Study on the reaction mechanism of the potassium bicarbonate alkali activation process in black liquor

The alkaline hydrothermal separation of cellulose is a crucial step in biofuel generation, wherein black liquor containing lignin and alkali is produced as a by-product. This study explored the reaction mechanism of the residual alkali during the activation process. In this reaction, the impregnated K reagent exhibited unusual behavior owing to its bonding with the lignin structure, which was confirmed by the K 2p peak shift in x-ray photoelectron spectra. This behavior resulted in the formation of a microporous and mesoporous substance with a high surface area of 2146 m2 g−1 without requiring additional chemical reagents. Furthermore, the activated carbon derived from black liquor possessed outstanding properties, allowing its use in supercapacitors. This study demonstrates that giant miscanthus-derived black liquor can be used as an activated carbon precursor for application in electric double-layer capacitors owing to its superior electrochemical capabilities.