(The) spectroscopic and chemical investigation of soil humic materials from Kuye San

Abstract

The soil fulvic and humic acids, extracted from the Kuye San region of the Okchun Metamorphic belt, are purified and characterized for their chemical composition, molecular size distributions, proton exchange capacities and spectroscopic characteristics. These materials were isolated and purified according to the recommended methods of the interlaboratory comparison exercise on characterization of humic materials from differing origins, enabling a more effective comparison of the results obtained from the characterization work with those of other laboratories. A particular emphasis was placed on the elucidation of the structural differences and determination of those parameters which are important for the assessment of the migrational behaviour of radionuclides in the aquatic environment. The results are compared with one another and with the commercially available humic acid from the Aldrich Co. and other humic materials isolated in a similar manner. They seem to show that the soil humic materials from Kuye San possess many of the properties commonly associated with humic substances. However, the elemental composition and spectrosopic analysis data also seem to indicate that these humic substances may have undergone a lower degree of aromatic condensation, and their structures consist of basic aromatic framework with significant amounts of various aliphatic functional groups. The acid capacity of humic and fulvic acids, determined by direct pH titration, are 2.65$\pm$0.20 and 7.07$\pm$0.08 meg/g respectively, which are significantly different from one another and with those of other humic materials from differing origins. The experiment verifies that $Eu^{3+}$ ions are extensively bound to fulvates as tridentate complexes. The loading capacity(LC) and the average complexation constant of the fulvic acid from Kuye San for the trivalent Eu ion are LC = 0.50 $\pm$ 0.01 and $\log\;\beta=5.86\pm0.15l\;mol^{-1}$. The results are in good agreement with the values det...