Comparison of sunlight-AOPs for levofloxacin removal: kinetics, transformation products, and toxicity assay on Escherichia coli and Micrococcus flavus

Deciphering the mechanism for encapsulation of MOF (Fe-glutaric acid) onto Se/SnO2 embedded CMC for effective aqueous sequestration of pharmaceutical pollutant via adsorption

Wastewater is commonly contaminated with many pharmaceutical pollutants, so an efficient purification method is required for their removal from wastewater. In this regard, an innovative tertiary Se/SnO2@CMC/Fe-GA nanocomposite was synthesized through encapsulation of metal organic frameworks (Fe-glutaric acid) onto Se/SnO2-embedded-sodium carboxy methyl cellulose matrix to thoroughly evaluate its effectiveness for adsorption of levofloxacin drug from wastewater. The prepared Se/SnO2@CMC/Fe-GA nanocomposite was analyzed via UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) to valuate optical property, size, morphology, thermal stability, and chemical composition. The results revealed that prepared Se/SnO2@CMC/Fe-GA nanocomposite was crystalline and porous having average particle size of 6.23 nm with energy band gap of 2.60 eV. Specific heat energy of Se/SnO2@CMC/Fe-GA nanocomposite was found to be 0.028 Jg-1 °C-1. Different experimental factors for example, time, temperature, concentration of LEVO, catalyst dose, ionic strength, and pH were optimized for maximum removal of levofloxacin from wastewater. The tertiary Se/SnO2@CMC/Fe-GA nanocomposite showed 99% removal efficiency for levofloxacin at pH = 7, with contact time of 60 min at 50 °C temperature. The adsorption kinetics followed pseudo-second order. Among adsorption isotherm models, Langmuir model was found most appropriate which revealed that the process was chemisorption. Main mechanism of adsorption is pore diffusion that is confirmed from Bangham, Boyd, Crank and PVSDM kinetic models. Spontaneity and endothermic nature of the process were confirmed by the values of thermodynamic parameters. Toxicity of effluent and impact of interfering ions on adsorption were also investigated. Swelling ratio of Se/SnO2@CMC/Fe-GA nanocomposite was calculated, and nanocomposite showed better results and chemical stability even after five cycles.

s-scheme3D/3D Bi0/BiOBr/P Doped g-C3 N4 with Oxygen Vacancies (Ov) for Photodegradation of Pharmaceuticals: In-situ H2O2 Production and Plasmon Induced Stability

Complications accompanying photocatalyst stability and recombination of exciton charges in pollutants degradation has been addressed through the construction of heterojunctions, especially S-scheme heterojunction with strong and distinctive redox centres. Herein, an S-scheme BiOBr (BOR) and g-C3N4PO4 (CNPO) catalyst (BORCNPO) with oxygen vacancy (Ov) was synthesized for levofloxacin (LVX) and oxytetracycline (OTC) photodegradation under visible light. The 3D/3D BORCNPO catalyst possessed C-O-Br bridging bonds for efficient charge transfer during the fabrication of S-scheme heterojunction. In-situ H2O2 formation affirmed by potassium titanium (IV) oxalate spectrophotometric method improved the mineralization ability of BORCNPO7.5 catalyst. Bi0 surface plasmon resonance (SPR) enhanced formation and involvement of ⋅O2 - and the stability of the catalyst which increased reaction rate with increasing cycling experiments. XPS and radical trapping experiments supported the S-scheme charge transfer mechanism formation with high degradation rate of LVX which was 3 times higher than OTC degradation rate. Mineralization of pollutants and their intermediates were demonstrated with florescence excitation and emission matrix (FEEM) and quadruple time of flight high performance liquid chromatography (QTOF-HPLC). This work advances development of highly stable and efficient catalysts for photodegradation of pollutants through the formation of S-scheme heterostructure.

Biotransformation of the Fluoroquinolone Antibiotic, Levofloxacin, by the Free and Immobilized Secretome of Coriolopsis gallica

Antibiotics play a crucial role in human and animal medical healthcare, but widespread use and overuse of antibiotics poses alarming health and environmental issues. Fluoroquinolones constitute a class of antibiotics that has already become ubiquitous in the environment, and their increasing use and high persistence prompt growing concern. Here we investigated a fungal secretome prepared from the white-rot fungus Coriolopsis gallica, which is able to effectively degrade the environmentally persistent fluoroquinolone, levofloxacin. We tested various physical-chemical factors such as concentrations of 1-hydroxybenzotriazol (HBT), of enzyme, and of antibiotic, and pH and temperature of the reaction for biotransformation of the antibiotic. We compared the free with the immobilized Coriolopsis gallica secretome proteins, and analyzed the collective reaction products for residual activity against E. coli (growth inhibition test). We also performed HPLC analysis. The results show that treatment with the free secretome yielded a highest removal efficiency of 50 mg L-1 levofloxacin in the presence of 2.5 mM HBT, whereas the immobilized secretome was only able to degrade 10 mg L-1 levofloxacin with the same concentration of mediator, but presenting the advantage of being reusable.

Insight into typical photo-assisted AOPs for the degradation of antibiotic micropollutants: Mechanisms and research gaps

Due to the incomplete elimination by traditional wastewater treatment, antibiotics are becoming emerging contaminants, which are proved to be ubiquitous and promote bacterial resistance in the aquatic systems. Antibiotic pollution has raised particular concerns, calling for improved methods to clean wastewater and water. Photo-assisted advanced oxidation processes (AOPs) have attracted increasing attention because of the fast reaction rate, high oxidation capacity and low selectivity to remove antibiotics from wastewater. On the basis of latest literature, we found some new breakthroughs in the degradation mechanisms of antibiotic micropollutants with respect to the AOPs. Therefore, this paper summarizes and highlights the degradation kinetics, pathways and mechanisms of antibiotics degraded by the photo-assisted AOPs, including the UV/O3 process, photo-Fenton technology, and photocatalysis. In the processes, functional groups are attacked by hydroxyl radicals, and major structures are destroyed subsequently, which depends on the classes of antibiotics. Meanwhile, their basic principles, current applications and influencing factors are briefly discussed. The main challenges, prospects, and recommendations for the improvement of photo-assisted AOPs are proposed to better remove antibiotics from wastewater.

Electrochemical oxidation of fipronil pesticide is effective under environmental relevant concentrations

Pesticide overuse has posed a threat to agricultural community as well as for the environment. In order to treat this pollution at its source, decentralized and selective technologies such as electrochemical processes appear especially relevant to avoid the possible generation of toxic degradation products. Electrochemical oxidation (ECO) is a promising electrochemically-driven process, but most studies evaluate performance under pollutant concentrations that are orders of magnitude higher than environmental relevant conditions. This work explores ECO treatment of fipronil using boron-doped diamond (BDD) as anode and titanium plate as cathode at small concentrations found in agricultural run-off. The effect of applied current density and initial contaminant concentrations were also studied. For a current density of 20 mA cm^-2 the decrease of COD and fipronil were about 97% and 100% after 360 min of electrolysis, respectively. Engineering figures of merit were evaluated to assess competitiveness of ECO decentralized propositions. Results suggest effective and feasible treatment of fipronil by ECO.

Biotransformation of the Fluoroquinolone, Levofloxacin, by the White-Rot Fungus Coriolopsis gallica

The wastewater from hospitals, pharmaceutical industries and more generally human and animal dejections leads to environmental releases of antibiotics that cause severe problems for all living organisms. The aim of this study was to investigate the capacity of three fungal strains to biotransform the fluoroquinolone levofloxacin. The degradation processes were analyzed in solid and liquid media. Among the three fungal strains tested, Coriolopsis gallica strain CLBE55 (BRFM 3473) showed the highest removal efficiency, with a 15% decrease in antibiogram zone of inhibition for Escherichia coli cultured in solid medium and 25% degradation of the antibiotic in liquid medium based on high-performance liquid chromatography (HPLC). Proteomic analysis suggested that laccases and dye-decolorizing peroxidases such as extracellular enzymes could be involved in levofloxacin degradation, with a putative major role for laccases. Degradation products were proposed based on mass spectrometry analysis, and annotation suggested that the main product of biotransformation of levofloxacin by Coriolopsis gallica is an N-oxidized derivative.