Determination of minimal duration essential and extractant ratio for humic acid isolation from rice straw compost

The method for accumulate humic substances especially humic acid is laborious and time consuming. The extraction, fractionation and purification periods of humic acid vary from 12 hours to 7 days. The common extractant ratio used for isolation is 1:10 which is recommended by International Humic Substances Society. However, the duration and extractant ratio for isolation of humic acid from different sources vary significantly. The objective of this study is to determine then minimum duration essential and extractant ratio for humic acid isolation from rice straw compost. A ratio of 1: 5 and 1: 10 of compost sample and chemical used were performed in humic acid extraction. A 5 g of compost sample was mixed with 0.5 M sodium hydroxide and were extracted for different extraction period (1, 3, 5, 7, 9, 12 and 24 hours). After the extraction period, the samples were centrifuged at 10, 000 rpm for 15 minutes. Then, the samples were acidified to pH 1 using 6 M hydrochloric acid and fractionated for 24 hours. The samples were centrifuged for 15 minutes at 10, 000 rpm after 24 hours. The humic acid samples were purified using 50 ml of distilled water and centrifuged three times at 10,000 rpm for 10 minutes. There was significant effect of different extraction periods and extractant ratio on the yield of humic acid. This study indicated that approximately 12 hours are required to extract humic acid from rice straw compost optimally and can be purified within 1 hour using distilled water. The significance of the study is humic acid from rice straw compost can be isolated within 12 hour of extraction period, 24 hours of fractionation period and 1 hour of purification period. Thus, this may help in reducing time and costs needed to produce the humate product from this compost. The extractant ratio of 1:10 is more preferred because of the higher humic acid yield obtained.