Facile preparation of biochar from biomass-derived lignin and cellulose for determination of 4-nitrophenol and 2-nitrophenol

The complex components in biomass materials exhibit distinct pyrolysis behaviors. These behaviors lead to the diverse structures of biochar prepared by direct pyrolysis. Additionally, Nitrophenols display different electrochemical redox behaviors on various carbon materials. These factors impose limitations on the applications of both the biochar in the determination of nitrophenols. In this study, lignin and cellulose were extracted from poplar biomass via a simple alkaline pulping method. The obtained crude lignin and crude cellulose were pyrolyzed separately to produce two types of carbon materials: lignin-derived and cellulose-derived carbon. Lignin-derived carbon exhibited a closely packed structure of carbon nanoparticles, while cellulose-derived carbon had an interconnected macroporous structure. Lignin-derived carbon possessed an enhanced response for the electrochemical reduction of 4-nitrophenol, while cellulose-derived carbon had a higher response for 2-nitrophenol. During the reduction of 4-nitrophenol, the hydroxyl group content was the dominating factor. Moreover, the trace-doped N-species was more crucial for 2-nitrophenol reduction. The detection limit for 4-nitrophenol on lignin-derived carbon was 0.0174 nm and detection limit for 2-nitrophenol on cellulose-derived carbon 0.0203 μM.