Microwave-assisted utilization of kraft lignin-derived activated carbon for efficient dye removal

The use of conventional petrochemical-based carbon precursors, high-energy pyrolysis-based carbonization processes, and difficulties in designing sustainable processes using activated carbon have hampered the sustainable production of activated carbon and its use in wastewater treatment processes. In this study, to overcome these limitations in the production and application of existing petrochemical-based activated carbon as a water treatment material, biomass-based kraft lignin was used as an eco-friendly carbon precursor. In addition, to increase process efficiency, activated carbon was prepared using energy-intensive microwave-assisted carbonization and applied to the dye wastewater removal process. First, kraft lignin was successfully converted into microporous activated carbon within 10 min through microwave-assisted carbonization and chemical activation processes. As a result, kraft lignin-derived activated carbon showed excellent adsorption capacity for MB of 543.82 mg/g and AO of 548.54 mg/g, respectively. In addition, through heat treatment using microwaves (low power conditions of 450 W, treatment within 2 min), it was possible to successfully achieve thermal decomposition of the adsorbed dye and recovery of the pores and texture properties of activated carbon. Finally, kraft lignin-derived activated carbon showed an excellent reuse efficiency of more than 97 %, even under the condition of reuse 5 times.