Distribution Of Oxygen-containing Functional Groups Research Articles

Hydrophilic 1T-WS2 Nanosheet Arrays toward Conductive Textiles for High-Efficient and Continuous Hydroelectric Generation and Storage.

Flexible hydroelectric generators (HEGs) are promising self-powered devices that spontaneously derive electrical power from moisture. However, achieving the desired compatibility between a continuous operating voltage and superior current density remains a significant challenge. Herein, a textile-based van der Waals heterostructure is rationally designed between conductive 1T phase tungsten disulfide@carbonized silk (1T-WS2@CSilk) and carbon black@cotton (CB@Cotton) fabrics with an asymmetric distribution of oxygen-containing functional groups, which enhances the proton concentration gradients toward high-performance wearable HEGs. The vertically staggered 1T-WS2 nanosheet arrays on the CSilk fabric provide abundant hydrophilic nanochannels for rapid carrier transport. Furthermore, the moisture-induced primary battery formed between the active aluminum (Al) electrode and the conductive textiles introduces the desired electric field to facilitate charge separation and compensate for the decreased streaming potential. These devices exhibit a power density of 21.6µWcm-2, an open-circuit voltage (Voc) of 0.65V sustained for over 10000s, and a current density of 0.17mAcm-2. This performance makes them capable of supplying power to commercial electronics and human respiratory monitoring. This study presents a promising strategy for the refined design of wearable electronics.

Distribution of oxygen-containing functional groups on defective graphene: properties engineering and Li adsorption.

In this study, the distribution of oxygen-containing functional groups on graphene with vacancies and topological defects was systematically investigated using advanced computational methods and the structure models for multi-defect graphene oxides (GOs) were proposed. All potential adsorption sites were considered through an automated structure generation program to identify energetically favorable structures. Unlike the pristine graphene surface where oxygen-containing functional groups always aggregate with each other, we observed a tendency for them to preferentially adsorb near defects. Furthermore, they may also be distributed on the same side or both sides of the defective graphene. These multi-defect GOs can exhibit either metallic or semiconducting properties. Notably, upon adsorbing the same oxygen-containing functional groups onto the surface of defective graphene, their electronic characteristics become homogeneous. The coexistence of vacancy/topological defects and oxygen-containing functional groups within the graphene lattice introduces intriguing mechanical anisotropic properties to graphene, including the uncommon negative Poisson's ratio. Additionally, these materials exhibit anisotropic optical behavior, displaying heightened absorption within the infrared and visible regions compared to pristine graphene. Finally, it is found that Li atoms are adsorbed stably on the surfaces of multi-defect GOs via the formation of LinO/LimOH clusters. The research findings presented in this paper, encompassing the development of structural models for multi-defect GOs, could provide crucial insights into the properties and potential applications of graphene oxides.

Moist-electric films based on asymmetric distribution of sodium alginate oxygen-containing functional groups

Moist-electric generation as a green process of power generation can effectively solve energy and environmental problems. In order to improve the moist-electric properties of moist-electric generator (MEG), this study designed and prepared a sodium alginate (SA)/multi-walled carbon nanotube (MWCNT) bilayer film hygroscopic generator with an asymmetric distribution of oxygen-containing functional groups (asym-SCM) by simple freeze-drying and pressing. The relative ratios of carbon and oxygen in the system were adjusted by changing the ratios of SA/MWCNT, and the advantages of constructing an asymmetric distribution of oxygen-containing functional groups on the moist-electrical properties of the material were verified. The asym-SCM MEG is able to draw moisture from the environment, generating an open circuit voltage up to ca. 0.65 V at low humidity (ca. 40%) and generating power continuously for up to 650 min. At 90% humidity, the asym-SCM MEG can achieve an output voltage of ca. 0.78 V, well above the power generation performance of most biomass materials moist-electric studies in the current phase. This MEG is green, biocompatible, biodegradable, promising to be used as a self-powered device for flexible wearable, biomedical and other applications.

Evolution of layer distance and structural arrangement of graphene oxide with various oxygen content and functional types in low temperature: A ReaxFF molecular dynamics simulation

Due to the oxygen–containing functional groups covering the graphene oxide surface, multilayer graphene oxide has different properties. The understanding of its atomic structure and layer stacking behavior at low temperature is far from complete. This work systematically revealed how the oxygen-containing groups density, type and temperature affect the spacing of multilayer GO layers through the ReaxFF molecular dynamics simulation method. We found that the density of oxygen-containing groups is the main variable that controls the distribution of surface oxidation areas and the degree of distortion of the graphene sheets. With the increase of C/O ratio, the distribution of oxygen-containing functional groups tends to aggregate, and the deformation of graphite flakes becomes more serious. The layer spacing of multilayer GO is affected by temperature. The types of released small molecules, the degree of pyrolysis of the graphene skeleton and the interlayer spacing are all affected by OH/O ratio. With more hydroxyl groups, it is easier to release long O-H chains, and the graphene skeleton is less likely to be pyrolyzed. This in–depth investigation has helped develop a fundamental understanding of the atomic structure of graphene oxide and has laid basic foundations for an effective control of graphene layer distance and properties.

Influence Mechanism of Surfactants on Wettability of Coal with Different Metamorphic Degrees Based on Infrared Spectrum Experiments.

Based on experiments, a numerical analysis is used to quantitatively explore the influence of coal and surfactant microstructures on wettability. First, based on an infrared spectrum experiment, the distribution of oxygen-containing functional groups, aromatic hydrocarbons, and aliphatic hydrocarbons of coal and surfactants was obtained. Second, the wettability relationship between coal and different surfactants was determined by optical titration, and the coal dust wettability and surfaces were optimized. The key factors of the active agent wetting ability affecting lignite wetting mainly depend on the carbonyl, ether, and carboxyl groups in the surfactant. The factors affecting non-stick coal and gas coal wetting mainly depend on the ether group and aromatic amine in the surfactant. The factors affecting fat coal wetting mainly depend on the ether group and hydroxyl group in the surfactant. Finally, the factors affecting coking coal and anthracite wetting mainly depend on the surfactant ether group, aliphatic amine, and aromatic amine. Then, combining the structural parameters with the coal wetting results, the quantitative mathematical relationship between coal dust wettability, the important influencing factors of the surfactant, and the wettability index was established. Finally, a perfect and reasonable wettability evaluation model between coal and the surfactants was established. The relative activity of methyl ether and aromatic ether is greater than that of methyl ether, and the influence on the lignite, coking coal, and anthracite wettability conforms to the model . The influence on the non-caking coal and fat coal wettability conforms to the model , while the influence on the gas coal wettability conforms to the model Z = A + B1X1 + B2X2. In general, this study provides scientific guidance for the compounding of high-efficiency and environmentally protective composite dust suppressors to realize clean mine production.

Superior antibacterial activity of reduced graphene oxide upon decoration with iron oxide nanorods

Iron oxide (Fe2O3) nanorods (NRs) decorated reduced graphene oxide (rGO) nanocomposite, endowed with high antibacterial activity, was prepared through the one-pot calcination of pre-synthesized Fe2O3 NRs in rGO aqueous dispersion. The Fe2O3 NRs were well infused between the rGO layers as revealed by the AFM, SEM, and TGA analysis, whereas the removal and distribution of oxygen-containing functional groups were distinguished with UV–vis and FT-IR spectroscopy. The antibacterial activity of Fe2O3/rGO nanocomposite towards methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Staphylococcus aureus (VRSA), and ciprofloxacin-resistant Staphylococcus aureus (CRSA) was investigated by disk diffusion method and growth curve analysis. The nanocomposite demonstrated excellent antibacterial activity as compared to bare rGO and inhibited nearly 87 % of the bacterial growth. The CRSA was more sensitive to nanocomposite compare MRSA and VRSA. More importantly, the nanocomposite obtained was found to achieve minimum inhibitory concentration (MIC) of ∼ 5 μg/mL. Besides, measurements of the charge transfer resistance, which is used to interpret bacterial response towards rGO or Fe2O3/rGO modified glassy carbon electrode, were performed using electrochemical impedance spectroscopy (EIS). The noteworthy antibacterial performance of the Fe2O3/rGO nanocomposite was probably attributed to the synergistic effect Fe2O3 NRs decorated rGO. The mechanism study suggested that nanocomposite can induce death to the bacteria by direct contact with the sharp edges of rGO and through the release of Fe3+ ions. The data, altogether, indicated that the Fe2O3 NRS decoration of rGO resulted in nanocomposite with enhanced antibacterial performance, hence, it may be used for developing new, safe, and effective antibiotics.

Effects of Upgrading Treatment on the Physicochemical Structure, Moisture Re-Adsorption Ability, and NOx Emission Characteristic of Lignite Particles

A typical Chinese lignite (HLH) was used for determining the correlation among upgrading temperature, moisture re-adsorption behaviors, and nitrogen evolution characteristics during the combustion process. The upgraded samples were obtained from four drying temperatures: 393, 423, 453, and 483 K in the ComDry (counter flow multi baffle dryer) system. By means of the utilization of the N₂ adsorption method and scanning electron microscope, the effects of drying temperature on the surface morphology and pore structural characteristics of lignite particles were determined. With the increase of drying temperature (Td), big pores collapsed into small ones leading to the enhancement of porosity, pore volume, and specific surface area, as well as the reduction of the average pore diameter. The distribution of oxygen-containing functional groups (C(O)) on the surface of the samples dried at different temperatures was identified by Fourier transform infrared spectroscopy. More carboxyl and hydroxyl converted into ether and anhydride, which were thermally stable in the process of drying treatment performed at higher temperatures, reducing the possibility of spontaneous combustion in lignite storage. Both the physical and chemical structural characteristics could be regarded as indicators reflecting the moisture re-adsorption behavior. The moisture content re-adsorbed by the upgraded coal particles expressed negative effects on inhibiting NO emission during the combustion process, and increasing Td could effectively inhibit the occurrence of moisture re-adsorption. The optimum Td for the upgrading treatment of HLH lignite by the ComDry system is 483 K.

Distribution of the functional groups in various coals with different spontaneous propensity

ABSTRACTThe distribution of oxygen-containing functional groups, aromatic hydrocarbons, and aliphatic groups in coal with different spontaneous combustion propensity were studied. Adiabatic method was used to determine the spontaneous combustion propensity of six different coal samples. FTIR was used to collect the spectrum of the coal, and the peak areas of the functional groups were analyzed. The proportion of C = C, CH3/CH2, OH, C = O, COOH, C-O, and C-O-O obtained based on the peak areas was calculated, and the spontaneous combustion propensity was characterized by the distribution of the functional groups. It was found that there is a good corresponding relationship between the content of aromatic functional groups and oxygen-containing functional groups with the self-heating time of the coal samples. The coal with shorter self-heating time has less aromatic groups and more oxygen-containing functional groups. With the increase of the spontaneous combustion propensity of coal, there are less aliphatic hydrocarbons functional groups generally. But among different coal samples, the contents of aliphatic hydrocarbons functional groups differ not great.

Nanotubols under H2O2 exposure: is it possible to poly-hydroxylate carbon nanotubes?

We present a combined experimental and theoretical study dedicated to analyze the variations in the surface chemistry of hydroxylated multiwalled carbon nanotubes (MWCNTs), so called nanotubols, when exposed to H2O2 at high temperatures. The formation, surface density, and distribution of oxygen-containing functional groups are studied by infrared (IR) and X-ray photoelectron spectroscopy (XPS), as well as density functional theory (DFT) calculations performed on model functionalized carbon nanotubes (CNTs). After H2O2 exposure, the initial composition of -OH, -C[double bond, length as m-dash]O, and -COOH substituents notably changes, with carbonyl -C[double bond, length as m-dash]O groups being the ones that show the most notable increase on the carbon surface. Our highly oxidized MWCNTs are partially soluble and form complex two-dimensional patterns at the air-water interface, as evidenced by Brewster angle microscopy. In a second step, these films can be transferred to solid substrates to form porous multilayered carbon nanostructures with complex morphologies. In particular, and for the first time, we report the synthesis of "stadium-like" configurations made of MWCNT units whose formation and stability are a direct consequence of the self-assembly process occurring at the air/water interface. DFT calculations suggest the formation of molecular islands of oxygen-containing functional groups on the CNT surface. In addition, nudged elastic band studies reveal that, for these adsorbed phases, the reaction between two neighboring OH groups to produce atomic oxygen and a physisorbed water molecule is characterized by energy barriers of ∼0.2 eV. These small values could be at the origin of the sizable increase in chemisorbed single-oxygen species determined by XPS data after H2O2 treatment at 60 °C. The simulation of the C 1s binding energies (BE) allows us to more clearly identify the different oxygen-containing functionalities as well as to reveal how the local atomic environment affects their characteristic BEs. Even if we were unable to polyhydroxylate our carbon nanotubes, we believe that H2O2-treated MWCNTs are interesting materials for more complex post-functionalization procedures that might lead to the fabrication of novel carbon nanostructures.

The medium-term effect of natural compost on the spectroscopic properties of humic acids of Czech soils

AbstractIn the current work, humic acids (HAs) isolated from natural compost and unamended and amended soils in a medium-time field experiment were characterized to evaluate the effects of the amendment at rates of 124, 239 and 478 t/ha on their chemical, compositional and structural features. The impact of the application of compost on their properties was observed over 3 years. Humic acids were characterized using spectral methods and elemental analysis. Humic acid isolated from compost was predominantly aliphatic, with a larger content of nitrogen and low degree of aromaticity and humification. The typical maximum (280/345 nm) of HA obtained from compost lies within the T (tryptophan-like) region, which can be ascribed to proteinaceous organic materials. On the other hand, the HAs obtained from amended soil were mainly aromatic in character, with a larger distribution of oxygen-containing functional groups, molecular weight and greater aromaticity. Fluorophores of HAs obtained from amended soil lie within the C (humic-like) region with typical maxima centred in the range 430–450/500–540 nm, occurring usually in HAs isolated from soil, peat and lignite. According to ultra-violet/visible and Fourier-transform infrared (FTIR) spectroscopy, the larger oxygen contents of these HAs are associated with the substitution of aromatic rings by oxygen-containing functional groups such as carboxylic, hydroxyls and ethers. On the basis of FTIR spectra, it was shown that HAs obtained from amended soil 2 and 3 years after compost application were enriched by peptid, aromatic and polysaccharide compounds absorbing at 1540, 1515 and 1040/cm, respectively.

The effect of air plasma treatment at atmospheric pressure on thermally modified wood surfaces

This study tests the hypothesis that thermal modification of wood influences the effectivity of air plasma treatment. Micro-veneers of European beech, Scots pine and Norway spruce were thermally modified at two different temperatures and subsequently plasma-treated for 1 and 3 s. The veneer surfaces were characterized in terms of morphology, wetting behaviour and surface chemistry. No severe changes in the veneer surfaces due to plasma treatment were observed by scanning electron microscopy. Plasma treatment increased surface free energy and wettability by water and urea–formaldehyde adhesive; it was more effective on thermally modified wood than on unmodified wood. X-ray photoelectron spectroscopy revealed a similar distribution of oxygen-containing functional groups on the wood surface after plasma treatment of thermally modified and unmodified beech wood. It is suggested that enhanced wettability through plasma treatment is due to the generation of carboxyl groups within the lignin network, which contribute to the polar part of the surface free energy. The high effectiveness of plasma treatment on thermally modified wood might thus be explained by its high relative proportion of lignin.

Assessment of the surface chemistry of wood-derived biochars using wet chemistry, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy

In order to understand the reactivity of biochar in soil, we thoroughly examined the carbonaceous surface of different biochars, paying particular attention to the distribution of oxygen-containing functional groups. Biochar was produced from pine, poplar and willow at two different temperatures (400 and 550°C) and characterised using elemental analysis and wet chemistry (Boehm and potentiometric titrations, cation-exchange capacity (CEC) measurement). In addition, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses were performed on both untreated and acid-washed biochar samples. Qualitative relationships were observed between data generated from the titration methods under investigation and XPS analyses, both describing the general distribution of oxygen-containing surface functional groups. Total acidity of biochar ranged widely, between 32 and 1067 mmol kg–1, and was mostly attributed to the presence of hydroxyl or phenol groups. The number of functional groups containing oxygen decreased with increasing pyrolysis temperature, mainly because of a decrease in the content of phenol groups. A quantitative comparison of titrations and CEC (i.e. biochar’s ion-exchange capacity) measurements was compromised by a masking effect caused by the biochar’s inorganic fraction (<8%). An acid-washing step with nitric acid was shown not to alter the biochar surface systematically. The use of potentiometric titrations with an acid-washing pretreatment proved to be suitable to quantify biochar acidic functional groups, and hence biochar acidity.

Preparation of TiO2/carbon nanotubes photocatalysts: The influence of the method of oxidation of the carbon nanotubes on the photocatalytic activity of the nanocomposites

A method for the preparation of efficient TiO2/multi-wall carbon nanotubes nanocomposite photocatalysts by precipitation of anatase TiO2 nanoparticles onto differently oxidized carbon nanotubes is presented. The precursor compound titanium(IV) bromide was hydrolyzed producing pure anatase phase TiO2 nanoparticles decorated on the surface of the oxidized carbon nanotubes. The oxidative treatment of the carbon nanotubes influenced the type, quantity and distribution of oxygen-containing functional groups, which had a significant influence on the electron transfer properties, i.e., the photocatalytic activity of the synthesized nanocomposites. The results of C.I. Reactive Orange 16 photodegradation in the presence of all the synthesized nanocomposites showed their better photocatalytic activity in comparison to the commercial photocatalyst Degussa P-25.

Surface and structural characterization of multi-walled carbon nanotubes following different oxidative treatments

Six commonly used wet chemical oxidants (HNO 3, KMnO 4, H 2SO 4/HNO 3, (NH 4) 2S 2O 8, H 2O 2, and O 3) were evaluated in terms of their effects on the surface chemistry and structure of MWCNTs using a combination of analytical techniques. X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDX) were used to characterize the extent of surface oxidation, while chemical derivatization techniques used in conjunction with XPS allowed the concentration of carboxyl, carbonyl, and hydroxyl groups at the surface to be quantified for each MWCNT sample. Our results indicate that the distribution of oxygen-containing functional groups was insensitive to the reaction conditions (e.g., w/w% of oxidant), but was sensitive to the identity of the oxidant. MWCNTs treated with (NH 4) 2S 2O 8, H 2O 2, and O 3 yielded higher concentrations of carbonyl and hydroxyl functional groups, while more aggressive oxidants (e.g., HNO 3, KMnO 4) formed higher fractional concentrations of carboxyl groups. IR spectroscopy was unable to identify oxygen-containing functional groups present on MWCNTs, while Raman spectra highlighted the frequently ambiguous nature of this technique for measuring CNT structural integrity. TEM was able to provide detailed structural information on oxidized MWCNT, including the extent of sidewall damage for different oxidative treatments.

Sorption of Aqueous Zn[II] and Cd[II] by Multiwall Carbon Nanotubes: The Relative Roles of Oxygen-Containing Functional Groups and Graphenic Carbon

Exposure of multiwalled carbon nanotubes (MWCNTs) to oxidizing acids and other oxidants introduces oxygen-containing functional groups such as hydroxyl, carboxyl, and carbonyl groups onto the surface. This research evaluated how changes in oxygen concentration and distribution of oxygen-containing functional groups influenced the sorption of aqueous zinc and cadmium on MWCNTs. Sorption results with natural char, activated carbon, and a suite of MWCNTs (of varying surface oxygen content) were obtained. Results confirmed that surface oxygen enhances the sorption of both Zn[II] and Cd[II] from aqueous solution. Although Zn[II] sorbed more strongly than Cd[II] for all materials studied, surface oxidation had more effect on the sorption of Cd[II] than of Zn[II]. Additional sorption experiments with Zn[II] and 16 MWCNTs of varying surface oxidation level and functional group distribution revealed the relative contributions of different types of surface sites to sorption. Sorption isotherms were fit using a two-site Langmuir adsorption model that incorporated the independent characterization of functional group distribution. Results showed that carboxyl-carbon sites were over 20 times more energetic for zinc sorption than unoxidized carbon (graphenic-carbon) sites, though both site types are important contributors to sorption.

Influence of Surface Oxides on the Colloidal Stability of Multi-Walled Carbon Nanotubes: A Structure−Property Relationship

As with all nanomaterials, a large fraction of the atoms in carbon nanotubes (CNTs) reside at or near the surface. Consequently, surface chemistry will play a crucial role in determining the fate and transport of CNTs in aquatic environments. Frequently, oxygen-containing functional groups (surface oxides) are deliberately grafted into the CNT surface to promote colloidal stability. To study the influence that both the oxygen concentration and the oxygen functional-group distribution have on the colloidal stability of multiwalled carbon nanotubes (MWCNTs), a suite of oxidized MWCNTs (O-MWCNTs) were created using different oxidizing agents and reaction conditions. Stable colloidal suspensions were prepared by low-power sonication of O-MWCNT powders in Milli-Q water. Results from TEM, AFM, DLS, and XPS measurements revealed that, irrespective of the surface chemistry, the colloidal suspensions were composed of individual nanotubes with comparable length distributions. The critical coagulation concentrations (CCC) of O-MWCNTs that exhibited different surface chemistries were measured with time-resolved dynamic light scattering (TR-DLS) using NaCl as the electrolyte. Over a range of environmentally relevant pH values, linear correlations were found to exist between the CCC, total oxygen concentration, and surface charge of O-MWCNTs. In contrast to surface charge, electrophoretic mobility did not prove to be a useful metric of colloidal stability. Information obtained from chemical derivatization studies, carried out in conjunction with XPS, revealed that the distribution of oxygen-containing functional groups also influences the colloidal stability of O-MWCNTs, with carboxylic acid groups playing the most important role. This study highlights the fact that quantitative relationships can be developed to rationalize the influence of surface chemistry on the behavior of nanomaterials in aquatic environments.

Manifestation of the loading effect in polypropylene oxidative plasma degradation processes

Changes in the surface composition of polypropylene films depending on the type of surface subjected to oxygen plasma treatment in a cylindrical reactor were studied by means of Fourier-transform attenuated total reflectance IR spectroscopy. It was found that an increase in the surface area of the film mounted as a cylinder on the reactor wall leads to a decrease in the etching rate and to an inhomogeneous concentration distribution of oxygen-containing functional groups and double bonds over the specimen length. It was shown that the concentrations of newly formed functional groups increase with an increase in the area of the treated surface.

Electrochemical catalytic modification of activated carbon fabrics by ruthenium chloride for supercapacitors

A novel method, electrochemical catalytic oxidation via a ruthenium redox couple in an aqueous RuCl 3 · xH 2O solution rather than the anodic deposition of Ru oxides, was developed to modify the microstructure and electrochemical properties of activated carbon fabrics (ACFs). The variation in microstructures (i.e., specific surface area and mean pore size) for the modified ACFs was examined by means of nitrogen gas adsorption isotherms. The distribution of oxygen-containing functional groups within the modified ACFs was identified by temperature programmed desorption (TPD) and X-ray photoelectron (XPS) spectra. Effects of the electrochemical catalytic modification on the electrochemical characteristics and reversibility of ACFs were investigated systematically by means of cyclic voltammetry (CV) and chronopotentiometry (CP) in 0.5 M H 2SO 4. The total specific capacitance of ACFs reached a maximum (ca. 180 F/g measured at 10 mA/cm 2) when they were catalytically modified at 1.15 V with a passed charge density of 5 C/cm 2. These modified ACFs were demonstrated to be an excellent candidate for the supercapacitor application.

Analysis of functional groups on the surface of plasma-treated carbon nanofibers.

Plasma chemically modified carbon nanofibers were characterized by X-ray photoelectron spectroscopy with regard to the content of carbon, oxygen, and nitrogen and the contribution of carboxylic groups or ester, carbonyl and hydroxylic groups or ether on the surface. Unfortunately, X-ray photoelectron spectroscopy only provides an average value of the first 10 to 15 molecular layers. For comparison, depth profiles were measured and wet chemical methods were applied to estimate the thickness of the functionalized layer and the distribution of oxygen-containing functional groups within the near-surface layers. The results indicate that the fiber surface is covered by a monomolecular oxygen-containing layer and that plasma treatment allows a complete oxygen functionalization of the uppermost surface layer. The best conditions for plasma treatment found within the set of parameters applied to generate complete functionalization are: plasma gas O(2)/Ar ratio 1:1, gas pressure 1-1.5 hPa, plasma power 80 W, treatment time >or= 5 min. Additionally, three quick and easy methods are presented to estimate the efficiency of plasma treatment with regard to surface functionalization: pyrolysis, contact angle measurements, and light permeability measurements of aqueous carbon nanofiber suspensions.

Distribution of oxygen-containing functional groups in some Nigerian coals

The results of a study on the distribution of the O-containing functional groups in some Nigerian coals are reported. Four coals of varying rank from four major Nigerian mines were analysed for the concentrations of the total oxygen and the predominant O-containing functional groups (hydroxyl, carbonyl and carboxyl). The total oxygen content was obtained from ultimate analysis by the standard ASTM method while the O-bearing functional groups were determined by wet chemical methods. It was observed in the four coals that oxygen in the form of hydroxyl accounted for the major fraction of the total oxygen, followed by the carbonyl oxygen and lastly the carboxyl oxygen. The concentration of each of the functional groups decreased with decrease in total oxygen content and with increase in carbon content. The total oxygen is, however, distributed differently among the O-containing functional groups in the different coals.