Effect of different superficial treatments on structural, morphological and superficial area of Kraft lignin based charcoal

Lignin is a biomass derived from an abundant renewable source, rich in carbon and with potential application in modern society. The goal of this work is to add more value to lignin through its thermal conversion in charcoal, as well contribute to solutions linked to environmental preservation. Charcoal was obtained from Kraft lignin and its surface was modified using chemical (acid attack) and physical (microwave plasma) methods, in order to get charcoals different characteristics. In this work, the prepared charcoals were characterized by field emission gun - scanning electron microscope (FEG-SEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and superficial area by BET analyses. Microscopic analyses evidenced morphological differences in the samples as consequence of the used superficial treatments. Raman spectroscopy results point to an increase in the carbon material disorder after chemical and physical treatments. The acid attack of charcoal increased its superficial area by 40% (403 m2/g) in relation to the charcoal without chemical treatment (287 m2/g). Physical treatment based on microwave plasma promoted a further increase in superficial area of 63% (468 m2/g). FT-IR showed that chemically treated charcoals presented more functional groups. Based on these results, it can be verified that the production of activated charcoal from lignin is viable and its superficial area can be increased using acid and plasma treatments, the latter being a more efficient and clean method.