In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.



Volume 54 No. 1 March 2005


Solvatochromic probes within ionic liquids; 3–11

Mihkel Koel

Abstract. Spectroscopic studies on a set of ionic liquids were performed using different solvato­chromic probe molecules. Different probes were found to characterize ionic liquids as solvents differently. Mixtures of ionic liquids with organic solvents exhibit nonlinear behaviour of polarity with composition as measured by Reichardt’s dyes.

Key words: ionic liquids, binary mixtures, solvatochromic shift, Reichardt’s dyes, Nile Red.

Arylation of substituted hydrazines with arylboronic acids; 12–15

Liina Raus, Olga Tšubrik, and Uno Mäeorg

Abstract. Copper-mediated arylation of di- and trisubstituted hydrazines with aryl- and hetero­arylboronic acids is described. Boronic acids were chosen because of their commercial and synthetic availability and mild reaction conditions of the corresponding C–N cross-coupling reactions.

Key words: N-arylation, C–N cross-coupling, arylboronic acid, hydrazine.

Oxidative decomposition of benzoic acid in the presence of metal ionic catalysts; 16–23

Rein Munter, Marina Trapido, and Yelena Veressinina

Abstract. Catalytic ozonation as one of the advanced oxidation processes gives a wide range of opportunities for the enhancement of the degradation of resistant compounds. The efficiency of catalytic ozonation with homogeneous (containing dissolved ions of Fe2+, Mn2+, Cu2+, Ni2+, Mo6+) and heterogeneous (Fe2O3, MnO2, Ni2O3, CuO, Al2O3, MoO3, TiO2) catalysts and non-accompanied ozonation was compared for the degradation of benzoic acid (BA). A combination of ozonation and the Fenton reagent was found to be quite effective for BA. Although a slight acceleration was followed in the catalytic ozonation of BA, a significant improvement in the COD removal was observed. The current study proved that catalytic ozonation may be efficient for the degradation of resistant compounds but the performance of catalysts in ozonation is quite sensitive towards treatment conditions and the compound.

Key words: catalytic ozonation, benzoic acid (BA), Fenton treatment, homogeneous catalysts, heterogeneous catalysts.

Interaction of metal cations with different humic substances from sea and lake sediments; 24–34

Monika Übner, Maili Treumann, Anu Viitak, and Margus Lopp

Abstract. Specific precipitation of metals (Zn2+, Mg2+, Mn2+, Pb2+, Cu2+) with different humic substances (humic, fulvic, and hymatomelanic acids) was studied. Zn2+ was selected as a model cation. From the humic substances sea humic acid was the best precipitating fraction in the whole pH range with Zn2+. At pH 7 both sea and lake humic acid gave the same metal/acid precipitation order: Pb2+ > Cu2+ > Zn2+ > Mn2+ > Mg2+. Humic acid (as a gel) from both sediments showed the best adsorption for heavy metals.

Key words: fulvic acid, heavy metals, humic acid, humic substances, hymatomelanic acid, lake sediment, sea sediment, stability constant.

Characteristics and natural attenuation of the Pääsküla landfill leachate; 35–44

Aare Selberg, Malle Viik, Kai Peet, and Toomas Tenno

Abstract. The leachate composition can vary throughout a landfill, and leachate production decreases with placement of the final cover. Anaerobic decomposition, which can produce a leachate with high concentrations of biogenous pollutants, occurs in the covered landfill. Pääsküla landfill (Tallinn, Estonia) was built as a temporal landfill on peat deposits in 1974. In June 2003 the landfill was closed and covered but the leachate will filter over many years. In March 2004 the leachate contained 62.6 mg/L total nitrogen (Ntot), 6.9 mg/L total phosphorus (Ptot), 668 mg O2/L COD, and 160 mg O2/L BOD7. In the leachate 91% of the nitrogen was determined as ammonia. In March 2004 the content of pollutants was higher than the corresponding values analysed in 1971 and 1993. It is connected with methane production in the closed landfill. The effluent enters the Vääna River through the Pääsküla River and in the sampling place of the Vääna River the values of pollutants were 2.4 mg/L Ntot, 0.05 mg/L Ptot, 26 mg O2/L COD, and 1.7 mg O2/L BOD7. The concentrations of pollutants had decreased as a result of dilution in the rivers but it is an insufficient antipollution measure.

Key words: landfill, leachate, natural attenuation, dilution, anaerobic decomposition.

Thermochemical liquefaction of reed; 45–56

Rein Veski, Vilja Palu, Hans Luik, and Kristjan Kruusement

Abstract. The current paper gives a survey about the use of reed biomass and reed peat for the production of liquid fuels and experimental data on the thermochemical liquefaction (semicoking at up to 520 °C, water conversion, and catalytic hydrogenation at 380 °C) of reed (Phragmites australis or P. communis). Reed is a new source of energy, for the burning of which experience is already evolving in Estonia. Liquefaction conditions have a great influence on the yield of products. In our study the highest yields of oil and oil plus coke (oil 25.7%, coke 28.5%) were obtained by using the Fischer retort. The yield of oil fractions washed successively out from pyrolytic water (in some cases also coke and catalyst) containing the reaction mixture with water (further divided to ether solubles and insolubles of water soluble oil), and benzene and acetone (water insoluble oil) as well as total oil decreases in the order: semicoking ® water conversion ® catalytic hydrogenation (except acetone solubles). The sharpest decrease was observed in the water soluble oil: from 15.1% to 0.7%. At the same time the proportion of the most desirable benzene solubles in total oil increased from 28.4% in the case of semicoking to 50.1% in the case of hydrogenation, which was accompanied with an increase in the carbon content in benzene solubles from 71.5% to 83.0%.

Key words: reed, Phragmites australis, thermochemical liquefaction, liquid fuels.

Abbreviations: A = acetone solubles of water insoluble oil, B = benzene solubles of water insoluble oil, E = ether solubles of water soluble oil, W = ether insolubles of water soluble oil, OM = organic matter.