentially enhancing OFL phototransformation. A clear difference was visible in the type of transformation products (TPs) formed during direct and indirect photolysis. The impact of indirect photolysis in the product profile was evaluated by examining the unique properties of TPs in direct and indirect photolysis. The primary transformation products were generated by oxidation and cleavage processes directed towards the ofloxacin piperazinyl, oxazine, and carboxyl groups. The toxicity assessment of TPs derived from OFL revealed that among the 26 identified TPs, TP3 (demethylated product), TP7 and TP8 (decarboxylated products), and TP15 (piperazine ring cleaved product) could potentially have some toxicological effects. These findings suggest that the phototransformation of OFL in the presence of various water components is necessary when assessing this antibiotic's environmental fate.

Fabrication of novel magnetic Mg0.8Cu0.2Fe2O4/SiO2/CeO2 nanocomposite synthesized by a simple ultrasonic-assisted route for organic dye removal using Fenton-like reaction

Fenton-like degradation of contaminants is considered to be a feasible method for eliminating environmental pollution. In this study, a novel ternary Mg_0.8Cu_0.2Fe₂O₄/SiO₂/CeO₂ nanocomposite was fabricated using a novel ultrasonic-assisted technique, and investigated as a Fenton-like catalyst for the removal of tartrazine (TRZ) dye. The nanocomposite was synthesized by first coating the SiO₂ shell around the Mg_0.8Cu_0.2Fe₂O₄ core via a Stöber-like process to form Mg_0.8Cu_0.2Fe₂O₄/SiO₂. Then, a simple ultrasonic-assisted route was used to synthesize Mg_0.8Cu_0.2Fe₂O₄/SiO₂/CeO₂ nanocomposite. This approach provides a simple and environmentally friendly way to produce this material without the use of any additional reductants or organic surfactants. The fabricated sample demonstrated excellent Fenton-like activity. The efficiency of Mg_0.8Cu_0.2Fe₂O₄ was significantly enhanced by the incorporation of SiO₂ and CeO₂, and complete removal of TRZ (30 mg/L) was achieved within 120 min using 0.2 g/L of Mg_0.8Cu_0.2Fe₂O₄/SiO₂/CeO₂. The scavenger test shows that the main active species is the strong oxidizing of hydroxyl radicals (HO^•). Consequently, the Fenton-like mechanism of Mg_0.8Cu_0.2Fe₂O₄/SiO₂/CeO₂ is explained based on the coexistence of Fe³⁺/Fe²⁺, Cu²⁺/Cu⁺, and Ce⁴⁺/Ce³⁺ redox couples. The removal efficiency of TRZ dye remained around 85% after the third recycling run, revealing that the nanocomposite could be employed to eliminate organic contaminants in water treatment. This research opened up a new avenue for expanding the practical application of new-generation Fenton-like catalysts.

Fulvic acid degradation in Fenton-like system with bimetallic magnetic carbon aerogel Cu-Fe@CS as catalyst: Response surface optimization, kinetic and mechanism

In this study, Cu-Fe bimetallic magnetic chitosan carbon aerogel catalyst (Cu-Fe@CS) was prepared by the sol-gel method to degrade Fulvic acid (FA) in Fenton-like system. Degradation experiment results showed bimetallic catalyst Cu-Fe@CS can degrade more FA than monometallic catalysts (Cu@CS and Fe@CS) due to the synergistic effect between the copper and iron. Plackett Buiman (PB) design showed that pH and temperature exhibited significant influence on FA degradation. The significant factors were optimized by Central Composite Design (CCD), the results revealed that the maximum FA removal reached 96.59% under the conditions of pH 4.07 and temperature 93.77 °C, the corresponding TOC removal reached 77.7%. The kinetic analysis implied that the reaction followed pseudo-first order kinetic with correlation coefficient (R²) = 0.9939. The Arrhenius fitting analysis revealed that Cu-Fe@CS had a lower activation energy (Ea) than Cu@CS and Fe@CS, meaning that reaction was easier to occur in Fenten-like system with Cu-Fe@CS. Catalyst still remained the higher FA and TOC removals of 96.28% and 77.33% after six runs, respectively. The FA removal was reduced by 65.53% with 12 mmol tertiary butanol (TBA) as scavenger, indicating that •OH played an important role in FA degradation. Finally, the catalytic degradation mechanism was proposed.

Optimization of heterogeneous Fenton-like process with Cu-Fe@CTS as catalyst for degradation of organic matter in leachate concentrate and degradation mechanism research

The heterogeneous Fenton-like process with bimetallic chelated magnetic chitosan aerogel (Cu-Fe@CTS) as catalyst was applied to treat pre-coagulated leachate nanofiltration concentrate. The process conditions were optimized by Box-Behnken Design (BBD) and the maximum UV₂₅₄ removal reached 96.06% under the conditions of temperature 87.62 °C, oxidant dosage 0.2395 mol/L and catalyst dosage 1 g/L. The TOC concentration was reduced from 847.5 to 99.7 mg/L and COD concentration was reduced from 1625 to 464 mg/L. The three-dimensional (3D) fluorescence analysis showed that most of Fulvic acid-like (FA-like) was removed. The adsorption experiment showed that the catalyst reached the adsorption balanced after 60 min and the corresponding FA adsorption removal reached 14.1%. The addition of Tert-butanol (TBA) reduced the FA removal by 59.4%, indicating that the hydroxyl radicals (OH) was the main active species. Experiments of the OH capture at different pH showed that the Fenton-like system produced more OH at pH of 4, at which the maximum FA removal was 96.61%, while the FA removal still reached 94.26% at pH of 7. The OH capture at different temperature showed that the Fenton-like system produced more OH at 90 °C. KI and TBA shielding experiments showed that OH was produced on the catalyst surface rather than being produced by catalysis of free metal ions in the solution.

Enhanced removal of pefloxacin from aqueous solution by adsorption and Fenton-like oxidation using NH2-MIL-88B

While Fe-based metal-organic frameworks (MOFs) can be used to remove antibiotics by adsorption, knowledge of how antibiotics are degraded by MOFs is still limited. In this study, one Fe-based MOF, NH₂-MIL-88B was used to remove pefloxacin from aqueous solution via a combination of adsorption and Fenton-like oxidation. NH₂-MIL-88B exhibited a high adsorption capacity for pefloxacin (41.37 mg·g^-1), with >99% removal efficiency within 120 min based on Fenton-like oxidation. To better understand the mechanisms involved in integrated adsorption and Fenton-like oxidation, various advanced characterization techniques were used to monitor the changes in morphology and composition of NH_2-MIL-88B before and after removal of pefloxacin. Scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) all supported adsorption and Fenton oxidation of pefloxacin. In addition, the pefloxacin degradation products identified by LC-UV and LC-MS provided information on the potential adsorption-Fenton oxidation mechanism. These results suggested that NH₂-MIL-88B has remarkably potential to be used in an integrated adsorption and Fenton-like process for the removal of antibiotics from aqueous solution.

Fenton Degradation of Ofloxacin Using a Montmorillonite–Fe3O4 Composite

In this work, FeM composites consisting of montmorillonite and variable amounts of Fe3O4 were successfully synthesized via a facile co-precipitation process. They were characterized using X-ray photoelectron spectroscopy (XPS), a field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDX), a transmission electron microscope (TEM), N2 adsorption–desorption, and Fourier transform infrared spectroscopy (FTIR) techniques to explain the effect of Fe3O4 content on the physicochemical properties of the Fe3O4–montmorillonite (FeM) composites. The FeM composites were subsequently used as heterogeneous Fenton catalysts to activate green oxidant (H2O2) for the subsequent degradation of ofloxacin (OFL) antibiotic. The efficiency of the FeM composites was studied by varying various parameters of Fe3O4 loading on montmorillonite, catalyst dosage, initial solution pH, initial OFL concentration, different oxidants, H2O2 dosage, reaction temperature, inorganic salts, and solar irradiation. Under the conditions of 0.75 g/L FeM-10, 5 mL/L H2O2, and natural pH, almost 81% of 50 mg/L of OFL was degraded within 120 min in the dark, while total organic carbon (TOC) reduction was about 56%. Although FeM composites could be a promising heterogeneous catalyst for the activation of H2O2 to degrade organic pollutants, including OFL antibiotic, the FeM-10 composite shows a significant drop in efficiency after five cycles, which indicates that more studies to improve this weakness should be conducted.

The Potential of Chaetoceros muelleri in Bioremediation of Antibiotics: Performance and Optimization

Antibiotics are frequently applied to treat bacterial infections in humans and animals. However, most consumed antibiotics are excreted into wastewater as metabolites or in their original form. Therefore, removal of antibiotics from aquatic environments is of high research interest. In this study, we investigated the removal of sulfamethoxazole (SMX) and ofloxacin (OFX) with Chaetoceros muelleri, a marine diatom. The optimization process was conducted using response surface methodology (RSM) with two independent parameters, i.e., the initial concentration of antibiotics and contact time. The optimum removal of SMX and OFX were 39.8% (0.19 mg L⁻¹) and 42.5% (0.21 mg L⁻¹) at the initial concentration (0.5 mg L⁻¹) and contact time (6.3 days). Apart from that, the toxicity effect of antibiotics on the diatom was monitored in different SMX and OFX concentrations (0 to 50 mg L⁻¹). The protein (mg L⁻¹) and carotenoid (μg L⁻¹) content increased when the antibiotic concentration increased up to 20 mg L⁻¹, while cell viability was not significantly affected up to 20 mg L⁻¹ of antibiotic concentration. Protein content, carotenoid, and cell viability decreased during high antibiotic concentrations (more than 20 to 30 mg L⁻¹). This study revealed that the use of Chaetoceros muelleri is an appealing solution to remove certain antibiotics from wastewater.

Fe3O4-Zeolite Hybrid Material as Hetero-Fenton Catalyst for Enhanced Degradation of Aqueous Ofloxacin Solution

A hetero-Fenton catalyst comprising of Fe3O4 nanoparticles loaded on zeolite (FeZ) has been synthesized using a facile co-precipitation method. The catalyst was characterized using various characterization methods and then, subsequently, was used to degrade ofloxacin (OFL, 20 mg·L−1), an antibiotic, via a heterogeneous Fenton process in the presence of an oxidizing agent. The effects of different parameters such as Fe3O4 loading on zeolite, catalyst loading, initial solution pH, initial OFL concentration, different oxidants, H2O2 dosage, reaction temperature, and inorganic salts were studied to determine the performance of the FeZ catalyst towards Fenton degradation of OFL under different conditions. Experimental results revealed that as much as 88% OFL and 51.2% total organic carbon (TOC) could be removed in 120 min using the FeZ catalyst. Moreover, the FeZ composite catalyst showed good stability for Fenton degradation of OFL even after five cycles, indicating that the FeZ catalyst could be a good candidate for wastewater remediation.

Mechanistic insight into ultrasound-induced enhancement of electrochemical oxidation of ofloxacin: Multi-response optimization and cost analysis

In this paper, a hybrid advanced oxidation process of sonoelectrochemical, in which ultrasound and electrochemical are applied simultaneously, has been used for the degradation of ofloxacin (bio-recalcitrant pharmaceutical pollutant). Response surface methodology based central composite design was applied to understand the parametric effects of ultrasonic power, current density, initial pH, and electrolyte dose. Enhanced ofloxacin degradation was obtained using sonoelectrochemical (≈95%) process in comparison to the electrochemical (≈60.6%) and sonolysis alone (≈7.2%) after 120 min treatment time. Multi-response optimization was used so as to maximize COD removal (70.12%) and minimize specific energy consumption (11.92 kWh (g COD removed)^-1)at the optimized parametric condition of pH = 6.3 (natural pH), ultrasonic power = 54 W, current density = 213 A m^-2, and Na₂SO₄ electrolyte dose = 2.0 g L^-1. It was revealed that ^•OH radicals contribute major to the ofloxacin degradation reaction among the other oxidizing agents. Degradation of the ofloxacin followed pseudo-first-order kinetics with a higher reaction rate, which confirmed the synergistic effect of 34% between ultrasound and electrochemical approaches. The degradation pathway of ofloxacin removal was elucidated at optimum condition by the temporal evolution of the intermediate compounds and final products using gas chromatography coupled with mass spectroscopy (GC-MS), liquid chromatography-mass spectroscopy (LC-MS), high-resolution mass spectroscopy (HR-MS), and Fourier transform infrared spectroscopy (FTIR). Atomic force microscopy (AFM) and field emission scanning electron microscope (FE-SEM) coupled with energy dispersed X-ray (EDX) were used to determine the morphology of electrodes. Operational cost analysis was done based on the reactor employed in the present study.