Formation Of Oxygen-containing Groups Research Articles

Effect of Oxidation Temperature on the Crystalline Phase of Polypropylene in Composites with Single-Walled Carbon Nanotubes

The effect of thermal oxidation on the crystalline phase of polypropylene in composites with single-walled carbon nanotubes has been studied. The composites are synthesized in propylene bulk using a homogeneous catalytic system rac-Me2Si(2-Me-4PhInd)2ZrCl2, activated by methylaluminoxane. The effect of thermal oxidation on thermophysical characteristics (the heat of melting and the melting temperature) measured by DSC and changes occurring in the polymer investigated by IR spectroscopy is studied. Changes in the structure of PP during thermo-oxidative degradation are studied by DSC at 140 and 170°С, that is, before and after melting of the samples. It is shown that the oxidized PP in the composites possesses a higher degree of crystallinity and a more perfect structure than the pure PP. At 170°С the effect of thermo-oxidative stabilization is observed only at low filling degrees (up to 3 wt %), in agreement with the TGA data. An analysis of IR spectra demonstrates that the presence of nanotubes in PP‑based composites during oxidation slows down the formation of oxygen-containing groups in the polymer. The conclusion is made that carbon nanotubes inhibit the thermal oxidation of polypropylene in the composites.

Thermo-electro dually activated carbon cloth as cathode material for aqueous hybrid zinc ion supercapacitor with ultrahigh stability and dramatically enhanced areal capacitance

The facile and low-cost technology for the fabrication of high-performance electrode material for supercapacitors is very important for green energy storage. Herein, the commercial carbon cloth (CC) with poor capacitance is subjected to thermal treatment at 430°C, followed by a potentiostatic oxidation at a constant potential of 2 V. Through the thermal activation process, the capacitance is increased to 1310 mF cm−2, and further enhanced to 2421 mF cm−2 after the additional potentiostatic activation. Nitrogen adsorption experiment and X-ray photoelectron spectroscopy analysis show that the prominent increase in specific surface area upon thermal-activation and the formation of oxygen-containing groups after electrochemical-activation are responsible for the greatly improved capacitive properties. The aqueous hybrid zinc ion supercapacitor (HZSC) constructed using the thermal-electro dually activated CCs cathode and Zn plate anode shows a high energy density of 1.21 mWh cm−2 at a power density of 4.75 mW cm−2. The HZSC displays superior long period stability with 94.65% capacitance retention after 8000 galvanostatic charge-discharge cycles. This work proposes a facile route to transform commercial carbon cloths into high performance self-standing cathode for the aqueous HZSCs, which will have noticeable effect on energy storage technology due to its stability, low-cost, environmental friendliness and safety.

Shearing bridge bonds in carbon nitride vesicles with enhanced hot carrier utilization for photocatalytic hydrogen production

The synergistic effect of morphology tailoring and the formation of oxygen-containing groups in g-C3N4 enhanced the production and separation of photoinduced carriers for photocatalytic H2 production.

Unraveling oxidative aging behavior of asphaltenes using ab initio molecular dynamics and static density functional theory

Asphalt aging is a major cause of cracking failure in asphalt pavement. However, owing to the lack of understanding of the asphalt aging mechanism, research on asphalt-targeted antiaging technology has encountered challenges. To address this issue, ab initio molecular dynamics simulations and density functional theory calculations based on the quantum chemistry framework were conducted to explore the reaction pathway and thermodynamic driving force of asphaltene aging. The physical properties of asphaltenes were evaluated to determine the effect of aging on asphaltene performance. The results indicate that asphaltenes undergo aging subreactions at different temperatures, including aromatization of naphthenes, formation of oxygen-containing groups, and homolysis of alkyl side chains. The free energy barriers of these reactions can be ranked in ascending order as aromatization < oxygen-containing group formation < homolysis. The molecular polarity, intermolecular binding energy, and solubility parameter of the asphaltene molecule increased significantly with aging, leading to enhanced agglomeration and reduced compatibility of asphalt components, resulting in the deterioration of asphalt cracking resistance.

Cathodic pre-polarization studies on the carbon felt/KOH interface: An efficient metal-free electrocatalyst for hydrogen generation

The recent decades have witnessed a booming research effort on the development of highly active electrode materials in electrocatalysis with the aim to replace the commonly used noble metal-based ones. Although non-noble metal electrodes can fulfill some requirements in terms of performance and price, their stability in alkaline media is generally weak. Additionally, from the environmental view point, the use of metals can cause water contamination. Therefore, the preparation of metal-free electrocatalysts represents an appealing approach to overcome the above-mentioned shortcuts. In this work, we used a simple electrochemical activation process, chronoamperometry measurements conducted in 1 M KOH at various overpotentials (−2, −2.5, −3, and −4 V vs. RHE) and pre-polarization periods (0.5, 2, 4, and 12 h), of commercially available and cheap carbon felt (CF) electrode to achieve good performance for hydrogen evolution reaction (HER) in alkaline media. Under optimized operating conditions (12 h of chronoamperometry measurement acquired at an overpotential of −4 V vs. RHE), the CF electrode exhibited an overpotential of 182 mV at 10 mA/cm 2 , a value surpassing that recorded for the most efficacious metal-free HER electrocatalysts published in the literature. The two CF samples exposed to 12 h of cathodic activation at −2.5 and −3.0 V vs. RHE recorded respectively Tafel slope ( b c ) values of 110 and 126 mV dec −1 . These b c values are close to the standard b c value of 120 mV dec −1 , suggesting the Volmer step as the main step controlling the HER. Increasing the applied cathodic potential to −4.0 V vs. RHE further decreased the b c value to 90 mV dec −1 , referring to increased accessible active catalytic sites for the HER. The cathodically activated CF surface's morphology and composition were assessed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) examinations. Raman spectroscopy was also conducted to assess the influence of the cathodic activation process on the structural defects/disorder of the CF surface. The formation of oxygen-containing groups on the CF surface after cathodic activation, as evidenced from XPS analysis, is believed to enhance water adsorption and act as active sites for hydrogen generation. The technique developed herein is simple and straightforward and can be easily implemented for almost any type of electrode.

Microplastics act as vectors for antibiotic resistance genes in landfill leachate: The enhanced roles of the long-term aging process.

Microplastics (MPs) are found to be ubiquitous and serve as vectors for other contaminants, and the inevitable aging process changes MP properties and fates. However, whether the MPs in aging process affects the fates of antibiotic resistance gene (ARGs) in aquatic environments is poorly understood. Herein, the physicochemical property alteration of MPs being aged in landfill leachate, an important reservoir of MPs and ARGs, was investigated, and microbial community evolution and ARGs occurrence of MP surface during the aging process were analyzed. Aging process remarkably altered surface properties, including increasing specific surface areas, causing the formation of oxygen-containing groups, and changing surface morphology, which further increased the probability of microbial colonization. The bacterial assemblage on MPs showed higher biofilm-forming and pathogenic potential compared to leachate. ARGs quantification results suggested that MPs exhibited selective enrichment for ARGs in a ratio of 5.7-103 folds, and the aging process enhanced the enrichment potential. Further co-occurrence networks suggested that the existence of non-random, closer and more stable ARGs-bacterial taxa relations on MP surface affected the ARG transmission. The study of ARG partitioning on MPs indicated that extracellular DNA was a nonnegligible reservoir of ARGs attached on MP surface, and that biofilm bacterial community influenced ARGs partitioning pattern during the aging process. This study confirmed that the aging process could enhance the potential of MPs as vectors for ARGs, which would promote the holistic understanding of MP behavior and risk in natural environments.

Mechanochemical Modification of Activated Carbon in Air

The effect exerted on the chemical properties and structure of activated carbon by the mechanical treatment as a modification procedure was studied. Mechanochemical modification of carbon samples was performed in a roller–ring vibration mill for 5 to 30 min. Samples were studied by X-ray diffraction, IR spectroscopy, and low-temperature nitrogen adsorption. X-ray diffraction analysis shows that the supply of mechanical energy increases the extent of structural disordering of activated carbon, which is manifested in an increase in microstrains. The mechanical treatment for more than 5 min led to a decrease in the specific surface area of the samples with a simultaneous increase in the total pore volume. The mechanical treatment for 5 min and less led to an increase in the specific surface area and to a decrease in the pore volume. The results of potentiometric titration and Boehm titration show that the modification leads to an increase in the concentration of phenolic and carboxyl groups. It is concluded that mechanochemical modification of activated carbon in air leads to its intense oxidation resulting in formation of oxygen-containing groups and in their decomposition.

Plasma Processing of Fibrous Carbon Materials prior to Their Metallization

The technology of plasma processing of carbon tape has been developed. Argon and air have been used as plasma-forming gases. By means of an IR spectrometer, it has been established that, upon processing in an air medium, there occurs formation of oxygen-containing groups on the surface of carbon tape. The influence of duration of plasma processing on adhesive strength between a carbon tape and copper coating has been determined. Mechanical and thermophysical properties of carbon-fiber-reinforced polymers made of carbon tape with copper coating and epoxy binder are given.

Sunlight mediated cadmium release from colored microplastics containing cadmium pigment in aqueous phase

The plastics industry is the biggest consumer of cadmium pigments. Little is known about the leaching of hazardous Cd2+ from colored microplastics containing cadmium pigment in aquatic systems. Here, we reported the release of Cd2+ from different sized microplastics containing cadmium pigment in aqueous phase under simulated sunlight. The release of Cd2+ was caused by the photo-dissolution of cadmium pigment. The release kinetics is highly size-dependent. It was relatively low for microplastics with size larger than 0.85 mm but increased significantly with decreasing size for microplastics smaller than 0.85 mm. The polymer matrix was oxidized during light exposure, leading to lower average molecular weight and the formation of oxygen-containing groups. Part of the polymer matrix was degraded into soluble organic carbon under simulated sunlight, resulting in continuous Cd2+ release from the pigment particles embedded in the polymer. The polymer degradation rate is also highly size-dependent. The degradation of the polymer matrix and the release of Cd2+ were intertwined. Cadmium leaching from microplastics from a commercial product containing cadmium pigment was confirmed in water under simulated sunlight. This work suggests that the photochemical processes of inorganic pigments will lead to the release of heavy metals from colored plastic debris.

Gas-Phase Mercury Removal by Modified Activated Carbons Treated with Ar-O2 Non-Thermal Plasma under Different O2 Concentrations

Abstract During the plasma modification process on activated carbon surface, reactive gas of O2 in the plasma field dominates the formation of oxygen-containing groups on activated carbon surface, which is a key factor that affects the mercury adsorption. Previous studies showed that change the O2 concentration would influence the generation of oxygen-containing groups and thus affect the mercury adsorption. It is important to investigate the effects of O2 concentration in the non-thermal plasma field on the mercury adsorption characteristic of modified activated carbon. This work presents the results of the novel use of non-thermal plasma in Ar-O2 gas to increase surface oxygen functionality on the surface of a commercially available biomass carbon. The volume fraction of O2 in the Ar-O2 mixture was varied from 10 % to 100 %. The surface physical and chemistry properties of modified activated carbon were analyzed by using BET, FT-IR and XPS techniques. Results showed that activated carbon modified by Ar-O2 non-thermal plasma showed significantly better mercury removal performance compared with the original activated carbon. Moreover, increase O2 concentration in the plasma field can further increase the mercury removal efficiency of modified activated carbon. Higher O2 concentration can produce more O radicals during plasma system and facilitated the formation of carbonyl and ester groups on activated carbon surface and thus enhanced the mercury removal. Temperature programmed desorption (TPD) results indicated that mercury reacted with ester groups were prior to carbonyl groups. When O2 concentration increased to 100 %, the ester groups of modified activated carbon dominated the mercury adsorption process.

Modification of Metallic Multiwalled Carbon Nanotubes Properties by 50 Hz Atmospheric Pressure Dielectric Barrier Discharge Plasma

In this study, multiwalled carbon nanotubes (MWCNTs) were modified using low frequency (50 Hz) nonequilibrium plasma, which was generated separately by oxygen and nitrogen dielectric barrier discharge plasma (DBD) at atmospheric pressure. The MWCNTs were treated with oxygen and nitrogen DBD plasma at atmospheric pressure under three different applied voltages, because the MWCNTs surface was closely related to the plasma treatment voltage. The surface and electrical properties of pristine and treated MWCNTs were studied using Transmission Electron Microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, while the electrical characteristics were measured using a Hall measurement and two-point probe. FTIR showed formation of oxygen-containing groups like C=O and COOH for the O2 DBD plasma, and addition of N–H vibration bending for the N2 DBD plasma. Raman spectroscopy revealed that the ratio of I D/I G increased with increasing discharge voltage of plasma. The ascended I D/I G may be ascribed to the production of several new defects owing to the introduction of oxygen- and nitrogen functional groups recognized by FTIR. The results of Hall measurement showed that the hall mobility increased with the increase of O2 and N2 DBD voltage. Highest hall mobility was measured for MWCNTs treated with nitrogen at 12 kV, which was 172.9 cm2/Vs. It was also found from the two-point probe IV curve that Ohmic behaviour of pristine MWCNTs tended to change to Schottky behaviour after DBD plasma treatment.

Comparative Study of Chromium(VI) Removal from Simulated Industrial Wastewater with Ion Exchange Resins

Ion exchange process is an alternative technique for removal of heavy metal ions from industrial wastewater. The main aim of this paper is to evaluate the performance of different ion exchange resins in removing Cr(VI) from wastewater. The effects of resin types and dosage, initial pH were examined systemically. The results showed that the performance of different resins had obvious difference for the removal of the Cr(VI) ions, in which the type of functional groups of the resin was the main factor. The SEM images indicated that the micro-morphology of resins before and after adsorption of the Cr(VI) presented a little difference. The EDS analysis showed that the adsorbed Cr(VI) was uniformly distributed at the surface of the resins with formation of oxygen-containing groups. The adsorption isotherms and kinetics of Cr(VI) by the different resins are also discussed.

Oxygen consumption and chemisorption in low-temperature oxidation of sub-bituminous pulverized coal

ABSTRACTStudying the effect of oxygen in coal oxidation is very important for understanding and controlling coal spontaneous combustion. However, the oxygen effect is not very easy to determine clearly due to the large effect of heat source on coal oxidation in temperature rising experiments. Here, focused on sub-bituminous coal, the oxygen effect was separated from coal oxidation by continuously measuring FTIR spectra of coal with respect to varying temperatures and under oxygen and nitrogen. The active groups’ real-time changes of coal oxidation, thermal treatment and oxygen effect were measured. The carboxylic ester and carboxyl units are the main functional groups that increase with temperatures increasing under oxygen and nitrogen, while the other functional groups decrease in quantity. The oxygen effect promoted the consumption of aliphatic hydrocarbons and hydroxyl groups and also promoted the formation of oxygen-containing groups (except hydroxyl). Four characteristic temperature stages involved in the oxygen effect and their key functional groups were identified. Simultaneously, the relationship of oxygen consumption and chemisorption in oxygen effect was analyzed. The starting temperature of oxygen chemisorption is between 50 and 60°C. The maximum contribution of oxygen effect was observed in methyl and methylene groups. These results are important for chemical control of coal spontaneous combustion. The oxidation of aliphatic hydrocarbon should be controlled before oxygen chemisorption. The value of oxygen consumption between 70 and 80°C can be measured accurately due to the constant chemisorption rate, which help to identify the tendency for spontaneous combustion. These results will help in better understanding of the reaction mechanism of coal oxidation, especially the oxygen effect.

Potential and pH dependence of photocurrent transients for boron-doped diamond electrodes in aqueous electrolyte

Using illumination at energies below the intrinsic diamond energy gap, photocurrent transients have been recorded for boron-doped diamond (BDD) as an electrode in an aqueous electrolyte of 0.1M KH2PO4. The commercially-supplied BDD was in the form of a free-standing, polycrystalline film grown by chemical vapour deposition (CVD), with a boron acceptor concentration of ≥1020cm−3. The effects of mechanical polishing of the BDD, of electrochemical hydrogen evolution and of electrochemical oxygen evolution (in 0.1M KH2PO4), on the potential dependence of the photocurrent transients have been examined. Measurements of the cathodic photocurrent at light switch-on have been used to determine the photocurrent onset potential as a measure of the flatband potential. Comparison with and between related literature observations has shown broad agreement across considerably varying BDD/electrolyte systems. The flatband potential shifted positively following electrochemical oxygen evolution, indicating the formation of oxygen-containing groups on the diamond surface, these increasing the potential drop across the Helmholtz layer. For the electrochemically oxidised electrode, the cathodic photocurrent transient at a fixed potential changed reproducibly with changing solution pH, owing to the participation of the oxygen-containing surface groups in acid–base equilibrium with the solution. This clear demonstration of BDD as a photoelectrochemical pH sensor is in principle extendable to mapping the spatial variation in pH across a BDD surface by use of a focussed light spot.

Chemical treatment of CNTs in acidic KMnO4 solution and promoting effects on the corresponding Pd–Pt/CNTs catalyst

Carbon nanotubes (CNTs) were chemically treated in acidic KMnO4 solution. XRD, nitrogen physisorption, FTIR and chemical titration were used to investigate the influence of the treatment conditions on the surface structure, the bulk structure, the types and the amounts of the formed surface oxygen-containing functional groups of CNTs. The results show that the structure is not changed clearly after treatment and the formation of oxygen-containing groups, e.g., carboxyls, on the CNT surface is dependent on the treatment conditions. Under the present conditions, the concentration of the employed sulphuric acid and the weight ratio of the solid KMnO4 and CNTs have clear influence on the formation of carboxyls, however, by comparison, the influence is slight when the treatment temperature is above 95°C. With the increasing of the amount of carboxyls, the dispersion of the corresponding Pd–Pt metal particles supported on CNTs is increased and the catalytic activity is promoted in the profile reaction of naphthalene hydrogenation to tetralin.

Possibility of producing carbon mesoporous sorbents from coal raw materials

Porous carbon material from anthracite (2.5% of ash) produced at different activation temperatures with different burning degree is studied. According to the data of IR-spectroscopy and element analysis, oxidation results in the removal of aliphatic groups and the formation of oxygen-containing groups. Air oxidation causes formation of fractures, meso- and macropores.

A comparative study of argon ion irradiated pristine and fluorinated single-wall carbon nanotubes

Effect of Ar(+) ion irradiation on the structure of pristine and fluorinated single-wall carbon nanotubes (SWCNTs) was examined using transmission electron microscopy (TEM), Raman, and x-ray photoelectron spectroscopy (XPS). The TEM analysis revealed retention of tubular structures in both irradiated samples while Raman spectroscopy and XPS data indicated a partial destruction of nanotubes and formation of oxygen-containing groups on the nanotube surface. From similarity of electronic states of carbon in the irradiated pristine and fluorinated SWCNTs observed by XPS, it was suggested that defluorination of nanotubes proceeded with breaking of C-F bonds.

Change in the surface properties of poly(vinylidene fluoride) films by treatment in direct-current discharge

It has been found that treatment in dc discharge results in a substantial and time-invariant increase in the surface energy of poly(vinylidene fluoride) films. This effect is obviously due to the formation of oxygen-containing groups on the polymer surface, a fact that is corroborated by Fourier-transform IR spectroscopy and X-ray photoelectron spectroscopy data. It has been shown that dc discharge is more effective in altering the contact properties of the polymer surface than low-frequency glow discharge.

Interactions of NO 2 with activated carbons modified with cerium, lanthanum and sodium chlorides

Highly porous wood-based activated carbon was impregnated with cerium, lanthanum and sodium chlorides using incipient impregnation method. On the samples prepared adsorption of NO 2 was carried out from moist (70% humidity) air either with or without the prehumidification. The materials were characterized using adsorption of nitrogen, thermal analysis, FTIR, and potentiometric titration. The results indicated that for all materials a significant amount of NO 2 was reduced to NO and released from the system. In the case of virgin carbons, the NO 2 interacting with the surface along with nitric and nitrous acids formed there in the presence of water significantly increased the acidity of the carbons by the formation of oxygen-containing groups and organic nitrates. On the other hand, when chlorides were present the capacity to interact with nitrogen dioxide increased since the inorganic phase, depending on the nature of metal, bound NO 2 in the forms of nitrates (Ce, La, Na), got oxidized/oxidized carbon surface (for Ce) or contributed to the formation of nitrosyl chloride (for Na).

Activated carbons modified with sewage sludge derived phase and their application in the process of NO 2 removal

Highly porous wood-based activated carbon was treated with species extracted from the surface of pyrolyzed sewage sludge. Their deposition on the external surface was visible by a change of the color of the carbon and on internal surfaces, by a decrease in porosity. The as-received carbon and its impregnated counterpart were heat treated at 950 °C at an inert atmosphere. Data for the adsorption on NO 2 was carried out from dry and moist (70% humidity) air. The results indicated that for all materials a significant amount of NO 2 was reduced to NO and released from the system. Heat treatment increases the capacity possibly as a result of an increase in basicity. The addition of the inorganic phase has a positive effect only when adsorption is run in moist conditions and inorganic nitrates and nitrites were formed. Otherwise, the NO 2 adsorbed and nitric and nitrous acids formed on the surface significantly increase the acidity of the carbons by the formation of oxygen-containing groups and organic nitrates.