Isolation of Kraft lignin

This technique includes different laboratory procedures outlined in Fig. 4.7 (schematic diagram). In addition, these procedures have been applied subsequently in order to produce pure Kraft Lignin (KL). Apart from these, they consist of three experimental processes as explained in the following subsections. 

1 Oil palm empty fruit bunch Kraft pulping 

The Kraft pulping process involves digesting of OPEFB fibers at elevated temperature and pressure in cooking liquor, which is an aqueous solution of sodium sulfide (Na2S) and sodium hydroxide (NaOH). The cooking liquor chemically dissolves the lignin that hinds the cellulose fibers together. 

During the Kraft pulping process, the lignin that dissolved from the raw material (OPEFB) is separated in the form of a liquor, rich in phenolic compounds, that represents the process effluent 

Conventionally, lignin can be separated from other black liquor components using acid precipitation method, in addition, the acid 

---