Activation of cellulose and peach wood impregnated with lignin dissolved in formic acid: Influence of evolution of mass yield and pore structure of AC

Background The performance of activated carbon (AC) is dependent on its pore structure. However, activation processes involving agents like K 2 C 2 O 4 can lead to significant carbon loss and reduced yield due to vigorous cracking reactions. To address this, the present study employed impregnation of the biomass feedstock with a formic acid lignin solution prior to activation. This approach aims to leverage the protective function of lignin to suppress cracking, enhance product yield, and investigate its regulatory mechanism on the structure of the resulting AC. Methods The method involves impregnating the cellulose and peach wood feedstocks with a formic acid-lignin solution. Subsequently, the impregnated materials undergo chemical activation using either ZnCl 2 or K 2 C 2 O 4 as the activating agent. Significant findings The results showed that lignin impregnation prior to activation enhanced the mass yield of AC compared to direct activation without lignin (76.9% versus 71.4%), because lignin serves as a precursor for stabilizing carbon structure formation. AC from ZnCl 2 activation generally exhibited higher specific surface areas (1655 m 2 g –1 versus 1226 m 2 g –1 via K 2 C 2 O 4 activation), while K 2 C 2 O 4 promoted severe carbon cracking but favored the formation of heavy organics in bio-oil. However, lignin impregnation reduced the specific surface area, possibly due to the formation of a protective layer that hindered activating agent penetration and interaction with the feedstock components (1655 m 2 g –1 versus 1308 m 2 g –1 via ZnCl 2 activation of lignin-impregnated precursor). AC obtained through ZnCl 2 activation exhibited a favorable adsorption ability for tetracycline, and all prepared ACs demonstrated exceptional removal efficiency for basic fuchsin due to its well-developed porosity. In addition, impregnation with lignin introduced more oxygen-containing functional groups, such as -OH and C O, onto the AC, significantly enhancing its surface hydrophilicity. Overall, this study provides a practical strategy for tailoring the yield, pore structure, and surface properties of biomass-derived AC for targeted environmental remediation.