Directional Oxidation of Pyrite in Acid Solution

This study aimed to investigate the oxidation mechanism of pyrite crystallographic direction by cutting pyrite samples to expose their (100), (110), and (111) planes. Differences in the oxidation rates of pyrite planes in acid solution were determined. The morphological changes of pyrite were evaluated by scanning electron microscopy and hyperdepth-3D microscopy. The oxidation products of pyrite were examined by Raman spectroscopy and X-ray photoelectron spectroscopy. Results showed that the aqueous oxidation of pyrite produced Fe(OH)3, Fe2O3, Fe2(SO4)3, and S8 on the surface. Moreover, the morphologies of corrosion patterns differed from one crystal plane to another: square, rectangular, and triangular etch pits were found on the (100), (110), and (111) planes, respectively. The corrosion patterns reflected the symmetrical arrangement of the crystallographic planes in the lattice on which they formed.

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Characterisation of High Temperature Oxidation Phenomena during AISI 430 Stainless Steel Manufacturing under a Controlled H2 Atmosphere for Bright Annealing

Metals ◽

10.3390/met11020191 ◽

2021 ◽

Vol 11 (2) ◽

pp. 191

Author(s):

Irene Collado García ◽

Andrés Núñez Galindo ◽

Juan F. Almagro Bello ◽

Juan M. González Leal ◽

Javier F. Botana Pedemonte

Keyword(s):

Oxide Scale ◽

Annealing Time ◽

Photoelectron Spectroscopy ◽

Outer Part ◽

Oxidation Mechanism ◽

Oxidation Products ◽

Temperature Oxidation ◽

430 Stainless Steel ◽

Aisi 430 ◽

Bright Annealing

Localised-in-the-edge oxidation of four AISI 430 alloys was investigated after an industrial bright annealing process. The oxidised surface of each specimen was characterised by X-ray photoelectron spectroscopy (XPS), Raman-spectroscopy and SEM. The results showed that the selective oxidation of Cr and Mn took place at the coil edges of AISI 430. This led to the formation of an oxide scale based on Cr2O3 and MnCr2O4. On the other hand, the formation of Cr(OH)3 and MnOOH in the outer part of the oxide scale was related to the effect of the H2–N2 environment on the annealing furnace. The results concluded that the composition of Cr and Mn in the alloy determined the composition of the oxidation products. However, the effect of annealing time was minor in this oxidation mechanism, which slightly contributed to an increase in the cation diffusion from the steel to the oxide. Finally, the results obtained indicate that the colouration of the coil edges displayed in each studied material varies according to the alloy chemical composition and annealing time.

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Improvement of Interfacial Adhesion in PP/PS Blends Enhanced with Polyethylene-Polyamine Surface Treated Carbon Fiber

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1061-1062.170 ◽

2014 ◽

Vol 1061-1062 ◽

pp. 170-174

Author(s):

Jian Li

Keyword(s):

Contact Angle ◽

Carbon Fiber ◽

Photoelectron Spectroscopy ◽

Interfacial Adhesion ◽

Morphological Changes ◽

Water Contact ◽

Polyethylene Polyamine ◽

Adhesion Behavior ◽

Interlaminar Shear ◽

Treated Carbon

The effects of surface treatment of a carbon fiber (CF) by Polyethylene-polyamine (PEPA) on the interfacial adhesion behavior and morphology of polypropylene/polystyrene (PP/PS) matrix blends filled CF composites were investigated. Effects of surface treated a commercial CF on mechanical properties are studied. Contact angle was measured to examine the changes in wettability of the carbon fiber. The chemical and morphological changes were characterized by using X-ray photoelectron spectroscopy (XPS). PP/PS/CF composites were fabricated with and without PEPA treatment, and their interlaminar fracture toughnesses were compared. The results showed that the interlaminar shear strength (ILSS) of composites has been greatly improved filled PEPA modification CF. The water contact angle of resin sample decreased 50% after addition of PEPA surface treated CF.

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Adsorption of PtCl62− from Hydrochloric Acid Solution by Chemically Modified Lignin Based on Rice Straw

Australian Journal of Chemistry ◽

10.1071/ch18282 ◽

2018 ◽

Vol 71 (12) ◽

pp. 931 ◽

Cited By ~ 3

Author(s):

Baoping Zhang ◽

Bowen Shen ◽

Meichen Guo ◽

Yun Liu

Keyword(s):

Hydrochloric Acid ◽

Acid Solution ◽

Rice Straw ◽

Hydrochloric Acid Solution ◽

Photoelectron Spectroscopy ◽

Selective Adsorption ◽

Adsorption Time ◽

Langmuir Isotherm Model ◽

Pseudo Second Order ◽

Modified Lignin

A novel adsorbent with the properties of selective adsorption based on rice straw was used to adsorb PtCl62− from hydrochloric acid solution by batch sorption. Many influencing factors for PtCl62− adsorption, such as initial concentration of PtCl62−, adsorption time, and concentration of hydrochloric acid, were optimized. The results suggested that the saturation adsorption capacity of PtCl62− was 218.8mgg−1 and the equilibrium adsorption time was 120min. The adsorbent had excellent selectivity on PtCl62− when the concentration of hydrochloric acid was lower than 0.5molL−1. The adsorption fitted well with the Langmuir isotherm model and pseudo-second-order kinetics model. The adsorption mechanism was investigated by FT-IR and X-ray photoelectron spectroscopy analyses and it indicated that PtIV was reduced to PtII by hydroxy groups and then coordinated with N through ion exchange between Cl− and PtCl42−.

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Phosphated Avocado Seed: A Renewable Biomaterial for Preparing a Flame Retardant Biofiller

10.21203/rs.3.rs-315473/v1 ◽

2021 ◽

Author(s):

DAVID Zuluaga-Parra ◽

L.F Ramos-deValle ◽

Saul Sanchez ◽

J.R. Torres-Lubián ◽

J.A. Rodríguez-Gonzalez ◽

...

Keyword(s):

Thermal Stability ◽

Chemical Modification ◽

Flame Retardant ◽

Photoelectron Spectroscopy ◽

Morphological Changes ◽

Ethylene Vinyl Acetate ◽

Chemically Modified ◽

Air Atmosphere ◽

Thermal Stability Of ◽

Avocado Seed

Abstract The cellulose and starch present in the avocado seed can be chemically modified to obtain biofillers with fire retarding characteristics. The resulting composites could be used as substitute of the corresponding halogenated composites. For this, the avocado seed was first washed, dehydrated and pulverized, and thereafter, chemically modified with phosphoric acid in the presence of urea. This was studied using infrared spectroscopy, nuclear magnetic resonance and X-Ray photoelectron spectroscopy, in order to determine the resulting chemical structure and confirm the presence of the proposed functional groups. In addition, scanning electron microscopy and elemental analysis were used, respectively, to establish the resulting morphological changes, as well as the elements present on the surface of the modified material. Thermogravimetric analysis was also carried out in order to establish the thermal stability of the material and predict the effect on the flame retardancy due to the mentioned chemical modification. Further tests established that the obtained modified structure and morphology of the avocado seed was highly dependent on the method used to dehydrate the pulverized avocado seed. It was also determined that chemical modification greatly increased the thermal stability of the avocado seed in air atmosphere. The flame-retardant effect of the modified avocado seed was assessed in polyethylene/ethylene-vinyl-acetate (PE/EVA) composites via cone calorimeter tests. These results showed that the modified avocado seed decreased the peak of the heat release rate (pHRR) by 50% and the total heat released (THR) by 15%. This phosphated avocado seed could be a good option as a renewable biofiller for polymer composites with enhanced flame-retardant properties.

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Formation and sink of glyoxal and methylglyoxal in a polluted subtropical environment: observation-based photochemical analysis and impact evaluation

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-11451-2020 ◽

2020 ◽

Vol 20 (19) ◽

pp. 11451-11467

Author(s):

Zhenhao Ling ◽

Qianqian Xie ◽

Min Shao ◽

Zhe Wang ◽

Tao Wang ◽

...

Keyword(s):

Southern China ◽

Oxidation Mechanism ◽

Receptor Site ◽

Oxidation Products ◽

Chemical Mechanism ◽

Major Pathway ◽

Mixing Ratios ◽

Heterogeneous Processes ◽

The Pearl River ◽

Improved Model

Abstract. The dicarbonyls glyoxal (Gly) and methylglyoxal (Mgly) have been recognized as important precursors of secondary organic aerosols (SOAs) through the atmospheric heterogeneous process. In this study, field measurement was conducted at a receptor site in the Pearl River Delta (PRD) region in southern China, and an observation-based photochemical box model was subsequently applied to investigate the production and evolution of Gly and Mgly as well as their contributions to SOA formation. The model was coupled with a detailed gas-phase oxidation mechanism of volatile organic compounds (VOCs) (i.e., Master Chemical Mechanism, MCM, v3.2), heterogeneous processes of Gly and Mgly (i.e., reversible partitioning in aqueous phase, irreversible volume reactions and irreversible surface uptake processes), and the gas–particle partitioning of oxidation products. The results suggested that without considering the heterogeneous processes of Gly and Mgly on aerosol surfaces, the model would overpredict the mixing ratios of Gly and Mgly by factors of 3.3 and 3.5 compared to the observed levels. The agreement between observation and simulation improved significantly when the irreversible uptake and the reversible partitioning were incorporated into the model, which in total both contributed ∼ 62 % to the destruction of Gly and Mgly during daytime. Further analysis of the photochemical budget of Gly and Mgly showed that the oxidation of aromatics by the OH radical was the major pathway producing Gly and Mgly, followed by degradation of alkynes and alkenes. Furthermore, based on the improved model mechanism, the contributions of VOC oxidation to SOA formed from gas–particle partitioning (SOAgp) and from heterogeneous processes of Gly and Mgly (SOAhet) were also quantified. It was found that o-xylene was the most significant contributor to SOAgp formation (∼ 29 %), while m,p-xylene and toluene made dominant contributions to SOAhet formation. Overall, the heterogeneous processes of Gly and Mgly can explain ∼ 21 % of SOA mass in the PRD region. The results of this study demonstrated the important roles of heterogeneous processes of Gly and Mgly in SOA formation and highlighted the need for a better understanding of the evolution of intermediate oxidation products.

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Effects of organic sulfur on oxidation spontaneous combustion characteristics of coking coal

Energy Exploration & Exploitation ◽

10.1177/01445987211049045 ◽

2021 ◽

pp. 014459872110490

Author(s):

Fei Gao ◽

Zhe Jia ◽

Mei-ling Qin ◽

Xiao-gang Mu ◽

Yi-fei Teng ◽

...

Keyword(s):

Sulfur Content ◽

Photoelectron Spectroscopy ◽

Spontaneous Combustion ◽

Characteristic Temperature ◽

Combustion Process ◽

Oxidation Products ◽

Organic Sulfur ◽

Scanning Calorimetry ◽

Clean Coal ◽

Spontaneous Combustion Of Coal

Research on the spontaneous combustion of coal caused by sulfur has always been focused on pyrite in coal but has rarely considered the influence of organic sulfur. In this paper, coal samples, rather than model compounds, were used to study the influence of organic sulfur content in coal on its spontaneous combustion process. The results of X-ray photoelectron spectroscopy and thermogravimetry, differential scanning calorimetry, and mass spectrometry indicate that organic sulfur in Shuiyu clean coal exists in forms of mercaptan, thioether, sulfone (sulfoxide), and thiophene. With the decrease of organic sulfur content, the characteristic temperature points and the peak values of the exothermic curves in the process of coal oxidation spontaneous combustion all shifted toward higher temperatures. The ignition activation energy of coal also increased, and the initial and peak gas evolution temperatures of the oxidation products shifted toward higher temperatures. These findings suggest that the reduction of organic sulfur content can inhibit the oxidation process and spontaneous combustion tendency of coal. This effectively reveals the mechanism of the spontaneous combustion of coal and is of great significance to future studies in this field.

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Mainz Isoprene Mechanism 2 (MIM2): an isoprene oxidation mechanism for regional and global atmospheric modelling

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-14033-2008 ◽

2008 ◽

Vol 8 (4) ◽

pp. 14033-14085 ◽

Cited By ~ 6

Author(s):

D. Taraborrelli ◽

M. G. Lawrence ◽

T. M. Butler ◽

R. Sander ◽

J. Lelieveld

Keyword(s):

Atmospheric Chemistry ◽

Oxidation Mechanism ◽

Tropospheric Chemistry ◽

Oxidation Products ◽

Chemical Mechanism ◽

Good Representation ◽

Chemical Production ◽

Global Models ◽

Mixing Ratios ◽

Isoprene Oxidation

Abstract. We present an oxidation mechanism of intermediate size for isoprene (2-methyl-1,3-butadiene) suitable for simulations in regional and global atmospheric chemistry models, which we call MIM2. It is a reduction of the corresponding detailed mechanism in the Master Chemical Mechanism (MCM v3.1) and intended as the second version of the well-established Mainz Isoprene Mechanism (MIM). Our aim is to improve the representation of tropospheric chemistry in regional and global models under all NOx regimes. We evaluate MIM2 and re-evaluate MIM through comparisons with MCM v3.1. We find that MIM and MIM2 compute similar O3, OH and isoprene mixing ratios. Unlike MIM, MIM2 produces small relative biases for NOx and organic nitrogen-containing species due to a good representation of the alkyl and peroxy acyl nitrates (RONO2 and RC(O)OONO2). Moreover, MIM2 computes only small relative biases with respect to hydrogen peroxide (H2O2), methyl peroxide (CH3OOH), methanol (CH3OH), formaldehyde (HCHO), peroxy acetyl nitrate (PAN), and formic and acetic acids (HCOOH and CH3C(O)OH), being always below ≈6% in all NOx scenarios studied. Most of the isoprene oxidation products are represented explicitly, including methyl vinyl ketone (MVK), methacrolein (MACR), hydroxyacetone and methyl glyoxal. MIM2 is mass-conserving with respect to carbon, including CO2 as well. Therefore, it is suitable for studies assessing carbon monoxide (CO) from biogenic sources, as well as for studies focused on the carbon cycle. Compared to MIM, MIM2 considers new species like acetaldehyde (CH3CHO), propene (CH2=CHCH3) and glyoxal (CHOCHO) with global chemical production rates for the year 2005 of 7.3, 9.5 and 33.8 Tg/yr, respectively. Our new mechanism is expected to substantially improve the results of atmospheric chemistry models by more accurately representing the interplay between atmospheric chemistry, transport and deposition, especially of nitrogen reservoir species. MIM2 allows regional and global models to easily incorporate new experimental results on the chemistry of organic species.

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Oxidation of Some Titanium Alloys in Air at Elevated Temperatures

Materials Science Forum ◽

10.4028/www.scientific.net/msf.595-598.967 ◽

2008 ◽

Vol 595-598 ◽

pp. 967-974 ◽

Cited By ~ 4

Author(s):

E. Godlewska ◽

M. Mitoraj ◽

B. Jajko

Keyword(s):

Thermal Cycling ◽

Titanium Alloys ◽

Constant Temperature ◽

Cross Sections ◽

Elevated Temperatures ◽

Mixed Oxides ◽

Oxidation Mechanism ◽

Testing Procedure ◽

Oxidation Products ◽

Outward Diffusion

This paper presents comparative studies on the performance of two titanium alloys (Ti- 6Al-1Mn, Ti-45.9Al-8Nb) in an oxidizing atmosphere at 700 oC and 800 oC. Testing procedure comprised thermogravimetric measurements at a constant temperature and in thermal cycling conditions (1-h and 20-h cycles at constant temperature followed by rapid cooling). The overall duration of the cyclic oxidation tests was up to 1000 hours. The oxidized specimens were analyzed in terms of chemical composition, phase composition, and morphology (SEM/EDS, TEM/EDS, XRD). The extent and forms of alloy degradation were evaluated on the basis of microscopic observation of specimen fractures and cross-sections. Selected specimens were examined by means of XPS, SIMS and GDS. Oxidation mechanism of Ti-46Al-8Nb was assessed a two-stage oxidation method using oxygen-18 and oxygen-16. Apparently, the oxidation of this alloy proceeded in several stages. According to XPS, already after quite short reaction time, the specimens were covered with a very thin oxide film, mainly composed of aluminum oxide (corundum). A thicker layer of titanium dioxide (rutile) developed underneath. These two layers were typical of the oxidation products formed on this alloy, even when tested in thermal cycling conditions. In general, the scale had a complex multilayer structure but it was thin and adherent. Under the continuous layer of titania, there was a fine-grained zone composed of mixed oxides. The alloy/scale interface was marked with niobium-rich precipitates embedded in a titanium-rich matrix. There were some indications of secondary processes occurring under the initial continuous oxide layers (e.g. characteristic layout of pores or voids). Thickness of inner scale layers clearly increased according to parabolic kinetics, while that of the outer compact layer (mainly TiO2) changed only slightly. The distribution of oxygen isotopes across the scale/alloy interface indicated two-way diffusion of the reacting species – oxygen inward and metals outward diffusion. Silicon deposited on Ti-6Al-1Mn alloy positively affected scale adhesion and remarkably reduced alloy degradation rate.

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Determination of Chlorbenside Residues Including Its Sulfoxide and Sulfone Oxidation Products

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/49.2.407 ◽

1966 ◽

Vol 49 (2) ◽

pp. 407-412

Author(s):

Harry Shuman ◽

Ugo R Cieri

Keyword(s):

Gas Chromatography ◽

Acetic Acid ◽

Acid Solution ◽

Aluminum Oxide ◽

Electron Capture ◽

Acetic Acid Solution ◽

Extraction Procedure ◽

Oxidation Products ◽

Aluminum Oxide Column

Abstract A method is presented for determining residues of chlorbenside including its sulfoxide and sulfone oxidation products. The method employs the Mills-Onley-Gaither extraction procedure. Chlorbenside and chlorbenside sulfoxide are converted to chlorbenside sulfone by a short oxidation with chromic-acetic acid solution. Chlorbenside sulfone is isolated from interfering pesticides and most oxidation products on an aluminum oxide column and determined by electron capture gas chromatography. Recoveries for mixtures of the three components added to apple samples at 0.3–5 ppm (calculated as chlorbenside) were between 92 and 110%.

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Dilution-Induced Physico-Chemical Changes of Metal Oxide Nanoparticles Due to Homeopathic Preparation Steps of Trituration and Succussion

Homeopathy ◽

10.1055/s-0039-1694720 ◽

2019 ◽

Vol 109 (02) ◽

pp. 065-078

Author(s):

Abhirup Basu ◽

Mayur K. Temgire ◽

Akkihebbal K. Suresh ◽

Jayesh R. Bellare

Keyword(s):

Temperature Change ◽

Photoelectron Spectroscopy ◽

Cupric Oxide ◽

Morphological Changes ◽

Metal Oxide Nanoparticles ◽

Fluid Motion ◽

Oxide Nanoparticles ◽

Chemical Changes ◽

Bubble Generation ◽

Physico Chemical

Abstract Background Although the presence of starting materials in extreme dilutions of homeopathic medicines has been established, the physico-chemical changes of these materials induced by the manufacturing steps—that is, solid–solid mixing involving grinding (trituration) and slurry mixing involving impact (succussion), followed by dilution—are still unknown. Methods We subjected cupric oxide and zinc oxide nanoparticles (NPs) to the homeopathic processes of trituration and succussion, followed by dilution up to 6 cH. Particle image velocimetry was employed to analyze the fluid motion during succussion and its effect on the NPs. The resulting microstructural and chemical changes at different dilution steps were determined by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and transmission electron microscopy. Results The succussion triggered multi-sized bubble generation and turbulent fluid motion up to a duration of 400 ms, with maximum average velocity of 0.23 m/s. Due to 1% transfer of kinetic energy from a moving eddy with this velocity, upon collision, the rate of temperature change in a particle of size 1 µm and 1 nm was predicted to rise by approximately 102 K/s and 106 K/s respectively. During trituration, the oxide NPs reduced to metals and did not aggregate by remaining within lactose, but they converted to oxidized finer NPs after impact. Silicate chains leached from the vial cross-linked after third dilution, forming large macro-particles and encapsulating the NPs that were retained and carried at higher dilution steps. Conclusion The results showed that the NPs sustained significant rate of temperature change due to energy transfer from moving eddies during succussion. Different physico-chemical changes, such as size reduction, successive reduction and oxidation of NPs, and morphological changes, were achieved through trituration and succussion. The retention of NPs within cross-linked poly-siloxane chains reveals the importance of both the borosilicate glass vial and the ethanol solution during preparation of homeopathic medicines.

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