Preparation of Activated Carbon from Lignin Product with Alkali

Abstract

Activated carbon was prepared with alkali from such lignin products as lignin sulfonic acid, thiolignin, and black liquor. Dry distillation of 1/1 or 1/2 mixture of lignin sulfonic acid and NaOH gave carbonaceous residue at temperature above 300°C (Fig.1). Powdery activated carbon with good quality were, obtained directly by -careful washing of the residue without further activating process. The yield of activated Carbon was remarkably decreased from 0.19 to 0.04 with the increase in the relative amount of NaOH (lignin sulfonic acid/NaOH ratio from 1/1 to 1/3), although Na₂CO₃ showed a limited effect (Fig.2). The eff ects of the alkali ratio and the carbonization and activation temperature on the yield and the total surface area of the prepared activated carbon are eValuated from the surface developing diagrams in Figs.4 and 5. The diagrams indicate that the optimum alkali ratio and the temperature are 1 and 450°C, respectively.
Under similar conditions, pu rified lignins gave high quality activated. carbon (Table 1). Thus, the specific surface area of the activated carbon from thiolignin was 2751 m²/g by BET method. This value is very close to the upper limit of the surface, area of graphite. Furthermore, a 'activated carbon of reasonable quality was prepared from black liquor by removal of its inorganic constituents with calcium oxide.