Humic acids form lignite.1. Analytical characteristics and thermal degradation

Abstract

Humic acids (HA) extracted from a lignite with two alkaline reagents have been studied. In contrast to humic acids extracted from soil HA, the lignite acids show no differences in their physical and chemical analyses with the exception of the total carbonyl content. After acid hydrolysis the analytical characteristics do not change, but their behaviour on Sephadex indicates a molecular condensation. The parent material has similar characteristics to those reported in the literature and also shows no analytical differences after acid hydrolysis, but a number of i.r. absorption bands, due to kaolinite, the only clay mineral present, disappear after this treatment. By pyrolysis/gas chromatography both the lignite and the humic acids produce severallow-b.p. compounds, the same in the three cases but in different amounts. By methylation it has been proved that a great part of such compounds are produced by radical reactions. Some, which do not increase on methylation, may indicate the presence of some longer chains in lignites.