from lignocellulosic wastes from the extraction of tannins. The use of vegetable tannins in the leather
industry has the serious drawback that it involves the mass destruction of trees. Currently, studies are
being conducted to obtain tannins from different lignocellulosic wastes. Two lignocellulosic wastes from
the extraction of tannins, defatted grape seeds and acacia seed shells, with high carbon and nitrogen
contents and a low ash content were obtained and investigated as a potential precursor for the preparation
of activated carbons. KOH chemical activation, with a previous pyrolysis step, was performed in a
conventional electric furnace varying the experimental conditions of KOH/precursor weight ratio, final
activation temperature, and inert flow gas. After activation the samples were washed with a solution
of HCl and water or just with hot water. The ACs obtained were essentially microporous with a specific
surface area up to 2000 m2 g and presented low ash content, less than to 0.10% in the case of adsorbent
materials from the defatted grape seeds and up to 3.60% for the materials from the acacia seed shells. The
best results were obtained with the largest KOH/precursor weight ratio or the highest activation temperature
(900 C). Their moderate nitrogen content (up to 1.5%) makes them especially suitable materials for
CO2 capture. Some of them were more effective for CO2 adsorption than the commercial activated carbon
F400 and therefore represent an attractive alternative to more expensive adsorbent materials.