Activated carbon from hydrolysis lignin: Effect of activation method on carbon properties

This study presents the effects of different activation methods to produce activated carbon from the hydrolysis lignin. Pretreatment of the feedstock with common mineral acids (HCL, HNO3, and H3PO4), different steam rates for physical activation, and different chemical activating agents (ZnCl2, Na2CO3, and KOH) for chemical activation were investigated. The pretreated biomass was carbonized and activated in one-stage process and the surface characteristics, such as total pore volume, pore size distribution and specific surface area, were investigated. The results showed that the activated carbon surface properties were not greatly affected by acid pretreatment. Brunauer-Emmett-Teller (BET) surface areas as high as 616 m2/g could be achieved with physical activation and 2054 m2/g with chemical activation. Different steam rates in the selected interval (0.5–2 cm3/min) did not change the pore size distribution but had small positive effect on the specific surface area, while chemical activation with ZnCl2 increased the mesoporosity, and activation with KOH increased the microporosity and oxygen groups in the form of ether and alcohol bonds.