The Influence of Heat and Two Stages Precipitation in the Process of Natural Polymer Purification from the Byproduct of Bioethanol Process Base on Empty Palm Fruit Bunch

摘要

The biopolymer material, lignin, was recovered from the black liquor by acidification of the black liquor using sulfuric acid. Several purification techniques were carried out to produce the high purity of lignin such as gradual precipitation of lignin from black liquor (first stage: precipitation at pH 7, second stage: precipitation at pH 2) and the diluting of crude lignin by sodium hydroxide then followed by re-precipitation at different temperature. Subsequently, the impurities of lignin product resulted from each purification techniques was determined as ash content that analyzed using temperature program furnace;;and the content of lignin was investigated using spectrophotometer UV-Vis. The result showed that the yield of lignin of material about 17% and ratio between lignin and ash content (3:1) produced from direct precipitation to pH 2. The single stage re-precipitation of filtered black liquor resulted the yield 11.30% and 4:1 of ratio between lignin and ash content at 50°C of optimum temperature. The two stages lignin purification reached optimum condition with the yield of lignin of material about 2.60% and 670:1 of ratio between lignin and ash content when using 5% H_2SO_4 in precipitation.