Investigation of Lignin-based activated carbon synthesis parameters on its structural properties

Activated carbon is a porous absorbent with reasonable specific surface area, pore volume, and pore size distribution for many applications such as adsorption. This material is obtained from various natural sources of carbon. Due to increasing demand for activated carbon, the economical precursors have been highly noticed. In the meanwhile, black liquor, industrial residue from Lignin Kraft process in paper factories, has high amount of carbon which can be used as an appropriate and cheap precursor for activated carbon production, and make high value added.

In this study, at first, lignin was extracted from black liquor, prepared from Iran wood & paper industries-Chouka factory, under defined conditions and investigation of pH effect, and then, powdered carbon was synthesized from extracted lignin using chemical activation method by phosphoric acid chemical agent. To consider the effects of activation temperature parameter on activated carbon structure, including specific surface area, pore volume, and pore size distribution, three activation temperature of 400, 500 and 600 ⁰C in impregnation ratio of 2 were investigated. To study the physical and morphological properties of sensitized absorbents, they were analyzed by BET, SEM, and FTIR methods.

The results confirmed that the highest amount of lignin with a similar structure to the degraded lignin was recovered at pH = 2. Investigation of the effect of activation temperature parameter suggested that the activation temperature of 500 °C can be a reasonable temperature for the synthesis of high specific surface area activated carbon and increasing the temperature above 500 °C is not effective. Among these sensitized adsorbents, the activated carbon sensitized in activation temperature of 500 ⁰C showed the highest specific surface area and the pore volume of 1573.31 m2/g and 0.89 cm3/g respectively, which exhibits the high potential of this precursor as activated carbon adsorbent.