Abstract
Fulvic acid becomes the most valuable humic substance because of the water-solubility and the physi-ological action. However, a little amount of fuvic acid is extracted in general from a variety of natural humic resources. Therefore, in this work, its preparation was examined by hot compressed water treatment of Xinjiang (China) weathered coal. The resulting water-soluble product was proved to be a sort of fulvic acid. The yield of the produced fulvic acid by this procedure was at most 26 [wt%]. The formed fulvic acid showed a higher content of oxygen and carboxyl group than those of the extracted one from the original weathered coal. Furthermore, the phenolic hydroxyl group content was higher than that of products of the ozone oxidation of humic acid from the same weathered coal, reported previously.
