E. V. Mal’tseva

Association constants of modified humic acids with biocides of the triazole series: Cyproconazole and tebuconazole

The interaction of humic acids with biocides of triazoles in dependence on the concentration of components in solutions was investigated by spectrofluorimetry. The complex behavior of intermolecular interactions between biocides and humic acids, including donor-acceptor and hydrophobic bonds, was established. The effect of conditions of mechanochemical modification of humic acids and pH on the efficiency of interaction with biocides is shown.

Influence of aggregation of asphaltenes on the rheological properties of oil

Photon correlation spectroscopy was used to determine the threshold concentrations of n-heptane for phase transitions of asphaltenes in model systems for two types of oil. The rheological properties exhibited by high-paraffin oil in the asphaltene aggregation process were analyzed. It was shown that the presence of resin and paraffi n fractions in oil prevents phase transition of asphaltenes at the threshold concentration of n-heptane for the model system, so that a higher precipitant concentrations is required for aggregation of asphaltenes and formation of oil sludge.

Electrochemical reduction of oxygen in the presence of humic acids

The effect of the nature of humic acids (HAs), their modification by mechanochemical methods, and the pH of the medium on the electrochemical reduction of oxygen is determined. The mechanical activation of caustobioliths, regardless of their nature, is shown to increase the role of quinone moieties in the composition of HAs, thus promoting the initiation of the electrochemical reduction of O2 in a basic medium. The conclusion is drawn that this changes not only the ratio of redox-active moieties in HAs, which determine the total antioxidant activity, but also their character.

Effect of mechanochemical modification on the surfactant and structural properties of humic and himatomelanic acids

The structural properties of humic and himatomelanic acids are studied by means of 1Н NMR spectroscopy and differential thermal analysis after mechanochemical modification of peat. The relationship between the structural modification of humic and himatomelanic acids and their surfactant properties in aqueous solutions is established. It is shown that the critical micelle concentration of transformed himatomelanic acids is halved in comparison to the initial sample, while the adsorption equilibrium constant grows by 9 times.

Effect of mechanical activation on the composition of mineral components in humic acids isolated from carbons

It is shown that the mechanical activation of oxidized and brown coals is accompanied by an increase in the yield of humic acids and in their content of functional groups. It was demonstrated by atomic-emission spectroscopy that, under a high-intensity mechanical treatment, mineral elements are redistributed in the coal substance and incorporated into the structure of humic acids.

Effect of the nature of an extractant on the composition and properties of lipids extracted from peat

The effect of an extractant on the yield of lipids depending on the moisture content of peat was studied. A maximum yield of lipids was obtained upon extraction with a mixture of methyl tert-butyl ether and ethanol in a ratio of 1: 1. It was found that the use of an ethyl acetate-ethanol or methyl tert-butyl ether-ethanol solvent mixture led to a decrease in the acid and peroxide numbers of lipids regardless of the moisture content of peat. The antioxidant activity of lipids increased with the moisture content of peat.

Role of modified humic acids from peat in the detoxification of tebuconazole

The acid-base properties of the initial and modified humic acids from high-moor peat were studied. It was found that the acid properties of humic acid preparations increased for CnCOOH groups and weakened for ArCOOH groups upon the mechanical activation of peat. The energies of dissociation and the degrees of dissociation of ionogenic acid groups were calculated. The detoxifying properties of the modified humic acid preparations toward the fungicide tebuconazole were studied.

Adsorption interactions of humic acids with biocides

The chemical composition of humic acids from brown coal (Aldrich) was determined by element analysis, 13C NMR spectroscopy, and potentiometric titration. The adsorption ability of humic acids with different biocides (cyproconasol, propiconasol, tebuconasol, irgarol 1051, and DCOIT) was studied. The adsorption ability of a mixture of biocides in aqueous solutions was higher than that of the individual components. The limiting concentration of humic acids at which adsorption of biocides was maximum was determined. Adsorption constants were calculated by the Freundlich equation for each biocide in aqueous solution.

Physicochemical and spectroluminescent properties of the humic acids of coals

The functional group composition, spectroluminescent properties, and catalytic effect of humic acids isolated from coals were studied. The constants of the complexation of humic acids with cadmium ions were determined by a fluorescence quenching method.

Composition of the water-soluble humic preparations of mechanically activated brown coals

Conditions for the solid-phase mechanochemical activation of coals, which make it possible to substantially increase the yield of water-soluble humic preparations enriched in humic acids and mineral elements, are given in this work. It was found that the humic preparations isolated from mechanically activated coals are characterized by an increase in the antioxidant activity and a change in the cationic and anionic composition. The concentration of acidic ionogenic groups in humic acids increased.