Evaluation of oxidation stability of lignite humic substances by DSC induction period measurement.
The stability of lignite humic acids and four regenerated humic acids was estimated by employing differential scanning calorimetry. Induction period for the oxidative decomposition of humic matter was calculated from non-isothermal measurements at six different rates of heating. To simulate the gradual evolution history of humic acids, different intensities of oxidation attack by nitric acid on the original lignite was used. Experimental data showed higher stability of natural humic acids in the temperature range where the decomposition step occurred. On the other hand, extrapolation to lower temperatures and calculated kinetic parameters did not correspond to the order observed at higher temperatures. An oscillating trend of calculated parameters of the two proposed parts of stability was observed, which agreed with data concerning regenerated humic acids production. The approach applied in this work represents a rapid and useful method for evaluation of organic matter stability.
Kucerík
Jirí
J
Department of Physical and Applied Chemistry, Faculty of Chemistry, Brno University of Technology, Czech Republic. kucerik@fch.vutbr.cz
Kovár
Jan
J
Pekar
Miloslav
M
Simon
Peter
P
D002152:Calorimetry, Differential Scanning / Q000379:methods; D018153:Czech Republic; D006812:Humic Substances / Q000032:analysis*; D012987:Soil / Q000032:analysis*; D013816:Thermodynamics
D006812:Humic Substances; D012987:Soil