Synthesis and some aspects of the formation mechanism of carbon structures under hydrothermal conditions

The formation of carbon structures upon the reactions of organic compounds with strong mineral acids under hydrothermal conditions was studied. The reactions were found to give amorphous carbon, microcrystalline graphite, nanodiamonds, diamond-like carbon, diamonds, C₆₀ and C₇₀ fullerenes, and carbolite. Hydrocarbons of various compositions including aromatics and naphthenes were detected among the reaction products. A possible mechanism of the formation of carbon structures with sp ² bond hybridization under hydrothermal conditions was proposed.     

Electroenzymatic reactions with oxygen on laccase-modified electrodes in anhydrous (pure) organic solvent

The electroenzymatic reactions of Trametes hirsuta laccase in the pure organic solvent dimethyl sulfoxide (DMSO) have been investigated within the framework for potential use as a catalytic reaction scheme for oxygen reduction. The bioelectrochemical characteristics of laccase were investigated in two different ways: (i) by studying the electroreduction of oxygen in anhydrous DMSO via a direct electron transfer mechanism without proton donors and (ii) by doing the same experiments in the presence of laccase substrates, which display in pure organic solvents both the properties of electron donors as well as the properties of weak acids. The results obtained with laccase in anhydrous DMSO were compared with those obtained previously in aqueous buffer. It was shown that in the absence of proton donors under oxygenated conditions, formation of superoxide anion radicals is prevented at bare glassy carbon and graphite electrodes with adsorbed laccase. The influence of the time for drying the laccase solution at the electrode surface on the electroreduction of oxygen was studied. Investigating the electroenzymatic oxidation reaction of catechol and hydroquinone in DMSO reveals the formation of various intermediates of the substrates with different electrochemical activity under oxygenated conditions. The influence of the content of aqueous buffer in the organic solvent on the electrochemical behaviour of hydroquinone/1,4-benzoquinone couple was also studied.     

Organically bound sulfur in refractory organic substances

The sulfur compounds of refractory organic substances (ROS) of different origin have been characterized. Total organic sulfur was determined by elemental analysis. Sulfur-containing amino acids methionine and cystine were analyzed chromatographically after hydrolysis with HCl or by proteolytic digestion using enzymes. The results obtained from elemental analysis show that the total amount of sulfur is strongly dependent on the origin of the samples, because of different environmental factors during the formation of ROS. For naturally occurring samples isolated from soil seepage water, bog lake water and ground water the carbon-to-sulfur atomic ratios (C/S) decrease with the stage of humification, because of preferential loss of carbon. In humic acids (HA) isolated from secondary effluent the high value of the nitrogen-to-sulfur ratio (N/S) was indicative of a large amount of protein-derived nitrogen and sulfur compounds. In the solutions from acid hydrolysis the total amount of amino acid carbon related to the dissolved organic carbon (DOC) was generally less than 5%. Percentages of cystine related to all the amino acids detected were in the range 4 to 16%; methionine was below the detection limit for most samples. The results show that cystine is very important among the amino acids released. Enzymatic release generally resulted in smaller amounts of amino acids, indicating that these molecules are not only present in bioavailable protein-like structures. The data were compared with those from other approaches reported in the literature for the speciation of sulfur forms in ROS, including potentiometric titration, differential reduction methods, and spectroscopic investigations.     

Study on gamma-ray-induced degradation of polymer electrolyte by pH titration and solution analysis

Degradation process of polymer electrolyte was investigated by pH titration and solution analysis. Perfluorosulfonic acid, which is generally used for fuel cells and sensors, was irradiated with gamma-ray. Irradiated samples were immersed in distilled water, and the suspensions were titrated with NaCl solution while pH was monitored. Initial pH without any sodium ion decreased as increase in absorbed dose, indicating acid release from polymer electrolyte. To identify the chemical structure of dissolved species, solution analysis was performed by ion chromatography, total organic carbon (TOC) analyzer, and inductively-coupled plasma atomic emission spectrometry (ICP-AES). It was shown that proton, sulfide ion, fluorine ion and organic carbon were detected in the solution, and the ratio among these ions and atoms changed depending on the irradiation conditions. It shows that the solution analysis can identify the scission site by irradiation sensitively, and gives useful information for investigation of polymer degradation process.     

Characterization of low molecular weight organic acids from beech wood treated in supercritical water

Japanese beech (Fagus crenata Blume), its cell wall components, and model compounds were treated by supercritical water (380°C, 100 MPa) for 5 s using a batch-type reactor to investigate the production behavior of low molecular weight organic acids. It was found that cellulose and hemicellulose were decomposed to formic acid, pyruvic acid, glycolic acid, acetic acid, and lactic acid, whereas lignin was barely decomposed to such organic acids under the given conditions. However, after prolonged treatment (380°C, 100 MPa, 4 min) of lignin, some organic acids were recovered owing perhaps to the decomposition of the propyl side chain of lignin. It was additionally revealed that the predominant organic acid recovered was acetic acid, which might be derived from the acetyl group of hemicellulose in Japanese beech.     

Iridium Modifier for Determination of Selenium by Graphite Furnace Atomic Absorption Spectrometry

ABSTRACT

The behaviour of thermally reduced or electrodeposited iridium modifier in graphite furnace atomic absorption spectrometry (GFAAS) for the determination of selenium was investigated. The performance of modification for standard solution of selenium as well as in the presence of chloride containing matrix (e.g. sea water) was examined. It was found that the graphite material plays a significant role in the determination of volatile elements by the formation of graphite intercalation compounds. Those compounds are responsible for the long-term performance of stabilisation of selenium in chloride containing solutions.     

Determination of manganese, iron and copper in sodium by chemical modification/graphite furnace atomic absorption spectrometry

Trace Mn, Fe and Cu in sodium were determined by chemical modification/graphite furnace atomic absorption spectrometry. The sodium sample was changed into NaOH in a desiccator by room temperature water vapor generated under reduced pressure, then the NaOH was dissolved in water and HNO(3) was added to give a clear solution. The solution was analysed by chemical modification/graphite furnace atomic absorption spectrometry. A nickel nitrate modifier was effective in improving integrated absorbance signals and the reproducibility of measurement. Analytical results for Mn, Fe and Cu were 170, 970 and 210 ng/g and relative standard deviations (n = 5) were 3.5, 5.8 and 6.7%, respectively. These results agreed with the values obtained from a chelating resin preconcentration/ICP-AES method.     

Determination of organic carbon in natural water with inductively coupled plasma/atomic emission spectrometry after evaporation of inorganic carbon

The performance of a continuous flow system interfaced with a sequential inductively coupled plasma/atomic emission spectrometer (ICP/AES) was evaluated for the determination of organic carbon in water. Optimal conditions for evaporation of carbonates before determination or organic carbon was established and working ranges were determined. The method applied for the determination of organic carbon in natural water was compared to determinations made by an elemental analyzer.     

Coprecipitation Behavior of Some Metals with Chitosan and Their Determination by Graphite Furnace Atomic Absorption Spectrometry

Chitosan is derived from chitin by deacetylation. Chitosan forms a complex with metal ions and is soluble an organic acid. The metal ions were concentrated in the precipitates of chitosan when the sample solution containing metal ions was adjusted to neutral after the chitosan solution was added. These properties are applied to the preconcentration of metal ions in water samples and their determination by graphite furnace atomic absorption spectrometry. Metal ions,such as ruthenium, indium, vanadium, strontium,rhodium were collected in the chitosan precipitates.     

Self‐Assembled Nanocomposite Organic Polymers with Aluminum and Scandium as Heterogeneous Water‐Compatible Lewis Acid Catalysts

While water‐compatible Lewis acids have great potential as accessible and environmentally benign catalysts for various organic transformations, efficient immobilization of such Lewis acids while keeping high activity and without leaching of metals even under aqueous conditions is a challenging task. Self‐assembled nanocomposite catalysts of organic polymers, carbon black, aluminum reductants, and scandium salts as heterogeneous water‐compatible Lewis acid catalysts are described. These catalysts could be successfully applied to various C? C bond‐forming reactions without leaching of metals. Scanning transmission electron microscopy analyses revealed that the nanocomposite structure of Al and Sc was fabricated in these heterogeneous catalysts. It is noted that Al species, which are usually decomposed rapidly in the presence of water, are stabilized under aqueous conditions.     

The impact of the cononsolvency effect on poly (N-isopropylacrylamide) based microgels at interfaces

The paper addresses the effect of solid interfaces on the cononsolvency effect for poly(N-iso propylacrylamide) based microgels containing different contents of the co-monomer allyl acetic acid (AAA). The cononsolvency effect is studied by dynamic light scattering (DLS) in solution and with atomic force microscopy (AFM) at surfaces against different mixtures of water and organic solvent (ethanol, iso-propanol, and tetrahydrofuran). For the studies at interfaces, the microgels are spin coated on silicon wafers that are precoated with poly(allylamine hydrochloride) (PAH). The minimum in particle volume due to cononsolvency shows a pronounced shift from 10–20 % of organic solvent to 40–50 % after deposition at the Si/PAH wafer. The strong shift indicates an increase of water to organic solvent ratio within the gel at the surface with respect to the bulk solution. In order to understand the increase of water to organic solvent ratio, shrinking/reswelling AFM experiments for different spin-coating conditions and under ambient conditions are carried out. Spin coating from water instead from different solvent mixtures has no effect on the cononsolvency. In ambient conditions, the cononsolvency effect disappears     

填充碳纳米管/石墨的复合型电磁波屏蔽膜

介绍一种填充碳纳米管/石墨的复合型电磁波屏蔽膜的组成、制备及其耐老化性能,实验发现：当碳纳米管/石墨的配比为1/7～1/2、有机聚合物/导电填料的配比为29.6/70.4～32.4/67.6时,该屏蔽膜具有最佳的电性能、屏蔽性能和加工性能,且在一定条件下具有负的温度系数。用多层结构模型讨论了该屏蔽膜的导电性,并与铜、镍蒸发膜的屏蔽特性进行了比较。     

Identification and determination of phenols and chloro-phenols in very dilute aqueous solutions by gas-liquid chromatography,paper chromatography and spectrophotometry

After concentration of the organic substances from water samples of 700 to 20,000 l by adsorption on active carbon and desorption with chloroform in a large Soxhlet apparatus, tlie organic compounds were separated by extraction into 5 different groups: acids, phenols, bases, neutral and amphoteric substances. The phenol group was investigated by gas and paper chromatography, ultraviolet difference spectrophotometry and infrared spectroscopy. Phenol, 2,4,6-trichlorophcnol, 2- and 3-cresol, 2,4-xylenol and 2,4-dichlorophenol were identified in samples of raw and treated water. Quantitative measurements proved to be possible with gas chromatography. The conditions for quantitative desorption and separation were studied.     

Reaction kinetics and mechanism for hydrothermal degradation and electrolysis of glucose for producing carboxylic acids

Electrolysis in subcritical water can convert biomass-derived saccharides into value-added chemicals and fuels without any additives. In this work, we aim to understand reaction behaviours of glucose under subcritical water degradation or electrochemical conditions for the purpose of developing a new method for producing useful carboxylic acids. Degradation of glucose was carried out using a continuous flow-type reactor in subcritical water at various operating conditions, and electrochemical reactions of their product solutions were conducted at identical conditions with a 500-mL batch autoclave. Gaseous products obtained were analyzed by gas chromatography-thermal conductivity detection (GC-TCD), and liquid products were analyzed by high-performance liquid chromatography (HPLC) and gas chromatography-flame ionization detection (GC-FID). The total organic carbon (TOC) in the aqueous product solution was determined by using a TOC analyzer. Based on the experimental results, a reaction pathway for glucose is proposed for subcritical water degradation and electrolysis.     

Photoactivated matrices in prebiotic evolution processes

The processes of abiogenesis of biologically important compounds (amino acids, peptides, pyruvic acid, etc.) under the conditions of adsorption in mineral (titanium dioxide, silica gel) or organic (melanoidin) matrices in the presence of UV radiation were studied. The photophosphorylation of ADP to ATP on clay (montmorillonite) with a yield of 30% and an organic matrix (flavoproteinoid microspheres) with a yield of 40% was examined. It was concluded that one of the factors responsible for the occurrence of the processes of building more complex carbon compounds during the prebiotic evolution period resulted in the origin of life, had been the presence of photoactivated matrices and their coevolution.     

Facile preparation of graphite intercalation compounds in alkali solution

Graphite intercalation compounds are often prepared by flake graphite, oxidants, inorganic acids, organic acids and intercalated ions which are usually hydrogen protons between the graphene planes. They are also known as the acid-treated graphite intercalation compounds. In this work, alkaline graphite intercalation compounds were prepared by flake graphite, K₂Cr₂O₇, concentrated H₂SO₄ and NaOH, and the morphology and structure were characterized by Electron microscopy and X-ray techniques. The results display that the combination of neutralisation heat and oxidation capability produced by K₂Cr₂O₇ can break the bonds to produce the spaces between the graphene planes and hydroxyl ions also intercalate into the graphene planes to form alkaline graphite intercalation compounds in alkali solution. The morphology and structure of alkaline graphite intercalation compounds are analogous to the ones of the acid-treated graphite intercalation compounds, but the intercalated ions and the expansion volume are different. The results show that the method is an innovation.     

毛细管离子色谱-串联质谱法测定热纤梭杆菌发酵液中的低相对分子质量有机酸

建立了一种测定热纤梭杆菌发酵液中的低相对分子质量有机酸的毛细管离子色谱-串联质谱方法。探索优化了色谱和质谱的检测条件,在最佳分析条件下同时检测8种有机酸。离子色谱以KOH水溶液作为流动相进行梯度洗脱;用IonSwift MAX-100毛细管柱进行分离;在喷雾电压为3.0 kV、喷雾气压强为2 000 kPa、成源温度为275℃的条件下,选择离子监测(SIM)模式下运行质谱。结果表明,柠檬酸和异柠檬酸两种同分异构体能够得到很好的分离,8种有机酸在一定浓度范围内具有良好的线性关系,相对标准偏差为1.45%~5.99%,相关系数为0.9696~0.9986,平均加标回收率为89.0%~110.0%,8种有机酸的检出限为0.01~0.50 mg/L。该方法进样量少,灵敏度高,重现性好,能够满足实际样品的检测要求,可用于嗜热厌氧菌发酵液中低分子量有机酸的测定。     

Determination of tributyltin in toluene extract from sea water by graphite furnace atomic absorption spectrometry with a new matrix modifier

A new matrix modifier composed of calcium and chromium[VI] was proposed for the determination of tributyltin (TBT) in toluene extract from sea water containing sediment by graphite furnace atomic absorption spectrometry (GFAAS). Fourteen inorganic and organic compounds (barium, calcium, chromium[VI], lanthanum, magnesium, nickel, palladium, strontium, calcium-chromium[VI], calcium-strontium, nickel isocaprylate, 5%-, 10%-aqueous solution of ascorbic acid and toluene-saturated solution of ascorbic acid) as a matrix modifier were comparatively studied and a matrix modifier composed from 5 microg of calcium and 1 microg of chromium[VI] was found to give the best performance. The interference effects of co-existing elements in sea water containing sediment (aluminium, iron, magnesium, sodium and strontium) were studied. TBT in eight toluene extracts was determined by GFAAS with the proposed matrix modifier. The relative standard deviation was 3.0% for 63 ng ml(-1) of TBT (n = 11). The recoveries were 88-104%. The characteristic mass was 7 pg. The linearity range was 0-250 ng mg(-1).     

溶剂浮选法分离富集污水中痕量羧酸类和胺类有机污染物的研究

本文报道了溶剂浮选法分离富集污水中痕量羧酸类有机污染物和胺类有机污染物的新方法。考察了溶液的pH值、通气速度、离子强度、浮选时间、相比以及不同溶剂对浮选效果的影响。在优化了浮选条件下溶剂浮选效率达到95％以上。采用本法对石化工业污水中的痕量羧酸类和胺类物质进行分离富集和鉴定,证明了该法的可行性。     

Thin‐Film Voltammetry of a Lutetium Bisphthalocyanine at Ionic Liquid|Water Interface

At room temperature, tetraoctylphosphonium bromide is a viscous ionic liquid, this gel‐like organic phase can be cast over a basal‐plane graphite electrode (BPGE). Cyclic voltammetry at such a modified electrode, in contact with an aqueous solution have revealed one reversible oxidation and five reversible reduction steps for a Lu^III bisphthalocyanine dissolved in the ionic liquid film, a proof that the highly reactive reduced species were protected from interaction with water in this highly lipophilic phase. It has also been shown that the redox properties are influenced by the ions in the aqueous phase, a property which has been attributed to ion‐pairing effects; obviously, the ion transfers at the organic|aqueous interface has been ignored. Electrochemistry of Lu(III)[(_tBu)₄Pc]₂ (cyclic voltammetry and square wave voltammetry) under similar conditions shows that the nature and concentration of the anion in the aqueous solution in contact with the ionic liquid film influences the potential of the electrode reaction. This can be attributed to variations of the interfacial potential and also because the organic phase is an anion exchanger. Moreover, SWV experiments suggest that the rate of the overall reaction varies with the nature and concentration of the anion of the aqueous electrolyte, which implies that the ion transfer through the organic|aqueous interface is slower than the electron exchange rate of the molecule at the surface of graphite.