Destruction of sodium lauryl sulfate in its aqueous solutions by contact glow discharge treatment

Degradation of the anionic surfactant sodium lauryl sulfate (C₁₂H₂₅SO₄Na, SLS) in its aqueous solutions with concentrations of 0.02–1.1 mmol/L acting as a liquid cathode of atmospheric-pressure dc discharge in air at a discharge current ranging within 20–100 mA has been studied. The products of degradation in the liquid phase have been identified, and the kinetic characteristics of their formation at an initial SLS concentration of 5 × 10^?3 g/L (～0.02 mmol/L) and a discharge current of 40 mA have been determined.     

Destruction of sulfonol in its aqueous solutions by contact glow discharge treatment: 2. Mechanisms and kinetic simulation

A mechanism for the degradation of Sulfonol in its aqueous solutions acting as a liquid cathode of atmospheric-pressure dc discharge in air and for the formation of the products has been proposed, and the chemical kinetics of the degradation processes has been numerically simulated.     

Chemical transformations in sodium chloride aqueous solutions under the action of low-temperature contact glow-discharge plasma

Changes in the composition of aqueous NaCl solutions during the course of their treatment with glow-discharge plasma in a gas-liquid plasma-chemical reactor have been studied. A mathematical model involving the steps of oxidation of water molecules and chloride ions and the steps of reduction of their chemical conversion products has been developed. For the first time, it has been found that the hydrogen peroxide content of the solution monotonically decreases with the concentration of NaCl and a change in chlorite, chlorate, and perchlorate concentrations has the appearance of an undulating curve with a maximum at c(NaCl) = 3 g/L. The predominant accumulation of hypochlorite ions in the solution has been detected only in the case of the plasma treatment of the NaCl solutions with concentrations higher than 5 g/L.     

Features of germanium tetrafluoride reduction with hydrogen in inductively and capacitively coupled radiofrequency discharges

The process of plasma-chemical conversion of germanium tetrafluoride in a radiofrequency discharge (13.56 MHz) has been studied. The dependences of the germanium yield on the specific energy input, the H₂/GeF₄ molar ratio, and the total pressure have been measured. The maximum germanium yield is more than 95%. The minimum specific energy consumption at an energy input of 9 MJ/mol is 9.4 MJ/mol or 2.6 kW h/mol Ge. A mechanism of plasma-assisted reduction of germanium tetrafluoride under the given the experimental conditions has been proposed.     

Polymerization and degradation of polyacrylonitrile in gas discharge

The plasma polymerization of acrylonitrile and the plasma degradation of polyacrylonitrile have been studied mass-spectrometrically in high-frequency gas discharge at low pressure. The polymerization was found to proceed without decay to gaseous products. During the polymerization, the monomer partial pressure in the closed plasma-chemical reactor decreased exponentially. When treating polyacrylonitrile in argon plasma, the polymer decayed to C, H₂ and N₂; in oxygen plasma, the species were C, H₂, N₂, H₂O, CO and CO₂. Unlike the thermal decomposition, no traces of monomer and oligomers were detected among the products of plasma degradation.     

Degradation of 4-Chlorophenol using a Gas–Liquid Gliding Arc Discharge Plasma Reactor

The gas–liquid gliding arc discharge plasma is used directly to study degradation and dechlorination of 4-Chlorophenol (4-CP) in solution. The typical AC waveforms of discharge voltage and current revealed that the discharge behavior was not definitely periodic. The chemical oxygen demand (COD) abatement of 4-CP solution with stainless steel electrode is higher than that with aluminum or brass electrode; When air was used as carrier gas the COD abated from 1,679.2 to 190 mg/L (i.e., 88.68% abatement) after 76 min plasma treatment; Increasing gas–liquid mixing rate could also increase the degradation of 4-CP; adding appropriate amounts of Fe²⁺ or iron chips to the solution were found to be favorable for 4-CP degradation. The main intermediates of 4-CP degradation are p-benzoquinone, hydroquinone, 4-chlorocatechol, p-chloronitrobenzene, and ring cleavage products (acetic acid, glycol, propanone, and others). Furthermore, possible pathways of 4-CP degradation in solution are proposed.     

Plasma-Chemical Conversion of Lower Alkanes with Stimulated Condensation of Incomplete Oxidation Products

Oxidative conversion of a mixture of natural gas and oxygen in a barrier-discharge plasma-chemical reaction was investigated experimentally. The process was conducted at atmospheric pressure and room temperature. The discharge was initiated by high-voltage pulses of 50–100 s duration at a repetition frequency of up to 2 kHz. The principal feature of the process was that in the plasma-chemical reactor conditions were created which stimulated the condensation of the products of incomplete oxidation of methane that resulted in the formation of aerosol even from nonsaturated vapor. The removal of intermediate reagents from the gaseous phases into the aerosol prevented them from further oxidation. Depending on the experimental conditions, the mass percentage of the components of the condensate formed varied within the following limits: formic acid from 20 to 40%, methanol from 8 to 15%, methylformate from 4 to 8%, and water from 40 to 60%. The conversion process has been realized on a laboratory setup of average power up to 1 kW. In the single-pass mode, a 57% degree of conversion of the mixture has been achieved. The energy value of the condensate is 15–20 kWh/kg.     

Synthesis and properties of a platinum catalyst supported on plasma chemical silicon carbide

A CO oxidation catalyst based on β–SiC and Pt nanoparticles has been synthesized and studied. The average size of Pt clusters on the surface of the plasma-chemical silicon carbide nanoparticles is close to 4 nm. It has been found that the rate of the CO oxidation reaction at low concentrations (100 mg/m³) in air at room temperature over the catalyst based on platinum and silicon carbide nanoparticles is 60–90 times that over a platinum black-based catalyst with a specific surface area of 30 m²/g. The Pt/SiC catalyst containing 12 wt % Pt has been found to provide the maximum CO oxidation rate.     

Investigation of the low-pressure plasma-chemical conversion of fluorocarbon waste gases

The kinetics of the plasma-chemical conversion of a number of saturated, as well as of unsaturated, fluorocarbon compounds is studied in an oxygen-based rf discharge by FTIR spectroscopy. Unsaturated fluorocarbons are rapidly converted into CF₄ and C₂F₆, which, in the presence of silica walls, are finally converted quantitatively into SiF₄ (etch reaction). The results of this investigation are used to design a plasma-chemical reactor for the conversion of fluorocarbon exhaust gases into SiF₄ in the vacuum line of a technological low-pressure plasma reactor. Furthermore, it is shown that the primary conversion product SiF₄ can be effectively converted into CaF₂ in a heterogeneous reaction with a CaO/Ca(OH)₂ absorber, also in the low-pressure line of the pumping system.     

Reduction–Oxidation of Chromium Ions in Aqueous Solution by Treatment with Atmospheric-Pressure Direct-Current Discharge in Argon

Kinetic features of the oxidation–reduction processes of chromium ions in a potassium dichromate aqueous solution subjected to treatment in argon atmospheric-pressure dc discharge have been investigated in the discharge current range of 20–80 mA and the dichromate concentration range of 0.1–0.5 mmol/L. The solution served as the discharge cathode. It has been revealed that the discharge treatment stimulates the reduction reactions of Cr⁶⁺ to Cr³⁺ ions and the reverse reactions of oxidation of Cr³⁺ to Cr⁶⁺ ions; i.e., the oxidation–reduction reactions are reversible. The limiting degree of reduction of Cr⁶⁺ ions has been found to depend on the discharge current and the initial concentration of the solution. The apparent rate constants of oxidation and reduction have been determined, and the energy efficiency of the process has been evaluated. The data are compared with the results obtained earlier for a discharge in air.     

Reaction Kinetics of Trans-Sobrerol and 8-p-Menthen-1,2-diol with Hydroxyl Radical in Aqueous Solution: A Combined Experimental and Theoretical Study

Trans-sobrerol (Sob) and 8-p-menthen-1,2-diol (Limo-diol) are the primary products in the atmospheric oxidation of α-pinene and limonene, respectively. Because of their low volatility, they associate more likely to the liquid particles in the atmosphere, where they are subject to the aqueous phase oxidation by the atmospheric oxidants. In this work, through experimental and theoretical study, we first provide the rate constants of Sob and Limo-diol reacting with hydroxyl radical (·OH) in aqueous solution at room temperature of 304±3 K and 1 atm pressure, which are (3.05±0.5)×10⁹ and (4.57±0.2)×10⁹ L/(mol·s), respectively. Quantum chemistry calculations have also been employed to demonstrate the solvent effect on the rate constants in aqueous phase and the calculated results agree well with the measurements. Some reaction products have been identified based on liquid chromatography combined with mass spectroscopy and theoretical calculations.     

A study of silicon tetrafluoride reduction with hydrogen in radiofrequency discharge

The process of plasma-chemical conversion of silicon tetrafluoride in a radiofrequency (13.56 MHz) discharge has been studied. The dependence of the yield of silicon on the specific energy input and the H₂/SiF₄ molar ratio has been examined in the pressure range of 0.1–0.3 Tort. The maximum yield of silicon is 60%, and the optimal specific energy consumption is 44.6 MJ per mole of Si. A mechanism has been proposed for the plasma-assisted reduction of silicon tetrafluoride under the given experimental conditions.     

Simultaneous electrodeposition behavior of dysprosium and terbium in 1-ethyl-3-methyl-imidazolium tetrafluoroborate ionic liquid

The simultaneous electrodeposition of dysprosium and terbium on platinum electrode in 1-ethyl-3-methyl-imidazolium tetrafluoroborate (EMIMBF₄) ionic liquid was investigated. The cyclic voltammetry, chronoamperometry and constant electrolysis experiments have been employed to examine the electrochemistry of dysprosium and terbium ions in 0.01 mol/L DyCl₃-0.023 mol/L TbCl₃-0.27 mol/L LiCl-EMIMBF₄ ionic liquid. The electrochemistry experiments indicated that the reduction of dysprosium and terbium ions in 0.01 mol/L DyCl₃-0.023 mol/L TbCl₃-0.27 mol/L LiCl-EMIMBF₄ ionic liquid was an irreversible process and simultaneous process. In 0.01 mol/L DyCl₃-0.023 mol/L TbCl₃-0.27 mol/L LiCl-EMIMBF₄ ionic liquid the diffusion coefficient of the diffusion process of species which controlled the total electrochemical reduction process have been determined to be (3.79–7.07) × 10⁻⁶ cm²/s from cyclic voltammetry and chronoamperometry results. XRD spectrum of constant electrolysis samples showed that dysprosium and terbium deposits were obtained.     

Liquid-Liquid Extraction of Indium(III) from the HCl Medium by Ionic Liquid A327H+Cl− and Its Use in a Supported Liquid Membrane System

Ionic liquid A327H⁺Cl⁻ was generated by reaction of tertiary amine A327 and HCl, and the liquid-liquid extraction of indium(III) from the HCl medium by this ionic liquid dissolved in Solvesso 100 was investigated. The extraction reaction is exothermic. The numerical analysis of indium distribution data suggests the formation of A327H⁺InCl₄⁻ in the organic phase. The results derived from indium(III) extraction have been implemented in a supported liquid membrane system. The influence of the stirring speed (600–1200 min⁻¹), carrier concentration (2.5–20% v/v) in the membrane phase, and indium concentration (0.01–0.2 g/L) in the feed phase on metal transport have been investigated.     

A soft chemistry synthetic method for preparing LiNi0.8Co0.2O2 with enhanced electrochemical performances

Polycrystalline LiNi_0.8Co_0.2O₂ powders were synthesized via the citric acid-assisted liquid phase evaporation method. The precursors are homogenously mixed in the solutions at an atomic scale which is also reflected by the particle distribution of the final products. The optimal synthesis temperature is located at 750?°C where the particle size, crystalline structure, and the cation disorder between Li⁺ and Ni²⁺ ions have been balanced. A high discharge capacity of 191?mAh?g^?? (3.0??.3?V at 30?mA/g) is achieved in the first cycle for the 750?°C-prepared sample with a capacity retention of 89.37% after 96 cycles. Cyclic voltammetry and the differential capacity curves also reveal a moderate stable crystal structure of 750?°C-prepared LiNi_0.8Co_0.2O₂ during the prolonged cycles.     

Synthesis of nanostructured electrocatalysts based on magnetron ion sputtering

Nanostructured platinum catalysts for electrochemical systems with proton-exchange membranes (PEMs) have been synthesized by magnetron ion sputtering on a carbon support. The design of the powder support stirrer has been optimized to ensure uniform surface coverage with platinum metal nanoparticles. The deposition parameters (discharge power, deposition time, and bias voltage) that make it possible to obtain electrocatalysts with a large specific surface area (up to 44 m²/g) have been determined. The resulting catalysts have been studied by transmission electron microscopy and X-ray diffraction. The samples with platinum particles 3 to 4 nm in size uniformly distributed over the carbon surface and forming a single phase exhibit the greatest efficiency. The electrodes based on the synthesized electrocatalysts have been tested in a liquid electrolyte and as a component of a fuel cell and PEM water electrolyzer. The voltage across the fuel cell with the synthesized Pt/C electrocatalyst (44 m²/g) at a current density of 1 A/cm² is as high as 0.55 V, which corresponds to a specific power of 550 mW/cm². Qualitative correlations between the parameters of the synthesized catalysts and the deposition conditions have been established.     

Development of Process for Fast Plasma-Chemical Through Etching of Single-Crystal Quartz in SF<Subscript>6</Subscript>/O<Subscript>2</Subscript> Gas Mixture

Process for deep plasma-chemical etching of single-crystal quartz plates in a SF₆/O₂ gas mixture was developed. The method of scientific experiment design based on the Taguchi matrix technique was used to rank basic technological parameters (bias voltage applied to the substrate holder, output power of the high-frequency generator, oxygen flow rate, and position of the substrate holder relative to the lower edge of the discharge chamber) as regards their influence on the etching rate. The ranking results were used to optimize the plasma-chemical etching process and perform a control experiment on through etching of windows with large linear dimensions (3 × 10 mm) in a single-crystal quartz plate (z-cut) with thickness of 369 μm.     

Plasma-chemical destruction and modification of chitosan in solution

The destruction of chitosan in a solution, which served as a cathode in an atmospheric pressure direct-current discharge, has been studied. The dependence of the viscosity-average molecular weight of chitosan on the treatment time has been obtained, and the effective degradation rate constants and the plasma-chemical yields of chain scission have been found at discharge currents of 15, 30, and 45 mA. The structural and chemical changes in the polymer have been studied by electronic absorption spectroscopy and infrared spectroscopy.     

Degradation kinetics of phenol and its decomposition products in the electrolyte cathode of direct-current atmospheric-pressure discharge

The degradation kinetics of phenol and the formation kinetics of its decomposition products in the liquid cathode (distilled water) of direct-current atmospheric-pressure discharge in air have been experimentally measured. The processes occurring in the liquid phase have been simulated on the basis of the previously proposed reaction kinetics scheme complemented by phenol decomposition reactions and the formation/decay reactions of its degradation products.     

Characterization of SEI layer formed on high performance Si–Cu anode in ionic liquid battery electrolyte

Formation of the SEI layer on Si–Cu film electrode in the ionic liquid electrolyte of 1 M lithium bis(trifluoromethylsulfonyl)imide/1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (LiTFSI/MPP-TFSI) was investigated using ex-situ ATR FTIR and X-ray photoelectron spectroscopy. The SEI layer is found to be composed of organic and inorganic compounds that are the decomposition products of MPP cation and TFSI anion, and effectively passivate the electrode surface during initial cycling. Formation of a stable SEI layer leads to an excellent capacity retention 98% of the maximum discharge capacity, delivering discharge capacities of > 1620 mAhg^? 1 over 200 cycles. The data contribute to a basic understanding of SEI formation and composition responsible for the cycling performance of Si-based alloy anodes in ionic liquid electrolyte-based rechargeable lithium batteries.