Determination of Minimal Fractionation Period Required for Extracting Humic Acid from Paddy Husk Compost

摘要

The process of isolating humic substances, especially, humic acid (extraction, fractionation andpurification) is time consuming, laborious and expensive. The objective of this study was to determine theminimum period required to fractionate humic acid from paddy husk compost. The rice straw compost wasproduced by mixing 80% of shredded rice straw, 10% of goat manure slurry, 5% of chicken feed and 5% ofmolasses. During the extraction process, 10 g of compost was placed in the centrifuge bottle, addedwith 100 mL of 0.5 M NaOH. The samples were equilibrated at room temperature for 24 h. After that, the mixturewas centrifuged at 10, 000 G for 15 min. During the fractionation process, the pH of the solution was adjustedto 1.0 by using 6 M hydrochloric acid. Then the humic acid was allowed to equilibrate for 1, 3, 5, 7, 9, 12 and24 h, respectively and the suspension was centrifuged. Purification was done subsequently to purify the humicacid.The yield of humic acid fractionated under 1 h was 0.26 g and was not statistically different from 3, 5, 7, 9,12 and 24 h. This indicates the fractionation period of 1 h also had the same time taken as 3, 5, 7, 9, 12 and24 h for the exchange sites of humic acid of compost to be saturated with H+ions after acidification. Phenolic,carboxylic and total acidity were determined and falls within the range reported by literatures. The optimumfractionation period of humic acid from paddy husk compost was 1 h as the yield of humic acid under differentfractionation periods were not significantly different. Therefore, by using 1 h of fractionation period it willabsolutely save the consumption of chemicals, electricity and labor costs.