Soda pulping is one of the most frequently used methods for the delignification of agricultural residues. During the pulping processes, the lignin is separated from the raw material in the form of solid dissolving in the solvent. The color of this admixture is dark brown and it is called black liquor. Conventionally, the lignin has been recovered from black liquor through precipitation with mineral acids such as hydrochloric and sulfuric acid. Koljonen et al. (2004) and Mussatto et al. (2007) noted that the recovery yield of lignin increased with decreasing the pH of black liquor. They also showed that the lignin is clearly recovered when the pH of liquor is adjusted to lower than 6.