Electrosynthesis of hydrogen peroxide from oxygen in a gas-diffusion electrode in solutions of mineralized exometabolites

The electrosynthesis of H₂O₂ in aqueous solutions (pH 1–9) of mineralized liquid and solid bio-wastes (exometabolites) for their processing in closed life-support systems was studied. It was shown that H₂O₂ can be obtained in these solutions by electrochemical reduction of oxygen in carbon black gas diffuse electrodes to concentrations of over 2 M with current efficiency 80%. The composition of the solution was found to affect the accumulation of H₂O₂ during the synthesis. The solutions can be concentrated further to 19 M H₂O₂. The results showed that the electrolytic method is promising for preparing H₂O₂ for closed life-support systems.     

Adhesion to mineralized tissue: Bonding to human dentin

We consider the conditions and demonstrable reactions which promote chemical bonding to human dentin. The desirability of developing durable adhesion to dentin is used as background for a discussion of feasible reactions to the dentin components, for possible use in new formulations. This is followed by a discussion of the demonstrable reactions found in the literature, as well as our own surface-sensitive IR work on the reaction between dentin protein and 2-hydroxyethyl methacrylate, an ingredient found in proprietary tissue replacement formulations.     

Improvement of metal recovery by electrodialysis

In every electrolysis process, increasing the efficiency of metal extraction is one way of reducing the loss of metal and so the pollution. For this purpose, electromembrane processes, the most important of which is electrodialysis, can be used on effluents of the electrolysis bath or on solutions undergoing electrodeposition. Electrodialysis is used just after electrodeposition to extract the metal from the effluent. It restores the concentration of the solution to the level of the bath. However, the flow of ions through the membrane pair is accompanied by a certain quantity of water. A model in agreement with the experimental results gives the main parameters involved in the transmembrane transfer and the optimal conditions. In another way, electromembrane processes are used in the solution while electrolysis is running. They give a relative enrichment of one of the metals. The model shows that this relative enrichment is always associated with a decrease in the true concentration. However, the overpotentials are reduced and the quantity of metal deposit increases. This relative enrichment can be obtained either by complexationelectrodialysis, by transport-depletion or by electro-electrodialysis. In each case, the energy consumption is indicated.     

Infrared spectroscopic characterization of mineralized tissues

Vibrational spectroscopy (Infrared and Raman), and in particular micro-spectroscopy and micro-spectroscopic imaging has been used to characterize developmental changes in bone and other mineralized tissues, to monitor these changes in cell cultures, and to detect disease and drug-induced modifications. Examples of the use of infrared micro-spectroscopy and micro-spectroscopic imaging are discussed in this review.     

Deacidification of citric acid solutions by electrodialysis

Electrodialysis is a useful process to deacidify citrus juices. Besides the known allanion exchange membrane process, two alternative electrodialysis processes were investigated: a three-stream process using cation and anion exchange membranes and a twostream process with alternately arranged bipolar and anion exchange membranes. The results taken from a laboratory electrodialysis cell show, that according to current efficiency, consumption of sodium hydroxide and by-production of sodium citrate or citric acid the alternative processes are favourable, especially the process using bipolar membranes.     

Polyketide exometabolites of the causative agent of rice blast and their role in pathogenesis

A polyketide exometabolite — 3,4,8-trihydroxy-3,4-dihydronaphthalen-1(2H)-one (3,4,8-TDH) — has been isolated from the culture liquids of four isolates of the phytopathogenic fungusPiricularia oryzae Cavara. It has been shown that all the natural isolates investigated, and also nonpathogenic rose mutants and a series of dwarf mutants synthesize 3,4,8-TDH. This substance was not detected in filtrates of cultures of albino mutants. One of the natural isolates produces, together with 3,4,8-TDH, another polyketide — piriculol. The role in pathogenesis of the exometabolites isolated is discussed.All-Union Scientific-Research Institute of Phytopathology of Gosagroprom SSR. Golitsyno. V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 572–577, July–August, 1988.     

Quantitative enrichment of trace levels of ions by electrodialysis

The effect of ionic strength on the rate of ion transport across ion-exchange membranes under either constant potential or constant current conditions in electrodialysis precludes direct application of this method to quantitative enrichment studies. Addition of an excess of electrolyte to a sample to normalize the ionic strength permits either dialysis mode to be employed. The rate of ion transport into a receiver electrolyte becomes directly proportional to concentration over at least 2.5 orders-of-magnitude. The concentration range for which linear enrichment is achieved for cations extends down to the 10^-7 M level with 30-min dialyses into a mixed 0.1 M MgCl₂—0.1 M HCl receiver. Alternatively, an internal standard approach can be used; however, the difficulty in matching the behaviour of membrane transport numbers as a function of ionic strength can limit the application of this approach.     

Study of ionic catalytic systems by the electrodialysis method

A special method of electrodialysis has been developed for investigation of the kinetics and mechanism of polymerization reactions involving ions. The ionic composition of homogeneous systems such as Cp₂TiRClAlRCl₂, RTiCl₃ + AlRCl₂, Ti(OR)₄ + AlR₃, and (RLi)_n has been studied. The composition of catalytically active ions has been determined. Using the regularities of “open” systems, the methods of determining the carbocation reactivity under electrodialysis conditions havebeen worked out. The impulse electrodialysis method has been suggested for studying ionic polymerization kinetics and evaluating the rate constants ofion reactions with the monomer and gegenion.     

Green synthesis and antifungal mechanism of silver nanoparticles derived from chitin- induced exometabolites of Trichoderma interfusant

The potent biocontrol agent Trichoderma interfusant (Fu21) derived by protoplast fusion of mycoparasitic T.virens NBAII Tvs12 and multistress (fungicides and abiotic stress) tolerant T. koningii MTCC796. The chitin-induced exometabolites harvested by culturing the diverse and stress tolerant Trichoderma fusant (Fu21) and utilized for synthesis of green silver nanoparticles (Ag-NPs). Green Ag-NPs characterized for size (62.6 nm in PSA), shape (spherical with 59.66 ± 4.18 nm under SEM), stability (51.2 mv as ZETA) and purity (3.40 ke V peak corresponded to the binding energy of silver under EDAX). A Fourier transform infrared spectroscopy exhibited electromagnetic spectra of various functional groups of exometabolites conforming the synthesis of green Ag-NPs. We investigated novel route and mechanism of mycelial degradation at minimum inhibitory concentration (MIC) of green nanoformulation (20 μg Ag.ml⁻¹) to restrain phytopathogen Sclerotium rolfsii. The antifungal action of green Ag-NPs on MIC at 3 DAI elevated the mycelial cell membrane leakages (sugars and proteins), lipid peroxidation, depressed the respiratory chain dehydrogenase activity and destroyed the structure of S. rolfsii mycelia (SEM morphology) which cause phytopathogen to die. The use of green Ag-NPs as antifungal agent is considered to be eco-friendly resource, alternate to fungicides and cost-effective means to diminish phytopathogen S. rolfsii causing stem rot in groundnut. Further, bioefficacy of green Ag-NPs against S. rolfsii may be tested under field condition in groundnut rhizosphere which proved sustainability and it's advancement towards greener chemistry.     

Nonequilibrium electrodialysis of aqueous solution of sodium dodecyl sulfate

Summary Special dialysis apparatus was constructed which enabled to trace a short time nonequilibrium dialysis by the continuous measurement of electric resistance of dialyzing solution. The apparatus is particularly suited for the study of the formation of micelles in surfactant solution. The dialysis curves were constructed by plotting the change of electric resistance against dialysis time. The diagrams consisted of a nearly straight line at low concentration and two nearly straight lines above a certain concentration, from which CMC was sharply determined and the constancy of a single ion concentration above CMC was also demonstrated.

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Zusammenfassung Es wurde ein neuartiger Dialyseapparat entwickelt, der es ermöglicht, die Nichtgleichgewichtsdialyse über kurze Zeiten auszuführen und den Lösungszustand der grenzflächenaktiven Substanzen, die die Mizellen enthalten, genauer zu bestimmen. Die gemessenen Dialysekurven, die die Abhängigkeit des elektrischen Widerstands von der Zeit geben, stellen unterhalb der CMC eine fast gerade Linie dar, während oberhalb der CMC jede Kurve aus zwei geraden Stücken mit einem Knick im Schnittpunkt besteht. Hieraus konnten wir die CMC genau bestimmen und die Konstanz der Zwischenmizellkonzentration feststellen.

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Authors wish to express their thanks to Assistant ProfessorS. Okazaki of Sophia University for her help in this research.     

Homolytical Reaction Peculiarities of Phosphororganic Compounds

Abstract

The influence of the transient cyclic radical structure on the reactivity of unsaturated compounds in the processes of homolytical phosphorylation, and allyl and vinyl-phosphonates in the processes of homolytical perfluoro-alkylation is shown by the MINDO/3 method of quantum chemistry computations. The addition of allylderivatives of amides and esters of carbonic, aminocarbonic and carbamino-acids to phosphocentric radicals yields five-membered cyclic radical structures with NH- and O-heteroatoms in the cycle:     

Determination of limiting current density for different electrodialysis modules

Limiting current density of ammonium nitrate solution in laboratory-, pilot-, and industrial-scale electrodialysis modules were determined to provide a method for the prediction of the limiting current density of ammonium nitrate solutions at any conditions. The current-voltage curve was measured in each case and the limiting current density was evaluated using the dependence of the derivative, dI/dU, on the electric current, I. The limiting current was determined as a current at which the derivative dI/dU equals zero. The developed method enables not only the prediction of the limiting current density but the limiting cut and limiting flux can be determined concurrently at any linear flow velocity of the diluate and inlet ammonium nitrate concentration. It could help to prevent working in the overlimiting region and to avoid undesirable decrease of current efficiency and pH changes. The limiting cut is the maximal cut that can be obtained at certain linear flow velocity and module geometry irrespective of the inlet ammonium nitrate concentration and it is very useful information when designing a new electrodialysis unit for specific application.     

Modeling of clarified tropical fruit juice deacidification by electrodialysis

Electrodialysis (ED) using two-stack configurations with homopolar or bipolar membranes was investigated for deacidification of tropical fruit juices (passion fruit, mulberry, naranjilla). The objective was to develop a mathematical treatment for ED to predict the behavior of a fruit juice at industrial scale from ED performances at laboratory scale. From parameters such as current efficiency, electric resistance of the anion exchange membrane, and coefficients of variation with temperature determined in a laboratory-scale stack, modeling was applied to a pilot-scale stack that has a total effective membrane area 70 times larger. If no fouling took place, and except for conductivity at pH higher than 3.8, the differences between the experimental and simulated values for pH, titrable acidity, voltage, and energy consumption were inferior to 7%, 16%, 20%, and 15%, respectively, for all the fruit juices and operating conditions. Moreover, the average electrical charge of citric acid species transferred was 2.16 for all fruit juices, indicating that the current transport was mainly due to the ionic species issued from the secondary dissociation of the citric acid.     

Analytical model of laminar flow electrodialysis with ion-exchange membranes

A boundary-value problem for electrodialysis with ion-exchange membranes is posed and its analytical solution obtained. The solution allows one to calculate concentration fields in desalination and brine compartments, the current-density distribution along the flow coordinate and the thickness of diffusion boundary layers. It also makes it possible to estimate the value of local limiting current-density and to obtain the dependence of the process on physico-chemical characteristics of ion-exchange membranes (transport numbers and conductivity). The mathematical model was verified by a local distributive analysis made by means of laser interferometry.     

Thermal behavior of in vitro mineralized anionic collagen matrices

In the present study porcine skin and bovine pericardium were used as a source of type I collagen. Both were submitted to an alkaline treatment and mineralized by the alternate soaking method. Thermal stability and extent of mineralization have been investigated using DSC and TG. After alkaline hydrolysis there is a decrease in thermal stability but mineralization stabilizes collagen structure. Thermogravimetric data have shown that the amount of hydroxyapatite present in bovine pericardium matrix (45%) was greater than on porcine skin matrix (20%). Presence of hydroxyapatite was confirmed by EDX.     

Peculiarities of the nitration of secondary polynitroalkanes

Conclusions In the interaction of salts of 1,1,1,3,5,5,5-heptanitro- or 1,5-difluoro-1,1,3,5,5-pentanitropentanes with nitrating systems based on HNO₃, 1,1,1,3,3,5,5,5-octanitro- or 1,5-difluoro-1,1,3,3,5,5-hexanitropentanes, 1,1,1,5,5,5-hexanitro- or 1,5-difluoro-1,1,5,5-tetranitropentan-3-ones, the O-bis-(2,2,2-trinitroethyl)nitromethyl ether of bis(2,2,2-trinitroethyl)carboxime or the O-bis(2-fluoro-2,2-dinitroethyl)nitromethyl ether of bis(2-fluoro-2,2-dinitroethyl)carboxime are formed. The ratio of the reaction products depends on the composition of the nitrating system. The data obtained permit us to consider that the nitrating reagent is a nonionized form of HONO₂ or AcONO₂.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1357–1361, June 1986.     

Peculiarities of temperature behavior of low-molecular fluorooligomers

The peculiarities of the behavior, structure, and properties of low-molecular fluoropolymers (fluorooligomers), namely, industrial fluoroparaffins and derivatives resulting from the thermal processing of ultradisperse powders of FORUM^® trademark, are studied. The results are obtained on the basis of the IR spectroscopic investigation of the products of pyrolysis of the fluorooligomers. The measurement data on rheological properties of the samples upon heating are analyzed.     

Peculiarities of the reactivities of 3-carboxyalkylsydnones

In contrast to the 3-alkyl analogs, the heteroring in 3-carboxyalkylsydnones is cleaved by the action of hydrogen chloride in alcohols. The kinetics of the previously known alkaline cleavage of the ring in 3-carboxyalkylsydnones and sydnoneimines were studied by a spectrophotometric method.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 450–453, April, 1976.     

Peculiarities of the synthesis of cage-like metallosiloxanes

The synthesis of individual Ni-, Mn-, and Na-containing cage-like organometallosiloxanes has been performed. A possible mechanism of the formation of stable metallosiloxane frameworksvia a transition complex and coordinately bound ion pairs has been proposed. Both monometallic and bimetallic organometallosiloxanes containing only atoms of a transition metal or two different (transition and non-transition) metals, respectively, have been prepared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 957–961, May, 1993.