In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.



Volume 50 No. 2 June 2001


Advanced oxidation processes – current status and prospects; 59–80

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Rein Munter

Abstract. The paper provides an overview of theoretical basis, efficiency, economics, laboratory and pilot plant testing, 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 drinking water: 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 from model solutions of Tallinn drinking water was tested using Aqua Juraperle (calcium carbonate) and activated alumina as filtration media. The experiments with Aqua Juraperle demonstrated that this filter medium does not maintain fluoride ions. Other water constituents, except iron, were not influenced by the filtration either. The total iron content was reduced by 50%. Filtration through activated alumina reduced the fluoride concentration in water. The sorption capacity of alumina was 4.5 g/kg and volumetric capacity 3.95 g/L. Different coagulants and their doses were tested to remove fluoride with coagulation as well. The coagulant consumption for fluoride removal 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 molar enthalpies of the ternary system o-xylene + hexan-2-one + nonane at 298.15 K; 89–94

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Abstract. Microcalorimetric measurements of excess molar enthalpies are reported for o-xylene + hexan-2-one + nonane and o-xylene + hexan-2-one at 298.15 K. The results for the ternary system are compared with those calculated by a modified Redlich–Kister equation. The temperature effect on the excess 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, and Imants TAURE

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

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

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

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Abstract. Batch sorption experiments were conducted with heavy metal solutions in 0.01 M CaCl2 at low equilibrium concentrations of Cu, Pb, Cd, and Cr in 10 different intact soil samples. Metal solid/liquid distribution coefficients Kd were determined from the adsorption isotherms obtained. 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 matter content and origin to represent differential behaviour with regard to heavy metal sorption. Correlations of Kd with soil parameters were observed together with varying sorption behaviour of metal cations to different soil types. Desorption of metals from soil phase to solution was found to be very small, suggesting that at least during the initial period after the metal pollutants have reached the soil surface they accumulate in the top humus layer. Heavy metal desorption into the water phase also depends on the character of the metal and on soil type.

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