PROPERTIES OF HUMIC ACIDS ISOLATED FROM BROWN COAL OF THE EKIBASTUZ COAL BASIN

Composition and physicochemical properties of humic acids (HA) extracted from brown coals of the Ekibastuz coal basin (the Republic of Kazakhstan) were studied by using the methods of IR spectroscopy, X-ray fluorescence analysis, and potentiometric titration.
In the analysis of multicomponent complex substances, which include HA, information may be limited due to the mutual influence of individual groups. However, the information obtained regarding the structural features of HA with a combination of various research methods can be very useful. Using IR spectroscopy, it was found that the studied humic acids contain aliphatic and aromatic alcohols, esters, carboxylic acids, as well as conjugated double bonds.
Electron (X-ray fluorescence ) spectroscopy showed the presence of polyenes in the studied humic acids, as well as aromatic fragments and their oxygen-containing derivatives, which is consistent with known data, according to which the main chain of humic acid molecules is built from fragments of diphenylcarboxylic acids.
By the methods of heterogeneous and homogeneous potentiometric titration, the content of carboxyl and hydroxyl groups in the structure of HA molecules was studied. It was shown that the results of potentiometric titration depend on the titration method (homogeneous and heterogeneous) and the concentration of humic acids in the system. It was established that the total content of acid groups (carboxyl and hydroxyl) depends on the concentration of humic acids and it is higher at low concentrations of HA.

1. Закорчевнй И.И., Михальская Л.Н., Швартау В.В. Гуминовые вещества и удобрения на их основе// Хiмія грунтів. – 2012. – Т. 13. -№. 1–2. – С. 60-77.

2. M. Hirade, Heavy Metals Complexed with Humic Substances in Fresh Water//Anal. Sci. -1992, -Vol. 8. –P. 453-459.

3. Weber J. M. Humic Substances and Their Role in the Environment (Eds: F. H. Frimmel, R. F. Christman), Wiley, Chichester, -1998. -210р.

4. Marinsky J. A., Reddy M. M., Ephraim J. H., Mathuthu A. S. Computational scheme for the prediction of metal ion binding by a soil fulvic acid. Anal. Chim. Acta 1995, -Vol. 302. –P. 309-322.

5. Hayes M. H. B., MacCarthy P., Malcolm R., Swift, Humic Substances II. In Search of Structure// Wiley-Intersci, Chichester. -1989. -32 р.

6. Swift R. S. OrganicMatter Characterization, in Method of Soil Analysis// Part 3. Chemical Methods (Ed: D. L. Sparks),Soil Science Society of America, Book Series No. 5. -1996, -P. 1011 - 1069.

7. Перминова И.В. Гуминовые вещества – вызов химикам XXI века // Химия и жизнь - XXI век. – 2008. – №1. – С. 50-56.

8. Юшкова Е.И., Павловская Н.Е., Даниленко А.Н. Исследование методом ВЭЖХ физико-химических свойств гуминовых кислот компостов и вермикомпостов разного периода созревания. // Сорбционные и хромотографические процессы. – 2010. – Т.10. - Вып. 3. - С. 409-418.

9. Орлов Д.С. Химия почв //Д.С. Орлов. – М.: Изд-во МГУ. – 1992. – C. 259.

10. Хилько С.Л., Рогатко М.И. Потенциометрические исследования растворов солей гуминовых кислот // Вестник Донецкого национального технического университета. – 2017. – №1(7). – С.49-54.

11. Pranzaş P.K., Willumeit R., Geheke R., Thieme J., Knöchel A.. Characterization of structure and aggregation procesşes of aquatic humic substances using small-angle scattering and x-ray microscopy // Anal.Bional. Chem. -2003. -V.376. - P.618-625.