Preparation and Characterization of K2CO3-Activated Kraft Lignin Carbon

A series of activated carbons (ACs) were prepared by K2CO3 activation from kraft lignin (KL) that was recovered from papermaking black liquor. The effects of process parameters such as the activation temperature (AT), activated period, K2CO3 to KL mass ratio, and N2 flow rate on the characteristics of the final product were determined. The ACs were characterized using nitrogen adsorption, morphology, and fractal dimension analyses. The results showed that the AT was the main factor influencing the yield, surface area, and pore structure. The yield of ACs obviously decreased from 50.6% to 20.5% with increasing AT from 600 °C to 1000 °C, and decreased with increasing K2CO3/KL mass ratio. Activation time and N2 flow rate had slight effect on the yield of ACs. The surface area and total pore volume increased as the AT rose to 900 °C and then decreased with further increases in temperature. The maximum surface area and total pore volume were 1816.3 m/g and 1.26 cm/g, respectively, at a K2CO3 to KL mass ratio of 3:1, AT of 900 °C, activation time of 2 h, and N2 flow rate of 70 cm/min. The pore structure of the ACs could be tailored by controlling the AT. As the AT was increased from 700 to 1000 °C, the mesoporosity increased from 11.6% to 95.9%. SEM images indicated that the morphology of ACs was modified by the AT. The K2CO3 was partially recycled.