EFFECTS OF HEAT ON THE ALKALI EXTRACTION OF HUMIC SUBSTANCES FROM PEAT

Solutions of 0.1M and 0.25M potassium hydroxide (KOH) were used to ext ract the humic substances from two different types of peat (sphagnum a nd Carex) at 20, 50 and 80-degrees-C. The effects of temperature on th e yield of humic and fulvic acids (HA and FA) and on the characteristi cs of the former were investigated. The highest extraction yields were obtained at the two higher temperatures and by using the most concent rated alkali solution. The higher temperatures resulted in a decrease of the HA/FA ratio in the sphagnum peat although the opposite generall y occurred with the Carex peat. As shown by chemical analyses and gel permeation chromatography, the HA released from sphagnum by hot KOH so lutions exhibited less oxidized molecules, a lower content of function al groups and larger molecular size than it did at room temperature; w hereas the characteristics of the HA released from Carex peat by heat depended on both the alkali concentration and the temperature employed for the extraction.