Sustainable process to produce activated carbon from Kraft lignin impregnated with H3PO4 using microwave pyrolysis

• Published in: Biomass & bioenergy Vol. 156; p. 106333
• Main Authors: Brazil, Tayra R., Gonçalves, Maraísa, Junior, Mauro S.O., Rezende, Mirabel C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2022
• Subjects: Activated carbon; Chemical activation; Kraft lignin; Microwave; Microwave; Chemical activation; Activated carbon; Kraft lignin
• ISSN: 0961-9534; 1873-2909
• DOI: 10.1016/j.biombioe.2021.106333

Currently, the demand for activated carbon (AC) has been growing thanks to its adsorption capacity to remove liquid and gaseous pollutants. Lignin is a biomass derived from an abundant renewable resource, rich in carbon, with potential applications in modern society. This work seeks to add greater value for the lignin, transforming it in AC and also to demonstrate the microwave pyrolysis effectiveness. ACs were obtained from Kraft lignin treated with different proportions of phosphoric acid in two different periods of time, using microwave pyrolysis in oxidizing atmosphere. The results of Fourier transform infrared spectroscopy and X-ray diffraction showed that the conversion of lignin to carbon material occurred successfully. The morphology of lignin, observed by scanning electron microscopy, showed a globular appearance and different diameters, which was converted into AC with very porous structures. Adsorption/desorption of N2 (BET) analyses showed that the AC presented high surface areas, between 635 and 1055 m2g-1, with the presence of micro and mesopores. The highest acid:lignin weight ratio favored higher values of AC surface area and pore volume. The maximum adsorption capacity of prepared AC was tested with methylene blue dye (MB) and amoxicillin (AMOX), and values of 140 and 220 mgg−1 were found, respectively. In the case of MB, the adsorption mechanism adjusted better to the Langmuir model and the AMOX to the Freundlich model. [Display omitted] •Development of a sustainable industrial society, making more conscious use of lignin, a molecule rich in carbon.•Activated carbons with high surface area were produced from Kraft lignin using H3PO4 as activating agent.•The adsorption of the methylene blue dye and amoxicillin antibiotic were successfully achieved.•Microwave pyrolysis has great potential for the production of carbon materials.