Influencing Factors in the Synthesis of Photoactive Nanocomposites of ZnO/SiO2-Porous Heterostructures from Montmorillonite and the Study for Methyl Violet Photodegradation

In this work, photoactive nanocomposites of ZnO/SiO2 porous heterostructures (PCHs) were prepared from montmorillonite clay. The effects of preparation methods and Zn content on the physicochemical features and photocatalytic properties were investigated. Briefly, a comparison of the use of hydrothermal and microwave-assisted methods was done. The Zn content was varied between 5 and 15 wt% and the characteristics of the nanomaterials were also examined. The physical and chemical properties of the materials were characterized using X-ray diffraction, diffuse-reflectance UV-Vis, X-ray photoelectron spectroscopy, and gas sorption analyses. The morphology of the synthesized materials was characterized through scanning electron microscopy and transmission electron microscopy. The photocatalytic performance of the prepared materials was quantified through the photocatalytic degradation of methyl violet (MV) under irradiation with UV and visible light. It was found that PCHs exhibit greatly improved physicochemical characteristics as photocatalysts, resulting in boosting photocatalytic activity for the degradation of MV. It was found that varied synthesis methods and Zn content strongly affected the specific surface area, pore distribution, and band gap energy of PCHs. In addition, the band gap energy was found to govern the photoactivity. Additionally, the surface parameters of the PCHs were found to contribute to the degradation mechanism. It was found that the prepared PCHs demonstrated excellent photocatalytic activity and reusability, as seen in the high degradation efficiency attained at high concentrations. No significant changes in activity were seen until five cycles of photodegradation were done.

Synthesis, structure, and visible-light-driven activity of o-YbFeO3/h-YbFeO3/CeO2 photocatalysts

Photo-Fenton-like oxidation of organic substances is one of the key advanced oxidation processes based on the reversible Fe2+↔Fe3+ transition and the generation of a strong oxidant ·OH in the presence of H2O2 and is currently considered as a promising method for the purification of polluted aqueous media. However, the absence of effective and stable photocatalysts of this process, operating under the action of visible light, necessitates the exploratory studies, mainly among iron oxides and ferrites of various compositions and structures. In this work, using the method of solution combustion followed by heat treatment in air the heterojunction nanocomposites based on ytterbium orthoferrite and cerium dioxide of the composition o-YbFeO3/h-YbFeO3/CeO2 (0–20 mol.%) with high absorption in the visible region and advanced photo-Fenton-like activity were obtained. The nanocomposites were studied by EDS, SEM, XRD, BET, and DRS methods. The photo-Fenton-like activity of the nanocomposites was investigated during the degradation of methyl violet under the action of visible (λmax = 410 nm) radiation. As a result, the formation of I-type heterojunction based on stable rhombic (55.4–79.0 nm) and metastable hexagonal (19.5–24.0 nm) modifications of ytterbium orthoferrite (o-YbFeO3 and h-YbFeO3, respectively) and cubic cerium dioxide CeO2 (13.2–19.2 nm) nanocrystals was established. It was shown that the obtained nanocomposites had foamy morphology and were characterized by a specific surface in the range of 9.1–25.0 m2/g, depending on the CeO2 content. It was found that nanocrystalline components were chemically and phase-pure, uniformly spatially distributed over the nanocomposite, and had multiple contacts with each other. Based on this fact and the established electronic structure of the nanocomposite components, the formation of I-type heterojunction with the participation of o-YbFeO3 (Eg = 2.15 eV), h-YbFeO3 (Eg = 2.08 eV), and CeO2 (Eg = 2.38 eV) was shown, the presence of which increased photocatalytic activity of the resulting nanocomposite. The optimal content of CeO2 in the nanocomposite was 5%, and the o-YbFeO3/h-YbFeO3/CeO2–5% sample was characterized by the highest rate constant of photo-Fenton-like degradation of methyl violet under the action of visible light equal to k = 0.138 min–1, which was 2.5 to 5 times higher than for nanocomposites based on ytterbium orthoferrite. The obtained results obtained indicate that the developed nanocomposites can be considered as a promising basis for the advanced oxidation processes for the purification of aqueous media from organic pollutants.

Synthesis, structure, and photo-Fenton activity of PrFeO3-TiO2 mesoporous nanocomposites

Porous nanocomposites based on PrFeO3-TiO2 were synthesized using the glycine-nitrate combustion method with different values of mass content of TiO2 (0–7.5 %) and subsequent heat treatment in air. The results of X-ray phase analysis and Raman spectroscopy confirmed the presence of ultradispersed TiO2, structurally close to that of anatase. The morphology, specific surface area, and porous structure of the obtained powders were characterized by scanning electron microscopy and adsorption-structural analysis, the results of which showed that the samples had a foam-like mesoporous structure.The specific surface area and the average pore size were in the ranges of 7.6–17.8 m2/g and 7.2–15.2 nm, respectively, and varied depending on the TiO2 content. The optical properties of the nanocomposites were studied by UV-visible diffuse reflection spectroscopy, the energy of the band gap was calculated as 2.11–2.26 eV. The photocatalytic activity of PrFeO3‑TiO2 nanocomposites was investigated in the process of photo-Fenton-like degradation of methyl violet under the action of visible light. It was shown that the maximum reaction rate constant was 0.095 min-1, which is ten times higher than the value for the known orthoferrite-based analogs. The obtained photocatalysts were also characterized by their high cyclic stability. Based on the studies carried out, the obtained porous PrFeO3-TiO2 nanocomposites can be considered to be apromising basis for photocatalysts applied in advanced oxidative processes of aqueous media purification from organic pollutants.

Effective and Simple NaOH-Modification Method to Remove Methyl Violet Dye via Ipomoea aquatica Roots

In this study, a simple chemical modification was applied to a sustainable and abundantly available resource, kangkong root (KR), to remove methyl violet 2B (MV) dye. The chemically modified adsorbent (NaOH-KR) was obtained using NaOH solution treatment. Batch adsorption experiments were carried out to investigate the effects of pH, ionic strength, contact time, adsorbent dosage, and initial dye concentration. A regeneration experiment was also carried out to assess the potential of reusability. The adsorption process was modelled using various kinetics and isotherm models, whereby the best-fitting models were evaluated by using the coefficient of determination ( R 2 ) and error functions. The Sips ( R 2 = 0.9714 , χ2 =0.16) and pseudo-second-order ( R 2 = 0.9996 , χ 2 = 0.007 ) models were identified to best represent the adsorption process. The Sips model predicted a maximum adsorption capacity at 551.5 mg g-1 for NaOH-KR, which is 55% improvement in performance when compared to nonmodified KR. Lastly, the regeneration experiment showed that NaOH-KR was able to maintain reasonable dye removal even after five consecutive cycles of regenerating and reusing.

High Value Utilization of Fern Extracts For Fabrication of Copper Nanoparticles: A Potent And Affordable Candidate For Water Treatment, Water Disinfection, Antioxidant Activity And Theranostic Agent.

This study reports a simple, green, and large–scale biosynthetic fabrication of spherical copper nanoparticles (Cu NPs), approximate 28 nm, using the aqueous extracts of Diaplazium esulentum (Retz.) Sw. fern. Characterization was carried out for morphology, size, elemental analysis, crystallinity and for identification of functionalities responsible for reduction and stabilization. Extraordinary remediation efficiency was obtained for the developed Cu NPs for the elimination of two industrially important pollutants; Methyl Violet 6B and Methylene Blue (greater than 92 % within 150 mins). A mechanism was postulated for the process using the data on the identification of NPs and also spent NPs apart from degraded products.Furthermore, the Cu NPs revealed excellent antibacterial activity against gram positive bacteria: Staphylococcus aureus, Streptococcus pneumonia and Bacillus subtilis, as well as gram negative bacteria: Pseudomonas aeruginosa, Escherichia coli and potential action against fungal strains; Aspergillus niger and Candida albicans.Additionally, the assay depicted that Cu NPs has fairly decent radical scavenging activity with IC50 value 2.11 mM. Moreover, the Cu NPs were found to exhibit profound anticancerous activity against two human cancer line cells.The present research work has implications for exploitation of DE fern extract for the development of Cu NPs and their numerous applications ranging from pollutants removal to antibacterial, antifungal, antioxidant and anticancerous agents.

Biosynthesis of 3D/2D Ceo2/Mos2 Nanocomposites with Enhanced Photocatalytic Activity to Degrade Organic Dye in Wastewater and Statistical Optimization of Reaction Parameters

Nanocomposites synthesized by alternative approaches like biosynthetic methods are safer than those prepared by traditional chemical techniques. Further, this approach is both economically and environmentally feasible. In this study, we report an eco-friendly methodology for preparing cerium dioxide/molybdenum disulphide (CeO2/MoS2) nanocomposites. Moringa oleifera peel was used as the reducing/stabilizing agent for synthesizing CeO2 nanoparticles. The prepared nanocomposite were characterized using FT-IR analysis, SEM and EDAX analysis, TEM and SAED pattern analysis, X-Ray Diffraction Pattern, Zeta Potential, UV-Visible Diffuse Reflectance Spectra, X-Ray Photon Spectroscopy and Photoluminescence spectra. Particle size and morphology were characterized by TEM and SEM. The photocatalytic pursuit of CeO2/MoS2 was explored by the degradation of methyl violet (MV) under visible light irradiation. Our methodology proved to be 96.25% effective in the degradation of MV. Further, we used this Response Surface Methodology for enhancing the process factors like volume of photocatalyst, time for degradation and concentration of MV.