Vol. 3, Issue 4, Part F (2017)

Abstract
The extraction, fractionation, and purification periods of humic acid are very time-consuming which may vary from 12 hours to 7 days. However, the duration for isolation of humic acid from different sources vary considerably. The objective of this study was to determine the minimal duration essential to isolate humic acid from the secondary forest soil of Universiti Malaysia Kelantan Jeli Campus. A 5 g of soil were mixed with 50 ml 0.5 M sodium hydroxide. An extraction period of 24 hours was used in this study. Samples were centrifuged at 10,000 G for 15 minutes after 24 hours. The dark-coloured supernatant liquor containing both humic acid and fulvic acid was decanted and the supernatant was acidified to pH 1 using 6 M hydrochloric acid. Different fractionation periods (2, 4, 6, 8, 10, 12, and 24 hours) were tested in this study. Samples were centrifuged at 10,000 G for 15 minutes at the end of each fractionation period. The humic acid was purified using 50 ml of distilled water and centrifuged at 10,000 G for 10 min for three times. There was significant effect of different fractionation periods on the yield of humic acid. Fractionation period immediately after acidification (2 hours) did not significantly affect the yield of humic acid but 4 hours is required to precipitate the humic acid. The humic acid can be purified within 1 hour using distilled water. The significance of this study is that humic acid of Universiti Malaysia Kelantan Jeli Campus secondary forest soils can be isolated within 24 hours of extraction period, 4 hours of fractionation period, and 1 hour of purification period instead of the existing range, hence this may help to facilitate reduction of time and costs required to isolate humic acid from this soil.