Hydrogen peroxide oxidation of humic acids and lignite

The H2O2 degradation of humic acids and lignite from Mír mine (South Moravian region, Czech Republic) resulted in oxidation of aromatic structures and cleavage of aromatic units. The hydrophilic fraction largely dominated the oxidation digest in both parental materials. The presence of polycyclic biomarkers α-Phyllocladane, De-A-lupane confirms the high plant contribution. Hopanoid structures and branched C15 and C17 (iso and anteiso) fatty acids show slight bacterial inputs. Short chain n-fatty acids (<C20) are ubiquitous in living kingdom, whereas long chain homologs are probably derived from higher plants. Phosphoric acid production through the H2O2 oxidation probably results from hydrolyses of pyrophosphate. From hydrophilic fractions of lignite and humic acids, malonic acid and succinic acid are dominant compounds and could indicate that methylene and ethylene chains are main bridge bonds connecting between the aromatic rings in the structure. The H2O2 oxidation of lignite was very selective for producing malonic acid and succinic acid in high yields and the oxidation degradation method appears to be a suitable new way for utilizing South Moravian lignite. For production of malonic acid and succinic acid, the results indicated that the appropriate condition especially was at 50 °C for 4 h and 40 °C for 4 h, respectively. But oxidation followed by reoxidation of lignite at 30 °C for 1 h could be also a reasonable way to produce that kind of molecules (particularly malonic acid). Lipophilic compounds represented the minor GC-amenable fraction of the total products obtained by oxidation of lignite.