Comparison of pretreatment process of sodium hydroxide and soaking in aqueous ammonia for delignification of rice husk

Abstract

In the manufacture of bioethanol made from lignocellulose, lignin content becomes the main inhibitor in the conversion of bioethanol. Cellulose is coated by lignin making it difficult to hydrolyzed into glucose. Therefore, pretreatment of lignocellulose raw materials is required. Pretreatment aims to separate the bond between lignin and cellulose (delignification), eliminate the content of hemicellulose and lignin, damage the crystalline structure of cellulose and increase the porosity of the material. The damage to the crystal structure results in cellulose easily decomposing into glucose. Furthermore, the sugar compounds will be fermented by microorganisms into ethanol. Control variables are the amount of rice husks (100 g), pH hydrolysis (4-5 hrs), while the research variable is the type of pretreatment solution (NaOH and NH4OH), soaking duration (1-7 hours), and the concentration of the pretreatment solution (3-17%). While observed parameter are changes in lignin and cellulose contents. The results showed that the higher the concentration of pretreatment solution, the smaller the remaining lignin obtained, and the greater the cellulose content obtained but the pretreatment with NH4OH resulted in greater content of cellulose compared to pretreatment with NaOH. This is because NH4OH solutions are more selective in eliminating lignin and do not dissolve β-cellulose and γ-cellulose.