Multiphase Oxidation Research Articles

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H2O2 Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze.

Particulate sulfate is one of the most important components in the atmosphere. The observation of rapid sulfate aerosol production during haze events provoked scientific interest in the multiphase oxidation of SO2 in aqueous aerosol particles. Diverse oxidation pathways can be enhanced or suppressed under different aerosol acidity levels and high ionic strength conditions of atmospheric aerosol. The importance of ionic strength to sulfate multiphase chemistry has been verified under laboratory conditions, though studies in the actual atmosphere are still limited. By utilizing online observations and developing an improved solute strength-dependent chemical thermodynamics and kinetics model (EF-T&K model, EF is the enhancement factor that represents the effect of ionic strength on an aerosol aqueous-phase reaction), we provided quantitative evidence that the H2O2 pathway was enhanced nearly 100 times and dominated sulfate formation for entire years (66%) in Tianjin (a northern city in China). TMI (oxygen catalyzed by transition-metal ions) (14%) and NO2 (14%) pathways got the second-highest contributions. Machine learning supported the result that aerosol sulfate production was more affected by the H2O2 pathway. The collaborative effects of atmospheric oxidants and SO2 on sulfate aerosol production were further investigated using the improved EF-T&K model. Our findings highlight the effectiveness of adopting target oxidant control as a new direction for sustainable mitigation of sulfate, given the already low SO2 concentrations in China.

Mn3O4-stabilized multiphase manganese oxides with micron cage structure for high-performance AZIBs

Aqueous zinc ion batteries (AZIBs) have become one of the most prospective energy storage devices due to their low cost, abundant resources, and hypotoxicity. However, AZIBs suffer from a bottleneck, that is, significant capacity fading during long cycle and bad performance at a high current density. In this work, we report a valuable cooperation strategy of multiphase Mn-based oxides (N-Mn3O4/MnO) via a two-step solvothermal method to obtain an attractive cathode for AZIBs. The high reversible specific capacity and superior rate capability of this cathode result from the facile charge transfer channel and ions (Zn2+/H+) insertion in the porous heterostructures featuring phase stability caused by the synergistic effects of N-doping, heterojunction and porous micron cage. Because the d-band centers of N-doped Mn3O4 are closer to the Fermi level, they are looked forward to overcoming the intrinsic activation barrier more effectively and promoting the reaction kinetics for electrochemical reactions. The N-Mn3O4/MnO cathode demonstrates a reversible specific capacity of 227.8 mAh g−1 over 1500 cycles at 5 A g−1. The capacity retention reaches up to 92.2% regarding the stable capacity of 247.2 mAh g−1 as the reference. The capacity retention rate of 77.2% and a loss of only 0.0091% per cycle are achieved at a high current density of 10 A g−1 for 2500 cycles. These results all prove the advantages of N-Mn3O4/MnO of the hybrid material. The meaning of this work is to put forward a compositional and structural design strategy for the Zn-Mn system for the cost-effective and high-performance rechargeable AZIBs. Besides, the application of a novel water-soluble binder (LA133) to AZIBs in this work is a solid step for the practical application of AZIBs.

Structural, optical, and electrical properties via two simple routes for the synthesis of multi-phase potassium antimony oxide thin films

Multi-phase ternary oxide glass thin films of potassium antimony oxide were synthesized via dip coating (DC) and spray pyrolysis (SP) methods. The growth of thin film was conducted on a non-conductive borosilicate glass substrate. Surface morphology was investigated and showed different characteristics. X-ray diffraction (XRD) analysis revealed the peaks corresponded to the monoclinic KSb3O5 and K2Sb4O11 phases. The structural parameter analysis shows that the lower values of micro strain (ε), dislocation density (δ), and stacking fault probability (SF) with higher number (N) of particle in the multi-phase thin film for the spray pyrolysis method confirm slightly larger crystallite size, less crystal imperfection, and less structural disorder. The lower average transmission, absorption, and extinction coefficients resulted to higher refractive index, permittivity, and electrical susceptibility for the sample synthesized by a spray pyrolysis method. In addition, the average energy band gap values (Eg) of 3.57 and 3.60 eV were obtained for the dip coating and spray pyrolysis methods, respectively. However, the lower Rs (14.69 × 107 Ω/sq.) with higher σh (85.09 S/cm) and the FOM(H-HR) (0.183 Ω-1) of the multi-phase K–Sb–O thin film for the dip coating method were obtained may be due to more interconnections generated at the interface and there are less residual on the surface of thin film.

Influence of precursor composition on oxidation behavior of SiBCN multiphase ceramic and oxidation resistance of SiC/SiBCN composites

Influence of precursor composition on oxidation behavior of SiBCN multiphase ceramic and oxidation resistance of SiC/SiBCN composites

Enabling Efficient Aerobic 5-Hydroxymethylfurfural Oxidation to 2,5-Furandicarboxylic Acid in Water by Interfacial Engineering Reinforced Cu-Mn Oxides Hollow Nanofiber.

Herein, a one-dimensional hollow nanofiber catalyst composed of tightly packed multiphase metal oxides of Mn2 O3 and Cu1.4 Mn1.6 O4 was constructed by electrospinning and tailored thermal treatment procedure. The characterization results comprehensively confirmed the special morphology and composition of various comparative catalysts. This strategy endowed the catalyst with abundant interfacial characteristics of components Mn2 O3 and Cu1.4 Mn1.6 O4 nanocrystal. Impressively, the tuning thermal treatment resulted in tailored CuI sites and surface oxygen species of the catalyst, thus affording optimized oxygen vacancies for reinforced oxygen adsorption, while the concomitant enhanced lattice oxygen activity in the constructed composite catalyst ensured the higher catalytic oxidation ability. More importantly, the regulated proportion of oxygen vacancy and lattice oxygen in the composite catalyst was obtained in the best catalyst, beneficial to accelerate the reaction cycle. Compared to other counterparts obtained by different temperatures, the CMO-500 sample exhibited superior selective aerobic 5-hydroxymethylfurfural (HMF) oxidation to 2,5-furandicarboxylic acid (FDCA, 96 % yield) in alkali-bearing aqueous solution using O2 at 120 °C, which resulted from the above-mentioned composition optimization and interfacial engineering reinforced surface oxygen consumption and regeneration cycle. The reaction mechanism was further proposed to uncover the lattice oxygen and oxygen vacancy participating HMF conversion process.

Development of SiC-ZrC-based ultra-high temperature ceramic coatings via composite method of polymer precursor pyrolysis plus gaseous reactive infiltration

SiC-ZrC-based composite coatings on carbon/carbon composites via ZrC polymer precursor pyrolysis (PPP) plus gaseous reactive infiltration (GRI) of Si or ZrSi 2 , separately denoted as GSIC and GZSIC, were comparatively studied to explore the feasibility and effectiveness of GRI of ZrSi 2 . This composite method by applying ZrSi 2 or Si was proven to similarly produce dense coatings with enhanced coating/substrate interfacial bonding strength for the formed zig-zag transition layer. Furthermore, the GRI of ZrSi 2 instead of Si further increased the UHTC (ZrC) content in the as-deposited coatings resulted from the reaction of infiltrated ZrSi 2 and pre-introduced graphite, enhancing the ablation resistance of the coatings for carbon/carbon composites due to the formed stable Zr-rich Zr-Si-O multiphase oxide. The average mass and linear ablation rates were −0.12 mg/s and 1.56 μm/s for GSIC and −0.3 mg/s and −0.53 μm/s for GZSIC specimens, respectively. The average linear ablation rate of the GZSIC specimen was decreased by ~134% when compared to the GSIC specimen. These results further indicate that the PPP + GRI method with metal silicide MeSi 2 (Me = Zr, Ti, Hf, Cr, etc.) will contribute to the optimal fabrication of dense composite coatings with controllable microstructure, adequate evenly-distributed ultra-high temperature ceramic (UHTC) phases, enhanced interfacial bonding strength and wide circumstance suitability for potential applications. The related work is ongoing in our laboratory. • SiC-ZrC-based coatings were made by precursor pyrolysis plus gaseous reactive infiltration. • Pre-introduced graphite reacted with infiltrated ZrSi 2 further improved ZrC content in the coatings. • The gaseous infiltrated ZrSi 2 instead of Si enhanced ablation resistance of the coatings. • The coating's linear ablation rate was reduced by ~134% as gaseous infiltrated with ZrSi 2 .

Femtojoule‐Power‐Consuming Synaptic Memtransistor Based on Mott Transition of Multiphasic Vanadium Oxides (Adv. Funct. Mater. 46/2021)

Memtransistors In article number 2102567, Hyungtak Seo and co-workers present a highly stable Mott memtransistor based on a multiphasic vanadium oxide film, which possesses not only tunable synaptic functions through controlling either drain or gate biases, but also ultralow power consumption. Their study promotes the potential of memtransistors for use in practical memory applications, including artificial synapse and neuromorphic processing.

Oxidation behaviors of CrNb, CrNbTi, and CrNbTaTi concentrated refractory alloys

The 1200 °C oxidation behaviors of CrNb, CrNbTi and CrNbTaTi are reported. All alloys formed some combination of BCC and Laves phases. However, additions of Ti produced a unique inflection point where the microstructure inverts to a Ti-rich BCC matrix with Laves phase precipitates. Further additions of Ta to CrNbTi were found to increase the overall phase fraction of BCC phase. The oxidation kinetics for CrNb and CrNbTi were similar and nearly parabolic throughout the duration of exposure. CrNbTaTi exhibited inferior oxidation kinetics and mixed mode behavior throughout oxidation testing. All alloys formed intricate multi-phase oxide structures, consisting of a combination of both simple and complex oxides. The resulting microstructures are characterized using a variety of analytical techniques and the results are discussed relative to modeling predictions using ab initio density functional theory (DFT).

Catalytic Behavior of Iron-Containing Cubic Spinel in the Hydrolysis and Hydrothermolysis of Ammonia Borane.

The paper presents a comparative study of the activity of magnetite (Fe3O4) and copper and cobalt ferrites with the structure of a cubic spinel synthesized by combustion of glycine-nitrate precursors in the reactions of ammonia borane (NH3BH3) hydrolysis and hydrothermolysis. It was shown that the use of copper ferrite in the studied reactions of NH3BH3 dehydrogenation has the advantages of a high catalytic activity and the absence of an induction period in the H2 generation curve due to the activating action of copper on the reduction of iron. Two methods have been proposed to improve catalytic activity of Fe3O4-based systems: (1) replacement of a portion of Fe2+ cations in the spinel by active cations including Cu2+ and (2) preparation of highly dispersed multiphase oxide systems, involving oxide of copper.

Novel method for high-performance simultaneous removal of NOx and SO2 by coupling yellow phosphorus emulsion with red mud

This study develops a novel method for simultaneously removing NOx and SO2 from coal-fired flue gas via coupling yellow phosphorus emulsion with red mud. The effects of different factors on the synergistic purification of sulphur-nitric acid were investigated in this study. The achieved removal efficiencies of NOx and SO2 were as high as 97.9% and 100%, respectively, under optimized conditions. This indicates that the yellow phosphorus emulsion coupled with red mud as a composite absorbent is favorable for simultaneous removal effect on NOx and SO2. The samples before and after the reaction were characterized using X-ray diffraction, X-ray fluorescence, inductively coupled plasma, scanning electron microscopy, and other methods, and the main product was identified as gypsum (CaSO4·2H2O) after desulfurization and denitrification. Adsorption kinetics, isotherm adsorption, and breakthrough curve models of NOx and SO2 adsorption on red mud were established. Moreover,the mechanism of multiphase oxidation and absorption reactions for simultaneous desulfurization and denitrification was also speculated.

Effect of surface structure unit of 3D needled carbon fiber preform on the ablation improvement of “Z-pins like” V0.9-Si0.1 rod for C/C–ZrC–SiC

The effects of the different surface structure units due to “Z-pins like” V0.9-Si0.1 rods on the improvement of the ablation resistance of C/C–ZrC–SiC were investigated. The ablation properties of the V0.9-Si0.1 rods acting on the surface of short-cut fibre web and laminated layers were tested for different ablation times. The results showed that although the ablation resistances of the composites with different surface structure units improved using neoteric “Z-pins like” V0.9-Si0.1 rods as polybasic multiphase oxide compensators, the improvement mechanisms were different. For an ablation time less than 180 s, the rods perpendicular to the short-cut fibre web resulted in a higher improvement in ablation resistance by a liquid/gas multicomponent oxide compensation mechanism. Whereas, for an ablation time over 180 s, the rods perpendicular to the laminated layers resulted in a higher improvement because of the oxide melting erosion experienced by the short-cut fibre web surface.

The Importance of the Representation of DMS Oxidation in Global Chemistry‐Climate Simulations

AbstractThe oxidation of dimethyl sulfide (DMS) is key for the natural sulfate aerosol formation and its climate impact. Multiphase chemistry is an important oxidation pathway but neglected in current chemistry‐climate models. Here, the DMS chemistry in the aerosol‐chemistry‐climate model ECHAM‐HAMMOZ is extended to include multiphase methane sulfonic acid (MSA) formation in deliquesced aerosol particles, parameterized by reactive uptake. First simulations agree well with observed gas‐phase MSA concentrations. The implemented formation pathways are quantified to contribute up to 60% to the sulfate aerosol burden over the Southern Ocean and Arctic/Antarctic regions. While globally the impact on the aerosol radiative forcing almost levels off, a significantly more positive solar radiative forcing of up to +0.1 W m−2 is computed in the Arctic (>60°N). The findings imply the need of both further laboratory and model studies on the atmospheric multiphase oxidation of DMS.

Secondary aerosol formation from dimethyl sulfide – improved mechanistic understanding based on smog chamber experiments and modelling

Abstract. Dimethyl sulfide (DMS) is the dominant biogenic sulfur compound in the ambient marine atmosphere. Low-volatility acids from DMS oxidation promote the formation and growth of sulfur aerosols and ultimately alter cloud properties and Earth's climate. We studied the OH-initiated oxidation of DMS in the Aarhus University Research on Aerosol (AURA) smog chamber and the marine boundary layer (MBL) with the aerosol dynamics and gas- and particle-phase chemistry kinetic multilayer model ADCHAM. Our work involved the development of a revised and comprehensive multiphase DMS oxidation mechanism, capable of both reproducing smog chamber and atmospheric relevant conditions. The secondary aerosol mass yield in the AURA chamber was found to have a strong dependence on the reaction of methyl sulfinic acid (MSIA) and OH, causing a 82.8 % increase in the total PM at low relative humidity (RH), while the autoxidation of the intermediate radical CH3SCH2OO forming hydroperoxymethyl thioformate (HPMTF) proved important at high temperature and RH, decreasing the total PM by 55.8 %. The observations and modelling strongly support the finding that a liquid water film existed on the Teflon surface of the chamber bag, which enhanced the wall loss of water-soluble intermediates and oxidants dimethyl sulfoxide (DMSO), MSIA, HPMTF, SO2, methanesulfonic acid (MSA), sulfuric acid (SA) and H2O2. The effect caused a 64.8 % and 91.7 % decrease in the secondary aerosol mass yield obtained at both dry (0 % RH–12 % RH) and humid (50 % RH–80 % RH) conditions, respectively. Model runs reproducing the ambient marine atmosphere indicate that OH comprises a strong sink of DMS in the MBL (accounting for 31.1 % of the total sink flux of DMS) although less important than the combined effect of halogen species Cl and BrO (accounting for 24.3 % and 38.7 %, respectively). Cloudy conditions promote the production of SO42- particular mass (PM) from SO2 accumulated in the gas phase, while cloud-free periods facilitate MSA formation in the deliquesced particles. The exclusion of aqueous-phase chemistry lowers the DMS sink as no halogens are activated in the sea spray particles and underestimates the secondary aerosol mass yield by neglecting SO42- and MSA PM production in the particle phase. Overall, this study demonstrated that the current DMS oxidation mechanisms reported in literature are inadequate in reproducing the results obtained in the AURA chamber, whereas the revised chemistry captured the formation, growth and chemical composition of the formed aerosol particles well. Furthermore, we emphasize the importance of OH-initiated oxidation of DMS in the ambient marine atmosphere during conditions with low sea spray emissions.

Boron vacancies of mesoporous MnO2 with strong acid sites, free Mn3+ species and macropore decoration for efficiently decontaminating organic and heavy metal pollutants in black-odorous waterbodies

Oxygen vacancy (OV), one frequently designed structural anion defect, can transport active oxygen species towards multi-phase pollutant oxidation by activating oxygen molecules or chemical oxidants. However, dissolved oxygen (DO), a desirable oxidant source for water organics degradation, is very difficult to be directly utilized by OV-abundant metal oxides without extra heat or light input. To solve this problem, in this study another anion defect, i.e., boron vacancy (BV), was successfully incorporated into ɑ-MnO2 via a two-step method, i.e., thermal NaBH4 treatment for boron doping followed by in situ wash-away of boron during organic dye elimination process. The NaBH4-modified ɑ-MnO2 exhibited much higher Rhodamine B (RhB) elimination than the original one. BV is capable of transforming DO into 1O2, OH and O2− radicals at 30 °C and without extra energy input, completely mineralizing RhB into inorganic carbon. Besides, NaBH4-induced strong acid sites, free Mn3+ species and large pore size contributed to adsorptive RhB removal. For the original ɑ-MnO2, surface lattice oxygen was the key oxidant for dye degradation. Malachite Green, Congo Red, Orange I and Methyl Blue were further tested as target substrates. The NaBH4-treated ɑ-MnO2 presented superiority over the pristine sample in adsorptive Pb2+ removal as well.

Effect of weld microstructure on brittle fracture initiation in the thermally-aged boiling water reactor pressure vessel head weld metal

Effects of the weld microstructure and inclusions on brittle fracture initiation are investigated in a thermally aged ferritic high-nickel weld of a reactor pressure vessel head from a decommissioned nuclear power plant. As-welded and reheated regions mainly consist of acicular and polygonal ferrite, respectively. Fractographic examination of Charpy V-notch impact toughness specimens reveals large inclusions (0.5–2.5 µm) at the brittle fracture primary initiation sites. High impact energies were measured for the specimens in which brittle fracture was initiated from a small inclusion or an inclusion away from the V-notch. The density, geometry, and chemical composition of the primary initiation inclusions were investigated. A brittle fracture crack initiates as a microcrack either within the multiphase oxide inclusions or from the de-bonded interfaces between the uncracked inclusions and weld metal matrix. Primary fracture sites can be determined in all the specimens tested in the lower part of the transition curve at and below the 41-J reference impact toughness energy but not above the mentioned value because of the changes in the fracture mechanism and resulting changes in the fracture appearance.

Nitrate Photolysis in Mixed Sucrose-Nitrate-Sulfate Particles at Different Relative Humidities.

Atmospheric particles can be viscous. The limitation in diffusion impedes the mass transfer of oxidants from the gas phase to the particle phase and hinders multiphase oxidation processes. On the other hand, nitrate photolysis has been found to be effective in producing oxidants such as OH radicals within the particles. Whether nitrate photolysis can effectively proceed in viscous particles and how it may affect the physicochemical properties of the particle have not been much explored. In this study, we investigated particulate nitrate photolysis in mixed sucrose-nitrate-sulfate particles as surrogates of atmospheric viscous particles containing organic and inorganic components as a function of relative humidity (RH) and the molar fraction of sucrose to the total solute (FSU) with an in situ micro-Raman system. Sucrose suppressed nitrate crystallization, and high photolysis rate constants (∼10-5 s-1) were found, irrespective of the RH. For FSU = 0.5 and 0.33 particles under irradiation at 30% RH, we observed morphological changes from droplets to the formation of inclusions and then likely "hollow" semisolid particles, which did not show Raman signal at central locations. Together with the phase states of inorganics indicated by the full width at half-maxima (FWHM), images with bulged surfaces, and size increase of the particles in optical microscopic imaging, we inferred that the hindered diffusion of gaseous products (i.e., NOx, NOy) from nitrate photolysis is a likely reason for the morphological changes. Atmospheric implications of these results are also presented.

Multiphase Oxidation of Sulfur Dioxide in Aerosol Particles: Implications for Sulfate Formation in Polluted Environments

Atmospheric oxidation of sulfur dioxide (SO2) forms sulfate-containing aerosol particles that impact air quality, climate, and human and ecosystem health. It is well-known that in-cloud oxidation of SO2 frequently dominates over gas-phase oxidation on regional and global scales. Multiphase oxidation involving aerosol particles, fog, and cloud droplets has been generally thought to scale with liquid water content (LWC) so multiphase oxidation would be negligible for aerosol particles due to their low aerosol LWC. However, recent field evidence, particularly from East Asia, shows that fast sulfate formation prevails in cloud-free environments that are characterized by high aerosol loadings. By assuming that the kinetics of cloud water chemistry prevails for aerosol particles, most atmospheric models do not capture this phenomenon. Therefore, the field of aerosol SO2 multiphase chemistry has blossomed in the past decade, with many oxidation processes proposed to bridge the difference between modeled and observed sulfate mass loadings. This review summarizes recent advances in the fundamental understanding of the aerosol multiphase oxidation of SO2, with a focus on environmental conditions that affect the oxidation rate, experimental challenges, mechanisms and kinetics results for individual reaction pathways, and future research directions. Compared to dilute cloud water conditions, this paper highlights the differences that arise at the molecular level with the extremely high solute strengths present in aerosol particles.

Evaluation of incipient oxidation behavior of ZrO2-Coated Zircaloy-4 by thermogravimetric analysis

The objectives of this study were to investigate the incipient oxidation behavior of ZrO₂-coated Zircaloy-4 (Zry-4), and evaluate the feasibility of producing ZrO₂ protective layer by vacuum annealing of ZrN coating. ZrO₂ coatings with tetragonal (t) and monoclinic (m) dominant phases were deposited on Zry-4 using unbalanced magnetron sputtering. The wettability tests and the widths of interdiffusion zones at film/substrate interface indicated the ZrO₂ coatings having good intrinsic adhesion on the Zry-4 substrate. The oxidation behavior of the coated specimens and blank Zry-4 substrate were evaluated by thermogravimetric analysis performed at 700, 800 and 900 °C in argon atmosphere. After oxidation, X-ray diffraction (XRD) patterns revealed that both thermally formed ZrO₂ and the deposited ZrO2 possessed an m-ZrO₂ dominant structure. The weight gain at 700 °C indicated no significant difference in the oxidation behavior between uncoated and ZrO₂-coated Zry-4, and the oxidation kinetics obeyed the parabolic law. However, the oxidation kinetics above 800 °C deviated from the parabolic law, where m-ZrO₂-coated Zry-4 showed the least weight gain at 800 °C, and t-ZrO₂-coated Zry-4 displayed a better oxidation resistance at 900 °C. Oxide nodules were observed on the uncoated Zry-4 specimens after oxidation; in contrast, the ZrO₂ coatings, both monoclinic and tetragonal phases, could act as a barrier to prevent the formation of oxide nodules. The azimuthal XRD cos2αsin2ψ technique was used to measure residual stress of t-ZrO₂ and m-ZrO₂ phases and reveal the distribution of each phase in the specimens. The results indicated that the oxide phases were not uniformly distributed in the specimens. The azimuthal XRD cos2αsin2ψ technique can be used as a convenient and nondestructive method to examine the uniformity of the phase distribution in a multi-phase oxide layer. The experimental results revealed that producing a ZrO₂ coating on Zry-4 by vacuum annealing of ZrN-coated Zry-4 was infeasible.

Heterogeneous Photo-Fenton Catalytic Degradation of Practical Pharmaceutical Wastewater by Modified Attapulgite Supported Multi-Metal Oxides

Chemical synthetic pharmaceutical wastewater has characteristics of high concentration, high toxicity and poor biodegradability, so it is difficult to directly biodegrade. We used acid modified attapulgite (ATP) supported Fe-Mn-Cu polymetallic oxide as catalyst for multi-phase Fenton-like ultraviolet photocatalytic oxidation (photo-Fenton) treatment with actual chemical synthetic pharmaceutical wastewater as the treatment object. The results showed that at the initial pH of 2.0, light distance of 20 cm, and catalyst dosage and hydrogen peroxide concentration of 10.0 g/L and 0.5 mol/L respectively, the COD removal rate of wastewater reached 65% and BOD5/COD increased to 0.387 when the reaction lasted for 180 min. The results of gas chromatography-mass spectrometry (GC-MS) indicated that Fenton-like reaction with Fe-Mn-Cu@ATP had good catalytic potential and significant synergistic effect, and could remove almost all heterocycle compounds well. 3D-EEM (3D electron microscope) fluorescence spectra showed that the fluorescence intensity decreased significantly during catalytic degradation, and the UV humus-like and fulvic acid were effectively removed. The degradation efficiency of the nanocomposite only decreased by 5.8% after repeated use for 6 cycles. It seems appropriate to use this process as a pre-treatment for actual pharmaceutical wastewater to facilitate further biological treatment.

Characterization of Multiphase Oxide Layer Formation on Micro and Nanoscale Iron Particles

The article presents a detailed study and characterization of the oxide layers on the surface of iron particles of various sizes. Ten iron samples with a size range from a few nm to 50 µm were studied in detail using SEM, TEM, XRD, and TGA analysis. The composition of the multiphase oxide layers on the powder surface was investigated. The main components of the oxide layer were FeO, Fe3O4, and Fe2O3. By the obtained data, a model for the calculation of a multiphase oxide layer thickness on the surface of iron particles was proposed. The proposed model was validated and can be used for the characterization and certification of micro– and nanoscale iron particles.