Meguru Tezuka

Plasma induced degradation of chlorophenols in an aqueous solution

The reactions of organic compounds in water induced by the plasma which was generated in a localized zone between an electrolytic solution and an anode were investigated. Each of three isomeric monochlorophenols, employed as models of pollutants, underwent the dechlorination followed by oxidative degradation and eventually decomposed to inorganic carbon. It was also clarified that the chlorine atom could be liberated as chloride ion. On the basis of the detailed analysis of the intermediate products and kinetical consideration, was proposed the reaction pathway, where the successive attack of hydroxyl radicals on the benzene rings of starting materials was presumed to be key steps, especially in the initial stage of overall reactions.

Plasma-induced degradation of aniline in aqueous solution

The liquid-phase oxidation induced by a gaseous plasma was investigated. The plasma was generated between an electrolytic solution and a tip of anode in contact with the surface of solution by means of contact glow discharge electrolysis (CGDE). Aniline dissolved in a neutral phosphate buffer solution was smoothly oxidized and eventually degraded to inorganic carbon. As the intermediate products, three isomeric aminophenols, of which p-isomer was predominant, were detected as well as some carboxylic acids such as oxalic, formic and malonic acids. It turned out that the decay of not only aniline but also total organic carbon (TOC) obeyed the first-order rate law. Furthermore, the effects of volume of solution and electrolytic current on the reaction rate were discussed in connection with the reaction mechanism and it was proposed that the hydroxyl radical might be the most likely oxidant responsible for the degradation of aniline.

Conjugative transfer of the IncP-7 carbazole degradative plasmid, pCAR1, in river water samples

The transfer of the IncP-7 carbazole degradative plasmid pCAR1 from Pseudomonas putida SM1443 (derived from strain KT2440) into bacteria of river water samples was monitored using a reporter gene encoding red fluorescent protein (RFP). The number of transconjugants drastically increased in the presence of carbazole, and most appeared to belong to the genus Pseudomonas. The results suggest that the presence of carbazole benefits the appearance of transconjugants belonging to the genus Pseudomonas. Intriguingly, we also detected the transfer of pCAR1 into non-Pseudomonas, Stenotrophomonas-like bacteria.

Lithium carbonate as a solid electrolyte

Abstract To make clear the property of Li2CO3 as a solid electrolyte, a study was made on the electrical properties of Li2CO3 doped with Li3PO4, CaCO3 and LiNO3 as a function of dopant concentration at 250–600°C. The samples were prepared by a melt-solidifying technique. Since the crystals grew essentially along the (002) plane of the monoclinic Li2CO3 structure, the conductivity, σ,was measured by impedance spectrometry both along and perpendicular to (002) using gold paste as electrodes. By the Tubandt method, Li2CO3 was a pure lithium ion conductor. The conduction along (002) was much larger than that perpendicular to (002). The conductivity of Li2CO3 was similar in magnitude to that of Li4SiO4, Li5AlO4 and Li2SO4. The conductivity increased proportionally with the Li3PO4 concentration, and decreased with an increase in LiNO3 and CaCO3 concentration. It was concluded that the conduction in Li2CO3 is essentially by interstitial lithium ions. The Frenkel constant and the mobility of lithium interstitial ions were calculated.

Oxidation of aromatic hydrocarbons with oxygen in a radiofrequency plasma

The reactions of three aromatic hydrocarbons, benzene, toluene, and styrene, with oxygen in a radiofrequency (r∫) plasma were investigated. Benzene was oxidized to yield phenol as a single volatile organic product. Similarly, toluene gave the ring oxidation products, cresols, as well as considerable amounts of methyl oxidation products, consisting mainly of benzaldehyde and benzyl alcohol. In contrast, the oxidation of styrene took place predominantly on the olefinic double bond to produce styrene oxide On basis of the products and effects of reaction variables, r∫ power and flow rates of hydrocarbons and oxygen, on the reaction rate, the oxidation mechanism was discussed, particularly focusing on the intermediate species responsible for the formation of major products.

Mineralization of aqueous pentachlorophenolate by anodic contact glow discharge electrolysis.

Exhaustive mineralization of pentachlorophenolate ion (PCP) in phosphate buffer was carried out using anodic contact glow discharge electrolysis (CGDE), in which plasma was sustained between the electrolyte and anode. During CGDE, PCP degraded smoothly. The amount of total organic carbon decreased significantly, indicating the eventual conversion of the carbon atoms of benzene nucleus to inorganic carbons. Furthermore, chlorine atoms in PCP were liberated as chloride ions. As a primary intermediate product, 2,3,5,6-tetrachloro-1,4-benzoquinone was detected, and oxalate and formate as byproducts were also found. It was revealed that disappearance of PCP obeyed first-order kinetics. The reaction rate was generally unaffected by both O2 and inert gases in the cell, although it decreased by raising initial pH of solution. In addition, a plausible reaction pathway involving hydroxyl radical was proposed.

Preparation and properties of molybdenum and tungsten dinitrogen complexes

Abstract Diazoalkane complexes of type [MF(NNCRR′)(dpe) 2 ][BF 4 ] (M = Mo or W; dpe = Ph 2 PCH 2 CH 2 PPh 2 ), which are easily derived from bis(dinitrogen) complexes [M(N 2 ) 2 (dpe) 2 ], undergo consecutive one- and two-electron oxidations and reductions under voltammetric conditions at a platinum electrode. The ESR spectra of the species generated by the controlled potential electrolysis show that primary oxidation occurred on the metal atom (M = Mo) and reduction on the two nitrogen atoms in the diazoalkane ligands (M = Mo or W).

Plasma-induced complete destruction of tetrachlorophenols in an aqueous solution

The complete destruction of tetrachlorophenols (TCPs) in water irradiated with a dc plasma was carried out. The plasma was generated locally between an electrolytic solution and the tip of an anode in contact with the surface by means of contact glow discharge electrolysis. From the beginning of the reaction, the TCPs were smoothly degraded. With the disappearance of the TCPs, the amount of total organic carbon (TOC) in water concurrently decreased, which signified the effective conversion of organic carbons to inorganic ones. In addition, all the chlorine atoms of the TCPs were eventually liberated as chloride ions. Thus, it was shown that TCPs could be thoroughly mineralized under these conditions. Furthermore, it was revealed that the decay of both the TCPs and TOC obeyed the first-order rate law. The apparent rate constant for the decay of TCPs rose with a decline in the pKa values of the TCPs, while for the decay of TOC the rate was substantially unchanged. The kinetic behaviour associated with the relative reactivity of TCPs could be interpreted on the basis of a reaction scheme involving successive attacks by the hydroxyl radicals generated in water by the action of the plasma.

Exhaustive breakdown of aqueous monochlorophenols by contact glow discharge electrolysis

The aqueous monochlorophenols were degraded by contact glow discharge electrolysis (CGDE), in which plasma was generated in a localized zone between an electrolytic solution and an anode. With the decay of monochlorophenols, the amount of total organic carbon (TOC) also decreased smoothly, indicating that carbon atoms of benzene nucleus could be eventually converted to inorganic carbons. Meanwhile, it was also clarified that chlorine atoms in the organics were liberated as chloride ions. In addition, it was revealed that the disappearance of monochlorophenols obeyed the first-order rate law, depending on the isomeric structures.

Aromatic cyanation in contact glow discharge electrolysis of acetonitrile

Contact glow discharge electrolysis of acetonitrile solution containing a variety of aromatic compounds was carried out. A stable discharge was sustained around a platinum wire anode in contact with a surface of solution, when a d.c. high voltage over 500 V was applied between the anode and cathode immersed in the solution under ambient pressure of argon. An aromatic substitution involving radicals produced through the homolytic dissociation of acetonitrile significantly occurred to result in the formation of corresponding cyanoaromatics as well as propionitrile, succinonitrile, and acrylonitrile. The effects of reaction conditions on the current yields of products were discussed in association with the reaction mechanism.