EFFECTS OF THE EXTRACTION TEMPERATURE ON THE CHARACTERISTICS OF A HUMIC FERTILIZER OBTAINED FROM LIGNITE

Solutions of 0.1 m and 0.25 m potassium hydroxide were employed to ext ract a humic fertilizer from lignite at 20, 50 and 80-degrees-C. The e ffects of the temperature on the yields of humic and fulvic acids and on the characteristics of the former were investigated. Higher extract ion temperatures did not significantly enhance yield in either case, a nd neither were the ratios between humic and fulvic acids significantl y affected. Humic acids released by hot 0.25 m KOH solutions held less N-rich material and exhibited a lower content of functional groups th an those obtained at 20-degrees-C. When 0.1 m KOH was employed at 50 a nd 80-degrees-C, changes in the molecular structure of humic acids wer e less apparent but there were fewer functional groups than in the hum ic acids obtained at 20-degrees-C. Increasing extraction temperatures were matched by the larger molecular size of humic acids extracted wit h both KOH solutions.