Novel WO3/Fe3O4 magnetic photocatalysts: Preparation, characterization and thiacloprid photodegradation

A highly sensitive fluorescence immunochromatography strip for thiacloprid in fruits and vegetables using recombinant antibodies

Thiacloprid (TCL) is a neonicotinoid insecticide. Its widespread use has led to high levels of residue in fruits and vegetables. Hence, it is important to detect TCL rapidly, accurately, and sensitively in fruits and vegetables. Recombinant antibodies (rAbs) can be synthesized rapidly with little batch-to-batch variation. In this study, recombinant single-chain variable fragment (scFv) antibody and full-length recombinant antibody against TCL were produced using three different expression systems (E. coli, yeast, and mammalian cell). The results of SDS-PAGE and non - competitive enzyme-linked immunosorbent assay (ELISA) indicated that the full-length rAb exhibited promising characteristics, and the IC₅₀ value of indirect competitive ELISA (ic-ELISA) was 2.63 μg L^-1. However, recombinant scFv antibody had little affinity for the antigen. To understand antibody recognition, the three-dimensional (3D) model of the variable fragment (Fv) was built via homologous modeling. The interaction between Fv and TCL was analyzed via molecular docking and the results of molecular docking showed that VAL-158, ALA-211, PHE-220, TRP-218, TRP-49, and ILE-100 were mainly responsible for antibody recognition. In addition, a time-resolved fluorescent microsphere-immunochromatographic test strip (TRFM-ICTS) was developed with a linear range and limit of detection of 0.01-10 ng mL^-1 and 0.003 ng mL^-1 within 15 min under optimal conditions. The IC₅₀ value was 4.268 ng mL^-1, and the recovery ranged between 79.4% and 118.6%, which was consistent with HPLC-MS. The TRFM-ICTS has great advantages in sensitivity and applicability.

FexO4-enhanced degradation of bisphenol A in visible light/peroxydisulfate system: production of singlet state oxygen

In this study, ferrous composites (Fe_xO₄) were prepared by microreactor to activate peroxydisulfate (PDS) for the degradation of bisphenol A (BPA) with visible (Vis) light irradiation. X-ray diffraction (XRD), energy-dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM) were used to characterize the morphology and crystal phase of Fe_XO₄. Photoluminescence (PL) spectroscopy combined with amperometric tests were used to determine the role of PDS on the performance of photocatalytic reaction. The main reactive species and intermediates for BPA removal were determined by electron paramagnetic resonance (EPR) measurement and quenching experiments. The result indicated that singlet state oxygen (¹O₂) contributed more to the BPA degradation than that of other reactive radicals (·OH, SO₄^·- and ·O₂^-); these reactive radicals and ¹O₂ formed by the reaction between photo-generated electrons (e^-) and holes (h⁺) of Fe_xO₄ and PDS. During this process, the consumption of e^- and h⁺ also improved their separation efficiency and thus enhanced the degradation of BPA. In addition, the photocatalytic activity of Fe_xO₄ in Vis/Fe_xO₄/PDS system was 3.2-fold and 6.6-fold higher than that of single Fe_xO₄ and PDS under Vis light, respectively. The Fe²⁺/Fe³⁺ cycle could effectively drive the photocatalytic activation of PDS through indirect electron transfer and the formation of reactive radicals. This work illustrated that the degradation of BPA was rapidly in Vis/Fe_xO₄/PDS system mainly through ¹O₂, which further improve our understanding on the efficient removal of organic contaminants in the environment.

Rapid Removal of Organic Pollutants from Aqueous Systems under Solar Irradiation Using ZrO2/Fe3O4 Nanoparticles

Pure water scarcity is an emerging, all-around problem that globally affects both the life quality and the world's economy. Heterogeneous photocatalysis under solar irradiation is a promising technique for the organic pollutants (e.g., pesticides, drugs) removal from an aqueous environment. Furthermore, the drawbacks of commercially available photocatalysts can be successfully overcome by using innovative nanoparticles, such as ZrO₂/Fe₃O₄. Four ZrO₂/Fe₃O₄ nanopowders with a different mass ratio of ZrO₂ and Fe₃O₄ were synthesized using the chemical co-precipitation method. XRD analysis showed the presence of magnetite and hematite Fe-oxide phases in all samples. The content of the magnetite phase increased with the addition of 19% ZrO₂. The efficiency of the newly synthesized ZrO₂/Fe₃O₄ nanoparticles was investigated in the rapid removal of selected pollutants under various experimental conditions. Nevertheless, the influence of the water matrix on photocatalytic degradation was also examined. The obtained data showed that using ZrO₂/Fe₃O₄ nanosystems, an appropriate removal rate of the selected pesticides and pharmaceuticals can be reached after 120 min of solar irradiation. Further, the total organic carbon measurements proved the mineralization of the target emerging pollutants. ZrO₂/Fe₃O₄ nanoparticles are economically feasible, as their removal from the suspension can be easily achieved using affordable, environmentally-friendly magnetic separation.

Detection of Neonicotinoids in agriculture soil and degradation of thiacloprid through photo degradation, biodegradation and photo-biodegradation

The social and ecological influence of Neonicotinoids (NEOs) usage in agriculture sector is progressively higher. There are seven NEOs insecticides widely used for the insects control. Among the NEOs, thiacloprid (THD) was extensively used for insect control during crop cultivation. This study targets to analyse the contamination levels of NEOs in agricultural soil and identify photo-biodegradation of THD degradation using pure isolates and mixed consortium. The photo degradation (PD), biodegradation (BD) and photo-biodegradation (PBD) of THD were compared. The corn field agricultural soils were polluted by four NEOs, among them THD had greater contamination level (surface soil: 3901.2 ± 0.04 μg/g) and (sub-surface soil: 3988.6 ± 0.05 μg/g). Three soil free enriched bacterial strains following Bacillus atrophaeus (PB-2), Priestia megaterium (PB-3) (formerly known as Bacillus megaterium), and Peribacillus simplex (PB-4) (formerly known as Bacillus simplex) were identified by microbiological and molecular 16s rRNA gene sequencing. The PD, BD and PBD of THD were conducted and degradation rate was detected by instrument UPLC-MS-MS. The PBD process with blue-LEDs showed better THD degradation efficiency than PD and BD, where the specific THD degradation rate was 85 ± 0.2%, 87 ± 0.5%, and 89 ± 0.3%, respectively for PB-2, PB-3 and PB-4. Then, the photo-biodegradation performance is greater at 150, 175, 200 rpm, pH 7.0-9.0, and temperature 30-35 °C. After the PBD system deliver four intermediate metabolites, the THD degradation process maybe through nitro reduction, hydroxylation and oxidative cleavage pathway.

Tailored functional materials as robust candidates to mitigate pesticides in aqueous matrices-a review

Pesticides are among the top-priority contaminants, which significantly contribute to environmental deterioration. Conventional techniques are not efficient enough to remove pollutants from environmental matrices. The development of functional materials has emerged as promising candidates to remove and degrade pesticides and related hazardous compounds. Furthermore, the nanohybrid materials with unique structural and functional characteristics, such as better material anchorage, mass transfer, electron-hole separation, and charged interaction make them a versatile option to treat and reduce pollutants from aqueous matrices. Herein, we present the current progress in the development of functional materials for the abatement of toxic pesticides. The physicochemical characteristics and pesticide-removal functionalities of various metallic functional materials (e.g., zirconium, zinc, titanium, tungsten, and iron), polymer, and carbon-based materials are critically discussed with suitable examples. Finally, the industrial-scale applications of the functional materials, concluding remarks, and future directions in this important arena are given.

Synthesis and photocatalytic degradation of rhodamine B using ternary zeolite/WO3/Fe3O4composite

Demand for freshwater increases day by day as impurity increases due to the industrial, domestic and municipal waste in the water. Inappropriate disposal of coal fly ash (CFA) is not eco-friendly, therefore the need is to convert it into some beneficial material like zeolite. Zeolite-based composites with metal oxides show high cation interchange capacity, fast adsorption, and high efficiency for the removal of wastewater pollutants. In this research work, metal oxide along with zeolite (derived for CFA) was prepared. Metal oxide (WO₃) and magnetite (Fe₃O₄) based zeolite composite was used adsorption enhanced photocatalytic degradation of rhodamine B dye. Ternary composite (zeolite/WO₃/Fe₃O₄) was characterized using a scanning electron microscope, x-ray diffraction, Fourier transform infrared spectroscopy. The bandgap energy of composite was estimated using Tauc plot method from the data obtained after UV-visible spectroscopy. The behavior of composite under acidic and basic conditions was analyzed using pH_pzcof the composite. Influencing parameters like pH, dye concentration, contact time, and catalyst dosage was optimized under ultraviolet irradiations (254 nm). The results show that maximum degradation was achieved with zeolite/WO₃/Fe₃O₄composite under optimized conditions of pH = 7, catalyst dosage = 10 mg/100 ml, RhB concentration 10 ppm, and time 60 min. The first-order kinetic model was best fitted to the experimental data. RSM was used as a statistical tool to analyze the data.