Preparation of activated carbon from paper black liquor lignin as high-performance electrode material

Black liquor, a major by-product of the paper industry, is often underestimated in terms of its industrial value. Effective utilization of black liquor has become a pressing concern. In this study, electrode materials were prepared using activated carbon derived from black liquor and the optimal conditions for the preparation of black liquor activated carbon with high electrochemical performance was determined. The electrochemical performance of activated carbons obtained through the processes of evaporation and concentration of black liquor, extraction of lignin from black liquor, and direct utilization of industrial lignin, were compared. The results revealed that the optimal conditions for preparing activated carbon were a carbonization temperature of 500 °C and an activation temperature of 700 °C. The specific capacitance was measured to be 389 F/g at 0.5 A/g, with capacitance retention of 100%. Moreover, even after 5000 charge/discharge cycles at a current density of 2.0 A/g, the energy density reached 22.2 Wh/kg. The specific surface area of the activated carbon was determined to be 2147.77 m²/g. One notable advantage of the activated carbon prepared by evaporating the black liquor is that it retained hetero-atoms such as S present in the black liquor. This feature resulted in a higher capacitance compared to other preparation methods.