Characterization of humic acids from original coal and its oxidization production.

Five coal samples obtained from Chinese coal-producing areas were oxidized by hydrogen peroxide (H2O2), and humic acids (HAs) were derived from original coal and its oxidizition samples. HAs were characterized by physical and chemical methods, between which was also comparison. Yield, ash, aromaticity, molecular weight and functional group of HAs showed variance between original coals. While, yield, molecular weight, and the quantity of oxygen-containing groups of HAs increased more from coals oxidized with H2O2. However, the increase of oxygen-containing functional groups depended on original coals. For Yimin lignite, the oxidation of H2O2 could obviously improve the carboxyl group content of HAs, thus promoting the adsorption of nitrogen. This study demonstrated that oxidation of coal by using H2O2 was one pretreatment way to obtain and modify HAs which could be used as prerequisite and functional material in agricultural field.