The effect of acid solutions on the physicochemical properties of isolated lignin from black liquor of oil palm empty fruit bunch (OPEFB) pretreatment

Abstract

Lignin is one of the potential biopolymers derived from the pretreatment process of lignocellulosic materials. In this study, lignin was obtained from the alkaline pretreatment black liquor of oil palm empty fruit bunch (OPEFB) by precipitation with acid solutions. The acidification treatments were conducted using sulfuric acid (H2SO4) and hydrochloric acid (HCl) solution at concentrations of 1 M until reaching the pH of 2, 3 and 4. The obtained lignins were characterized for their physicochemical properties such as yield, content, morphology and particle size, then functional group. The addition of acid solution and targeted pH influenced the yield and content of precipitated lignin and affected the properties of precipitated lignin. All the isolated lignin resulted in similar yields, 0.99%, with the lignin content varied from 38-90%. While the lower pH in the hydrochloric acid resulted in higher content of the obtained lignin. The morphology of the isolated lignins showed the various size of particle sizes with their distribution. Then, the results of functional group testing via Fourier transform infrared spectroscopy (FTIR) showed no changes in the structure of functional groups at both acid solutions employed and towards the commercial lignin.