unit [3].
Fig. 2 is a schematic diagram of the black liquor structure, which
comprises lignin and polysaccharide clusters, salt ions and water.
Note that, the lignin, the bonding agent of wood or fibrous plant fibers, is a polymer formed by phenyl-propane structures. During
the pulping operation, the lignin is fragmented and the carbohydrates are dissolved and converted into acids of low molar mass