NDLI: Hydration of humic and fulvic acids studied by DSC

Content Provider	Springer Nature Link
Author	Kučerík, Jiří Bursáková, Petra Průšová, Alena Grebíková, Lucie Schaumann, Gabriele Ellen
Copyright Year	2012
Abstract	Qualitative and quantitative aspects of hydration of four humic acids (HA) and three fulvic acids (FA) originating from different sources were investigated. DSC experiments at subambient temperatures were carried out in order to monitor differences in ice behavior originating from freezable water surrounding humic molecules. It was found that kinetic effects play a significant role in hydration processes of both HA and FA. In fact, the hydration took part over 21 days which was detected as a progressive decrease in ice melting enthalpy. Simultaneously, the peak shapes and positions changed indicating structural changes in the physical structure of the humic substances. In case of FA, the dependency of melting enthalpy on water concentration showed a linear trend resembling a complete hydration previously observed for water-soluble hydrophilic polymers. In contrast, the melting enthalpy of some HA increased in a step-like way with increasing water content, suggesting preservation of original hydrophobic scaffold during the hydration. The differences between the rather young FA and the rather old HA lead to the conclusion that water can play a significant role in processes of humification. We assume that separation of hydrophobic and hydrophilic domains and thus increase in nanoscale heterogeneity represents an important physical contribution to the overall humification process. It was also demonstrated that the higher content of oxygen in humic molecules is not the only indicator of higher water holding capacity. Instead the porosity of humic matrix seems to contribute as additional parameter into these processes.
Starting Page	451
Ending Page	459
Page Count	9
File Format	PDF
ISSN	13886150
Journal	Journal of thermal analysis
Volume Number	110
Issue Number	1
e-ISSN	15728943
Language	English
Publisher	Springer Netherlands
Publisher Date	2012-01-20
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Humic and fulvic acids Hydration Water Differential scanning calorimetry Humification Measurement Science and Instrumentation Inorganic Chemistry Physical Chemistry Polymer Sciences Analytical Chemistry
Content Type	Text
Resource Type	Article
Subject	Physical and Theoretical Chemistry Condensed Matter Physics

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