R. A. Abramovitch

In situ remediation of soils contaminated with toxic metal ions using microwave energy

Following onto our work on the in situ remediation of soils contaminated with PAHs, PCBs and other polychlorinated organic compounds using microwave energy, we now report a preliminary investigation on the in situ remediation of soils contaminated with toxic metal ions: Cd(II), Mn(II), Th(IV), Cr(III) and mainly Cr(VI). The soil is partially vitrified in the process, and extraction with hot (70 degrees C) 35% nitric acid for 4.5 h leads to the recovery of very small amounts of the metals which had been spiked into the clean soil: Cd, Mn, and Cr(III) are completely immobilized (unextractable), Th is mostly unextractable, and Cr(VI) partially extractable at very high levels of spiking, but almost completely unextractable using the US EPA Toxicity Characteristic Leaching Procedure. This suggests that contaminated soils which are not going to be used for agricultural purposes can be remediated safely to preset depths without fear of the toxic metal ions leaching out for a long time.

In situ decomposition of PCBs in soil using microwave energy

Abstract The decomposition of individual PCBs and of Aroclors in soil using microwave energy and graphite fibers occurs quantitatively in a machinable ceramic alumina bomb. As a model for in situ remediation, the reactions were then carried out in open vessels equipped with rudimentary condensers, and using either pencil lead (as a cheap graphite rod equivalent) or iron wire. Most of the chlorinated aromatics decomposed (none left in the soil), and a small portion was desorbed, collected, and dechlorinated quantitatively by catalytic hydrogenation. This procedure should allow soil remediation to any preset depth by using the appropriate length of graphite or iron rods. When 14C-2,2′,5,5′-tetrachlorobiphenyl was used (with thinner pencil lead) 27% was desorbed and 1–2.5% of 14CO2 was evolved. The remaining material could not be extracted from the soil under any conditions, and this suggests that the dechlorinated fragments are very tightly bound, and possibly encapsulated, by the vitrified soil.

Decomposition of PCB's and other polychlorinated aromatics in soil using microwave energy

Abstract Conditions are described whereby hexachlorobenzene, pentachlorophenol, 2,2′,5,5′-tetrachlorobiphenyl, and 2,2′,4,4′,5,5′-hexachlorobiphenyl are decomposed in soil using microwave energy. The most efficient decompositions are achieved in the presence of Cu 2 O or Al powder and 10N NaOH. Minute amounts of mixtures of decomposition products are extractable from the soil following remediation, but the vast majority of the decomposition products are not, and are probably either mineralized or very tightly bound to the soil. The higher the chlorine content of the biphenyl, the less efficient the decomposition. A modified ceramic alumina bomb is described which allows the bomb walls to remain much cooler than the one used earlier.

NEW RING SYSTEMS FROM 1,2-BENZISOTHIAZOLE-1,1-DIOXIDES AND RELATED COMPOUNDS

Abstract Ring-expansions and ring-annulations based on 3-substituted 1,2-benzisothiazole-1,1-dioxides have lead to a variety of novel heterocyclic systems. The reaction of 3-substituted (1 H )-1-isoindolones with 1-diethylamino-1-propyne has also resulted in new, ring-expanded molecules in good to modest yields.

Substitution in the Pyridine Series: Effect of Substituents

Publisher Summary This chapter focuses on the effects of substituents present in a pyridine nucleus upon the position and ease of attack at carbon by a suitable heterolytic or homolytic reagent. Reactions involving pyridine N-oxides and pyridinium salts are discussed. The various theoretical approaches agree with the simple resonance theory representation of the valence structure of pyridine in predicting that nucleophilic substitution should take place readily at the 2-, 4-, or 6-positions but not at the 3- or 5-position. The pyridinium cation should be even more susceptible to nucleophilic attack. Again, differences of opinion exist as to whether the 2- or the 4-position should be more reactive. Some calculations indicate that the attack at C-4 can occur more readily than at C-2, while others predict exactly the opposite, depending not only upon the use of ground state π-electron densities or atom localization energies for predictive purposes, but also upon the values of the parameters used in the calculations. Finally, the chapter illustrates intramolecular cyclizations onto a pyridine ring.

In situ decomposition of PAHs in soil and desorption of organic solvents using microwave energy

Abstract The decomposition of individual PAHs (benzo[ a ]pyrene, benzo[ b ]fluoranthene, dibenz[ a , h ]anthracene, benz[ a ]anthracene, 1-nitropyrene and benzo[ f ]quinoline) in soil in an open vessel using microwave energy is reported. No PAHs remain in the soil after remediation. An attempt to use 14C-labelled benzo[ a ]pyrene to determine the fate of that contaminant on remediation led only to the observation of the formation of 0.3% of 14CO2. None of the other decomposition products could be extracted, isolated or quantified. Using a similar procedure, a variety of organic solvents (cyclohexane, 1,1,1-trichloroethane, tetrachloroethylene, benzene, toluene and xylene) could be efficiently desorbed and collected from contaminated soil. These experiments offer a valid model for the in situ remediation of these pollutants from contaminated soil.

Application of microwave energy to organic synthesis: improved technology

Abstract The application of microwave energy to the sulfonation of naphthalene and anthraquinone, to the amination of p -chloronitrobenzene, and to the hydrosilylation of 2- and 4- vinylpyridine has been studied. Though faster (5 – 360-fold) reactions were observed problems were encountered with the available microwave technology. These were overcome by using a microwave oven equipped with stirring facility and both temperature and pressure control.

Arylations using diazonium tetrafluoroborate and pyridine : A convenient source of aryl radicals☆

Benzenediazonium tetrafluoroborate together with one equivalent of pyridine provides a convenient source of phenyl radicals via the homolysis of N-phenylazopyridinium tetrafluoroborate. Partial rate factors and total rate ratios have been determined for attack of a number of aromatic substrates by phenyl radicals produced in this way and are found to be similar to the values obtained using benzoyl peroxide as the source of phenyl radicals. The ratios of isomers formed in the decompositions in moderate and in large excesses of pyridine differ from one another. The results are discussed.

Remediation of waters contaminated with pentachlorophenol

We describe a simple method of remediating waters contaminated with pentachlorophenol (PCP), which involves filtering the water through clean soil. The filtrate is contaminant free and no PCP can be extracted from the soil. If the soil it treated with dilute acid, the filtrate is still contaminant free but 28.7% of the PCP can be extracted from the contaminated soil. Irradiating the soil with microwave energy either destroys or binds the PCP to the soil irreversibly such that none can be extracted after long periods of time.

Microwave-Assisted Alkylations of Activated Methylene Groups

Abstract Alkylations under ‘dry conditions’ of nitrophenylacetates, of an indole, and of methyl benzylidene glycinate induced by microwaves have been studied, leading to a very simple synthesis of arenes linked by a long hydrocarbon chain. N-Alkylation of the indole occurs, and monoalkylated methyl benzylideneglycinate is obtained, but in poor yield.