Chemistry June 2001 Vol 50/2 []

CONTENTS & ABSTRACTS

In English. Summaries in Estonian

Proceedings of theEstonian Academy of Sciences.

Chemistry



Volume 50 No. 2June 2001



Advanced oxidation processes – current status andprospects; 59–80

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Rein Munter

Abstract. The paper provides an overviewof theoretical basis, efficiency, economics, laboratory and pilot planttesting, design and modelling of different advanced oxidation processes(combinations of ozone and hydrogen peroxide with UV radiation and catalysts).

Key words: water, wastewater,chemical oxidation, ozone, hydrogen peroxide, UV radiation, solid catalyst.

Fluoride in drinkingwater: The problem and its possible solutions; 81–88

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Yelena Veressinina, Marina Trapido,Viktor Ahelik, and Rein Munter

Abstract. Removal of fluoride ions frommodel solutions of Tallinn drinking water was tested using Aqua Juraperle(calcium carbonate) and activated alumina as filtration media. The experimentswith Aqua Juraperle demonstrated that this filter medium does not maintainfluoride ions. Other water constituents, except iron, were not influenced bythe filtration either. The total iron content was reduced by 50%. Filtrationthrough activated alumina reduced the fluoride concentration in water. Thesorption capacity of alumina was 4.5 g/kg and volumetric capacity3.95 g/L. Different coagulants and their doses were tested to removefluoride with coagulation as well. The coagulant consumption for fluorideremoval was 80 mg Al2(SO4)3 per 1 mg F–.The use of lime milk as a coagulant for water defluoridation is not expedient.

Key words: drinking water,fluoride content and removal, filter media, activated alumina, Aqua Juraperle,coagulation.

Excess molarenthalpies of the ternary system o-xylene + hexan-2-one +nonane at 298.15 K; 89–94

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Helle KIRSS, Mati KUUS, EnnSIIMER, and Ludmilla KUDRYAVTSEVA

Abstract. Microcalorimetricmeasurements of excess molarenthalpies are reported for o-xylene + hexan-2-one + nonaneand o-xylene + hexan-2-oneat 298.15 K. The results for the ternary system are compared with thosecalculated by a modified Redlich–Kister equation. The temperature effect on theexcess enthalpy is discussed.

Key words: heat of mixing, ternary system, o-xylene, hexan-2-one, nonane.

Algal biomass from Fucus vesiculosus (Phaeophyta):Investigation of the mineral and alginate components; 95–102

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Kalle TRUUS, Merike VAHER, andImants TAURE

Abstract. Mineral composition ofalgal biomass from Fucus vesiculosus(the Baltic Sea, Estonia) is rich in light elements (Mg, K, Ca, Na) andhalogens (Br, I). Arsenic content is also high (over 300 ppm); the contentof other toxic elements (Hg, Sb, Se, etc.) is extremely low. Mineralization ofthe algal whole biomass does not depend on seasonal varieties. The content of a-L-guluronic acid residues, and therefore the viscosity of alginatesfrom the Baltic F. vesiculosus, isrelatively low. Viscosic properties depend significantly on the storing andprocessing conditions of biomass; the polymer chain of alginates from thisbrown alga species is especially sensitive to high isolation temperatures.

Key words: Fucus vesiculosus, mineral composition,alginates, viscosity.

Heavy metal sorptionby different Estonian soil types at low equilibrium solution concentrations;103–114

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Priit ALUMAA, Eiliv STEINNES,Uuve KIRSO, and Valter PETERSELL

Abstract. Batch sorption experimentswere conducted with heavy metal solutions in 0.01 M CaCl2 atlow equilibrium concentrations of Cu, Pb, Cd, and Cr in 10 different intactsoil samples. Metal solid/liquid distribution coefficients Kd were determined from the adsorption isothermsobtained. Their values varied over a range from 57 to 53 000 mL/g.The soils used in the experiment were chosen according to their organic mattercontent and origin to represent differential behaviour with regard to heavymetal sorption. Correlations of Kdwith soil parameters were observed together with varying sorption behaviour ofmetal cations to different soil types. Desorption of metals from soil phase tosolution was found to be very small, suggesting that at least during theinitial period after the metal pollutants have reached the soil surface theyaccumulate in the top humus layer. Heavy metal desorption into the water phasealso depends on the character of the metal and on soil type.

Key words: soil, Cu, Pb, Cd, Cr,sorption, distribution coefficients, organic matter, correlations.