Lignin Isolation from Pulp

Several different enzymatic, chemical and mechanical methods have been developed for the isolation of lignin from wood and pulp. However, due to the heterogeneous nature of wood and pulp fibers and the heterogeneity that exists between individual fibers, no method is currently available for the quantitative isolation of native or residual lignin without the risk of structural changes during the isolation. Even if the perfect isolation technique could be found, the product would at best represent the average structure of native or residual lignin components. However, the information gained about the chemical reactivity and structure of isolated lignin is valuable. Thus, the three most commonly employed methods for isolating residual lignin are described below.