A Fe(II)/Fe(III) arány meghatározása EPR spektroszkópiai úton marosvécsi (Brâncoveneşti), mikházi (Călugăreni) és felsőrépai (Vătava) római kori vassalakokban

A Fe(II)/Fe(III) arány a régészeti vassalakok egyik fontos jellemzője. Ismerete megkönnyíti a leletek bucavasgyártáshoz (kohósalak) vagy feldolgozáshoz (kovácssalak) kapcsolását. A vizsgált vassalakok rövid jellemzése után a dolgozat ismerteti a javasolt EPR spektroszkópiai módszerrel a Fe(II)/Fe(III) arányra nyert előzetes eredményeinket

Photocatalytic Self-Cleaning PVDF Membrane Blended with MWCNT-ZnO Nanocomposites for RhB Removal

Polyvinylidene fluoride (PVDF) membranes blended with various amounts of MWCNT-ZnO (0.1%–3%) nanocomposites were prepared by the phase inversion method. The effect of nanocomposites blending on the membrane structural and morphological properties was investigated by XRD, FT-IR and SEM techniques. Contact angle measurement reveals that the hydrophilicity of the membrane increases with the increase of nanocomposite content; a reduction of the contact angle from 103° for PVDF to 49° for hybrid membrane was obtained. An optimum amount of 0.5% of MWCNT-ZnO blended in a PVDF hybrid membrane assured 85% removal rate of RbB under UV light irradiation. It was observed that the pollutant removal occurs through the simultaneous action of two processes: adsorption and photocatalysis. By blending with MWCNT-ZnO nanoparticles, the PVDF membrane acquires photocatalytic properties which assure a self-cleaning property in the membrane, increasing its lifetime

Numerical Simulation of Coupled Processes of Membrane Filtration and Advanced Oxidation (AOPs) in Photolysis Reactors for Water Decontamination

(1) Introduction: Chemical pollutants disposed of various branches of industry pose a significant threat to both the aquatic environment and human health. A specific class of pollutants is given by hardly biodegradable organic compounds coming mainly from pharmaceuticals, personal care products and industrial dyes. These pollutants are identified in water bodies (surface or underground) used as a source of water in drinking water treatment plants, the classic technologies for their elimination being inefficient. Exploring new processes and transposing them on an industrial scale in order to develop innovative, operationally and energy-efficient technologies is a complex approach, supported by both theoretical and experimental investigations, numerical modeling and virtual experiment, being basic steps in shortening the time required and increasing accuracy for developing new methods. (2) Materials and methods: Based on laboratory-level and functional model studies, the combined advanced oxidation processes (by photolysis and photocatalysis) and separation at the interface of photocatalytic ultrafiltrating membranes impregnated with elements based on carbon nanotubes (MWCNTs) decorated with ZnO particles, in the presence of active oxygen species (dissolved ozone), were investigated. The paper presents a methodology and a numerical model for modeling hybrid processes of advanced oxidation and membrane separation in photolysis reactors, as a preliminary step in the development of a water decontamination technology on an industrial scale. The model deals with a coaxial reactor configuration, being based on concepts from fluid mechanics (CFD—Computational Fluid Dynamics) assembled in a multi-physical model that incorporates elements of fluid flow, radiation distribution in the reactor and the dynamics of dissolved ozone photolysis processes, both in the reactor volume and at the filter membrane interface. (3) Results: The results obtained from virtual experiments, at different operating parameters of the reactor allowed the determination of the flow regime in the reactor by highlighting active areas, evaluating the efficiency of disinfection processes and photochemical processes (photolysis, photocatalysis) and by analyzing the reaction dynamics of dissolved ozone in the presence of UV radiation, useful in establishing the technical specifications necessary to make the model on a real scale

Enhanced Plasmonic Photocatalysis of Au-Decorated ZnO Nanocomposites

The rapid development of technological processes in various industrial fields has led to surface water pollution with different organic pollutants, such as dyes, pesticides, and antibiotics. In this context, it is necessary to find modern, environmentally friendly solutions to avoid the hazardous effects on the aquatic environment. The aim of this paper is to improve the photocatalytic performance of zinc oxide (ZnO) nanoparticles by using the plasmonic resonance induced by covering them with gold (Au) nanoparticles. Therefore, we evaluate the charge carriers’ behavior in terms of optical properties and reactive oxygen species (ROS) generation. The ZnO-Au nanocomposites were synthesized through a simple chemical protocol in multiple steps. ZnO nanoparticles (NPs) approximately 20 nm in diameter were prepared by chemical precipitation. ZnO-Au nanocomposites were obtained by decorating the ZnO NPs with Au at different molar ratios through a reduction process. X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) confirmed the simultaneous presence of hexagonal ZnO and cubic Au phases. The optical investigations evidenced the existence of a band-gap absorption peak of ZnO at 372 nm, as well as a surface plasmonic band of Au nanoparticles at 573 nm. The photocatalytic tests indicated increased photocatalytic degradation of the Rhodamine B (RhB) and oxytetracycline (OTC) pollutants under visible light irradiation in the presence of ZnO-Au nanocomposites (60–85%) compared to ZnO NPs (43%). This behavior can be assigned to the plasmonic resonance and the synergetic effects of the individual constituents in the composite nanostructures. The spin-trapping experiments showed the production of ROS while the nanostructures were in contact with the pollutants. This study introduces new strategies to adjust the efficiency of photocatalytic devices by the combination of two types of nanostructures with synergistic functionalities into one single entity. ZnO-Au nanocomposites can be used as stable photocatalysts with excellent reusability and possible industrial applications

The Influence of Ag⁺/Ti⁴⁺ Ratio on Structural, Optical and Photocatalytic Properties of MWCNT–TiO₂–Ag Nanocomposites

In this paper, we propose a simple procedure to obtain multi-walled carbon nanotubes (MWCNTs) decorated with TiO2–Ag nanoparticles (MWCNT–TiO2–Ag). The MWCNTs were decorated with TiO2–Ag via combined functionalization with –OH and –COOH groups and a polymer-wrapping technique using poly(allylamine)hydrochloride (PAH). TiO2-modified Ag nanoparticles were synthesized via the Pechini method using a mixture of acetylacetonate-modified titanium (IV) isopropoxide with silver nitrate (with Ag+/Ti4+ atomic ratios of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%) and L(+)-ascorbic acid as reducing agents. XRD analysis revealed the formation of nanocomposites containing CNT, anatase TiO2, and Ag. The presence of nanoparticles on the MWCNT surfaces was determined using TEM. The morphology of the TiO2–Ag nanoparticles on the MWCNT surfaces was also determined using TEM. UV–Vis investigations revealed that an increase in the ratio between Ag+ and Ti4+ decreased the band gap energy of the samples. The characteristic vibrations of the TiO2, Ag, and C atoms of the graphite were identified using Raman spectroscopy. The photocatalytic activity of the MWCNT–TiO2–Ag nanocomposite was assessed by examining the degradation of Allura Red (E129) aqueous solution under UV irradiation. The dye photodegradation process followed a pseudo-first-order kinetic with respect to the Langmuir–Hinshelwood reaction mechanism. The spin-trapping technique evidenced that •O2− was the main species generated responsible for the Allura Red degradation

Spectroscopic Characterization of Iron Slags from the Archaeological Sites of Brâncoveneşti, Călugăreni and Vătava Located on the Mureş County (Romania) Sector of the Roman Limes

Iron slag samples unearthed from archaeological sites lying on the Eastern limes sector of Roman Dacia (the Brâncoveneşti and Călugăreni auxiliary forts and the Vătava watchtower) were studied in order to assess the probability of local iron working (smelting and smithing) during the 2nd–3rd centuries CE. Structural-mineralogic aspects revealed by PXRD analysis and FTIR spectroscopy indicate different slag types corresponding to different iron production and processing stages allowing the supposition that refining of the bloom and processing of the refined iron took place on the sites. The FTIR absorption bands obtained in the spectral domain 2000–400 cm−1 show that mineralogically the samples are constituted mainly of silicates associated with minor quantities of aluminates and carbonates. The fayalite, haematite, and magnetite phases appearing on both the X-ray diffractograms and the FTIR spectra agree with the redox conditions of the slag formation process which result from the Fe3+/Fe2+ ratio determined using the EPR-method. The bulk macro-elemental PXRF and ICP-MS spectroscopy data support the slag typization proposed on the basis of the probable working conditions; trace-elemental bulk composition suggests that the provenance of the raw materials may be different

All-in-one supercapacitor devices based on nanosized Mn4+-doped WO3

In this study, nanosized Mn-doped WO3-based materials were used as electrode materials for high-performance supercapacitor devices. Various Mn concentrations (0.5, 1, and 1.5%) were used to change the defect structure of WO3, which improved the material's electrical properties. A thorough morpho-structural and defect structure analysis of the undoped and doped WO3 was performed through various characterization techniques, among which EPR and PL spectroscopy gave insight into the effect that Mn-doping caused on the defect structure and optical properties of WO3. The presence of Mn4+ ions and a high concentration of oxygen vacancies was observed, strongly influencing the electrode material when used in symmetric supercapacitors, where the electrochemical performance was tested. The symmetric supercapacitors were designed without booster materials (like carbon black) and showed increased specific capacitance (115 F/g) and energy density (16 Wh/Kg) values

Impact on the Photocatalytic Dye Degradation of Morphology and Annealing-Induced Defects in Zinc Oxide Nanostructures

In this study, three different morphologies, nanoflower (NF), nano sponge (NS), and nano urchin (NU), of zinc oxide (ZnO) nanostructures were synthesized successfully via a mild hydrothermal method. After synthesis, the samples were annealed in the atmosphere at 300, 600, and 800 °C. Although annealing provides different degradation kinetics for different morphologies, ZnO NS performed significantly better than other morphologies for all annealing temperatures we used in the study. When the photoluminescence, electron paramagnetic resonance spectroscopy, BET surface, and X-ray diffraction analysis results are examined, it is revealed that the defect structure, pore diameter, and crystallinity cumulatively affect the photocatalytic activity of ZnO nanocatalysts. As a result, to obtain high photocatalytic activity in rhodamine B (RhB) degradation, it is necessary to develop a ZnO catalyst with fewer core defects, more oxygen vacancies, near band emission, large crystallite size, and large pore diameter. The ZnO NS-800 °C nanocatalyst studied here had a 35.6 × 10–3 min–1 rate constant and excellent stability after a 5-cycle photocatalytic degradation of RhB

Nitrogen-Doped WO₃ Nanoparticles as Electrode Materials in All-in-One Supercapacitor Devices

The effect of the annealing temperature on 1% nitrogen-doped WO3 materials was studied, which were then used as electrode materials for high-performance supercapacitor (SC) devices. The supercapacitive performance of the proposed materials was strongly influenced by the doping element and the annealing temperature by directly changing the defect structure of the host material. The 1% N-doped WO3 materials annealed at different temperatures were thoroughly characterized through various characterization techniques, including electron paramagnetic resonance and photoluminescence spectroscopy, giving insight into the effect of N-doping on the defect structure and optical properties of WO3. When the WO3:N materials were used as electrode material in symmetric SCs, the doping element and the annealing temperature improved the electrochemical performance. No booster materials (such as carbon black) were used in the symmetric SC designs, showing increased specific capacitance (102 F/g) and energy density (14.6 W h/kg) values

Electrospun Nanosystems Based on PHBV and ZnO for Ecological Food Packaging

The electrospun nanosystems containing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and 1 wt% Fe doped ZnO nanoparticles (NPs) (with the content of dopant in the range of 0–1 wt% Fe) deposited onto polylactic acid (PLA) film were prepared for food packaging application. They were investigated by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), antimicrobial analysis, and X-ray photoelectron spectrometry (XPS) techniques. Migration studies conducted in acetic acid 3% (wt/wt) and ethanol 10% (v/v) food simulants as well as by the use of treated ashes with 3% HNO3 solution reveal that the migration of Zn and Fe falls into the specific limits imposed by the legislation in force. Results indicated that the PLA/PHBV/ZnO:Fex electrospun nanosystems exhibit excellent antibacterial activity against the Pseudomonas aeruginosa (ATCC-27853) due to the generation of a larger amount of perhydroxyl (˙OOH) radicals as assessed using electron paramagnetic resonance (EPR) spectroscopy coupled with a spin trapping method