微生物燃料电池影响因素及作用机理探讨

以生活污水为初始接种体, 以醋酸钠水溶液为原料, 构建了一个无媒介体、无膜的单室微生物燃料电池, 考察了溶液的浓度、外电阻、温度和氧气的加入等因素对电池性能的影响, 监测了电池外电压和两极电极电势的变化过程, 分析了微生物燃料电池的运行机理. 研究结果表明: (1) 阳极吸附的微生物的活性是影响电池输出电压(输出功率)的关键因素. 营养液初始浓度越高, 微生物活性越高, 输出最大电压越高, 输出电压与浓度之间的关系符合MONOD方程; 溶液中溶氧的存在使微生物活性明显降低, 但溶氧浓度降低到一定程度后, 活性逐步恢复; 随着电池温度的升高, 微生物活性快速上升, 但温度突变到50 ℃后, 微生物活性明显降低; (2) 电池换水后, 由微生物活性所决定的阳极电势迅速达到平衡, 而阴极电势需要较长的时间才能达到极大值; (3) 随电流密度的变化, 两极电极电势相应发生变化, 其变化趋势符合原电池的基本规律; (4) 随外电阻的变化, 电池输出功率出现极大值, 即当外电阻为200 Ω时, 电池输出功率达到346 mW/m2.     

Determination of ciprofloxacin and enrofloxacin by the sensitized fluorescence of europium in the presence of the second ligand and micelles of anionic surfactants

The effect of surfactants and the second ligand on the fluorescence properties of europium(III) binary chelates of ciprofloxacin and enrofloxacin is studied. It is shown that the fluorescence intensity of the europium chelates of antibiotics increases by a factor of 4 in the presence of 1,10-phenanthroline and by a factor of 5 in sodium dodecylbenzenesulfonate micelles. The detection limits for ciprofloxacin and enrofloxacin are 2.3 × 10^?7 M. The developed procedures for determining antibiotics were officially tested on the pharmaceutical Ciprolet and blood serum.     

Influence of oxygen pressure on the photocatalytic oxidation of the azo dye Chrome Yellow with TiO<Subscript>2</Subscript> as the catalyst

The photocatalytic oxidation of the azo dye Chrome Yellow dissolved in water on TiO₂ at high oxygen pressures was is reported. An increase of the oxygen pressure from 0.1 to 0.7 MPa increases the rate of the reaction by a factor of 1.6.     

Ion binding to cucurbit[6]uril: structure and dynamics

Molecular dynamics simulations are used to study the microscopic structure and dynamics of cations bound to cucurbit[6]uril (CB[6]) in water and in aqueous solutions of sodium, potassium, and calcium chloride. The molarities are 0.183 M for the salts and 0.0184 M for CB[6]. The cations bind only to CB[6] carbonyl oxygens. They are never found inside the CB[6] cavity. Complexes with Na(+) and K(+) mostly involve one cation, whereas with Ca(2+) single- and double-cation complexes are formed in similar proportions. The binding dynamics strongly depends on the type of cation. A smaller size or higher charge increases the residence time of a cation at a given carbonyl oxygen. When bound to CB[6], sodium and potassium cations jump mainly between nearest or second-nearest neighbors. Calcium shows no hopping dynamics. It is coordinated predominantly by one CB[6] oxygen. A few water molecules (zero to four) can occupy the CB[6] cavity, which is limited by the CB[6] oxygen faces. Their residence time is hardly influenced by sodium and potassium ions. In the case of calcium the residence time of the inner water increases notably. A simple structural model for the cation activity as "lids" over the CB[6] portal cannot, however, be identified. The slowing of the water exchange by the ions is a consequence of the generally slower dynamics in their presence and of their stable solvation shells.     

Photochemical reactions of hypericin with alcohols and albumins. Kinetics and mechanism of the primary processes

The photochemical reactions of the hypericin sodium salt with alcohols and albumins yielding the corresponding semiquinone radical were studied by means of microsecond and nanosecond pulse photolysis. The decay of the semiquinone radical follows the second-and first-order rate law for alcohol solutions and the NaHY-albumin system, respectively. The lifetime and the yield of the semiquinone radical decrease in the presence of oxygen. In the oxygen-saturated solutions, the lifetime of the semiquinone radical increases with an increase in the albumin concentration in the solution from 1 to 50 mg/ml. This effect is caused by a decrease in the reactivity of the semiquinone radical toward oxygen due to the steric hindrance created by albumin and is not associated with an increase in the solvent viscosity.     

Protecting the protectors: reducing the biological toxicity of UV sunscreens by zeolite encapsulation

The phototoxic and photoallergic effects of the once popular UV sunscreen p-aminobanzoic acid are related, in part, to its ability to sensitize the formation of singlet oxygen as well as other reactive oxygen species. In this work we demonstrate that the sunscreen-photoinduced inactivation of a model protein, horseradish peroxidase, is reduced by approximately a factor of three when the sunscreen is encaspsulated in zeolite sodium Y. These results provide evidence that using the technology of zeolite encapsulation to prepare a supramolecular sunscreen that minimizes the skin contact of active ingredients may reduce the adverse effects of "naked" sunscreens on biological systems. These radiation-induced effects, unfortunately, frequently accompany the desirable UV-screening role of these products. These results provide an important benchmark for the use of zeolite encapsulation as a means of improving the safety of UV sunscreens for topical application.     

Solubility of oxygen in aqueous sodium carbonate solution at pressures up to 10 MPa

The solubilities of oxygen in 0.2, 0.5, 0.7 and 1.0 M Na₂CO₃ solution have been measured at 300.15 K and under pressures up to 10 MPa using a magnetically stirred autoclave and a direct sampling technique. The accuracy of apparatus was verified by duplicating the solubility of oxygen in pure water in literature. The experimental data of the solubility of oxygen in aqueous sodium carbonate solution were shown that the solubility of oxygen increases with increasing pressure and decreases with increasing salt concentration due to salting-out effect. The experimentally measured data were satisfactorily compared with the predicted values by our model based on non-primitive mean spherical approximation (MSA) and perturbation theory.     

Crown-Ether Type Podands as Alkali Metal Cation Extractants: Influence of the Number of Oxygens in the Chain

Several polyether-type podands were synthesized that contained a variable number of potential donor oxygen atoms (four to twelve) and an aromatic ring in the chain. Extraction experiments were performed to elucidate the influence of the number of oxygen atoms on the extraction selectivity towards alkali metal picrates, from aqueous to dichloromethane phases. The results show that the extraction efficiency for lithium picrate is almost independent of the number of oxygen atoms in the podand. The extraction efficiency for sodium picrate was found to increase significantly with the number of oxygen atoms up to about seven, but for the potassium to cesium picrates the extraction efficiency increased up to about eight oxygen atoms. The increase in extraction efficiency may be rationalized in terms of the saturation of the cation’s first coordination sphere: after a critical number of oxygen atoms is reached and the first coordination sphere is saturated, the much smaller detected increases in the extraction efficiency may be seen as a statistical effect. The discrimination between sodium and potassium pirates is only achieved when the podands possess seven or more oxygen atoms. Under the experimental conditions used, the podands studied are unable to discriminate between potassium, rubidium and cesium picrates.     

Effect of cationic composition of electrolytes based on the M2MoO4-M2Mo2O7-UO2MoO4 (M = Li, Na, K, Cs) system on the oxygen factor of the uranium electrolytic oxides

The effects of the electrolyte composition, deposition potential, temperature, and the salt-solvent cation on the oxygen factor (the [O]/[U] atomic ratio) of uranium oxides obtained by potentiostatic electrolysis of molybdate melts are studied. It is shown that the oxygen factor of the cathodic product increases with the melt temperature. The shift of the deposition potential toward more electronegative values, an increase in the Mo₂O^2? ₇ ion concentration, and a decrease in the UO₂MoO₄ concentration favor the cathodic formation of uranium oxides with lower oxygen factors. All other conditions being the same, the oxygen factor decreases with increasing the salt-solvent cation radius. The observed anomalous behavior of the Li₂MoO₄-based electrolytes can be caused by a lower activity in the melts of the O^2? anions that are capable of forming stable complexes Li₃O⁺ with lithium cations. The obtained results can be reasonably explained in terms of the model of ionic composition of the uranyl-containing tungstate melts, which is based on the concept of involvement of the uranyl ions in the complexes’ formation and stepwise solvolysis.     

Synthesis and evaluation of the influence of 5-sulfanyl-1,2,3-triazol-1-ylaminocarboxylic acid derivatives on kinetics of ascorbic acid oxidation

1,2,3-Thiadiazolylureas containing amino acid residues were synthesized. These compounds were converted to 5-sulfanyl-1,2,3-triazol-1-ylaminocarboxylic acid sodium salts under alkaline conditions. These salts were found to inhibit the oxidation of ascorbic acid with air oxygen. In the presence of the equimolar amount of 5-sulfanyl-1,2,3-triazoles, the rate of diminution of ascorbic acid decreased by 1.5—3 times, whereas in the case of their two-fold excess by a factor of 5.     

Application of the Sublattice Method to Analysis of the Chemical Bond in the Peroxides of Alkali Metals

Self-consistent calculations of the valence electron density and the sublattice and difference densities of alkali metal peroxides were carried out. It was established that the oxygen atoms in potassium, sodium, and rubidium peroxides are grouped into pairs, linked into chains by common valence density contours. In lithium peroxide the oxygen pairs are linked into chains through the lithium atoms.     

Burning of Sodium Chlorate Based Formulations

The burning velocity of sodium chlorate based formulations with polyethylene and kerogen under atmospheric conditions was studied in relation to composition, i.e., oxygen excess factor.     

Organic Thiocarboxylate Electrodes for a Room‐Temperature Sodium‐Ion Battery Delivering an Ultrahigh Capacity

Organic room‐temperature sodium‐ion battery electrodes with carboxylate and carbonyl groups have been widely studied. Herein, for the first time, we report a family of sodium‐ion battery electrodes obtained by replacing stepwise the oxygen atoms with sulfur atoms in the carboxylate groups of sodium terephthalate which improves electron delocalization, electrical conductivity and sodium uptake capacity. The versatile strategy based on molecular engineering greatly enhances the specific capacity of organic electrodes with the same carbon scaffold. By introducing two sulfur atoms to a single carboxylate scaffold, the molecular solid reaches a reversible capacity of 466 mAh g⁻¹ at a current density of 50 mA g⁻¹. When four sulfur atoms are introduced, the capacity increases to 567 mAh g⁻¹ at a current density of 50 mA g⁻¹, which is the highest capacity value reported for organic sodium‐ion battery anodes until now.     

Modified Ceria-Zirconia Fluorite-Like Catalysts for the Combustion of Methane

For dispersed ceria-zirconia-based solid solutions prepared via the polymerized complex method and annealed at 700℃, effects of bulk doping by Ca, Mn, Co, Bi or Nb cations and surface modification by Mn and Pt on their structural features, surface/bulk oxygen reactivity and catalytic activity in methane combustion are considered. With up to 20 mol% doping, a structural type of homogeneous solid solutions of anion-deficient fluorite with disordered anion vacancies is formed. Doping by transition metal cations or Pt increases the mobility and reactivity of the surface/bulk oxygen. A broad variation in specific rates of methane combustion for the studied systems was observed, suggesting structural sensitivity of this reaction. In general, there is no universal relationship between the oxygen mobility, the reactivity and the catalytic activity in methane combustion, which is explained by the factor of specific methane activation on surface active sites. For the Pt-promoted samples, Pt efficiency in methane activation depends on the Pt-support interaction, and the most favorable ones being mixed Pt/MnOx and Pt/NbOx clusters on the surface of the supports that exhibit high lattice oxygen mobilities.     

Role of pyromucic acid in the autooxidation of furfural

Pyromucic acid (PA) in aqueous solution is oxidized by molecular oxygen with opening of the furan ring and formation of -formylacrylic, fumaric, and formic acids. The process is accompanied by the interlinked oxidative decarboxylation of PA and the acids formed from it. PA is the major intermediate in the autooxidation of furfural. When PA and furfural are cooxidized, the rate of transformation of each compound increases by a factor of two; this is a sign of the interlinking of two radical processes evolving in one system. A probable scheme for the oxidation of PA in water by molecular oxygen is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 9–13, January, 1971.     

Zinc sulfide nanoparticles: a mechanism of formation in aqueous solutions and optical properties

The formation of sols and precipitates of zinc sulfide as a result of the exchange reaction in an aqueous solution was studied. The precipitates consist of aggregates of primary particles about 3 nm in size. The primary ZnS particle size in aqueous sols increases with an increase in the concentration of zinc sulfate and sodium sulfide, with the accumulation of the final reaction product, and with temperature. This effect does not exceed an 1.5-fold increase. At the first step, the particles with a considerable fraction of the amorphous phase are formed and undergo intragrain crystallization. The photoluminescence properties of aqueous sols of zinc sulfide were studied. They are caused by defects in the ZnS lattice and by the presence of the lattice oxygen.     

PHOTOOXIDATION OF XANTHOBILIRUBIC ACID IN AQUEOUS SOLUTION: PRODUCT AND MECHANISM STUDIES

Abstract— Xanthobilirubic acid, an oxodipyrrylmethene with a chromophore very similar to that of bilirubin, was aerobically irradiated as its sodium salt in borate buffer at pH 8. Two photooxidation products, methylethylmaleimide and 5-formyl-2,4-dimethyl-1 H -pyrrole-3-propanoic acid, were isolated. These products can be rationalized on the basis of either a Type I or a Type II (singlet oxygen) photooxygenation mechanism. The reaction is inhibited by azide, a singlet oxygen quencher, and sensitized by methylene blue. However, both the self-sensitized and the methylene blue-sensitized reactions are enhanced, rather than inhibited, by high concentrations of 1,4-diazabicyclo[2.2.2]octane, another known singlet oxygen quencher. It is therefore proposed that the diazabicyclooctane can also act as an electron donor.
The self-sensitized photooxidation of xanthobilirubic acid is an autocatalytic reaction. This is supported by the fact that addition of a previously irradiated solution to a freshly-prepared solution significantly increases the rate of photodegradation. A similar catalyst is formed, but much more slowly, from xanthobilirubic acid in the dark in the presence of oxygen.     

Studies of the antenna effect in polymer molecules 25. Photozymes with rose bengal chromophores

Several copolymers of poly(sodium styrenesulfonate-styrene-vinylbenzylchloride) and poly(sodium styrenesulfonate-2-vinylnaphthalene- vinylbenzylchloride) containing various amounts of rose bengal chromophores attached to the polymer chain were synthesized. The copolymers are soluble in water and can solubilize large hydrophobic compounds. They are efficient genarators of singlet oxygen, and act as photosensitizers in the oxidation of singlet oxygen acceptors which are dissolved in the water phase and solubilized in the hydrophobic polymeric microdomains.     

3-Chloroalkylfurans in the reaction with sodium diethyl phosphite

Reduction of 3-acylfurans with lithium alumohydride in ether yields stable secondary alcohols. By treatment with thionyl chloride in the presence of pyridine, they are converted to the corresponding chlorides. 3-(1-Chloroethyl)furan and 5-methyl-3-(1-chloroethyl)furan react with sodium diethyl phosphite to give two products: 3-(1-diethoxyphosphorylethyl)furans and 3-ethyl-2-(diethoxyphosphoryloxy)furans. The methyl group in position 5 of the furan ring increases the relative phosphate content of the mixture by a factor of approximately 2.5. Blocking of position 2 or both positions 2 and 5 of the ring with methyl groups leads to phosphoate formation only. The reaction of 2,5-dimethyl-3-(1-chloro-2-methylpropyl)furan also occurs according to the Michaelis-Becker scheme. The products of the side chain dehydrohalogenation with sodium diethyl phosphite were not found.