Biomass-Based Activated Carbon and Activators: Preparation of Activated Carbon from Corncob by Chemical Activation with Biomass Pyrolysis Liquids

Pyrolysis liquids are the main products in biomass pyrolysis, and the strong acidity limits its utilization. Likewise, activators are required in the process of preparing biomass-based activated carbon, and current activators are usually chemical agents and not sustainable. Both issues are addressed with the new concept of using acidic pyrolysis liquids as the activator of biomass-based activated carbon. In the present research, corncob-based activated carbon was prepared with phosphoric acid and pyrolysis liquids (bio-oil and wood vinegar) as activators. The effects of activation temperature and the types of activators on the structure and surface chemical properties of activated carbon were investigated. Results show that the adsorption performance and specific surface area of activated carbon prepared with bio-oil are not as good as that prepared with phosphoric acid and wood vinegar, but its yield is relatively high. Some alkali and earth alkaline metals remain on the activated carbon prepared by bio-oil and wood vinegar. At 450 °C, the surface area and pore volume of activated carbon prepared with bio-oil and wood vinegar were much smaller than the ones prepared with phosphoric acid. Increasing the activation temperature may improve the performance of activated carbon. The specific surface area of activated carbon prepared with wood vinegar as the activator can reach 384.35 m²/g at an activation temperature of 850 °C, which is slightly inferior to that prepared with phosphoric acid as the activator. However, the adsorption amount of methylene blue exceeds the activated carbon prepared with phosphoric acid. This shows that wood vinegar can be used as an activator to prepare biomass-based activated carbon to achieve sustainability of the entire preparation process of biomass-based activated carbon.