Optimization of Two-Step Alkali Process of Lignin Removal from Basswood

The aim of the research described in this article was to optimize the basic sulphur process of lignin removal from the raw radially cut basswood (Tilia Cordata) pieces of various thicknesses. Lignin removal took place chemically in several consecutive steps in which the influence of individual parameters was investigated (solutions of NaOH + Na₂SO₃, KOH + Na₂SO₃, its concentrations, time of leaching, efficacy of whitening agents, effect of sample washing between individual baths, etc.). Through experiments, it was found that the change of fresh NaOH + Na₂SO₃ solution during the experiment had no significant effect. In contrast, skipping the washing of the samples with boiling distilled water after the hydroxide bath had a significant effect on the rate and efficiency of lignin removal with H₂O₂ in the following step. When comparing the lignin removal efficiency of NaOH + Na₂SO₃ and KOH + Na₂SO₃, the delignification process was clearly demonstrated to be more effective using the KOH + Na₂SO₃ solution. Application of the above-mentioned procedures has helped to streamline the lignin removal process from solid basswood.